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A-level Biology > 4 - DNA, RNA And Classification / Variation > Flashcards

4 - DNA, RNA And Classification / Variation Flashcards

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1
Q

What are the 4 bases

A

Adenine
Thymine
Guanine
Cytosine

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2
Q

What are histones

A

Proteins that DNA get wound around

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3
Q

What charge is DNA

A

Slightly negative

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4
Q

What charge are histones

A

Slightly positive

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5
Q

What is the combination of DNA and histones called

A

Nucleosome

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6
Q

What is gene expression

A

Characteristic functional in a phenotype

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7
Q

DNA is wrapped + coiled around histone proteins to form a substance called what?

A

Chromatin

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8
Q

Do prokaryotes have histones

A

No

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9
Q

Why do prokaryotes not have histones

A

More simple
Usually smaller genomes as Si plaid functions

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10
Q

How does DNA exist in prokaryotes

A

DNA is circular, free in cytoplasm in 2 forms
- circular chromosomes
- small amounts in circular plasmids

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11
Q

Are mitrochondria and chloroplasts found in both prokaryotes and eukaryotes

A

No
Only eukaryotes as memebrane bound

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12
Q

Do mitochondria and chloroplasts have their own DNA

A

Yes

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13
Q

Eukaryotic cells contain …………. DNA that exist as ………….

A

Linear
Chromosomes

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14
Q

Where are chromosomes found in a eukaryotic cell

A

Nucleus

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15
Q

What has to happen to DNA so that it can fit into the nucleus and why

A

It’s very long so wound up

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16
Q

Are histones protines?

A

Yes

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17
Q

What do histone proteins do

A

Support the DNA

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18
Q

Do prokaryotes carry DNA in chromosomes

A

Yes

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19
Q

Describe the DNA molecules in prokaryotes

A

Shorter
Circular
Isn’t wound around histones

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20
Q

How does DNA in prokaryotes fit into cells

A

Supercoiling

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21
Q

What is a gene

A

A sequence of DNA bases that codes for either a polypeptide or functional RNA

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22
Q

The sequence of amino acids in a polypeptide forms the ………….. of a protein

A

Primary protein

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23
Q

What determines the order of amino acids in a particular polypeptide

A

The order of bases in a gene

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24
Q

What is each amino acid coded for by

A

three bases in a gene called a triplet

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25
Q

What is the first stage of protein synthesis

A

DNA is first copied to messenger RNA

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26
Q

Genes that don’t code for a polypeptide code fro what

A

functional RNA

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27
Q

What is functional RNA

A

RNA molecules other than mRNA, which preform special tasks during protein synthesis, and ribosomal RNA, which forms part of ribosomes

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28
Q

What is a called genome

A

The complete set of genes in the cell.

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29
Q

What is a cells proteome

A

The full range of proteins that the cell is able to produce

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30
Q

What are introns

A

In eukaryotic DNA, genes that do code for polypeptides contain sections that don’t code for amino acid , called introns

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31
Q

Can there be several introns within a gene

A

Yes

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32
Q

What are exons

A

Bits of a gene that do code for amino acids

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33
Q

Introns are ……… durning protien synthesis and why

A

Removed
So they don’t affect the amino acid order

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34
Q

Does prokaryotic DNA have introns

A

No

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35
Q

Eukaryotic DNA also contains regions of multiple repeats outside of genes, what does this mean

A

These are DNA sequences that repeat over and over

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36
Q

In eukaryotic DNA do multiple repeated outside of genes code for amino acids, so what are they called

A

No
Non coding repeats

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37
Q

What is an allele

A

A form of a gene

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38
Q

Why does each allele have slightly differnt versions of the same polypeptide

A

The order of bases is slightly differnt

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39
Q

How many pairs of chromosomes do humans have

A

23 pairs

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40
Q

What are pairs of matching chromosomes called

A

Homologous pairs

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41
Q

Describe homologous pairs

A

Both chromosomes are the same size and have the same genes, although the pay could have differnt alleles.
Alleles coding fro the same characteristics will be found at the same fixed position (locus) on each chromosome in anhomologous pair

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42
Q

Centre of a chromosome name

A

Centromere

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43
Q

What is an allele

A

Version of a gene

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44
Q

What is a gene

A

Section of DNA that codes for a particular characteristics

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45
Q

What is loci

A

Location of the gene in a chromosome

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46
Q

What is a chromosome

A

DNA in nucleus of eukaryotic cells is linear and arranged in chromosomes

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47
Q

What is chromatin

A

DNA wrapped and coiled around histone proteins

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48
Q

What does DNA stand for

A

Deoxyribose nucleic acid

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49
Q

What is a polypeptide

A

Chain of amino acid connected by peptide bonds

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50
Q

in prokaryotes, DNA isn’t wound around histones so how does it fit in the cell

A

Condenses by supercoiling

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51
Q

What is a codon

A

Sequence of 3 DNA / RNA nucleotides that correspond with a specific amino acid

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52
Q

What are exons

A

Code for an amino acid

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53
Q

What are introns

A

Don’t code of amino acids
(Removed during protein synthesis )

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54
Q

Does prokaryotes have both exons and introns

A

only exons

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55
Q

What. Happens first transcription or translation

A

Transcription

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56
Q

Where does transcription happen

A

In the nucleus

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57
Q

Where does translation happen

A

In the cytoplasm by the ribosome

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58
Q

What is splicing

A

Process of cutting out introns
Leaving on exons

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59
Q

What does a mRNA triplet code match to

A

A specific amino acid

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60
Q

What is a codon

A

mRNA strand being read in triplets

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61
Q

Where is an anticodon found

A

On tRNA

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62
Q

Explain transcription

A

The hydrogen bonds in the DNA, between complementary base pairs, is broken by an enzyme.
• two exposed strands, one used as a template.

  1. One of the DNA strands is used as a template to make the mRNA molecule, the template is called the antisense strand.
  2. Free nucleotides line up by complementary base pairing and adjacent nucleotides are joined by phosphodiester bonds thus forming a molecule of mRNA.
    • The enzyme RNA polymerase catalyses the formation of phosphodiester bonds.
  3. When a stop codon is reached this ceases. As the RNA polymerase moves away the DNA rejoins, with only 12 bases being exposed at a time to reduce the chance of damage to the DNA.
  4. In eukaryotic cells the pre-mRNA is then spliced to remove the introns leaving just a strand of exons.
  5. The mRNA then moves out of the nucleus through a pore and attaches to a ribosome in the cytoplasm which is the site of next stage of protein synthesis called translation.
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63
Q

What is broken in DNA during transcription to expose the 2 strands

A

Hydrogen bonds between complementary base pairs.

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64
Q

What is the template strand in transcription called

A

Antisense strand

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65
Q

How do adjacent nucleotides join up and for a mRNA molecule
And what is the catalyst

A

Phosphodiester bonds
Enzyme RNA polymerase catalysed

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66
Q

When does the RNA polymerase move away and the DNA rejoins in transcription

A

When a stop codon is reached

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67
Q

How many bases on DNA are exposed at one time in transcription
And why

A

12
To reduce chance of damage to DNA

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68
Q

What happens to pre-mRNA to produce mRNA

A

Splicing to remove introns

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69
Q

How does mRNA exit the nucleus
And where does it go

A

Through a nuclear pore
and attached to a ribosome in the cytoplasm

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70
Q

Why is DNA kept in the nucleus during protien synthesis

A

It’s more prone to damage ( mutations) outside the nucleus

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71
Q

Describe translation

A
  1. mRNA attaches to a ribosome
  2. transfer RNA collects amino acids from the cytoplasm and carries them to the ribosome.
    • can only carry one type of amino acid, and a triplet of bases (anticodon) at the other.
  3. tRNA attaches itself to mRNA by complementary base pairing
    • two molecules attach to mRNA at a time.
  4. The amino acids attached to two tRNA molecules join by a peptide bond and then tRNA molecules detach themselves from the amino acids, leaving them behind.
  5. This process is repeated thus leading to the formation of a polypeptide chain until a stop codon is reached on mRNA
    • this ends the process of protein synthesis.

A ribosome can join up to 15 amino acids per second until the stop codon is reached. Furthermore up to 50 ribosomes can move along the same strand of mRNA behind one another so that several proteins can be assembled simultaneously.

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72
Q

What is the simplifed definition of translation

A

Amino acids join together to form a polypeptide chain

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73
Q

How many tRNA molecules can attach to mRNA at one time

A

2

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74
Q

What is the bond between 2 amino acids

A

Peptide bond

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75
Q

Is tRNA single or double stranded

A

Single

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76
Q

Describe the length of
DNA, mRNA and tRNA

A

DNA - long
mRNA- variable
tRNA- short

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77
Q

What shape is mRNA

A

Single helix / strand

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78
Q

What is the shape of tRNA

A

Clover

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79
Q

What type of sugar is in DNA

A

Deoxyribose

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80
Q

What type of sugar is in mRNA

A

Ribose

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81
Q

What type is sugar is in tRNA

A

Ribose

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82
Q

What bases are in DNA

A

Adenine (check )
Thymine
Cytosine
Guanine

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83
Q

What bases are in mRNA and tRNA

A

Adenine
Uracil
Cytosine
Guanine

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84
Q

Is DNAs quantity Large or small and is it constant

A

Large and constant

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85
Q

is mRNA quantity large or small and is it constant

A

Smaller
Varies

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86
Q

is tRNA quantity large or small and is it constant

A

Smaller
Varies

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87
Q

What is the stability in
DNA, mRNA and tRNA

A

DNA - stable
mRNA - unstable
tRNA - relatively stable.

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88
Q

How many possible triplets are there
And how many AA are there

A

64
20 AA

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89
Q

What are the features of the genetic code

A

non-overlapping: meaning that each triplet is only read once and triplets don’t share any bases.
• Genes are separated by non-coding repeats of bases.
• is degenerate: meaning that more than one triplet codes for the same amino acid,

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90
Q

What does genetic code being degenerate reduce

A

Mutations

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91
Q

homologous pairs consist of ……. Chromosomes that carry the same gene

But they arnt identical, why?

A

2
They can carry differnt alleles of the same gene

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92
Q

What sex chromosomes do females have

A

2 X chromosomes

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93
Q

What sex chromosomes do males have

A

X and Y chromosome

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94
Q

What does homologous pair of chromosomes contain

A

Contain the same set of genes

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95
Q

What 3 groups are in an amino acids

A

Carboxylic acid
Amino group
r group changes

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96
Q

What is required to form the bond between amino acids and tRNA molecule to from
And where else is thus required in translation

A

ATP
To join 2 amino acids together

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97
Q

What is the genetic code

A

The sequence of base triplets (codons) in mRNA which codes for specific amino acids

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98
Q

What does it mean that the genetic code is universal

A

The same specific base triplets code for the same amino acid in all living things

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99
Q

What are gametes

A

The sperm and eggs cells
They join togetehr during fertilisation to from a zygote
Which divides and develops into a new organism

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100
Q

How many chromosomes do normal body cells have (in humans)
What is the term to describe thus

A

46
Diploid

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101
Q

How many chromosomes are in the gametes in humans
And what is the term to describe this

A

23
Haploid

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102
Q

T or f
Fertilisation is random

A

T

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103
Q

What does random fertilisation produce

A

Zygotes with differnt combinations of chromosomes to both parents

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104
Q

What increases genetic diversity within species

A

The mixing of genetic material in sexual reproduction

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105
Q

Where does meiosis happen

A

In reproductive organs

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106
Q

What happens before meiosis starts

A

The DNA unraveled and replicates so there are two copies of each chromosomes called chromatids
The DNA then condensed to from double armed chromosmes, each made form 2 sister chromatids. The sister chromatids are joined in the middle by a centromere

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107
Q

How are 2 sister chromatids joined

A

By a centromere

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108
Q

Describe meiosis 1

A

The chronometer arrange themselves into homologous pairs
These homologous pairs are then separated halving the chromosome number

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109
Q

Describe meiosis 2

A

The pairs of sister chromatids that make up each chromosome are separated (the centromere is divided)

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110
Q

What is the product of meiosis

A

4 haploid cells that are genetically differnt from each other are produced

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111
Q

What can happen to chromatids in meiosis 1

A

homologous pairs of chromosomes come togetehr and pair up
The chromatids twist around each other and bits of the chromatids swap over
The chromatids still contain the same genes but now have a differnt combination of alleles

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112
Q

What 2 main events happen during meiosis that lead to genetic variation

A

1) crossing over of chromatids
2) independent segregation of chromosomes

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113
Q

How does crossing over of chromatids lead to genetic variation

A

Each of the four daughter cells formed form meiosis contain chromatids with differnt alleles

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114
Q

How independent segregation of chromosomes leaded to genetic variation

A

Each homologous pair of chromosomes in your cells is made up of one chromosome for, your mum (maternal) and one form your dad ( paternal )

When the homologous pairs are separated in meiosis, it’s completly random which chromosome form each pair ends up in which daughter cell

So the 4 daughter cells produced by meiosis have completely differnt combinations of those paternal and maternal chromosomes

This shuffling of the chronometer leads to genetic variation of any potential offspring

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115
Q

Outcomes of mitosis

A

Produced cells with the same number of chromosomes as the parent cell

Daughter cells are genetically identical to each other and to the parent

2 daughter cells

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116
Q

Outcomes of meiosis

A

Produced cells with half the number of chronometer as the parents cell

Daughter cells are genetically differnt form one another and the parent cells

Produced 4 daughter cells

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117
Q

My do mitosis and meiosis have differnt outcomes

A

Mitosis only involves one division which separates the sister chromatids, whereas meiosis has two divisions, which separate the homologous pairs, and then the sister chromatids. There’s no pairing or separating of homologous chromosomes in mitosis, and so no crossing over ot independent segregation of chromosomes.

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118
Q

In humans
How many chromosomes do the daughter cells have after meiosis

A

23

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119
Q

What is it called when something goes wrong in meiosis and the cell produced contains a variation in the number of whole chromosomes or parts of chromosomes

A

Chromosome mutation
Caused by errors during meiosis

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120
Q

What does chromosome mutations lead to

A

Inherited conditions because the errors are Present in the gametes

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121
Q

What is non disjunction

A

Failure of the chromates to separate properly

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122
Q

What does non-disjunction of chromosomes 21 during meiosis lead to

A

Down syndrome

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123
Q

What is Down syndrome caused by

A

A person having an extra copy of chromosome 21
Non disjunction means that chromosome 21 fails to seperate properly during meiosis so one cell gets an extra copy of 21 and another gets none
When the gamete with the extra copy fuses to another gamete at fertilisation, the resulting zygote will have 3 copies of chromosomes 21

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124
Q

What do gene mutations involve

A

A Changw in the DNA base sequence of chromosomes

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125
Q

What two types of gene mutations are there

A

Substitution
Deletion

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126
Q

What is substitution mutation

A

One bass is substituted with another

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127
Q

What is a deletion mutation

A

One base is deleted

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128
Q

What does a mutation in a gene chase

A

order of DNA bases Change
So amino acid changes
So the sequnce if amino acid changes
So the protein coded for could be altered

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129
Q

Why do not all mutations affect the offer of amino acids

A

The degenerate nature of the genetic code means that some amino acids are coded for by more than one DNA triplet
This means that not all substitutions will result in a change to the amino acid sequence of the protein
some substitution will still change for the same amino acid

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130
Q

Will substitution mutation always leads to changed in the amino acid sequence

A

No

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131
Q

Will deletion mutation always leads to changed in the amino acid sequence

A

Yes

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132
Q

how does deletions affect amino acids sequence

A

It will change the number of bases present
Which will cause a shift in all the vase triplets after it

133
Q

T or f
Mutations occur spontaneously

A

T

134
Q

somethings cause an increase in rate of mutations
are called what

A

Mutagenic agents

135
Q

Give some examples of mutagenic agents

A

Ultraviolet radiation
Ionising radiation
Some chemicals and some viruses

136
Q

What are the phases of meiosis

A

Interphase
Prophase
Megaphone
anaphase
Telophase
Prophase 11
Metaphase 11
Anaphase 11
Telophase 11
Cytokinesis 11

137
Q

What is the DNA like in interphase

A

Already 2x the amount
DNA in nucleolus as chromatin
(The nucelar envelope is intact)

138
Q

describe the dna in prophase

A

DNA in chromosomes
The sisterchromasomes joined at the centromere

139
Q

When does the nucelar envelope break down in meiosis

A

Prophase

140
Q

In prophase 1
Meiotic spindles form long proteins called ……

A

Microtubules

141
Q

What happens in metaphase 1 in meiosis

A

Pairs of chromosomes line up on equator on spindle fibres

142
Q

What phase can independent assortment only happen in in meiosis

A

Metaphase 1

143
Q

What 3 things in meiosis can lead to genetic variation

A

Independent assortment
Random fertilisation
Crossing over

144
Q

What does crossing over mean ( meiosis )

A

Can have section of DNA exchange when they overlap

145
Q

The closer the gene is to the chromosome the ………
It is to be exchanged in crossing over

A

Less likeY

146
Q

Describe anaphase 1 meiosis

A

Homologous pairs separate + are pulled to centriole by spindle fibres attached to centromeres

147
Q

Describe telophase in meiosis

A

Chromomes reach poles

148
Q

Describe cytokinesis meiosis

A

Nuclear membrane reforms
Chromosomes —> chromatin

149
Q

Descirbe prophase 2 meiosis

A

The chromosomes condense and become visible again
The nuclear envelope breaks down
Spindle fibres begin to develop

150
Q

Describe metaphase 2 meiosis

A

Chromosomes line up at equator
Spindle fibres attach to centromere - breaking centromere

151
Q

Describe anaphase 2 meiosis

A

Sister chromatids are pulled to opposite ends of the cells be spindle fibres

152
Q

How does structure of DNA relate to its function

A

• The sugar-phosphate backbone/double stranded so protects the bases and therefore maintains the genetic code

• Long molecule so can store a lot of information

• Base sequence so allows coding for amino acid sequence in a polypeptide

• Double stranded so each strand acts as a template so allows accurate replication

• Many hydrogen bonds so keeps double strands stable

• Hydrogen bonds are weak so allows unzipping of the strands during replication

• Complimentary base pairing so allows accurate replication

• Coiled so it is compact so a lot of information can be stored

153
Q

What is a gene mutation

A

Change in the base sequence of chromosomes

154
Q

what 2 ways can gene mutation happen during dna replication

A

Base deletion
Base substitution

155
Q

What do not all base subsititutions cause a change in sequence of encoded amino acids

A

Due to the degenerate nature of the genetic code

156
Q

What are mutagenic agents

A

Increase rate of gene mutation

157
Q

What is essential for evolution to take place by natural selection

A

Variation

158
Q

Without natural selection what can’t happen

A

Species can’t evolve and survive changing conditions

159
Q

What can a mutated cell developer into

A

A tumour

160
Q

Only what can mutations result in

A

New alleles

161
Q

Meiosis and random fertilisation does not result in……….. but does result in…..

A

New alleles

NEW COMBINATIONS of ALLELES

162
Q

What is a substitution mutation

A

one base takes the place of another

163
Q

What is a deletion mutation

A

where one base is removed

164
Q

in a deletion mutation,
Because the sequence changes completly after the mutation it is referred to as what

A

Frameshift

165
Q

the earlier a deletion mutation happens the …….. effect it has

A

Bigger

166
Q

What is chromosomes non-disjunction
+ examples of where life is possible

A

sometimes something goes wrong during gamete formation and a gamete will have two of one type of chromosome not one. This means that if it is fertilised by a normal gamete the resulting embryo will have cells with three of one type of chromosome (this is called trisomy).
In humans this would usually make the embryo non-viable, however there are conditions where life is possible -
Three of chromosome number 21 – known as Down’s syndrome
Three of chromosome number 18 – known as Edward’s syndrome
Three of the sex chromosomes – XXY – known as Klinefelter’s syndrome
Or XYY Jacob’s syndrome

167
Q

Do formation of bivalent and chiasmata happen in mitosis or meiosis

A

Meiosis

168
Q

Does separation of chromatids happen in mitosis and meiosis

A

Both

169
Q

Fern reproduction lifecycle

A

In this life-cycle (the fern) meiosis results in the formation of spores not of gametes. The spores divide by mitosis to become what is called a gametophyte. The eggs and sperm are produced by mitosis and fuse to form a diploid zygote.

170
Q

What is disjunction

A

Disjunction is the normal separation or moving apart of chromosomes toward opposite poles of the cell during cell division

171
Q

What is non disjunction

A

Nondisjunction means that a pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cell.

172
Q

Advantages of sexual reproduction

A

Variation so can adapt for survival to changing conditions
Happens over many gernation ( the offspring are more adapted than the parents)

173
Q

Disadvantages of sexual reproduction

A

Slower (need a mate)
Courtship behaviour
Raid young

174
Q

Advantages of asexual reproduction

A

Clones - many if favourable conditions
Quick as no mate (energy efficient)

175
Q

Disadvantages of asexual reproduction

A

Less genetic variation so less resistant to disease
More vulnerable to changing conditions
Completion for same resorses
Slower rate of evolution

176
Q

What is the genetic diversity

A

The number of differnt alleles of genes in a species or population

177
Q

What is genetic diversity within a population increased by

A

Mutations in the dna - forming new alleles

Differnt alleles being introduced into a population when individuals form another population migrate into them and reproduce. This is known as gene flow

178
Q

What does genetic diversity allow

A

Natural selection

179
Q

What is a population

A

A group of organisms of one species living in a particular habitat

180
Q

What is genetic bottleneck

A

An event that causes a big reduction in a population

181
Q

How does a genetic bottleneck neck reduce genetic diversity

A

A big reduction in population
This reduces the number of differnt alleles in the gene pool and so reduces genetic diversity
The survivors reproduce and a larger population is created from a few individuals

182
Q

What is a gene pool

A

The complete range of alleles in a population

183
Q

Name a type of genetic bottleneck neck

A

Founder effect

184
Q

What is the founder effect

A

Describes what happens when a few organisms from a population start a new colony and there are only a small number of differnt alleles in the inital gene pool

The frequency of each alleles in the new colony might be very differnt to the frequency of those alleles in the origional population
Thus may lead to a higher incidence of genetic disease

185
Q

Give an example of why founder effect might occur

A

Migration leading to geographical separation or if a new colony is separated form the origional population

186
Q

What does natural selection do

A

Increase advantageous alleles in a population

187
Q

What are the 3 types of adaptations

A

Behavioural
Physiological
Anatomical

188
Q

What is a behavioural adaptation

A

Ways an organism acts that increase its chance of survival and reproduction

189
Q

What is a physiological adaptation

A

process inside an organisms body that increases its chance of survival

190
Q

What is an anatomical adaptation

A

Structual fractures of an organismsbody that increases its chance for survival

191
Q

What is directional selection

A

Individuals with alleles for a characteristics of an extreme type and more likely to survive and reproduce. This could be in response to an environmental change

192
Q

What is stabilising selection

A

Individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce.
It occurs when the environment isn’t changing and it reduces the range if possible characterists

193
Q

How do you test the effect of antibiotics using agar plates

A

The bacteria you will use are likely to have been grown in a liquid broth (a mixture of distilled water, bacterial culture and nutrients).

Use a sterile pipette to transfer the bacteria from the broth to an agar plate (a Petri dish containing agar jelly). Spread the bacteria over the plate using a sterile plastic spreader.

Use sterile forceps to place paper discs soaked with different antibiotics spaced apart on the plate. Make sure you add a negative control disc soaked only in sterile water

Lightly tape a lid on, invert, and incubate the plate at about 25 °C for 48 hours. This allows the bacteria to grow (forming a ‘lawn’). Anywhere the bacteria can’t grow can be seen as a clear patch in the lawn
of bacteria. This is called an inhibition zone.

The size of an inhibition zone tells you how well an antibiotic works, the larger the zone the more bacteria were inhibited form growing.

A similar techniques can be used to test the effects of antiseptics or disinfectants on microbial growth

194
Q

What are antiseptic techniques used when investigating bacterial growth

A

To prevent contamination of cultures by unwanted microorganisms.
This is important because contamination can effect the growth of the microorganisms you are working with
It’s also u,pirates to avoid contamination with disease causing microbes that could make you ill

195
Q

What aseptic techniques should be used when testing the effects of antibiotics using agar plates

A

• Regularly disinfect work surfaces to minimise contamination. Don’t put any utensils on the work surface.
Contaminated utensils should be placed in a beaker of disinfectant.
• Use sterile equipment and discard safely after use. E.g. glassware can be sterilised before and after use in an autoclave (which steams equipment at high pressure). Pre-sterilised plastics instruments are used once, then discarded.
• Work near a Bunsen flame. Hot air rises, so any microbes in the air should be drawn away from your culture.
• Minimise the time spent with the lid off the agar plate, to reduce the chance of airborne microorganisms contaminating the culture.
Briefly flame the neck of the glass container of broth just after it’s opened and just before it’s closed — this causes air to move out of the container, preventing unwanted organisms from falling in.
You should also take steps to protect yourself, e.g. wash your hands thoroughly before and after handling cultures.

196
Q

What is the difference between genes and alleles

A

• Alleles differ between individuals of the same species
• All individuals of the same species will have the same genes
• You can have different frequency of alleles in a population

197
Q

WhT is natural selection
Use rabbits as an example

A
  • Have a population of identical rabbits
    • Mutations allow variation to arise
    • Having a population with diversity in their phenotypes ( eg, rabbits with different colored fur in a forest)
    • Some characteristics are better suited for their environment , so a selection for a certain advantageous characteristic
    • Individuals who don’t have the characteristic die out
    • Individuals with characteristics will survive and reproduce and pass these genes /characteristics down to their offspring
    • This happens over many generations
198
Q

What is a genotype

A

The selection of genes an organisms has (alleles)

199
Q

What is a phenotype

A

the characteristics expressed ( eg. hair colour), —it is also effected by the environment

200
Q

Examples of a behavioral adaptation

A

Hibernating

201
Q

Example of physiological adaptation

A

Temperature regulation

202
Q

example of anatomical dapatatiom

A

Cacti have spines to prevent being eaten

203
Q

In order for natural selection to occur there needs to be what within a population

A

Variation

204
Q

What is genetic diversity determined by

A

The number of differnt alleles of a gene In a population

205
Q

What 5 points do you need to make for a question on natural selection

A

• New alleles are brought about by mutations
• The new allele is advantageous and therefore organisms are more likely to survive
• And reproduce
• And pass on the advantageous allele to their offspring
• Therefore the frequency of the allele in the population will increase

206
Q

What are new alleles brought about by

A

Mutations

207
Q

What is the shape of the directional selection curve

A

BeLL curve

208
Q

Does the curve change in directional selection

A

It doesn’t
The bell curve just shifts

209
Q

Stabilising selection

A

Selection for the mean value
Extremes are selected agasit

210
Q

Disrupted selection

A

For extremes
Medium is unflavoured

211
Q

What is phylogeny

A

The study of the evolutionary history of groups of organisms
They tell us who is related to whom and how closely related they are to

212
Q

T or f
All organisms have evolved form shared common ancestors

A

T

213
Q

How can the fact that all organisms have evolved from shared common ancestors be shown

A

On a phylogenetic tree

214
Q

What does the first branch represent on a phylogenetic tree

A

A common ancestor of all the family members

215
Q

What does each of the following branched after the first beach represent om the phylogenetic tree

A

Represents another common ancestor form which a differnt group diverged

216
Q

Closely related species on a phylogenetic tree diverged away From each other ……

A

Most recently.
( their branches are close together)

217
Q

What is taxonomy

A

The science of classification
It involves naming organisms and organising them into groups

218
Q

Why is classification important

A

Makes it easier to inventory and study

219
Q

What do scientists now take into account what when classifying organisms
And how does they group organisms

A

Phylogeny
According to their evolutionary relationships

220
Q

How many levels of group s are used to classify organisms
And what are they called

A

8
These groups are called taxa, each group is called a taxon

221
Q

How are the groups arranged in taxonomy

A

Arranged in a hierarchy, with the largest groups at the top and the smallest group sat the bottom
Organisms can only belong to one group at each level in the hierarchy - there is no overlap

222
Q

How are organisms first sorted in taxonomy

A

Into 3 large groups ( or taxa)
Called domains

223
Q

What are the 3 domains

A

Eukarya
Bacteria
Archaea

224
Q

What is the order of classification in taxonomy

A

Domain

Kingdom
Phylum
Class
Order
Family
Genus
Species

225
Q

T or f
As you move down the taxonomy hierarchy there are less groups at each level but more organisms in each group

A

F
There are more groups but less organisms in each group

226
Q

Do the organisms in a group become more or less closely related in classification hierarchy

A

More closely related

227
Q

Species definition

A

A species is a group if similar organisms able to reproduce to give fertile offspring

228
Q

What group in the classification hierarchy contains only one type of organisms

A

Species

229
Q

Why do scientists constantly update classification systems

A

Because if discoverues about new species and new evidence about known organisms

230
Q

The nomenclature used for classification is called ….,,

A

Binomial system

231
Q

What is the binomial system for classification

A

All organisms are given one internationally accepted scientific name,e in Latin and has 2 parts

232
Q

What are the 2 parts of the binomial system for classification

A

The first part of the name is the genus name and has a capital letter
The second part is the species name and begins with a lower case letter
Names are always written in italics ( or underlined if handwritten)

233
Q

Why is the binomial system used for classification

A

To avoid the confiscation of using common names

234
Q

What is courtship behaviour

A

It’s carried out by organisms to attract a mate of the right species

235
Q

Is courtship behaviour species specific

A

Yes
Only members of the same species will do and respond to the courtship behaviour.

236
Q

What is courtship behaviour being species specific important

A

This allows members of the same species to recognise each other, preventing interbreeding and making reproduction more succssefull
( as mating with the wrong species won’t produce fertile offspring )

237
Q

Because of specificity of courtship behaviour , it can be used to do what

A

Classify organisms

238
Q

How is courtship behaviour used to classify organisms

A

The more closely related species are, the more similar their courtship behaviour

239
Q

Give some examples of courtship behaviour

A

Fireflies give off pulses of light. The pattern of flashes is specific to each species.
Crickets make sounds that are similar to Morse code, the code being different for different species.
Male peacocks show off their colourful tails. This tail pattern is only found in peacocks.
Male butterflies use chemicals to attract females. Only those of the correct species respond.

240
Q

What is variation

A

The differences that exists between individuals

241
Q

Is their variations between species or within species

A

Both

242
Q

What can variation be cause by

A

Genetic factors
Environment
Or a combo

243
Q

How can variation be caused by genetic factors

A

Differnt species gave differnt genes , which cause variation between species. Individuals of the same species have the same genes, but differnt alleles - this causes variation within a species

244
Q

Examples of how variation within a species can be caused but differnce in environment t

A

Climate
Food
Lifestyle

245
Q

When investigating variation you usually. Only Look at what

A

A sample of the population not the whole thing

246
Q

Why do you usually only. Take a sample of the population not the whole thing when studying variation

A

It would be too time consuming or impossible to catch all the individuals in the group.
So Samples are used as models for the whole population

247
Q

What should a sample be

A

To make sure the sample isn’t biased, it should be random
To ensure any variation observed in the sample isn’t just due to chancem it’s important to analyse the results statistically , this allows you to be more confident that the results are true and therfore will reflect what’s going on in the whole population

248
Q

What can you use to look for variation between species

A

Mean

249
Q

How to find mean

A

Total of all the values in your data
————————————————
The number of values in your data

250
Q

What does a normal distribution look like

A

As bell shapes graph
Most samples will include values either side of the mean
A Normal distribution is symmetrical about the mean

251
Q

What does the standard deviation tell you

A

How much the values in a single sample vary
It’s a measure of the spread of values about the mean

252
Q

What does a large distribution mean

A

The values in the sample vary a lot

253
Q

What does a small standard Deviation look like on a graph

A

All the values are similar and close to the mean , so the graph is steep

254
Q

What does a large standard Deviation look like on a graph

A

Here the values vary a lot
So the graph is fatter

255
Q

How can standard deviation be plotted on a graph of mean values

A

Using error bars

256
Q

What are error bars

A

They extend one standard deviation above and one below the mean ( so total length of an error bar is twice the standard deviation )

257
Q

What technology’s have been usefull for clarifying evolutionary relationships

A

Genome sequencing
Comparing amino acid sequences
Immunological comparisons

258
Q

What is conjunction

A

What one bacteria cell transfers dna to another bacteria cell

259
Q

How is antibiotic resistance directional selection

A

1) Variation - some strains of bacteria are resistant and some arnt
2) Competition - the non resistant bacteria are killed of by the penicillin
3) Survival of the fittest - the resistant bacteria survive
4) Passing on of genes - the resistant bacteria reproduce and pass on the adaptation to their offspring

260
Q

How is human birth weight is stabilising selection

A

The phenotypes with successful characteristic are preserved and those of greater diversity are reduced this selection doesn’t occur due to changes in the environment. If the environment stays the same then the individuals closest to the mean are favoured as they have the alleles that have given them the survival advantage . A new born babies weights, those with birth weight around 3kg are more likely to survive than the extremes.

261
Q

What is intraspecies variation

A

Differences within species

262
Q

How does evolution via natural selection work

A
  • relies on mutation within species
  • this variation is acted on by selection pressures
  • only the fittest individuals survive to bree
263
Q

What is interspecies variation

A

Differences between species

264
Q

What is sampling

A

Take a selection of individuals form the targeted population
These individuals will represents the whole population

265
Q

What are the 2 problems with sampling
+ explain

A

Sampling bias - the selection process may be biased. The investigations may be making unrepresentative choices either deliberately or unwittingly

Chance - even if sampling bias is avoided the individuals chosen, by chance, may not be representative

266
Q

How can you avoid bias

A

Random sample - random number generator for coordinates

Use a large sample size and appropriate analysis of data collected will also help

267
Q

Learn the standard deviation equation

A

…

268
Q

What is Carl Linnaeus do

A

Grouped organisms by structure and characterists
Grouped organisms by the binomial system

269
Q

What is the binomial system

A

The genus goes first with the capital letter
Followed by the species with a lower case
They are written in italics

270
Q

What is a species

A

A group of organisms who share similar genes and can reproduce to produce fertile offspring

271
Q

What is phylogeny

A

The evolutionary relationship between organisms
- the phylogeny reflect the evolutionary branch that led to the organism

272
Q

What is the order of classification

A

Domain
Kingdom
Phylum
Class
order
Family
genus
Species

273
Q

What is the domain, kingdom, phylum and class for a mammle

A

Eukarya
Animalia
Chordata
Mammalian

274
Q

What 5 things are in the Chordata phylum

A

Fish
Reptiles
Amphibians
Mammals
Birds

275
Q

What can a phytogenic tree show

A

How closely organisms are related
Common ancestors

276
Q

When an evolutionary split occurs on a phytogenic tree
What is it called

A

Branching point or divergent point

277
Q

Why is courtship behaviour carried out

A

To attract the mate of the right species

278
Q

Eg
Of corurtshop behaviour

A

Releasing chemicals
Series of displayed ( eg, in birds)

279
Q

What is does it mean that courtship behaviour is species specific

A

only members of the same species will do and respond to that courtship behaviour. This allows members of the same species to recognise each other, preventing interbreeding and making reproduction more successful (as mating with the wrong species won’t produce fertile offspring).

280
Q

As courtship behaviour is specific what can it be used to do

A

Classify organisms

281
Q

The more closely related species are, the more
……. Their courtship behaviour

A

Similar

282
Q

What can courtship behaviour be a way to do

A
  1. Can be a way to signal reproductive maturity.
    1. Way to for a bond with their pair, to increase reproductive success – not necessary for all species.
    2. Synchronise mating with other individuals – in some species
283
Q

What are the Several different ways to investigate genetic diversity:

A

• Genome sequencing
• mRNA sequencing
• Amino acid sequencing
• Immunological comparisons

284
Q

Why is
• Genome sequencing
• mRNA sequencing
• Amino acid sequencing
• Immunological comparisons
More accurate then classifying organisms by appearance alone

A

because:
• The characteristics could be coded for by more than one gene.
• The same characteristics could have arisen separately.
• The characteristics could be influenced by the environment and not the genes.

285
Q

The difference between different species is called?

A

Interspecific

286
Q

What is genome sequencing

A

• use gene technology to read the base sequences of organisms. The genetic diversity of a species can be measured by sampling DNA.
• More closely related individuals should have less variation in the DNA base sequences.
• Huge advances have been made in this field in the last 50 years.

287
Q

What is mRNA sequencing

A

• Traits are due to genes being expressed, through expression mRNA is used.
• So by looking at mRNA we can see what genes are expressed and what they code for.
• More closely related organisms should have more similar mRNA sequence.

288
Q

What is amino acid sequencing

A

• The sequence of amino acids can also be studied as this can be taken back to the mRNA sequence and thus the DNA sequence.
• Related organisms have similar DNA sequences , hence similar amino acid sequences, hence similar proteins.
Example: cytochrome C is a short protein found in many species. The more similar the AA sequence is for cytochrome C the more closely the species is related.

289
Q

What are the 5 kingdoms

A

Bacteria
animals
Plants
Fungi
Protoctista

290
Q

What did Carl woese do

A

The 3 domain system
Used chemical analysis

291
Q

What are the 3 domains

A

Archaea
True bacteria
Eukaryotes

292
Q

What are archaea

A

Primitive bacteria
(Usually extremophiles)

293
Q

Biodiversity definition

A

The variety of living organism in an area

294
Q

Habitat definition

A

The place where an organism lives

295
Q

Community

A

All the populations of differnt species in a habitat

296
Q

What is local biodiversity

A

Variety of differnt species living in a small habitat that’s local to you

297
Q

What is global biodiversity

A

Variety of species in earth

298
Q

Where is biodiversity the greatest on earth

A

The equator
It decreases towards the poles

299
Q

What is species richness

A

A measure of the number of differnt species in a community

300
Q

How can species richness be worked out

A

By taking random samples of a community and counting the number of differnt species

301
Q

The number of differnt species in a community effect biodiversity,
What else?

A

The population size of those species too
(Species in a very small numbers shouldn’t be related the same as those with a bigger population )

302
Q

What the index of diversity another way of measuring

A

Another way of measuring biodiversity

303
Q

How is index of diversity calculated

A

using an equation that takes both the number of species In a community and the abundance of each species into a punt

    N(N-1) d= ———————
  Sum of (n(n-1)

N- total number of organism of all species
n - total number of organisms of one species

304
Q

The number of species in community and the abundance of each species is also known as ….

A

T he species diversity

305
Q

The higher the index of diversity the ……,…… an area is

A

More diverse

306
Q

If all the individuals are of the same species the index of diversity is ….

A

1

307
Q

What farmin practices reduce biodivsity

A

1) Woodland clearance - thus us down to increase area of farmland, it directly reduces the number of trees and sometimes the number of different tree species. It also destroys habitats, so some species could lose their shelter and food source. This means that species will die or be forced to migrate to another suitable area, further reducing biodiversity.

2) Hedgerow removal — this is also done to increase the area of farmland by turning lots of small fields into fewer large fields. This reduces biodiversity for the same reasons as woodland clearance.

3)Pesticides — these are chemicals that kill organisms (pests) that feed on crops.
This reduces diversity by directly killing the pests. Also, any species that feed on the pests will lose a food source, so their numbers could decrease too.

4) Herbicides — these are chemicals that kill unwanted plants (weeds). This reduces plant diversity and could reduce the number of organisms that feed on the weeds.

5) Monoculture — this is when farmers have fields containing only one type of plant. A single type of plant reduces biodiversity directly and will support fewer organisms (e.g. as a habitat or food source), which further reduces biodiversity.

308
Q

What are some examples of conservation schemes to protect biodivsirty

A

• Giving legal protection to endangered species.
• Creating protected areas such as SSSis (Sites of Special Scientific Interest) and AONBs (Areas of Outstanding Natural Beauty). These restrict further development, including agricultural development.
• The Environmental Stewardship Scheme which encourages farmers to conserve biodiversity, e.g. by replanting hedgerows and leaving margins around fields for wild flowers to grow.

309
Q

How have advances in techniques of genome sequences clarify evolutionary relationships

A

Genome sequencing — Advances in genome sequencing have meant that the entire base sequence of an a higher percentage of similarity in their DNA base order, e.g. humans and chimps share around 94%, humans and mice share about 86%.
Genome sequencing has clarified the relationship between skunks and members of the Mustelidae family leg weasels and badgers). Skunks were classified in the Mustelidae family until their DNA sequence was revealed in be significantly different to other members of that family. So they were reclassified into the family Mephitida.

310
Q

How have advances in techniques of comparing amino acid sequecnes clarify evolutionary relationships

A

Comparing amino acid sequence — Proteins are made of amino acids. The sequence of amino acids in a protein is coded for by the base sequence in DNA (see p. 82). Related organisms have similar DNA sequences and so similar amino acid sequences in their proteins. E.g. cytochrome C is a short protein found in many species. The more similar the amino acid sequence of cytochrome C in two different species, the more closely related the species are likely to be.

311
Q

How have advances in techniques of immunological comparisons clarify evolutionary relationships

A

Immunological comparisons — Similar proteins will also bind the same antibodies (see p. 44).
E.g. if antibodies to a human version of a protein are added to isolated samples from some other species, any protein that’s like the human version will also be recognised (bound) by that antibody.

312
Q

What where early estimates of genetic diversity were made by

A

looking at the frequency of measurable or observable characteristics in a population

Since differnt alleles determine differnt characteristics a wide variety of each characteristic in a population indicated a high number of differnt alleles and so a high genetic diversity

313
Q

How have gene technologies allowed us to measure genetic diversity directly

A

For example:
• Different alleles of the same gene will have slightly different DNA base sequences.
Comparing the DNA base sequences of the same gene in different organisms in a population allows scientists to find out how many alleles of that gene there are in that population.
Different alleles will also produce slightly different mRNA base sequences, and may produce proteins with slightly different amino acid sequences, so these can also be compared.

314
Q

What do new technology to measure genetic diversity directly allow a

A

Accurate estimates
Also allow the genetic diversity of differnt species to be compared more easily

315
Q

Impact of agriculture

A

Agriculture ecosystems controlled by humans, farmers select 1 species so reduced genetic variety by reducing alleles to the ones they desire
It’s economical to take up a large area , give little space for anything else
Competition and addition of pesticides adds up to a loss of species diversity

316
Q

What does biodiversity reflect

A

How well an ecosystem functions

317
Q

The higher to species diversity index to …… stable the ecosystem usually is

A

More

318
Q

What will effect an ecosystem

A

A change in climate

319
Q

Why is an ecosystem with a higher diverts index more stable to change in conditions

A

More likely to have at least one species which may survive a change in conditions

320
Q

Is the species diversity index low or high in extreme environments
And why

A

Low
Only few species have necessary adaptations to survive harsh conditions
Usually results in an unstable ecosystem, the species community are dominated by the climate
Rather than the species within them

321
Q

Definition of species diversity

A

Refers to the number of differnt species and the number of individuals species within a community

322
Q

Definition of genetic diversity

A

Refers to the variety of genes posses by the individuals that make up any one species

323
Q

Definition of ecosystem diversity

A

Refers to the range of differnt habitats within a particular area

324
Q

What is biodivisty

A

General term used to describe the variety of the living world

325
Q

What is usefull to know to find biodiversity

A

Number of differnt species in a given area
The proportion of the community that is made up of an individual species

326
Q

What is the diversity index calc

A

N ( N - 1 )
D = ———————
Sum of (n - 1 )

N- total number of all species (add up frequencies)
n - total number of organisms of each species

327
Q

Limitations of the old sequencing techniques

A

Expensive and inefficient

328
Q

Advantages of new sequencing
(Next gerneTion sequencing)

A
  • many happen at same time
  • micr scale
  • fast
  • low cost
  • shorter length
  • step towards personalised medicine
329
Q

Uses of sequencing

A
  • knowing the sequence of genome for a pathogen
  • doctors can find source of infection
  • identify antibiotic resistant strains of bacteria
    Track progress of an outbreak
    Indenting regions of a pathogen r that may be useful to target in development of drugs

A-level Biology (8 decks)

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