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AS AQA Biology - Burnley College (2023-24) > Genetic Info, Variation & Relationships 3.4 > Flashcards

Genetic Info, Variation & Relationships 3.4 Flashcards

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1
Q

DNA, genes and chromosomes (AO1)

Describe the structure of prokaryotic DNA

A

Circular;
No introns;
Not associated with histones;
Short;
Plasmids;

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2
Q

DNA, genes and chromosomes (AO1)

Which organelles contain DNA with the same structure as prokaryotes

A

Mitochondria

Chloroplasts

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3
Q

DNA, genes and chromosomes (AO1)

Describe the structure of eukaryotic DNA

A

Linear;

Introns;

Associated
with histones;

Long;

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4
Q

DNA, genes and chromosomes (AO1)

DNA molecule and its associated proteins (e.g. histones) form a _______________.

A

chromosome

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5
Q

DNA, genes and chromosomes (AO1)

Differences between DNA in the nucleus of a plant cell vs. DNA in a prokaryotic cell.

A

1. Associated with histones v no histones;
2. Linear v circular;
3. No plasmids v plasmids;
4. Introns v no introns;
5. Longer v shorter;

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6
Q

DNA, genes and chromosomes (AO1)

Define a gene

A

A sequence of DNA bases that codes for a polypeptide

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7
Q

DNA, genes and chromosomes (AO1)

In addition to polypeptides, what can genes also code for?

A

ribosomal (rRNA)
&
transfer (tRNA)

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8
Q

DNA, genes and chromosomes (AO1)

Define locus

A

Fixed position of a gene on a
chromosome / DNA molecule

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9
Q

DNA, genes and chromosomes (AO1)

Define homologous chromosomes

A

Carry the same genes
(but different alleles)

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10
Q

DNA, genes and chromosomes (AO1)

In eukaryotic DNA, genes contain _______ and _______.

A

introns
and
exons

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11
Q

DNA, genes and chromosomes (AO1)

Define exon

A

DNA base sequences that code for sequence of amino acids

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12
Q

DNA, genes and chromosomes (AO1)

Define intron

A

DNA base sequences that DO NOT code for sequence of amino acids

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13
Q

DNA, genes and chromosomes (AO1)

TRUE or FALSE:

In eukaryotes, much of the nuclear DNA does not code for polypeptides.

A

TRUE

e.g. only 1% of human DNA contains genes that code for polypeptides

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14
Q

DNA, genes and chromosomes (AO1)

Location of non-coding multiple repeats of DNA base sequences.

A

between genes

OR

intergenic

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15
Q

DNA, genes and chromosomes (AO1)

Define non-coding

A

DNA that does not code for polypeptides

OR

DNA that does not code for sequences of amino acids

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16
Q

DNA & Protein Synthesis (AO1)

Define genome

A

All the DNA in a cell

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17
Q

DNA & Protein Synthesis (AO1)

Define proteome

A

The full range of proteins produced by cells

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18
Q

DNA, genes and chromosomes (AO1)

A sequence of three DNA bases, called a _________________ , codes for a specific amino acid.

A

triplet

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19
Q

DNA, genes and chromosomes (AO1)

A sequence of three RNA bases, called a _________________ , codes for a specific amino acid.

A

codon

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20
Q

DNA, genes and chromosomes (AO1)

TRUE or FALSE:
Within a gene, there can be multiple introns.

A

TRUE

There can also be multiple exons

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21
Q

DNA, genes and chromosomes (AO1)

A DNA triplet has the bases ACT, what are the bases in the mRNA codon?

A

UGA

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22
Q

DNA, genes and chromosomes (AO1)

The genetic code is ‘universal’.
Define this term.

A

The same 3 bases used in DNA triplets code for the same amino acid in all organisms

OR

The same 3 bases used in mRNA codons code for the same amino acid in all organisms

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23
Q

DNA, genes and chromosomes (AO1)

The genetic code is ‘non-overlapping’.
Define this term.

A

Each DNA base is read only once in the triplet

OR

Each base is read only once in the codon

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24
Q

DNA, genes and chromosomes (AO1)

The genetic code is ‘degenerate’.
Define this term.

A

More than one codon / triplet codes for a single amino acid

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25
Q

DNA, genes and chromosomes (AO1)

Suggest one advantage of showing the genetic code as base sequences on mRNA, rather than triplets on DNA.

A

Ribosomes assemble polypeptides using mRNA code

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26
Q

DNA & Protein Synthesis (AO1)

Which codons code for the amino acid ‘Tyr’?

A

UAU

UAC

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27
Q

DNA & Protein Synthesis (AO1)

Which codons code for the amino acid ‘Ser’?

A

UCU
UCC
UCA
UCG
AGU
AGC

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28
Q

Structure of DNA and RNA (AO1)

What are the structural differences between a DNA molecule and a mRNA molecule (4 marks).

A

1. DNA has deoxyribose whereas mRNA has ribose;
2. DNA has thymine whereas mRNA has uracil;
3. DNA long whereas mRNA short;
4. DNA is double stranded / double helix whereas mRNA is single stranded
5. DNA has hydrogen bonds whereas mRNA has no hydrogen bonds
OR
DNA has (complementary) base pairing whereas mRNA does not;

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29
Q

Structure of DNA and RNA (AO1)

Give structural similarities between a DNA molecule and a mRNA molecule (4 marks).

A

1. Both polymers of nucleotides;

2. Nucleotides have pentose, (nitrogen-containing organic) base and a phosphate (group);

3. Both Cytosine, guanine and adenine (as bases);

4. Both have phosphodiester bonds;

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30
Q

DNA & Protein Synthesis (AO1)

TRUE or FALSE:

Transfer (tRNA) is a monomer

A

FALSE

tRNA is a polynucleotide

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31
Q

DNA & Protein Synthesis (AO1)

TRUE or FALSE:

tRNA only contains phosphodiester bonds

A

FALSE

Its cloverleaf structure is mainted by hydrogen bonds

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32
Q

DNA & Protein Synthesis (AO1)

Describe the structural differences between the structure of mRNA and the structure of tRNA.

A

1. mRNA contains no hydrogen bonds whereas tRNA has some hydrogen bonds.

2. tRNA has an amino acid binding site whereas mRNA does not

3. mRNA has codons whereas tRNA has anticodons

4. mRNA longer
OR Has more nucleotides than tRNA;

5. Different mRNAs have different lengths whereas all tRNAs are similar / same length;

6 mRNA is a straight molecule whereas tRNA has a clover-leaf shaped molecule;

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33
Q

DNA & Protein Synthesis (AO1)

TRUE or FALSE:

The nucleotides of both mRNA and tRNA contain the nitrogenous base uracil.

A

TRUE

tRNA and mRNA are both polymers of RNA nucleotides

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34
Q

DNA & Protein Synthesis (AO1)

Bond present in both mRNA and tRNA.

A

phosphodiester

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35
Q

DNA & Protein Synthesis (AO1)

Transcription is the production of _________ from DNA.

A

mRNA

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36
Q

DNA & Protein Synthesis (AO1)

Describe transcription in prokaryotes
(5 marks).

A

1. DNA helicase breaks hydrogen bonds between complementary base pairs.

2. Only one DNA strand acts as a template.

3. Free RNA nucleotides align by complementary base pairing.

4. Uracil is used in place of thymine and base pairs with adenine.

5. RNA polymerase joins adjacent RNA nucleotides

6. via phosphodiester bonds.

7. This forms mRNA and no splicing occurs.
(as prokaryotes contain no introns).

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37
Q

DNA & Protein Synthesis (AO1)

What is splicing?

A

The removal of introns from pre-mRNA to produce mature mRNA

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38
Q

DNA & Protein Synthesis (AO1)

TRUE or FALSE:

Splicing only takes place in eukaryotic organisms

A

TRUE

Eukaryotic DNA contains introns that must be removed via splicing

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39
Q

DNA & Protein Synthesis (AO1)

Describe how mRNA is formed by transcription in eukaryotes (5 marks)

A

1. DNA helicase breaks hydrogen bonds between complementary base pairs.

2. Only one DNA strand acts as a template.

3. Free RNA nucleotides align by complementary base pairing.

4. Uracil is used in place of thymine and base pairs with adenine.

5. RNA polymerase joins adjacent RNA nucleotides

6. via phosphodiester bonds.

(this produces pre-mRNA)

7. Pre-mRNA is spliced and introns are removed.

This produces (mature) mRNA

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40
Q

DNA & Protein Synthesis (AO1)

Site of transcription

A

nucleus

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41
Q

DNA & Protein Synthesis (AO1)

Through which structure does mRNA exit the nucleus?
(in eukaryotes)

A

nuclear pore

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42
Q

DNA & Protein Synthesis (AO1)

Describe how mRNA is produced from an exposed template strand of DNA (3 marks).

Do not include DNA helicase or splicing in your answer.

A

1. Free RNA nucleotides align by complementary base pairing.

OR Uracil is used in place of thymine and base pairs with adenine.

2. RNA polymerase joins adjacent RNA nucleotides

3. via phosphodiester bonds.

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43
Q

DNA & Protein Synthesis (AO1)

A
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44
Q

DNA & Protein Synthesis (AO1)

In a eukaryotic cell, the base sequence of the mRNA might be different from the sequence of the pre-mRNA.

Explain why (2 marks).

A

1. Introns in pre-mRNA;

2. These are removed via splicing

(this makes mRNA shorter than pre-mRNA)

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45
Q

DNA & Protein Synthesis (AO1)

Describe how the production of messenger RNA (mRNA) in a eukaryote cell is different from the production of mRNA in a prokaryote cell (2 marks).

A

1. Pre-mRNA only produced in eukaryote cell;

2. Splicing only occurs in eukaryote cell;

3. Introns removed in eukaryote cell

OR Introns not present in prokaryote cell;

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46
Q

DNA & Protein Synthesis (AO2)

Scientists produced a short, single-stranded, artificial nucleic acid, called PNA. The PNA binds to a small section of DNA.

The scientists introduced PNA into cells and discovered that these cells produced less mRNA than cells that did not contain PNA.

Suggest how PNA affected the transcription of the section of DNA (2 marks).

A

1. PNA is complementary to DNA

OR PNA forms base pairs with DNA;

2. Preventing/reducing RNA polymerase activity/binding

OR Prevents RNA nucleotides binding

OR Reducing/stopping transcription;

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47
Q

DNA & Protein Synthesis (AO2)

A

Serine Alanine Glycine Proline
(must be in this order)

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48
Q

DNA & Protein Synthesis (AO2)

A

1.   Allele

2.   Locus/loci

3.   Transcribed

4.   Translated

5.   Golgi (apparatus)/Rough endoplasmic reticulum

6.   Tertiary

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49
Q

DNA & Protein Synthesis (AO1)

Translation is the production of [1] from the sequence of [2] carried by mRNA.

A

[1] polypeptides

[2] codons

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50
Q

DNA & Protein Synthesis (AO1)

Site of translation

A

Ribosomes
OR
Rough endoplasmic reticulum

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51
Q

DNA & Protein Synthesis (AO1)

A

Site of translation, catalyse the joining of amino acids by condensation reactions;

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52
Q

DNA & Protein Synthesis (AO1)

Describe the role of tRNA in translation (2 marks).

A
  1. Anticodon on tRNA binds to complementary codon on mRNA;
  2. tRNA brings specific amino acid to ribosome;
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53
Q

DNA & Protein Synthesis (AO1)

Describe the role of ATP in the process of translation in protein synthesis (2 marks).

A
  1. Releases energy;
  2. So peptide bonds form between amino acids;

OR So amino acid joins to tRNA;

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54
Q

DNA & Protein Synthesis (AO1)

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation (3 marks).

A
  1. tRNA brings specific amino acid to ribosome;
  2. Anticodon on tRNA binds to codon on mRNA;
  3. Amino acids joined together via peptide bonds

OR Amino acids joined together by condensation (using energy from ATP hydrolysis);

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55
Q

DNA & Protein Synthesis (AO1)

Describe the role of a ribosome in the production of a polypeptide (3 marks).

A

1. mRNA binds to ribosome;
2. Two mRNA codons used at any one time;
3. Allows tRNA with anticodons to bind
4. Catalyses formation of peptide bond between amino acids (held by tRNA molecules);
5. Moves along mRNA to the next codon;

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56
Q

DNA & Protein Synthesis (AO1)

Describe how a polypeptide is formed by translation of mRNA (6 marks).

A

1. mRNA attaches to ribosomes
2. Ribosome finds the start codon / AUG;
3. tRNA anticodons bind to complementary mRNA codons;
4. tRNA brings a specific amino acid;
5. Amino acids join by peptide bonds;
(catalysed by the ribosome)
6. with the use of energy from ATP hydrolysis;
7. tRNA released
(after amino acid joined to polypeptide);
8. The ribosome moves along the mRNA to form the polypeptide;

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57
Q

DNA & Protein Synthesis (AO1)

A

W = amino acid binding site

X = anticodon

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58
Q

DNA & Protein Synthesis (AO1)

A

Process = Translation

Molecule Q = tRNA

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59
Q

DNA & Protein Synthesis (AO1)

On mRNA, the first codon is AUG.

Give the base sequence of…..

the complementary DNA triplet:

AND

the missing anticodon:

A

DNA triplet: TAC

Anticodon: UAC

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60
Q

DNA & Protein Synthesis (Maths)

Haemoglobin is a protein. It is made of two alpha polypeptides and two beta polypeptides.

Each alpha polypeptide has 141 amino acids and each beta polypeptide has 146 amino acids.

Calculate the minimum number of DNA bases needed to code for the number of amino acids in one alpha polypeptide.

A

423

Remember: 3 DNA bases in a triplet codes for 1 amino acid

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61
Q

DNA & Protein Synthesis (Maths)

The two DNA strands of a particular gene contain 168 guanine bases between them. The relationship between the numbers of guanine bases (G), adenine bases (A), thymine bases (T) and cytosine bases (C) in these two strands of DNA is shown in the following equation.

G = 4 (A + T) – C

Use this information and your understanding of DNA structure to calculate the maximum number of amino acids coded by this gene.

A

Answer = 70 amino acids

Step by step working:
168 = 4 (A+T) - 168
336 = 4 (A+T)
84 = A + T
A = 42, T = 42

Total DNA = 168 + 168 + 42 + 42 = 420 base pairs
One template strand = 210 bases
3 DNA bases codes for 1 amino acid
210 bases codes for 70 amino acids

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62
Q

DNA & Protein Synthesis (AO1)

Function of stop codon

A
  1. Stop translation
  2. Signals to ribosome to detach from polypeptide and mRNA;

(This ensures polypeptide produced is the correct length)

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63
Q

DNA & Protein Synthesis (AO1)

A

Isoleucine

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64
Q

DNA & Protein Synthesis (AO1)

Give the DNA base sequence that codes for threonine.

A

TGG

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65
Q

Mutations (AO1)

Define gene mutation

A

1. Random change in the base sequence of DNA.

2. Results in the formation of a new allele.

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66
Q

Mutations (AO1)

TRUE or FALSE:

Mutations arise spontaneously during DNA replication.

A

TRUE

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67
Q

Mutations (AO1)

Types of mutation

A

Substitution
Addition
Deletion
Inversion
Translocation
Non-disjunction

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68
Q

Mutations (AO1)

______________ mutations involve only changing one base in the DNA triplet

A

Substitution

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69
Q

Mutations (AO1)

Describe and explain the different consequences following a subsitution mutation

A

1. No change in primary structure due to degenerate genetic code or mutation in an intron

2. Changes primary structure BUT no change in tertiary structure as amino acid with similar property coded for.

3. Change in primary structure and change in tertiary structure due to changing position of hydrodgen / disulphide / ionic bond

4. Codes for a stop codon so polypeptide produced is much shorter / non-functional

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70
Q

Mutations (AO1)

Due to the [1] nature of the genetic code, not all base substitutions cause a change in the [2] of encoded amino acids.

A

[1] degenerate

[2] sequence

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71
Q

Mutations (AO1)

A substitution could change the amino acid coded and therefore change the [1] structure.

This may change the nature or [2] of the hydrogen, ionic or disulphide bonds between the amino acid R groups.

This may change [3] structure of the polypeptide.

A

[1] primary

[2] position

[3] tertiary

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72
Q

Mutations (AO1)

Consequence of substitution mutation resulting in a stop codon.

A

1. Shorter polypeptide produced

2. If stop codon is introduced towards the start of the primary structure, protein likely to be non-functional.

3. If stop codon is introduced towards the end of the primary structure, tertiary structure may be unaffected.

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73
Q

Mutations (AO1)

What mutations cause a ‘frame shift’

A

Additions

Deletions

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74
Q

Mutations (AO1)

What is a frame shift?

A

1. Occurs when DNA bases are added or deleted within the sequence.

2. This results in an alteration of the base triplets downstream from the mutation.

3. This changes many amino acids in the primary structure (as per the below image)

75
Q

Mutations (AO1)

Mutations produce new _________

A

alleles

76
Q

Mutations (AO2)

A

Substitution

77
Q

Mutations (Maths)

A

1395

465 x 3 (3 bases code for 1 amino acid)

78
Q

Mutations (AO2)

A mutation can lead to the production of a non-functional enzyme. Explain how (6 marks).

A

1. Random change in DNA base sequence

2. Change in amino acid sequence / primary structure (of enzyme);

3. Change in position of hydrogen / ionic / disulfide bonds;

4. Change in the tertiary structure;

5. Change in shape of active site;

6. Substrate not complementary / cannot bind (to enzyme / active site) / no enzyme-substrate complexes form.

79
Q

Mutations (AO2)

A

1. Mutation causes frame shift;

2. Changes primary structure / amino acid sequence (after this);

3. Affects position of hydrogen / ionic / disulphide bonds (between r groups of amino acids);

4. Changes tertiary structure of protein (so non-functional);

80
Q

Mutations (AO2)

What is the effect of a single base substitution in an intron?

A

1. Introns are non-coding for amino acids

2. (So) not translated / no change in mRNA produced / no effect (on protein) / no effect on amino acid sequence;

81
Q

Mutations (AO1)

Explain how a mutation can have a positive effect on an individual

A

1. Results in change in polypeptide that positively changes the properties (of the protein);

e.g. makes active site of enzyme more complementary to substrate;

2. May result in increased reproductive success OR May result in increased survival chances;

82
Q

Mutations (AO1)

Explain how a mutation can have a no effect on an individual

A

1. Genetic code is degenerate (so amino acid sequence may not change);

OR Mutation is in an intron (so amino acid sequence may not change);

2 Does change amino acid but no effect on tertiary structure;

83
Q

Mutations (AO1)

Define mutagenic agent

A

Increase the rate of gene mutations

84
Q

Mutations (AO1)

Mutagenic agent examples

A

1. High energy radiation e.g. x rays, gamma rays, alpha and beta particles, ultraviolet light

2. Carcinogens e.g. nitrous acid can remove an NH2 group from cytosine in DNA, converting the base to uracil

3. Biological agents e.g. viruses which can insert their genetic material into the host cell’s genome

85
Q

Meiosis (AO1)

Meiosis produces daughter cells that are genetically ____________ from each other.

A

different

86
Q

Meiosis (AO1)

Example gametes

A

Egg cell
Sperm cell
Pollen
Spores

87
Q

Meiosis (AO1)

Prior to meiosis, interphase first takes place and [1] replication creates a copy of each chromosome which now comprises [2] chromatids held together by the [3].

A

[1] semi-conservative
[2] sister
[3] centromere

88
Q

Meiosis (AO1)

Meiosis involves two nuclear [1] - called meiosis 1 and meiosis 2 - that typically result in the formation of four [2] daughter cells from a single diploid parent cell.

A

[1] divisions
[2] haploid

89
Q

Meiosis (AO1)

Diploid (2n)

A

Parent cells with a pair of homologous chromosomes (which carry the same genes but different alleles).

90
Q

Meiosis (AO1)

Key event in meiosis 1 that creates haploid (n) daugher cells

A

Independent segregation of homologous chromosomes

91
Q

Meiosis (AO1)

A rare process called __________ __________ also occurs during meiosis 1.

A

crossing over

92
Q

Meiosis (AO1)

Draw out meiosis with 1 pair of homologous chromosomes

A
93
Q

Meiosis (AO1)

Key event in meiosis 2

A

Sister chromatids are pulled apart and move to opposite poles of the cell during anaphase.

Meiosis 2 is essentially the same as mitosis

94
Q

Meiosis (AO1)

TRUE or FALSE:

Independent segregation takes place during meiosis 2

A

FALSE

It takes place during meiosis 1

95
Q

Meiosis (AO1)

Independent segregation AND crossing over produce……………………….

A

new combinations of alleles

96
Q

Meiosis (AO1)

Describe how the process of meiosis results in haploid cells.

Do not include descriptions of how genetic variation is produced in meiosis (4).

A

1. Semi-conservative DNA replication;
2. Two nuclear divisions;
3. First division - separation of homologous chromosomes via independent segregation;
4. Second division - separation of sister chromatids;
5. Produces 4 haploid cells / gametes;

97
Q

Meiosis (AO1)

Describe the process of crossing over and explain how it increases genetic diversity (4).

A

1. Homologous pairs of chromosomes associate / form bivalent;

2. Chiasmata form;

3. Equal lengths of non-sister chromatids exchanged;

4. This produces new combinations of alleles;

98
Q

Meiosis (AO1)

Describe and explain the processes that occur during meiosis that increase genetic variation (5).

A

1. Homologous chromosomes pair up;
2. Independent segregation;
3. Maternal and paternal chromosomes are re-shuffled in any combination AND move to opposite poles;
4. Crossing over leads to exchange of parts of non-sister chromatids / alleles between homologous chromosomes;
5. Both create new combinations of alleles;

99
Q

Meiosis (Maths)

Equation for working out possible combinations of chromosomes in gametes

A
100
Q

Meiosis (Maths)

If there are 6 pairs of homologous chromosomes, how many different combinations are there in the gametes?

A
101
Q

Meiosis (Maths)

A
102
Q

Meiosis (AO1)

Give two differences between mitosis and meiosis (2).

A

1. One division mitosis whereas two divisions in meiosis;
2. Daughter cells genetically identical in mitosis whereas daughter cells genetically different in meiosis;
3. Two cells produced in mitosis whereas (usually) four cells produced in meiosis;
4. Diploid to diploid/haploid to haploid in mitosis whereas diploid to haploid in meiosis;
5. Crossing over only in meiosis;
6. Independent segregation only in meiosis;

103
Q

Meiosis (AO1)

Genetic variation within a species is increased during meiosis by crossing over and the independent segregation of homologous chromosomes.

Apart from mutation, explain one other way genetic variation within a species is increased (2).

A

1. Random fusion of gametes

2. Produces new combinations of alleles

104
Q

Meiosis (AO1)

Name of mutation involving meiosis

A

Non-disjunction

105
Q

Meiosis (AO1)

Explain how non-disjunction occurs

A

Meiosis 1 - homologous chromosomes not separating correctly during independent segregation;

Meiosis 2 - sister chromatids do not split;

106
Q

Meiosis (AO2)

Using figure 1 below, describe how the change in chromosome number in Patau syndrome was produced (2).

A

1. Non-disjunction during meiosis;

2. Homologous chromosomes (meiosis 1) OR sister chromatids (meiosis 2) do not separate;

107
Q

Meiosis (AO2)

A nondisjunction mutation causes Down’s Syndrome which results in 3 chromosome 21s . This is known as as ________________.

A

trisomy 21

108
Q

Meiosis (AO2)

A

After first meiotic division – B;

After second meiotic division – E;

109
Q

Meiosis (AO2)

A
110
Q

Meiosis (AO2)

A
111
Q

Meiosis (AO2)

A

D

112
Q

Meiosis (AO2)

A

6

113
Q

Selection (AO1)

Genetic diversity is the number of different [1] of genes in a population. This enables [2] selection to occur.

A

[1] alleles
[2] natural

114
Q

Selection (AO1)

Which processes create new combinations of alleles and therefore genetic variation?

A

Independent segregation;

Crossing over;

Random fusion of gametes

115
Q

Selection (AO1)

What creates new alleles and therefore genetic variation?

A

random mutations

116
Q

Selection (AO1)

Describe and explain which processes - other than mutations - that result in increases in genetic variation within a species (4 marks).

A

1. Independent segregation of homologous
chromosomes/pairs;

2. Crossing over between homologous
chromosomes/pairs (non-sister chromatids);

3. Random fertilisation of gametes;

4. (Produces) new combinations of alleles;

117
Q

Selection (AO1)

Bullet point the key mark points for natural selection (5 marks).

A
  • Random mutations produce phenotypic variation (within a population)
  • (Named) selection pressure in the environment (biotic or abiotic)
  • Organisms with (named) advantegous phenotypes are more likely to survive AND reproduce
  • Pass on advantageous alleles to the next generation
  • Fequency of advantageous allele increases over many generations in the gene pool / population
118
Q

Selection (AO1)

TRUE or FALSE:

Organisms develop advantageous phenotypes because of a change in the environment.

A

FALSE

Random mutations produce phenotypic variation, then SELECTED FOR/AGAINST

119
Q

Selection (AO1)

Types of selection

A

Directional

Stabilising

120
Q

Selection (AO1)

Which type of selection favours one extreme phenotype?

A

Directional

121
Q

Selection (AO1)

Directional selection examples

A

Antibiotic resistance
Giraffe neck length
Peppered moth

Select FOR one extreme + select AGAINST the other

122
Q

Selection (AO1)

Which type of selection favours the mean / most common phenotype?

A

Stabilising

Select AGAINST the extremes

123
Q

Selection (AO1)

Stabilising selection examples

A

Birth weight of human babies

Number of eggs produced by birds

124
Q

Selection (AO1)

Which type of selection reduces variation and therefore the opportunity for evolutionary change?

A

Stabilising

125
Q

Selection (AO1)

Which type of selection brings about evolutionary change?

A

Directional

126
Q

Selection (AO1)

Natural selection results in species that are better adapted to their environment. These adaptations may be anatomical, physiological or ______________.

A

behavioural

127
Q

Selection (AO2)

Clostridium difficile is a bacterial species that causes disease in humans.

Antibiotic-resistant strains of C. difficile have become a common cause of infection acquired when in hospital.

Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria becoming a common cause of infection acquired when in hospital (3 marks).

A

1. Random mutations produce bacteria with alleles for antibiotic resistance;

2. Antibiotics is the selection pressure

OR Resistant bacteria survive & reproduce;

3. More antibiotics used in hospital (compared with elsewhere)

OR (So) high frequency of resistance allele (in bacterial population);

128
Q

Selection (AO2)

Mammals feed their young on milk. A lipase called CEL digests the triglycerides in milk. The ability to produce CEL occurred due to a gene mutation.

Describe how natural selection may have led to all mammals in a population producing CEL (4 marks).

A

1. Example of directional selection;

2. Random mutation results in a new allele;

3. Those with the (new) allele able to digest milk/triglycerides;

4. Individuals with CEL/allele more likely to survive reproduce;

5. Increase in frequency of allele in population (over many generations);

129
Q

Selection (AO2)

In Africa today, most of the human population are resistant to malaria caused by P. vivax.

Use your knowledge of natural selection to explain why this resistance is so common in Africa (4 marks).

A

1. Random mutation produced allele;

2. Those with allele/resistance survive malaria/P vivax;

3. More likely to survive, reproduce and pass on the allele;

4. Increase in frequency of allele in population (over many generations);

130
Q

Species & Taxonomy (AO1)

Two organisms belong to the same species if they are able to produce _____________ offspring.

A

fertile

131
Q

Species & Taxonomy (AO1)

Define species

A

A group of similar organisms that are able to breed to produce fertile offspring

132
Q

Species & Taxonomy (AO1)

Examples of courtship behaviour

A

Bright colours and/or patterns;
Songs;
Smells / pheromones;
Dances / movement;
Gift-giving;

133
Q

Species & Taxonomy (AO1)

Give two ways in which courtship increases the probability of successful mating (2).

A

(Any 2 from…)
1. Attracts/recognises same species;
2. Attracts/recognises mate/opposite sex;
3. Indication of sexual maturity / fertility / synchronises mating;
4. Stimulates release of gametes;
5. Form pair bond;

134
Q

Species & Taxonomy (AO2)

A

Sine song is very similar / same length for both, so closely related;

But have different peaks in pulse song;

135
Q

Species & Taxonomy (AO1)

A [1] classification system attempts to arrange species into groups based on their [2] origins and relationships.

It uses a hierarchy in which smaller groups are placed within larger groups, with no [3] between groups.

A

[1] phylogenetic
[2] evolutionary
[3] overlap

136
Q

Species & Taxonomy (AO1)

Define taxon

A

Each group in the heirarchy

e.g., Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

137
Q

Species & Taxonomy (AO1)

List the taxons by number of organisms in each group - from largest to smallest group.

A

(Largest) Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species (Smallest)

138
Q

Species & Taxonomy (AO1)

List the taxons from most related to least related group

A

(Most related) Species, Genus, Family, Order, Class, Phylum, Kingdom, Domain (Least related)

139
Q

Species & Taxonomy (AO2)

A

Shows smaller groups within larger groups;

With no overlap (between groups);

140
Q

Species & Taxonomy (AO2)

A

Domain - Eukarya

Kingdom - Animalia

Phylum - Chordata

Class - Mammalia

Order - Rodentia

Family - Muridae

141
Q

Species & Taxonomy (AO2)

A

Phylum

142
Q

Species & Taxonomy (AO2)

A

Aves

143
Q

Species & Taxonomy (AO2)

Hummingbirds belong to the order Apodiformes. One genus in this order is Topaza.

Name one other taxonomic group to which all members of the Apodiformes belong.

A

Kingdom / phylum / class

144
Q

Species & Taxonomy (AO1)

Name of sytem used to universally identify each species with a genus and species

A

Binomial system

145
Q

Species & Taxonomy (AO1)

Describe how organisms are grouped in a phylogenetic classification system (2).

A

1. Hierarchy of groups with no overlaps

OR smaller groups within larger groups with no overlaps;

2. Grouped according to evolutionary relationships / ‘common ancestry’ ;

146
Q

Species & Taxonomy (AO1)

The more closely related two species, the more [1] their shared [2] ancestor.

A

[1] recent
[2] common

147
Q

Species & Taxonomy (AO2)

A

X - mackloti and olivaceus have a more recent common ancestor with each other (than with papuana);

Y - papuana and mackloti have a more recent common ancestor with one another (than with olivaceus);

148
Q

Species & Taxonomy (AO2)

A

Most closely related: Synodontis batensoda

Most distantly related: Mochokus niloticus

149
Q

Species & Taxonomy (AO2)

A

6

150
Q

Investigating diversity (AO1)

Genetic diversity within, or between species, can be made by comparing…..

A
  • Frequency of measurable or observable characteristics
  • Base sequence of DNA
  • Base sequence of mRNA
  • Amino acid sequence of proteins
151
Q

Investigating diversity (AO1)

The genetic diversity of species is measured by comparing differences in the base sequence of DNA or differences in the base sequence of mRNA.

Give two other ways in which genetic diversity between species is measured.

A

Comparing measurable or observable characteristics;

Comparing amino acid sequences/primary structures (of a/named/the same protein);

152
Q

Investigating diversity (AO1)

The more similar the DNA base sequence of two species, the more [1] related they are and the more [2] their shared common ancestor.

A

[1] closely
[2] recent

153
Q

Investigating diversity (AO1)

In classification, comparing the base sequence of a gene provides more information than comparing the amino acid sequence for which the gene codes. Explain why (3).

A

1) DNA base sequence is longer than amino acid sequence;

2) Genes contain introns;

3) Same amino acid may be coded for by more than one codon / degenerate code;

154
Q

Investigating diversity (AO2)

Genetic diversity in soil species was traditionally inferred by making observations after growing prokaryotes on agar plates.

However, it is estimated that less than 10% of prokaryotes found in soil will grow if spread on an agar plate in a laboratory.

In recent years, our knowledge of prokaryotic biodiversity in the soil has increased.

Suggest why (2).

A

1. DNA/genome sequencing now used;

2. Now can analyse/identify more prokaryote species (in the community);

3. Rather than just recording measurable / observable characteristics;

155
Q

Investigating diversity (AO1)

Littorina littorea is a species of snail found on rocky sea shores.

A student investigated variation in snail shell height in two populations of snails.

Give two ways in which the student could ensure his samples would provide a reliable measure of the variation between individuals in each population.

A

1. Select at random;

2. Large sample / number of snails (more than 10);

156
Q

Investigating diversity (AO1)

Why should sampling be random?

A

To reduce bias

This also make the results / experiment more reliable

157
Q

Investigating diversity (AO1)

Why should a sample be large?

A

To ensure it is representative;

To calculate a mean so results are more reliable;

Identify anomolus results;

158
Q

Investigating diversity (AO3)

The student noticed there was a difference in shell height between these populations of snails. He wanted to investigate if the difference was significant.

Give a suitable null hypothesis to use in his investigation and name the statistical test to use with these data.

A

1. No significant difference between mean height (in these populations);

2. T-test;

159
Q

Investigating diversity (AO3)

The student could determine the median, mode and range from his measurement of shell heights in two populations of snails.

Give two other statistical values the student could calculate from his measurement of shell heights in these populations.

A

Mean and standard deviation

160
Q

Investigating diversity (AO2)

A

Top to bottom C N D I;

OR

Top to bottom N C D I;

161
Q

Investigating diversity (Maths)

A

4 different bases
11 bases in total

(4 / 11) x 100 = 36 to 36.4 %

162
Q

Investigating diversity (AO2)

Haemoglobins are chemically similar molecules found in many different species.

Differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic (evolutionary) relationships between species.

Explain how (5).

A

1. Random mutations change DNA base sequence;

2. Causing change in amino acid sequence;

3. Mutations build up over time;

4. More mutations / more differences (DNA base sequence / amino acid sequence / primary structure) between distantly related species;

OR accept converse

5. Distantly related species have earlier common ancestor;

OR Closely related species have recent common ancestor;

163
Q

Biodiversity (AO1)

Biodiversity can be measured in a wide a range of habitats, from a small local habitats to the entire ____________.

A

earth

164
Q

Biodiversity (AO1)

Two ways of measuring biodiversity

A

Species richness

Index of biodiversity

165
Q

Biodiversity (AO1)

Define species richness

A

Number of different species in a community

166
Q

Biodiversity (AO1)

Define community

A

All the populations of the different species living together in the same area (habitat or ecosystem) at the same time.

167
Q

Biodiversity (AO1)

Define index of biodiversity

A

The relationship between the number of species in a community and the number of individuals in each species.

168
Q

Biodiversity (AO1)

What is the below equation for?

A

To calculate the index of biodiversity (d)

169
Q

Biodiversity (AO1)

What does the ‘N’ represent?

A

Total number of individuals from all species

170
Q

Biodiversity (AO1)

What does the ‘n’ represent?

A

Number of individuals for each species

171
Q

Biodiversity (AO1)

Which symbol represents ‘sum of’?

A
172
Q

Biodiversity (AO1)

The greater the index of biodiversity, the more _____________ in the habitat.

A

biodiversity

173
Q

Biodiversity (Maths)

A

3.8

174
Q

Biodiversity (AO1)

Explain why it is more useful to calculate an index of diversity than to record species richness (2).

A

1. Index of diversity also measures number / population size of each species;

2. So useful because may be many of some species

OR may be few of other species;

175
Q

Investigating diversity (AO3)

It was important that the sampling procedure was standardised when collecting the Slate Drake mayflies from the two sites.

Give one way in which the sampling procedure could be standardised.

A

Same size of area (sampled)

OR Same size net/mesh

OR Same sampling time

OR Samples taken at same time of day/on same day;

176
Q

Biodiversity (AO3)

A

5

177
Q

Biodiversity (Maths)

A

4.92

178
Q

Biodiversity (AO3)

A

1. Significant increase in species richness on Islay and Colonsay and (significant) fall on Harris;

2. Change in diversity on Islay not significant;

3. Greater than 5% probability of difference being due to chance on Islay

OR For other differences less than 0.1% probability of difference by chance (for species richness on Colonsay, Harris, Islay)

OR Less than 1% probability of getting this change/difference by chance (for diversity index on Colonsay, Harris);

179
Q

Biodiversity (AO2)

The UK government pays farmers to leave grassy strips around the edges of fields of crops. These grassy strips contain a variety of plant species. Leaving the strips is an attempt to encourage biodiversity of animals.

Give two reasons why the grassy strips increase the biodiversity of animals.

A

1. Increase in plant diversity leads to more types of food for animals;

2. Increase in variety of animals leads to increase in predator species;

3. Increase in habitats

180
Q

Biodiversity (AO2)

Deforestation often involves clearing large areas of forest for use as agricultural land.

Deforestation reduces the diversity index of an area cleared in this way. Explain why (2).

A

1. Fewer habitats

2. Reduced food sources

3. Reduces total number of species (N)

4. Reduces numbers of each species (n)

181
Q

Biodiversity (AO2)

Suggest two reasons for conserving rainforests

A

1. Conserve / protect / species / plants / animals / organisms

OR for biodiversity;

2. Conserve/protect habitats/niches

OR provides/many habitats/niches;

3. Reduces climate change;

4. Source of medicines/drugs/wood;

5. Reduces erosion/eutrophication;

6. For tourism;

182
Q

Biodiversity (AO2)

A

4

183
Q

Biodiversity (AO3)

Suggest how a student would obtain data to give a more accurate value for the index of diversity for a habitat.

A

1. Take more samples and find mean;

2. Method for randomised sampling e.g. using a random number generator to generate coordinates;

184
Q

Biodiversity (AO1)

Species richness and an index of diversity can be used to measure biodiversity within a community.

What is the difference between these two measures of biodiversity?

A

Species richness measures only number of different species

OR species richness does not measure number of individuals.

AS AQA Biology - Burnley College (2023-24) (5 decks)

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