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A level Biology > Unit 4 > Flashcards

Unit 4 Flashcards

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1
Q

Define gene

A

A section of dna that contains a code for making a polypeptide and functional rna (the code is a specific sequence of bases)

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2
Q

Define allele

A

Alternate form of a gene at the same locus of a homologous chromosome

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3
Q

Define chromosome

A

Tightly coiled dna in nucleus of eukroyotic cell (23 pairs)

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4
Q

What’s a homologous pair

A

A Chromosome that has identical gene but different alleles

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5
Q

How is dna stored in a eukaryotes

A

-dna is stored in Chromosomes in the nucleus
-dna is liner
Dna is bound and tightly coiled around a protein called his tones
-dna and go stones is called a nucleosome

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6
Q

Dna in prokaryote cell

A

-short circular dna
-no host ones
No nucleus not membrane bound

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7
Q

How is ribosomal dna and mitochondrial dna are similar

A

-short
-circular
-not his tone bound

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8
Q

3 key features of genetic code

A

-degenerate
-universal
-non overlapping

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9
Q

What’s a Start codon

A

First triplet bases at the start of mrna and initiates translation
And codes for an amino acid

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10
Q

What is a stop codon

A

Final three bases of a gene that stop translation and doesn’t code for an amino acid. Marks the end of a polypeptide

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11
Q

What does it mean when we say dna is degenerate

A

There are 20 different amino acids that genetic code has to be able to code
-combination of 3 bases are needed to make 20 amino acids
-(4^n)

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12
Q

Advantage of degenerate

A

Each amino acid is coded by more then one triplet of bases
And this is an advantage because of a point mutation occurs and the base changes it could potentially code for the same amino acid therefore not altering the polypeptide

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13
Q

What does it mean when we say dna is universal

A

same Triplet bases code for the same amino acid in every organism

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14
Q

What is the advantage of dna is being universal

A

Genetic engineering

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15
Q

What does it mean when we say dna is non overlapping

A

Each base in a gene is only part of one triplet of bases that code for an amino acid
-read as discrete units

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16
Q

What is the advantage of non overlapping

A

If a mutation occurs is only effects on triplet therefore only one amino acids in a polypeptide

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17
Q

What is an intron

A

Sections of dna that don’t code for proteins in eukaryotes they needed to be spliced in mrna

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18
Q

Exon

A

Sections of dna that code for amino acids

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19
Q

Genome

A

Complete set of dna in a cell

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20
Q

Proteome

A

Full range of proteins in one cell

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21
Q

Do genomes stay the same

A

Yes genomes don’t Change but proteomes do depending on what protein is needed

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22
Q

What is rna

A

Is a polymer of nucleic acid made from ribose a nitrogenous base (AUTG) and a phosphate group

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23
Q

Characteristics of rna

A

Is much shorter then dna and is single stranded

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24
Q

Function of rna

A

Copy and transfer the genetic code for dna in the nucleus to the ribosomes

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25
Q

3 types of rna

A

Mrna trna rRNA

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26
Q

Characteristics of mrna

A

Much shorter so it’s able to leave the nucleus. Dna cant leave the nucleus because 1. It’s too big 2. Might be damaged by enzymes
It is short lived so it doesn’t get damaged
Contains codons which are one triplet base that code for one amino acid

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27
Q

What is trna

A

tRNA is a clover shaped rna held tigether by hydrogen bonds contain anticodons and an amino acid binding site

28
Q

rRNA

A

Rna and proteins to make ribsoomes

29
Q

Transcription

A

Last weeks 5 mark answer:
A. At a specific gene, an enzyme (DNA helicase) breaks the hydrogen bonds between bases to expose nucleotides

B. Free floating RNA nucleotides pair with complementary nucleotides on the DNA template strand: U pairs with A, A pairs with T, C pairs with G and G pairs with C

C. RNA polymerase moves along the strand and catalyses the formation of phosphodiester bonds between adjacent RNA nucleotides to form pre mRNA

D. mRNA is formed by removal of introns from the pre mRNA andsplicingof exons together

E. mRNA moves from the nucleus to the cytoplasm through nuclear pores in the nuclear envelope

30
Q

Translation

A

Translation:
A. A ribosome binds to the start codon on the mRNA

B. tRNA molecules with complementary anticodons to the first two codons on the mRNA bind to the mRNA

C. The ribosome catalyses a condensation reaction to form peptide bonds between amino acids attached to adjacent tRNA molecules. This process requires ATP.

D. The ribosome moves along the mRNA molecule to the next codon to catalyse the peptide bond between the next two adjacent amino acids.

E. As this occurs, tRNA molecules are released to be reloaded with an amino acid

F. When the ribosome reaches a stop codon the ribosome, mRNA, last tRNA and complete polypeptide are released

31
Q

What is meiosis

A

Produces genetically different haploid cells. From one diploid parent cell into 4 haploid cells
And includes two nuclear divisions

32
Q

How is variation introduced

A

1.independent segregation
2. Crossing over
3. One sperm cell and one egg cell

33
Q

What is independent segregation

A

During meiosis I, when the homologous pairs are lined up opposite from each other the equator of the cell. It is random which side the homologous pair lay. So when the homologous pair are separated it ends up in one daughter cell

34
Q

How do we calculate the number of possibilities of overlapping

A

2^23

35
Q

What is crossing over

A

During meiosis I The homologous pairs line up opposite eachother
They chromatids can become twisted around eachother this caused tension and the chromatid snaps and breaks off and results in a recombination on the other chromosome and becomes a new combination of alleles

36
Q

Difference between mioeisis and mitosis

A

Nuclear divisions
Identical and variation
Haploid and diploid

37
Q

How do you identify meiosis in a life cycle

A

2n ——> n

38
Q

What else increases variation

A

2 different gametes. (2^23)^2

39
Q

How does chromosomes mutation occur

A

Non dysfunction during meiosis

40
Q

What is non dysfunction

A

When chromoatids do not separate equally or correctly during anaphase

41
Q

Non dysfunction can occur in two forms

A
  1. Polyploidy
  2. Aneuploidy
42
Q

What is polyploidy

A

Changes in a whole set of chromosomes

43
Q

What is anaploydi

A

Extra chromosomes

44
Q

Define genetic diversity

A

Number of different alleles of a gene in a pop

45
Q

What is natural selection

A

Can only occur when there is genetic diversity within a pop

46
Q

What is evolution

A

Change in allele frequency over generations

47
Q

What does natural selection allow

A

Better adapted to environment

48
Q

What type of adaptations are there

A

Anatomical physiological behavioural

49
Q

How does natural selection occur

A
  1. A new allele is formed through a random mutation
  2. If the new allele is advantageous then the organism is more likely to survive and increases chances of survival and reproduce
  3. The advantageous allele is then past on to the offspring and next generations
    4, the allele frequency increases
    4.
50
Q

Two types of NS

A

Directional and stabilising

51
Q

What is DIRECTIONAL NS

A

One of the extreme traits has been selected and occurs due to change in environment right shifted

52
Q

What is stabilising selection

A

The modal trait has been selected occurs when there is no change in the environment
Standard deviation increases
Extremes decrease

53
Q

What is courtship

A

Behaviour that results in mating,
Essential for successful mating to produce fertile offspring and recognising same species

54
Q

What is species

A

A group of similar organisms that can breed to produce fertile offspring

55
Q

What are courtship rituals

A

Colourful feathers skin
Sequence of movements
Fighting
Chemical attraction

56
Q

What is the importance of courtsahip

A

-successful reproduction
Helps recognise their from the same species
Synchronises mating behaviour( to determine whether they are sexually mature)
2) ensure survival or offspring by producing a pair bond

57
Q

What do similar courtship rituals reveal about a species

A

That they are more closely related if they have similar courtship rituals

58
Q

What is the binomial system

A

Identifying species
Genus + species

59
Q

Why do different species look similar

A

-similar environments
-similar selective pressures
-Produce similar proteins there for similar physical characteristics
-have similar alleles that will have selective advantages

60
Q

Classification scale

A

D
K
P
C
O
F
G
S

61
Q

What is heu racy

A

-small groups a
Ranged within larger groups
-no overlapping between groups

62
Q

Why do we have a classification system

A

-understand relationships between species and keep track of change
-universal
Grouping organisms

63
Q

How do we classify species

A

-dna -mrna-amino acids -immunology

64
Q

Phylogeny

A

According to revolutionary origins
And what’s more closely related and which species share a common ancestor

65
Q

What term is used to describe populations of different species living in the same
habitat?

A

communities

A level Biology (11 decks)

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