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Biology AQA A Level > Genetics, population, evolution and ecosytems Ch. 17, 18, 19 > Flashcards

Genetics, population, evolution and ecosytems Ch. 17, 18, 19 Flashcards

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1
Q

Gene

A

A section of DNA, (a sequence of nucleotide bases) that codes for a polypeptide chain

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2
Q

Universal

A

Same DNA in a range of organism

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3
Q

Diploid

A

A cell containing two complete sets of chromosomes, one from each parent

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4
Q

Genome

A

All the genes contained within one cell including the mitochondria and chloroplast

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5
Q

Locus

A

The position/location of a gene on a chromosome

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6
Q

Degenerate

A

More than one triplet code codes for the same amino acid

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7
Q

Allele

A

An alternate form of a gene/ One of the different forms of the gene

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8
Q

Histone

A

The protein around which DNA is folded around the nucleus

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9
Q

Homologous chromosomes

A

A pair of chromosomes where one is provided by the mother and one by the father

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10
Q

Proteome

A

The full range of proteins coded for by a genome

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11
Q

Intron

A

Sequences of non-coding DNA

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12
Q

Exon

A

Sequences of coding DNA

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13
Q

Chromosome

A

One of the two thread-like strands from when a chromosome divides

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14
Q

Non-overlapping

A

Each base does not code for more than one amino acid. Each base is only read once.

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15
Q

Genotype

A

The genetic make up of an organism.

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16
Q

Phenotype

A

the characteristic of an organism , often visible, as a result of both phenotype and the environment

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17
Q

How many alleles of a gene can there be on one chromosome?

A

One

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18
Q

Homozygous

A

When the alleles of a gene are the same on both chromosomes.

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19
Q

Heterozygous

A

When the alleles of a gene are different.

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20
Q

Dominant allele

A

An allele that is always expressed in the phenotype of an organism

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21
Q

Recessive allele

A

The effect of the allele is shown as the phenotype in a diploid organism when there is two of the recessive allele

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22
Q

Homozygous Dominant

A

When both alleles are dominant

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23
Q

Heterozygous Recessive

A

When both alleles are recessive

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24
Q

Codominant

A

When the two alleles contribute to the phenotype. It results in either a blend of both or both being shown.

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25
Q

Multiple alleles

A

When a gene has more than two allele forms. (still only two of the forms can ever be present).

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26
Q

Mutation

A

Any change to the genotype due to change in DNA, which can then be inherited.

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27
Q

Modification

A

Change in phenotype, which is not inherited (e.g piercing)

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28
Q

Monohybrid inheritance

A

The inheritance of a single gene

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29
Q

Pure-breeding

A

When the alleles are homozygous

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30
Q

First Filial generation

A

The offspring of the parents (F1)

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31
Q

Second Filial generation

A

The offspring of two F1s

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32
Q

How many alleles of a gene can there be in a gamete?

A

One

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33
Q

How many alleles of a gene can there be in a cell

A

Two

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34
Q

How do you calculate ratios?

A

Divide the numbers by the smallest number. That way you will always get 1:

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35
Q

When is it most likely that actual results will be close to theoretical results?

A

When there is a large sample size.

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36
Q

Dihybrid inheritance

A

Two different genes and characteristics are inherited.

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37
Q

How would you get the genotypes from RrGg?

A

Think expand the brackets (Rr)(Gg). RG Rg rG rg

38
Q

What’s the rato for RrGg and RrGg?

A

9: 3: 3: 1

39
Q

What’s the Law of Independent assortment?

A

Each allele may combine randomly with another.

40
Q

IA IB IO, which are codominant and recessive?

A

IA and IB are codominant, IO is recessive.

41
Q

How many chromosomes does a human cell have?

A

46, 23 pairs

42
Q

What are the female and male sex chromosomes?

A

XX Girls, XY Boys

43
Q

Why is it said that males determine the sex of the offspring?

A

As all female gametes will have an X, whereas the male gametes will have either X or Y. Therefore, if the male gamete is the X the offspring will be a girl, but if its a Y is will be a male.

44
Q

What is a sex-linkage?

A

A gene that is on the X or Y chromosome.

45
Q

Why is there generally no homologous genes on both X and Y?

A

Because the X chromosome is longer than the Y .

46
Q

Why is it more likely for males to get diseases that are X recessive?

A

As males only have one X chromosome and therefore only one allele and no dominant, therefore the recessive allele is presented.

47
Q

Give an example of sex-linked disease

A

Haemophilia, which slows down clotting. Confined mainly to males because females die with it and males only have one X chromosome.

48
Q

Why is it said that in a male haemophilia is inherited from his mother?

A

Its a allele carried on the X chromosome which can only come from the mother.

49
Q

What is an Autosome?

A

Any chromosome that is not the sex chromosomes

50
Q

What is Autosomal linkage?

A

Any two or more genes that are on the same chromosome

51
Q

Assuming there is no cross-over what happens to linked genes in meiosis?

A

Linked genes will be in the same gamete because they are transferred together.

52
Q

What determines blood type?

A

The antigens on the cell-surface membrane of red blood cells.

53
Q

What blood type do you have if you have IA IO?

A

A

54
Q

What blood type do you have if you have IA IA?

A

A

55
Q

What blood type do you have if you have IA IB?

A

AB

56
Q

What’s epistasis?

A

When the allele of one gene affects or masks the expression of another in the phenotype.

57
Q

What is wild type?

A

A gene or characteristic of a species that occurs in nature, so not a mutant allele.

58
Q

What is back crossing?

A

When an offspring is breed with its parent.

59
Q

How many type of gametes can be produces in an autosomal linkage?

A

Only ever two.

60
Q

What is dominant epistasis?

A

When it’s the dominant allele in the epistatic allele that masks/ affects the other gene.

61
Q

What is recessive epistasis?

A

When it is a recessive allele in the epistatic allele that masks/affects the other gene.

62
Q

When is the chi squared test used?

A

To test the null hypothesis. If there is a statistically difference between the sets and if it is due to chance

63
Q

What is a null hypothesis?

A

There is no statistically significant difference between x and y and and difference is due to chance

64
Q

What is the formula for chi squared?

A

Sum of [ observed number - expected number)^2 / expected number ]

65
Q

How do you calculate the degrees of freedom?

A

Number of categories - 1

66
Q

What is the percentage to look at for the critical value

A

0.05 / 5%

67
Q

When do you accept or reject the null hypothesis?

A

Reject if the number is bigger than the critical value, accept if smaller.

68
Q

If the x^2 at 0.99 for 3 degrees of freedom is 1.2. And your x^2 gave you 1. What would you conclude?

A

You can accept the null hypothesis with 99% confidence so there is no statistically significant difference and any difference is due to chance.

69
Q

If the x^2 at 0.99 for 3 degrees of freedom is 1.2. And your x^2 gave you 1.5, what would you conclude?

A

You cannot accept the null hypothesis with 99% confidence.

70
Q

If the x^2 at 0.01 for 3 degrees of freedom is 6.4 . And your x^2 gave you 5, what would you conclude?

A

You cannot reject the null hypothesis with 99% certainty but can accept the null hypothesis with 1% certainty.

71
Q

If the x^2 at 0.01 for 3 degrees of freedom is 6.4 . And your x^2 gave you 6.6, what would you conclude?

A

You can reject the null hypothesis with 99% certainty therefore the is a statistically significant difference and any difference is not due to chance.

72
Q

Suggest reasons for why observed ratios are not often the same as expected?

A
  • Fertilisation is random
  • not large enough sample size
  • There may be a more advantageous or disadvantageous allele ;
73
Q

Population

A

A group of organisms of the same species occupying a particular space that can potentially interbreed.

74
Q

Gene pool

A

All the alleles of all the genes of all individuals in a populations at any given time

75
Q

Allele frequency

A

The number of times an allele occurs within the gene pol.

76
Q

What is the Hardy-Weinberg principle?

A

A mathematical model which predicts that allele frequency will not change from generation to generation.

77
Q

When does the Hardy-Weinberg principle work?

A

When there is : No mutations, no migration, no selection, large population and mating is random.

78
Q

Give the two equations for the Hardy-Weinberg principle

A

p + q = 1

p^2 + 2pq + q^2 = 1

79
Q

What is the genetic factors for variation within a population?

A

Mutation, meiosis and recombination and random fertilisation of gametes.

80
Q

What is the environmental factors for variation within a population?

A

Competition for resources, disease and predation

81
Q

Intra-specific competition

A

Within a species

82
Q

Inter-specific competition

A

Between a species

83
Q

What is a selection factor?

A

The environmental factor limiting the population of a species.

84
Q

Disruptive selection

A

Favours both extremes and the mean is selected against

85
Q

Directional selection

A

Favours one extreme from the mean

86
Q

Stabilising Selection

A

Favours the mean and goes against the extreme ends.

87
Q

Continuous Variation

A

a continuous range of values

88
Q

Discontinuous Variation

A

Values are in categories

89
Q

What does evolution do to the allele frequency

A

Changes the allele frequency

90
Q

Speciation

A

The evolution of a new species from existing ones.

Biology AQA A Level (15 decks)

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