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BIO > Patterns of Inheritance > Flashcards

Patterns of Inheritance Flashcards

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Biology 101 flashcards
1
Q

What is leaf chlorosis?

A

A reduced amount of chlorophyll in the leaves of a plant.

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2
Q

What causes leaf chlorosis?

A

Lack of light.
Mineral deficiencies.
Viral infections.

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3
Q

What is etiolation?

A

The development of plants in the absence of light, resulting in:
small unexpanded leaves,
elongated shoots,
lack of chlorophyll (leaf chlorosis).

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4
Q

What is an allele?

A

A different form of the same gene occupying the same locus on the chromosome.

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5
Q

What processes lead to genetic variation from sexual reproduction?

A

Independent assortment.
Crossing over.
Reduction and fusion of gametes.

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6
Q

What is mendel’s first law? (law of segregation)

A

When an organism forms gametes, only one of the pair of alleles enters each gamete. (law of segregation)

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7
Q

What is the phenotype ratio for the monogenic cross of two heterozygous individuals?

A

3:1

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8
Q

What is codominance?

What phenotype ratio will it give?

A

A gene where both alleles can be expressed simultaneously. (there is no dominant and recessive allele)
1:2:1

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9
Q

What is dihybrid inheritance?

A

Inheritance of two characteristics, controlled by two pairs of alleles independently of each other.

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10
Q

What is the phenotype ratio for the dihybrid cross of two double heterozygous individuals?

A

9:3:3:1

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11
Q

What is epistasis?

A

The interaction between two genes, where the expression of one gene is modified by another gene.
At a different loci.

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12
Q

What is the epistatic gene?

A

The gene which modifies the expression of another gene at a different loci. (the hypostatic gene)

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13
Q

What is the hypostatic gene?

A

The gene which has its expression altered in epistasis (by the epistatic gene).

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14
Q

What is recessive epistasis?

A

Where the epistatic gene will stop the expression of the hypostatic gene if it is homozygous recessive.

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15
Q

What is the phenotype ratio for a dihybrid cross of two double heterozygotes with recessive epistasis?

A

9:3:4

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16
Q

What is dominant epistasis?

A

Where the epistatic gene will stop the expression of the hypostatic gene if it is homozygous dominant or heterozygous.

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17
Q

What is the phenotype ratio for a dihybrid cross of two double heterozygotes with dominant epistasis?

A

12:3:1

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18
Q

What is epistasis by complementary action?

A

Epistasis where the gene is only expressed if both genes are either heterozygous or homozygous dominant.

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19
Q

What is the phenotype ratio for a dihybrid cross of two double heterozygotes with epistasis by complementary action?

A

9:7

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20
Q

What is a karyotype?

A

A photographic representation of chromosomes in a genome in order of size.

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21
Q

Which chromosomes determine sex?

A

The sex chromosomes X and Y.

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22
Q

What does it mean for two genes to be linked?

A

They are found on the same chromosome (different loci).

This means the alleles will be inherited together, unless crossing over occurs forming a chiasma between the two loci.

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23
Q

What is sex-linkage?

Can you give any examples? (2)

A

When a gene is found on the sex chromosome.

e.g: red-green colourblindness (X-linked), haemophilia (X-linked).

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24
Q

What is autosomal linkage?

A

Linkage not occurring on a sex chromosome.

When genes are linked, alleles are usually inherited together, unless crossing over occurs forming recombinants.

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25
Q

What will be the phenotype ratio for a dihybrid cross of two double heterozygotes where the two genes are linked with no recombinants?

A

3:1

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26
Q

How can linkage be determined?

A

Cross AaBb with aabb.
If no linkage the phenotype ratio will be 1:1:1:1.
If linkage with no recombinants the phenotype ratio will be 1:1.

27
Q

What does recombination frequency measure?

A

How much crossing-over has occurred.

28
Q

How can recombination frequency be calculated?

A

total number of recombinants / total number of offspring

29
Q

What is the significance of recombination frequency?

A

greater than or equal to 50% indicates no linkage.

less than 50% indicates linkage.

30
Q

How does the proximity of linked genes on the chromosome affect recombination frequency and why?

A

Closer genes have a lower recombination frequency as they are less likely to be separated by crossing-over.

31
Q

What does a distance of one centimorgan on a chromosome represent?

A

A 1% change in recombination frequency.

32
Q

What is the chi-squared test used for?

A

To calculate whether a set of actual, observed results differs significantly from expected results or whether any deviation is due to chance.

33
Q

What is the null hypothesis in the chi-squared test?

A

That there is no significant difference between the observed and expected results.

34
Q

What does the term “degrees of freedom” mean in the context of a chi-squared test?

A

The number of different categories - 1

35
Q

What does it mean if the chi-squared value is larger than the critical value for a particular significance level?

A

You should reject the null hypothesis.

36
Q

What is the key principle of the hardy weinberg equilibrium?

A

Allele frequency always adds up to 1.

37
Q

What does p^2 represent in the hardy-weinberg equation?

A

The frequency of homozygous dominant individuals.

38
Q

What does 2pq represent in the hardy-weinberg equation?

A

The frequency of heterozygous individuals.

39
Q

What conditions must be met for the hardy-weinberg equilibrium to be maintained? (7)

A 
Population is large.
Random mating within population.
No selection pressures (no differential mortality between alleles).
Population is closed (no migration).
No mutation between alleles.
No genetic drift.
The characteristic is not sex-linked.
40
Q

What does the term “stabilising selection” mean?

A

Generation to generation, natural selection will keep the frequency of alleles approximately constant (no evolution).

41
Q

What does the term “directional selection” mean?

A

Selection pressures mean the most common phenotypes are no longer favoured by natural selection, so there is a change in allele frequency (evolution) over many generations.

42
Q

What is disruptive selection?

A

When natural selection causes allele frequency to change in two different directions in a population, forming two groups. (divergent evolution)

43
Q

What is genetic drift?

A

Change in allele frequency within a population.

44
Q

What is bottlenecking?

A

When the population of a species decreases significantly for at least one generation, decreasing genetic diversity.

45
Q

What is the founder effect?

A

When a new colony is started, the gene pool is much smaller and a non-random selection of alleles from the previous population.

46
Q

What is speciation?

A

The formation of a new species from an existing one.

47
Q

What is sympatric speciation?

A

Speciation between two groups in the same environment, usually through reproductive isolation.

48
Q

What is allopatric speciation?

A

Speciation occuring due to geographical isolation.

49
Q

What are the 4 sympatric prezygotic reproductive barriers?

A

Temporal
Ecological
Behavioural
Mechanical

50
Q

What is a temporal reproductive barrier?

A

Different breeding seasons.

51
Q

What is an ecological reproductive barrier?

A

Inhabiting different areas within the same habitat.

52
Q

What are behavioural reproductive barriers?

A

e.g: different courtship displays/mating rituals.

53
Q

What are mechanical reproductive barriers?

A

Incompatible sexual organs.

54
Q

What are the 3 postzygotic reproductive barriers?

A

Hybrid inviability
Hybrid sterility
Hybrid breakdown

55
Q

What is hybrid inviability?

A

Offspring does not survive embryonic development.

56
Q

What is hybrid sterility?

A

The first generation of hybrid offspring are sterile.

57
Q

What is hybrid breakdown?

A

The second generation of hybrid offspring are sterile.

58
Q

What is artificial selection?

A

When a breeder chooses individuals with desired phenotypes for breeding and prevents other individuals from breeding, changing the allele frequency in the population.

59
Q

What is the selection agent in artificial selection?

A

Humans

60
Q

Does natural selection or artificial selection result in faster evolution?

A

Artificial selection

61
Q

What are the 2 main ethical issues of selective breeding?

A

Reduction in the gene pool of the population. (loss of genetic diversity)
Interbreeding can result in organisms with health problems due to genetic diseases.

62
Q

Why is a reduction in the gene pool bad for a population?

A

There is a loss of genetic diversity, so the population will be less likely to survive environmental changes and disease.
Potentially useful alleles are lost from the species.

63
Q

How can useful alleles that may be lost from a population due to selective breeding be preserved?

A

Preservation of “wild types”.

64
Q

Why does genetic drift happen more quickly in small populations?

A

Rare alleles have a higher frequency amongst the population.

BIO (33 decks)

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