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CELS 191 > Inheritance > Flashcards

Inheritance Flashcards

1
Q

What is a gene

A

Information packed in discrete particles which can be passed on from parents to offsprings
Offsping contain 2 copies of each gene - one from mother one from father

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2
Q

What is phenotype

A

The observable characteristics of an individual

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3
Q

What does a phenotype result from

A

Genotype and the environment

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4
Q

What is genotype

A

Combination of alleles of the relevant gene

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5
Q

What is atavism

A

The reappearance of a trait in a pedigree/family

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6
Q

Atavism is bet described by

A

the dominant and recessive nature of alleys in determining phenotype

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7
Q

State Mendel’s first law

A

Law of segregation

Genes segregate at meiosis so that each gamete only contain one of the 2 genes possessed by the parent

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8
Q

State Mendel’s second law

A

Law of independent assortment
Alleles of different genes on nonhomologous chromosomes assort independently during gamete formation. Individual chromosomes have no effect on where the other chromosome go during meiosis

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9
Q

What is a test cross

A

Cross with homozygous recessive to determine unknown genotype of parent

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10
Q

If a homozygous recessive is test crossed with a homozygous dominant, what will the offspring phenotype ration be

A

All of one phenotype

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11
Q

If a homozygous recessive is test crossed with a heterozygous, what will the offspring phenotype ratio be

A

1:1

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12
Q

What are causes of deviation from simple Mendelian ratios (4)

A

Lethal allele
Polymorphic
Incomplete dominance
Complete dominance

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13
Q

What is it meant by polymorphic

A

A gene coded for many alleles, leading to various phenotypes

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14
Q

What is incomplete dominance

A

When one allele/phenotype does not completely dominate over the other, resulting in the offspring showing a phenotype that is the mix of the parents (heterozygous genotype)

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15
Q

What is co-dominance

A

1 gene with 2 alleles expressed side by side and the organism shows the phenotypic effects of both alleles equally

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16
Q

Give an example of co-dominance

A

ABO blood antigen system
- the ABO blood groups in humans are determined by 3 alleles of a single gene
- A person’s blood group may be one of 4 types: A, B, AB, O and these letters refer to 2 carbohydrates A and B
- A person’s blood cell may have
carb A = blood type A
carb B = blood type B
neither carb = type O
carb A and B = type AB which shows co-dominance

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17
Q

What is epistasis

A

Where one gene at one locus alters the phenotype expression of a gene at a second locus

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18
Q

Outline the basic metabolic pathway of epistasis

A

Gene A determines whether or not color is produced - (A) or nor (a)
Gene B codes for coat color - (B) or (b)
Gene B is said to be under epistatic control of gene A

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19
Q

What is a polygenic trait

A

A phenotype controlled by many genes that have an additive effect

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20
Q

Examples of polygenic traits (3)

A

skin color, weight, height

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21
Q

How is a polygenic trait typically distributed in a population

A

Normal distribution

The more genes involved, the higher number of phenotypic classes

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22
Q

Incomplete dominance, complete dominance, epistasis and polygenic trait are examples of what?

A

How some phenotypic traits are affected by several loci

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23
Q

Discuss how environment factors may affect phenotype and provide examples

A

It can smooth out differences among phenotypes
eg. diseases, height/weight, nutrition, life expectancy
Hydrangeas are blue in acidic soil but pink in alkaline soil

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24
Q

Explain how the environment smooths out the phenotype of wheat height

A

Height of weight is discrete with 3 values but the environment will cause wheat to grow in between these 3 values and can cause in normal distribution

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25
Q

What is pleiotropy

A

When one gene has many effects

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26
Q

Examples of pleiotropy (3)

A
  • Sickle cell produces many symptoms
  • colouration of pattern and cross eyes of siamese cats produced by the same gene
  • eye colour, wing length and body hair traits in Drosophila all affected by one gene
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27
Q

Homogametic

A

having 2 of the same sex chromosomes

In humans = female

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28
Q

Heterogametic

A

having 2 different sex chromosomes

In humans = male

29
Q

Define linked genes

A

When 2 genes are close together on the same chromosome and do not assort independently

30
Q

What is a sex-linked gene

A

A gene located on either sex chromosomes

31
Q

What is a hemizygote

A

A diploid organism or cell with only 1 copy of the chromosome

32
Q

In a X-linked gene inheritance, how will the mutant allele be inherited if the father carried the mutant allele mated with a dominant homozygote mother

A

The daughters will have the normal phenotype but will be carriers for the mutation
No mutant allele will be passed onto sons

33
Q

If a carrier female for an X-linked disorder mates with a normal male, how will the mutation/disorder be passed on

A

Half the sons and half the daughters will receive the mutation. 50% chance that daughters will be carriers like their mother but the 50 % chance that sons will have the disorder

34
Q

If a carrier female for an X-linked disorder mates with a male who also has the disorder, how will the disorder be passed on

A

Half the sons and half the daughters will have the disorder regardless of sex
Daughters free of disorder will be carriers
Sons free of disorder will be free of the mutated allele

35
Q

Examples of X-linked inheritance

A

Eye color in Drosophila

Red-green color blindness

36
Q

Examples of X-linked disorders

A

Duchenne muscular dystrophy

Hemophilia

37
Q

Linked genes

A

Genes located near each other on the same chromosome which tend to be inherited together in genetic crosses

38
Q

If the occurrence of parental types has a frequency greater than 50%, what does that indicate

A

linked genes

39
Q

Explain how crossing over lead to recombinants

A

During late prophase I of meiosis, the 2 chromatids of a tetrad (1 maternal, 1 paternal) cross over at random points and swap genetic material

40
Q

What is the recombinant frequency

A

The proportion of recombinants

41
Q

What determines the recombinant frequency

A

The distance between 2 genes. The further the 2 genes are, the higher the probability that a chiasma will form between then, the 2 genes will cross over therefore higher recombinant frequency

42
Q

What type of linkage results in parental types only and no recombinants

A

complete linkage

43
Q

What type of linkage results in recombinants

A

Incomplete linkage

44
Q

What does 1 map unit equal to

A

1% recombinant frequency

45
Q

Recombinant frequency of distant/unlinked genes

A

50%

46
Q

What does a recombinant frequency of 0%-50% equal to

A

Close genes

47
Q

How is the recombinant frequency calculated

A

of recombinant/total number x 100

48
Q

Define gene pool

A

localized group of individuals of the same species

49
Q

‘The total aggregate of genes (and their alleles) in the population at one time’ refers to what

A

Gene pool

50
Q

5 assumptions of Hardy-Weinberg Equilibrium

A 
Large population size
Random mating
No mutations
No migration
No natural selection
51
Q

Why does genetic drift occur more rapidly in small populations

A

The smaller the population, the more likely that chance events can cause allele frequency fluctuations from one generation to the next

52
Q

‘A random change in allele frequencies due to sampling error over generations’ describes what

A

Random genetic drift

53
Q

Define bottleneck effect

A

Sharp reduction in population size due to environmental events or human activities

54
Q

What is founder effect

A

Reduced genetic variation from original population when a new colony/population is established by a small number of individuals from the original population

55
Q

Natural selection (2)

A

Process whereby organisms better adapted to their environment tend to survive and produce more offspring
Alters gene frequency

56
Q

What is the only mechanism that consistently causes adaptive evolution

A

Natural selection

57
Q

State the 3 types of natural selection

A

Stablising
Directional
Disruptive

58
Q

Stabilising selection (2)

A

Favours average/intermediate phenotype and act against extreme phenotypes
Results in reduction in variation but does not change the mean

59
Q

Example of stabilizing selection

A

head size at childbirth

60
Q

Directional selection

A

Favors one extreme phenotype

Results in peak shifting in one direction and changes the mean value towards one extreme

61
Q

Example of directional selection

A

Long necks of giraffe

62
Q

Disruptive selection

A

Favors the 2 extremes

Result in 2 peaks

63
Q

Example of disruptive selection

A

2 bill morphologies displayed by West African blacked bellied seek crackers

64
Q

What is sexual selection

A

A mode of natural selection where members of one biological sex choose mates of the other sex to mate
Tends to be females choosing mates with favourable traits

65
Q

What is frequency dependent selection

A

Evolutionary process where the fitness of a phenotype depends on its frequency relative to other phenotypes in a given population. In positive frequency-dependent selection, the fitness of a phenotype increases as it becomes more common.

66
Q

Which mode of selection favors the extremes

A

frequency dependent selection

67
Q

Artificial selection (Not a type of natural selection)

A

Human selection of preferred phenotype of a species resulting in altered gene frequency

68
Q

Gene flow/migration affects on the population (4)

A

Brings more alleles
Changes proportions of existing alleles
Changes population size
Makes 2 populations more similar

69
Q

Cline

A

Environmental gradient across extended geographical range resulting in gradual change in proportions as different environments exert different selection pressures

CELS 191 (8 decks)

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