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Biology: Module 6: Genetics, Evolution and Ecosystems > Patterns Of Inheritance & Variation > Flashcards

Patterns Of Inheritance & Variation Flashcards

1
Q

Types of factors that contribute to phenotypic variation

A

Environmental, genetic

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2
Q

Environmental factor that contributes to phenotypic variation in animals

A

Diet

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3
Q

Examples of phenotypic variations caused by environmental conditions in plants

A

Etiolation, chlorosis

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4
Q

Etiolation

A

When a plant has elongated stems and has a pale colour due to a lack of chlorophyll because of insufficient light in the environment

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5
Q

Chlorosis

A

When the leaves look pale or yellow because the cells aren’t producing enough chlorophyll

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6
Q

Environmental factors that lead to chlorosis

A

Lack of light leading to chlorophyll production decreasing to conserve resources, mineral deficiencies of iron or magnesium, viral infections

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7
Q

How is genetic variation created within a species?

A

Sexual reproduction

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8
Q

How can sexual reproduction lead to genetic variation within a species?

A

Meiosis, random fusion of gametes at fertilisation

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9
Q

F1 generation

A

Generation produced by mating dominant and recessive homozygous individuals, all offspring are heterozygous

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10
Q

F2 generation

A

The offspring of mating two heterozygous individuals

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11
Q

Phenotypic ratio in an F2 generation in monogenic inheritance

A

3:1

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12
Q

Codominance

A

When two equally dominant alleles occur for a gene as the genotype is heterozygotic so are both expressed in the phenotype

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13
Q

How is codominance represented?

A

Capitals with a letter index

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14
Q

Phenotypic ratio in an F2 generation in codominance

A

1:2:1 (Homozygous, heterozygous, homozygous)

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15
Q

Multiple alleles

A

When a gene has more than two versions

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16
Q

Example of a characteristic caused by multiple alleles

A

Blood group

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17
Q

Characteristics of the multiple alleles involved in determination of blood group

A

IA and IB are codominant, IO is recessive, IA and IB are dominant to IO

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18
Q

X linkage

A

When a person assigned male at birth only has one copy of gene on the X chromosome so conditions caused by recessive alleles are more common in people assigned male at birth

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19
Q

Why is X linkage a thing?

A

The Y chromosome is smaller than the X chromosome so there are fewer genes on it

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20
Q

How to represent X linkage

A

X to an index, Y

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21
Q

Phenotypic ratio when a carrier female mates with a normal male and the characteristic is X linked

A

Half of all AMABs will have disorder, half of AFAB will be carriers

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22
Q

Phenotypic ratio for dihybrid inheritance

A

9:3:3:1

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23
Q

Why may an actual phenotypic ratio be different from the theoretical one?

A

Fertilisation is random so small sample can be skewed by a few chance events, genes being studied are both on the same chromosome in linkage

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24
Q

Linkage

A

Genes are on the same chromosome

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25
How are linked genes inherited?
As one unit, no independent assortment unless they are separated by chiasmata
26
The closer genes are on a chromosome...
The less likely they are to be separated during crossing over
27
Why may a ratio for linkage not be the expected?
Crossing over
28
Equation for recombination frequency
Recombination frequency = Number of recombinant offspring/ Total number of offspring
29
What does a recombination frequency of 50% indicate?
No linkage
30
What recombination frequency suggests linkage?
Less than 50%
31
How to use recombination frequencies to map a chromosome
Recombination frequency of 1% is 1 map unit on a chromosome
32
Epistasis
Interaction of genes at different loci
33
Examples of gene epistasis
Gene regulation
34
Hypostatic
Gene that is affected by another gene
35
Epistatic
Gene that affects the expression of another gene
36
Recessive epistasis
Homozygous presence of a recessive allele prevents expression of another allele at a second locus
37
Phenotypic ratio for recessive epistasis
0.37712962962962965
38
Dominant epistasis
Presence of dominant allele at one gene locus masks the expression of alleles at a second locus
39
Phenotypic ratio for dominant epistasis
0.5020949074074074
40
Complementary epistasis
Homozygous recessive genotypes at either locus masks the expression of the dominant allele at the other locus
41
Phenotypic ratio for complementary epistasis
9:7
42
Role of chi squared test
To determine the significance of the difference between observed and expected results
43
Degrees of freedom for chi squared test
n - 1
44
Factors that lead to continuous variation
Polygenetic, environmental
45
Factors that lead to discontinuous variation
A few genes
46
Allele frequency
Relative frequency of a particular allele in a population
47
Gene pool
Sum total of all the genes in a population at a given time
48
Letter that represents the frequency of a dominant allele in the Hardy-Weinberg equation
p
49
Letter that represents the frequency of a recessive allele in the Hardy-Weinberg equation
q
50
Equations for Hardy-Weinberg
p + q = 1, p^2 + 2pq + q^2 = 1
51
Hardy-Weinberg Principle
In a stable population with no disturbing factors, the allele frequencies will remain constant from one generation to the next and there will be no evolution
52
Assumptions for the Hardy-Weinberg Principle
No mutations, no migration, equal fertility of each phenotype, each phenotype is as preferable as each other, large population required
53
p^2
Frequency of homozygous dominant genotype in the population
54
2pq
Frequency of heterozygous genotype in the population
55
q^2
Frequency of homozygous recessive genotype in the population
56
Role of the Hardy-Weinberg Principle
To calculate allele frequencies in a population
57
Allele
A version of a gene with a unique base sequence
58
Recessive
An allele that won't be expressed in the phenotype if there are any dominant alleles present
59
Which type of variation has an additive effect?
Continuous
60
Factors that can affect the evolution of a species
Stabilising selection, directional selection, genetic drift, genetic bottleneck, founder effect
61
Stabilising selection
When the mean value is selected for and the extreme values are selected against
62
Effect of stabilising selection on the normal distribution curve
Gets narrower
63
Directional selection
When the organisms with extreme phenotypes are selected for as a result of a change in the environment
64
Example of directional selection
Peppered moths in the industrial revolution
65
Genetic drift
Changes in allele frequency due to the random nature of mutations
66
Which populations will genetic drift have a larger effect in?
Small populations
67
Why will genetic drift have a larger effect in small populations?
Smaller gene pool
68
Genetic bottleneck
A large decrease in population size that lasts for at least one generation
69
Founder effect
When a new colony is established by a few individuals, leading to the creation of a small population
70
What is the founder effect an example of?
Genetic drift
71
Types of speciation
Allopatric, sympatric
72
Allopatric speciation
When some members of a population are separated from the larger population by a physical barrier and are geographically isolated, leading to the evolution of a new species
73
How does allopatric speciation lead to the evolution of a new species?
Selection pressures different in different environments, different alleles considered advantageous, different alleles selected for
74
Example of allopatric speciation
Darwin's finches
75
Sympatric speciation
When organisms are isolated by reproductive mechanisms but live in the same habitat, leading to the evolution of a new species
76
Examples of mechanisms of reproductive isolation
Ecological isolation, behavioural isolation, mechanical isolation, gametic isolation, temporal isolation
77
Artificial selection
Organisms with alleles that are advantageous to the breeder are selected for so its frequency increases
78
Example of selective breeding in plants
Hybridising okra with hibiscus to confer resistance to yellow vein mosaic disease
79
Examples of selective breeding in animals
Belyaev's Foxes, breeding of dachshunds for small size and short legs so they could follow prey into burrows (I don't trust any dog whose stomach touches the floor)
80
Example of maintaining resources of genetic material
Seed banks
81
Importance of maintaining resources of genetic material
Used in selective breeding
82
Use of genetic resources from seed banks
Outbreeding to reduce the occurrence of homozygous recessive conditions due to inbreeding
83
Ethical considerations surrounding the use of artificial selection
Can lead to health problems and homozygous recessive conditions
84
Examples of health problems occurring as a result of the use of artificial selection
Big dogs have hip and heart problems, skull of the King Charles spaniel is too small to accommodate the brain
85
Heterozygous
2 different alleles at a gene locus
86
Genotype
Combination of alleles possessed by an organism
87
Sex linkage
When an allele can be found on the X chromosome but not on the Y chromosome

Biology: Module 6: Genetics, Evolution and Ecosystems (4 decks)

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