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Module 6 > Patterns of inheritance and variation > Flashcards

Patterns of inheritance and variation Flashcards

1
Q

What do plants with pale or yellow leaves have?

A

Chlorosis

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2
Q

Why do plants have chlorosis?

A

Cells don’t produce normal amounts of chlorophyll

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3
Q

What is a result of chlorosis?

A

Reduces ability to make food by photosynthesis.

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4
Q

What factors affect whether a pant has chlorosis?

A

Environmental

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5
Q

What environmental factors cause chlorosis?

A
  • Lack of light
  • Mineral deficiencies
  • Virus infections
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6
Q

How does both genetic and environmental factors affect leaves?

A

Genetic factors code for green leaves and environment results in final leaf appearance.

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7
Q

What is an organisms body mass determined by?

A

Genetic and environmental factors.

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8
Q

Define genotype.

A

Genetic make up of an organism.

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9
Q

Define phenotype.

A

Observable characteristics of an organism.

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10
Q

What are the actual characteristics that an organism displays influenced by?

A

The environment

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11
Q

For most genes in your body … alleles are inherited.

A

Two

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12
Q

What are modifications?

A

Changes made to a phenotype by the environment which are not inherited.

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13
Q

What is a dominant allele?

A

Version of the gene that will always be expressed if present in the organism.

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14
Q

What is a recessive allele?

A

Only be expressed if 2 copies of this allele are present in an organism.

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15
Q

Define homozygous.

A

Two identical alleles for a characteristic.

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16
Q

Define heterozygous.

A

Two different alleles for a characteristic.

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17
Q

Define continuous variation.

A

Characteristic can take any value within a range.

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18
Q

What causes continuous variation?

A

Genetic and environmental.

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19
Q

What genes control continuous variation?

A

Polygenes

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20
Q

What are polygenes?

A

A number of genes.

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21
Q

Give an example of continuous variation.

A

Mass

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22
Q

Define discontinuous variation.

A

Characteristic can only appear in specific values.

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23
Q

What causes discontinuous variation?

A

Genetic (mostly)

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24
Q

What genes control discontinuous variation?

A

One or two genes

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25
Q

Give an example of discontinuous variation.

A

Blood group, round and wrinkled pea shape

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26
Q

What is speciation?

A

Formation of a new species as a result of evolution.

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27
Q

Define species.

A

Members of species will be able to interbreed to give fertile offspring.

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28
Q

What can lead to speciation?

A

Alleles can undergo random mutations.

Members of a population can become isolated.

Accumulation of mutations and changes in allele frequencies over many generations eventually lead to large changes in phenotype.

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29
Q

What is allopatric speciation?

A

Members are separated from each other by a physical barrier.

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30
Q

Explain allopatric speciation.

A

Environments differ in the different areas, so different selection pressures. So different physical features are benefical and so are passed on to their offspring.

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31
Q

How can allopatric speciation lead to the founder effect?

A

If a small population is separated.

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32
Q

What is sympatric speciation?

A

Occurs when members of two different species interbreed and form fertile offspring. New offspring will have different number of chromosomes. This stops gene flow.

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33
Q

Give an example of sympatric speciation.

A

Fungus farming ants

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34
Q

Give an example of allopatric speciation.

A

Galapagos islands

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35
Q

What are the results of prezygotic fertilisation barriers?

A

Prevent fertilisation and the formation of a zygote.

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36
Q

What are postzygotic reproductive barriers?

A

Reduce viability or reproductive potential of offspring.

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37
Q

Define polymorphic.

A

Display more than one distinct phenotype.

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38
Q

Define wild type allele.

A

Allele coding for the most common characteristic.

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39
Q

What is artificial selection/ selective breeding?

A

The selection for breeding of plants or animals with desirable characteristics by farmers or breeders.

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40
Q

What is inbreeding?

A

Breeding of closely related individuals.

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41
Q

What are the problems of inbreeding?

A

Limits the gene pool and so decreasing genetic diversity reduces the chances of a population of inbred organisms evolving and adapting to changes in their environment.

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42
Q

What are seed banks?

A

Keep seeds of wild type and domestic varieties. An important genetic resource.

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43
Q

What are gene banks?

A

Store biological samples. Usually frozen.

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44
Q

What do gene banks store?

A

Sperm, eggs

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45
Q

What are alleles from gene banks used for?

A

Increase genetic diversity in a process called outbreeding.

46
Q

What is outbreeding?

A

Breeding unrelated or distantly related varieties.

47
Q

What are the results of outbreeding?

A

Reduces occurrence pf homozygous recessives and increases the potential to adapt to environmental change.

48
Q

What does the Hardy-Weinberg principle state?

A

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.

49
Q

What are the two equations used in the Hardy-Weinburg principle?

A

p^2 + q^2 = 1

p + q = 1

50
Q

What is p^2?

A

Frequency of homozygous dominant genotype in the population.

51
Q

What is q^2?

A

Frequency of homozygous recessive genotype in the population.

52
Q

What is 2pq?

A

Frequency of heterozygous genotype in the population.

53
Q

What is the allele frequency?

A

Frequency of a particular allele in a population.

54
Q

What is the gene pool?

A

Total sum of all the genes in a population at any given time.

55
Q

What does the Hardy-Weinberg principle assume?

A

Population of diploid organisms is large, isolated, no mutations, no selection pressures.

56
Q

What will upsetting the equilibrium of an environment result in?

A

Evolution

57
Q

What factors lead to changes in allele frequencies and so affect the rate of evolution?

A
  • Mutations lead to new alleles which give genetic variation.
  • Gene flow changes the allele frequency within a population.
  • Genetic drift. Change in allele frequency due to random mutations.
  • Natural selection leads to an increase in individuals with characteristics which improve their chances of survival.
  • Sexual selection leads to an increase in frequency of alleles which code for characteristics which improve mating success.
58
Q

What is gene flow?

A

Movement of alleles between populations.

59
Q

What sort of populations does genetic drift occur in?

A

Small

60
Q

Give two types of limiting factors which affects the size of a population.

A

1) Density-dependent factors

2) Density-independent factors

61
Q

What are density-dependent factors?

A

Dependent on population size.

62
Q

What do density-dependent factors include?

A

Competition, predation, communicable disease.

63
Q

What are density-independent factors?

A

Affect populations of all sizes.

64
Q

What do density-independent factors include?

A

Climate change, natural disasters, human activities.

65
Q

What is monogenic inheritance?

A

Inheritance of a single gene

66
Q

What is codominance?

A

Two different alleles occur for a gene, which are both equally dominant. Both alleles expressed in phenotype.

67
Q

Why for codominance are an upper case and lower case letter not used, what is used instead?

A

Upper and lower implies one is dominant over the other, instead a letter is chosen and then a superscript.

68
Q

What are multiple alleles?

A

When genes have more than two alleles.

69
Q

For multiple alleles, why can only two alleles be present in an individual?

A

Organisms only carry two versions of a gene.

70
Q

What is the 23rd pair of chromosomes known as?

A

Sex chromosomes

71
Q

What is larger, the X or the Y chromosome?

A

X- contains many genes not involved in sexual development.

72
Q

What are sex linked genes?

A

Genes carried on the sex chromosomes.

73
Q

What does it mean that the X is larger than the Y chromosome?

A

There are a number of genes on the X chromosome that males only have one copy of.

74
Q

What is the result of males only having one copy of some genes?

A

Any characteristic caused by a recessive allele on the section of the X chromosome, which is missing in the Y chromosome, is more frequent in males.

75
Q

Give an example of a sex-linked disorder.

A

Haemophilia

76
Q

What happens in people with haemophilia?

A

Blood clots slowly.

77
Q

Who are more at risk of getting haemophilia?

A

Males

78
Q

Why are males more likely to get haemophilia?

A

If a male inherits the recessive allele on their X chromosome, they cannot have a corresponding dominant allele on their Y chromosome, and so develop the condition.

79
Q

What does a dihybrid cross show?

A

Inheritance of two different characteristics, caused by two genes, which may be located on different pairs of homologous chromosomes.

80
Q

Why can the actual ratio of offspring produced differ from the expected?

A
  • Fertilisation of gametes is a random process.

- Genes are linked so, if no crossing over occurs the alleles will be inherited together.

81
Q

What are linked chromosomes?

A

Linked

82
Q

What are recombinant offspring?

A

Different combinations of alleles than either parent.

83
Q

How are genes less likely to separated during crossing over?

A

If they are close to each other om the chromosome.

84
Q

How are lined genes inherited?

A

As one unit.

85
Q

What is autosomal linkage?

A

When genes that are linked are found on one of the other pairs of chromosomes.

86
Q

Why are the ratios observed in dihybrid crosses significantly different from those expected?

A

Due to linkage

87
Q

What does a recombinant frequency of 50% indicate?

A

There is no linkage and genes are on separate chromosomes.

88
Q

What does a recombinant frequency of less than 50% indicate?

A

Genes are linked.

89
Q

As the degree of crossing over reduces, the recombinant frequency gets…

A

…smaller.

90
Q

What does the degree of crossing over determined by?

A

How close the genes are on the chromosome.

91
Q

What is the null hypothesis?

A

There is no significant difference between what we expect and what we observe.

92
Q

What does it mean if the chi squared value is less than the critical value?

A

No significant difference

93
Q

What does it mean if the chi squared value is greater than the critical value?

A

Significant difference.

94
Q

If the chi squared value is less than the critical value do we accept or reject the null hypothesis?

A

Accept

95
Q

If the chi squared value is more than the critical value do we accept or reject the null hypothesis?

A

Reject

96
Q

What is epistasis?

A

Interaction of genes at different loci.

97
Q

What is a hypostatic gene?

A

A gene affected by another gene.

98
Q

What is a epistatic gene?

A

A gene that affects the expression of another gene.

99
Q

What are population bottlenecks?

A

Large reductions in population size.

100
Q

What is a positive of genetic bottleneck?

A

Beneficial mutation will have a much greater impact and lead to quicker development of a new species.

101
Q

What is the founder effect?

A

Smaller populations arise due to the establishment of new colonies by few isolated individuals.

102
Q

What is the founder effect an extreme example of?

A

Genetic drift.

103
Q

How does the founder effect work?

A

New populations have a much smaller gene pool and display less genetic variation.

104
Q

What is stabilising selection?

A

Norm is selected for and extremes are selected against.

105
Q

What is a result of stabilising selection?

A

Reduction in frequency of alleles at the extremes and increase in frequency of average alleles.

106
Q

What is directional selection?

A

Occurs when there is a change in the environment and the normal phenotype is no longer the most advantageous.

107
Q

Where does the allele frequency shift towards in directional selection?

A

Towards extreme phenotypes.

108
Q

What is an example of stabilising selection?

A

Birth weight of babies

109
Q

What is an example of direction selection?

A

Peppered moths during the industrial revolution.

110
Q

What is an example of disruptive selection?

A

Finches observed by Darwin in the Galapagos

111
Q

What is disruptive selection?

A

Extremes are selected for and norm is selected against.

Module 6 (3 decks)

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