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Biology A2 Rafa > 6.2 Patterns of Inheritance > Flashcards

6.2 Patterns of Inheritance Flashcards

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1
Q

Define genotype

A

genetic makeup of an organism

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2
Q

Define phenotype

A

visible characteristics of an organism

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3
Q

What contributes to phenotypic variation?

A

Environmental and genetic factors

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4
Q

Environmental examples of factors affecting phenotypic variation

A

diet in animals and etiolation or chlorosis in plants

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5
Q

What is etiolation?

A

When plants grow in places with insufficient light

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6
Q

What is chlorosis?

A

Where leaves produce insufficient chlorophyll due to dim light or soil with insufficient magnesium

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7
Q

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

A
  • Meiosis- allele shuffling in prophase 1
  • independant assortment of chromosomes in meta/anaphase 1
  • independent assortment of chromatids in meta/anaphase 2
  • Random fusion of gametes - any can combine
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8
Q

What is monogenetic inheritance?

A

the inheritance of a characteristic controlled by a single gene

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9
Q

Define allele

A

Version of a gene

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10
Q

Define heterozygous

A

not true-breeding; having different alleles at a particular gene locus on a pair of homologous chromosomes

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11
Q

Define homozygous

A

true-breeding; having identical alleles at a particular gene locus on a pair of homologous chromosomes

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12
Q

Define dihybrid

A

involving two gene loci

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13
Q

What is independent assortment?

A

the alleles of two or more different genes get sorted into gametes independently of one another

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14
Q

What happens when two heterozygous dihybrids are crossed?

A

You get a 9:3:3:1 ratio.

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15
Q

Define codominance

A

where both alleles present in the genotype of a heterozygous individual contribute to the individuals phenotype

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16
Q

Define multiple alleles

A

characteristic for which there are three of more alleles in the populations gene pool

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17
Q

Define sex-linked

A

gene present on (one of) the sex chromosomes

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18
Q

What are autosomes?

A

All chromosomes apart from sex chromosomes

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19
Q

What is specific about autosomal pairs?

A

they are all completely homologous

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20
Q

Why are sex chromosomes not fully homologous?

A

XX and XY are different

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21
Q

Examples of sex-linked characteristics

A

colour blindness and haemophilia A

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22
Q

What is autosomal linkage?

A

gene loci present on the same autosome that are often inherited together

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23
Q

Why are linked genes likely to be passed on together?

A

Because their loci are close together on the chromosome

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24
Q

Examples of genetic factors that affect variation

A
  • gene mutations
  • chromosome mutations
  • sexual reproduction
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25
Q

Examples of how gene mutations lead to variation

A
  • Physical agents (x-rays, gamma, UV)
  • Chemical agents (benzopyrene, mustard gas, nitrous acid, aromatic amines)
  • Biological agents (some viruses, trasponsons, food contaminants such as mycotoxins, alcohol)
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26
Q

What are transposons?

A

‘jumping genes’

remnants of viral nucleic acid that have been incorporated into our genomes

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27
Q

Examples of chromosome mutations

A
  • deletion
  • inversion
  • translocation (one piece of chromosome breaks off and attaches to another part)
  • duplication
  • non-disjunction (one pair of chromosomes fails to separate, leaving one gamete with an extra chromosome)
  • aneuploidy
  • polyploidy
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28
Q

Describe aneuploidy

A

chromosome number is not exact multiple of haploid number

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29
Q

Describe polyploidy

A

where you have an extra set of chromosomes

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30
Q

What is monogenic?

A

determined by a single gene

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31
Q

Why did Mendel use pea plants?

A
  • easy to grow

- can be cross fertilised

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32
Q

What is a test cross?

A

You test the plants that youve been given with a known strain

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33
Q

Define dihybrid

A

involving two gene loci

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34
Q

Ratio dihybrid unlinked

A

9:3:3:1

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35
Q

What do we assume in dihybrid inheritance?

A
  • genes on separate chromosomes

- genes inherited independently

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36
Q

What are males for X linked genes?

A

hemizygous

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37
Q

What is X inactivation

A

mechanism that prevents expression of twice the number of X-linked genes than males

  • in every female cell nucleus, one X chromosome inactivated
  • X chromosome which is inactivated is chosen at random
38
Q

Why are only female cats tortoiseshell?

A

-inactivation of X chromosomes so random between orange and black pigment expression

39
Q

Ratio of autosomally linked genes with no crossing over

A

3:1

40
Q

If the gene loci are further apart on the chromosome, does it increase or decrease the chance of recombinant alleles forming?

A

There is a greater chance of recombinant alleles forming when they are further apart on a chromosome

41
Q

Define epistasis

A

interaction of non-linked gene loci where one masks the expression of the other

42
Q

If alleles at the first locus are epistatic to those at the second locus, what are those at the second locus to those at the first?

A

hypostatic

43
Q

Describe recessive epistasis

A

the homozygous presence of a recessive allele prevents the expression of another allele at the second locus

44
Q

Do genes have to be linked or non-linked for recessive epistasis?

A

Non-linked, found on two different chromosomes

45
Q

Example of recessive epistasis

A

Colour of salvia flower

46
Q

Example of dominant epistasis

A

feather colour in chickens

47
Q

Ratio of dominant epistasis

A

13: 3
12: 3:1

48
Q

Ratio of recessive epistasis

A

9:3:4

49
Q

Example of complementary genes

A

Coat colour in mice

50
Q

Define crossing over

A

the reciprocal exchange of parts of chromatids between homologous chromosomes

51
Q

If you see a pathway, what is it likely to be?

A

epistasis

52
Q

If you see alleles of genes written with superscript, what is it most likely to be?

A

codominance

53
Q

What ratio indicates complementary gene action?

A

9: 7
9: 3:4
9: 3:3:1

54
Q

What is the chi squared test?

A

statistical test designed to find out if the difference between observed and expected data is significant or due to chance

55
Q

Null hypothesis for chi squared test

A

There is no statistically significant difference between the observed and expected data. Any difference is due to chance

56
Q

When can we use chi squared?

A
  • data are in categories and are not continuous
  • strong biological theory to predict expected values
  • large sample size
  • data are in raw counts (cant be ratios/ percentages)
  • no zero scores in raw count data
57
Q

What happens when the chi squared value is less than the critical value?

A

difference is due to chance
not significant
accept null hypothesis

58
Q

What happens when the chi squared value is more than the critical value?

A

the difference is statistically significant

we reject the null hypothesis

59
Q

What is continuous variation?

A

variation that produces phenotypic variation where the quantitative traits vary by very small amounts between one group and the next

60
Q

What is discontinuous variation?

A

genetic variation producing discrete phenotypes - two or more non-overlapping categories

61
Q

What are characteristics that exhibit discontinuous variation controlled by?

A

alleles of a single gene locus

monogenic

62
Q

What is continuous variation determined by?

A

polygenic, many genes

63
Q

What happens to the range of characteristics when you increase the number of gene loci in continuous variation?

A

greater range of characteristics

64
Q

What happens when discontinuous variation is not monogenic?

A

different loci have large and DIFFERING effects on phenotype

65
Q

What is directional selection?

A

type of natural selection that occurs when an environmental change favours a new phenotype and so results in a change in the population mean

66
Q

What is the founder effect?

A

when a small sample of an original population establishes in a new area; its gene pool is not as diverse as that of the parent population

67
Q

What is a genetic bottleneck?

A

a sharp reduction in size of a population due to environmental catastrophes such as earthquakes, floods, disease or human activities such as habitat destruction, overhunting or genocide, which reduces genetic diversity. As the population expands it is less genetically diverse than before.

68
Q

What is stabilising selection?

A
  • natural selection leading to constancy withing a population
  • intermediate phenotypes are favoured and extreme selected against
  • reduces genetic variation
69
Q

Three types of selection

A
  • stabilising
  • directional
  • destructive
70
Q

Example of stabilising selection

A

Birth mass of babies

71
Q

When does genetic drift arise?

A

after a genetic bottleneck or as a result of the founder effect

72
Q

Define population

A

members of a species, living in the same place and at the same time, that can interbreed

73
Q

Factors affecting allele frequencies within populations

A
  • population size
  • mutation rate
  • migration
  • natural selection
  • changes to environment
  • isolation
  • non-random mating
  • genetic drift
  • gene flow
74
Q

What does the Hardy Weinberg principle assume?

A
  • population large enough to make sampling error negligible
  • mating is random
  • no selective advantages
  • no mutation, migration or genetic drift
75
Q

What is p in Hardy-Weinberg?

A

frequency of dominant allele

76
Q

What is q in Hardy-Weinberg?

A

frequency of recessive allele

77
Q

Define allopatric speciation

A

formation of two different species from one original species, due to geographical isolation

78
Q

Define sympatric speciation

A

formation of two different species from one original species, due to reproductive isolation, while the populations inhabit the same geographical location

79
Q

Define speciation

A

the splitting of a genetically similar population into two or more populations that undergo genetic differentiation and eventually reproductive isolation, leading to the evolution of two or more species

80
Q

What are the two types of isolating mechanism?

A

geographical and reproductive

81
Q

What leads to reproductive isolation?

A

biological and behavioural changes

82
Q

Examples of biological changes that can lead to isolation

A

MUTATION=
-changing foraging behaviour or enabling to exploit new niche (diurnal cannot breed with nocturnal)
CHANGE IN CHROMOSOME NUMBER =
-prevent gamete fusion
-make zygotes less viable
-infertile hybrid offspring
-CHANGES IN ANIMAL GENITALIA/ PLANT FLOWER STRUCTURE

83
Q

Examples of behavioural changes that lead to isolation

A

change in courtship behaviour

84
Q

What is artificial selection?

A

selective breeding of organisms: involves humans choosing the desired phenotypes and interbreeding those phenotypes individually, therefore selecting the genotypes that contribute to the gene pool of the next generation of these organisms

85
Q

Examples of animals being artificially selected

A
  • cattle (milk, meat, leather)
  • sheep and goats (wool and meat)
  • horses (transport, racing military)
  • pigs (meat)
  • pigeons (flight capacity, plumage)
  • poultry
  • dogs
  • cat
86
Q

Examples of plants being artificially selected

A

cereal (wheat, barley, maize,millet), rice, fruit and veg

87
Q

What are plants artificially selected for?

A 
yield
short maturation time
pest resistance
infection
frost 
drought
flooding and wind
improved flavour
88
Q

What inbreeding depression?

A

if related individuals are crossed

increased chance of inheriting harmful allele

89
Q

What is hybrid vigour?

A

two individuals of different varieties crossed

individuals are heterozygous at many different gene loci

90
Q

How can breeders increase hybrid vigour?

A

outcross cultivated varieties with varieties like their WILD ancestors

91
Q

Ethical considerations of artificial selection

A
  • domesticated animals retain juvenile characteristics so they cant defend themselves and become easy prey
  • livestock have more meat and less fat = victims of low temp in winter

Biology A2 Rafa (14 decks)

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