6.2 - Patterns of inheritance Flashcards

1
Q

what are some examples of continuous variation?

A

height
waist circumference
fur length

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2
Q

what are some examples of discontinuous variation?

A

blood group
violet flower colour

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3
Q

what causes genetic variation in meiosis?

A

crossing-over of alleles, independent assortment of chromosome
random fusion of gametes in fertilization

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4
Q

what are inherited characteristics that are continuous usually known as?

A

polygenic - e.g skin colour

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5
Q

what are inherited characteristics that are discontinuous usually known as?

A

monogenic e.g flower colour

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6
Q

Define a homozygote

A

An organism that carries 2 of the same allele

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7
Q

Define a heterozygote

A

An organism that carries 2 different alleles

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8
Q

Define the locus

A

The fixed position of a gene on a chromosome. Alleles of a gene are found at the same locus on each chromosome in a pair

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9
Q

what phenotypic ratio can be expected from a dihybrid cross of two heterozygous?

A

9 : 3 : 3 : 1
all dom: 1st Dom 2nd rec: 1st rec 2nd dom: all rec

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10
Q

what is the phenotypic ratio for a codominant heterozygous cross?

A

1 : 2 : 1
homozygous A : heterozygous AB : homozygous B

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11
Q

what is an autosome?

A

any chromosome that isn’t a sex chromosome

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12
Q

why are genes on the same autosome said to be linked?

A

won’t be affected by independent assortment, only crossing over

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13
Q

what are the mutagenic agents?

A

Physical (xrays uv light)
Chemical (mustard gas nitrous acid)
Biological (transposons food virus)

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14
Q

what are the types of chromosme mutation?

A
  • deletion (lost)
  • inversion (180 flip)
  • translocation (other chromosome)
  • duplication
  • non disjunction (down syndrome extra chromosome)
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15
Q

what is aneuploidy?

A

chromosome number is not an exact multiple of the haploid (some chromosomes fail to separate during meiosis)

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16
Q

what is polyploidy?

A

diploid fertilised by a haploid will result in triploid
two diploids make a tetraploid

17
Q

when does genetic variation occur?

A

prophase 1 - crossing over
Anaphase 1 + 2 - independent assortment

18
Q

how do you test for phenotypically similar individiuals?

A

do a test cross

19
Q

what is a dihybrid cross?

A

simultaneous inheritance of two characteristics

20
Q

what gene has multiple alleles?

A

human blood groups
also codominant

21
Q

what is an example of a sex linked disease?

A

colour blind
Haemophilia A

22
Q

what is the example of colour sex linkage in cats?

A

Xco and Xcb make a tortoishell which males cannot be because it is X chromosome expression

23
Q

what is autosomal linkage?

A

gene loci present on the same autosome (non-sex chromosome) that are often inherited together

24
Q

what is epistasis?

A

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

25
what are the factors affecting evolution of a species?
natural selection stabilising selection - environment unchanged directional selection - environment change genetic drift genetic bottleneck - reduced diversity from decrease to increase founder effect - descends from small no. ancestors
26
what are organisms adaptaitons?
anatomical behavioural physiological
27
what is allopatric speciation?
physical barrier
28
what is sympatric speciation?
single ancestral species in the same region, but due to chromosomal error which leads to reproductive isolation
29