CBG12 Flashcards

1
Q

What is an autosome?

A

chromosome that is not a sex chromosome

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2
Q

what is hemizygous

A

A chromosome in a diploid organism is hemizygous when only one copy is present. Hemizygosity is also observed when one copy of a gene is deleted, or in the heterogametic sex when a gene is located on a sex chromosome.

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3
Q

What is a recessive lethal gene? give an example

A

can cause organism to die only when present in homozygous 1/4 of offspring die in hetergozygous cross eg. manx cat with no tail hetero= tailess homo = normal recessive = die in utero ratio 2:1 not 3:1

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4
Q

How many genotypes and phenotypes are there in human blood groups?

A

6 genotypes 4 phenotypes A B O AB complete and codominance occur

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5
Q

What is an example of incomplete/partial dominance

A

eg. sna drgaon homozygotes are red/white hetero= pink more red than white. red homo partially dominates looks like blending but not often due to haplo insufficiency - 1 copy of red allele not enough for phenotype

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6
Q

What is codominance give an example

A

2 alleles encode different gene products contributions of both alleles are visible in phenotype eg. 2 forms of glycoprotein (M or N) on RBC L^M or L^N alleles at locus chromosome 4 mating between heterozygotes gets 1:2 :1 ratio

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7
Q

What is an example of 2 genes effected a single trait? eg. dihybrid cross 9:3:3:1 phenotypes

A

can be seen in skin pigmentation in corn snakes 2- independent genes 4 phenotypes camoflage, orange, black, albino

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8
Q

What is epistasis?

A

effect of one gene being dependent on presence of another. epistatic gene interferes with phenotypic expression of other - hypostatic gene

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9
Q

What is dominant epistasis?

A

WwYy selfing leadings to mendalin genotype F2 ratio 9:3:3:1 and 12:3:1 phenotype eg. in fruit colour in summer squash presence of W/Y effects and W dom to Y epistatically.

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10
Q

What is polygenic inheritance/additive?

A

when phenotypic effects of alleles and poly genes are additive. eg. kernal colour in wheat 2 genes each with 2 alleles with additive gene action each A/B add oone unit of colour each a/b add 0 phenotypic sum of additive colour eg. AABB =4 darkest.

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11
Q

How many phenotypic classes would do polygenes give?

A

5 classes eg. AABB aaBB Aabb AaBb AABb more genes gives more classes giving continuous distribution

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12
Q

What is penetrance?

A

% of individual in population exhibiting phenotype associated with their allele

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13
Q

What is expressivity?

A

degree to which a given alle is expressed at the phenotypic level

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14
Q

What does variable pentetrance, expressivity and penetrance and expressivity look like?

A
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15
Q

What happens in autosomal recessive?

A

males and females equally effected

skips generation

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16
Q

What happens in autosomal dominant?

A

males and females equally effected

doesnt skip generatoon

afflicted offsping has afflicted parent

17
Q

What is the result of incomplete pentrance of an autosomal dominant trait?

A

expect to see phenotype in parent but dont as incomplete penetrance

eg. poluactyly - extra toe.

18
Q

Give an example of variable expressivity of an autosomal dominant trait?

A

eg. type 1 osteogenesis - brittle bone disease.

different levels of disease

19
Q

For a single gene what things can cause deviations from expected mendalian genetics?

A
  1. sex linkage
  2. incomplete dominance
  3. codominance
  4. multiple alleles
  5. lethal genes
  6. variable expressivity
  7. variable penetrance
20
Q

What is implicated when inheritance gives rise to phenotypic classes expressed in 1/16th?

what are deviations from this?

A

interaction of 2 genes.

deviations from this are epistasis and polygenic inheritance.