Genetics and Evolution-Gene Interactions

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  • Created by: jessica
  • Created on: 06-02-13 13:33
What are the different interactions between alleles within a single gene?
Complete, incomplete/partial and co dominance.
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What is epistasis?
Interactions between genes
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What is penetrance and expressivity?
Interactions between genes and the environment.
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What is complete dominance?
This is the base default Mendelan setting. In heterozygotes the F1 generation will all be one characteristic or the other.
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What is incomplete dominance?
When the alleles are not completely dominant over the other.
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How is incomplete dominance presented in the phenotype?
The heterozygous phenotype is intermediate to the two parent phenotypes, which are homozygous.
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What is the F2 ratio incomplete dominance?
1:2:1
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How is co dominance displayed in the phenotype?
The heterozygote displays the phenotype of both homozygotes.
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Give an example of co dominance?
ABO blood groups are specified by 3 alleles, giving rise to 4 blood types.
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Where are the genes for blood type located?
Chromosome 9
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What does Ia produce?
A antigen on the red blood cells.
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What does Ib produce?
B antigen on the red blood cells.
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What does Io produce?
No antigen as it is defective.
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How do Ia, Ib and Io interact to create the different blood types?
Ia and Ib are co-dominant, meaning that the red blood cells will have both A and B antigens present on the membrane surface. Ia and Ib are completely dominant to Io.
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How does epistasis arise?
The phenotypic effects arise when 2 or more genes interact and the genes are no longer independent of each other. One gene masks the expression of the other gene.
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How does epistasis change the F2 phenotypic ratios?
there will always be less than four phenotypes.Particular kinds of epistasis can produce 9 different F2 phenotypic ratios
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How can phenotype be modified?
Action of other genes (genetic background), Sensitivity to the environment (genotype-environment interaction)
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What is penetrance?
the proportion of individuals carrying a particular allele that expresses the associated phenotype.For normal Mendelan genes the alleles must be fully penetrative.
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What is expressivity?
Measures the extent to which a genotype exhibits its phenotype, i.e. the intensity of the phenotype. The genotype is reacting/interacting with environmental circumstances.
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What is haploinsufficiency?
When the allele dose does not reach normal levels of function and therefore generates a dominant mutation.
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When does a dominant negative mutation occur?
When a spoiler protein binds to the wild type polypeptide, distorting it.
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What does a 12:3:1 ratio show?
Dominant epistasis
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What does a 9:3:4 ratio in F2 show?
Epistasis
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When is incomplete penetrance seen in a human pedigree?
When a dominantly inherited phenotype disappears in the second generation, but appears in the next.
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Other cards in this set

Card 2

Front

What is epistasis?

Back

Interactions between genes

Card 3

Front

What is penetrance and expressivity?

Back

Preview of the front of card 3

Card 4

Front

What is complete dominance?

Back

Preview of the front of card 4

Card 5

Front

What is incomplete dominance?

Back

Preview of the front of card 5
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