chapter 5 Flashcards

(46 cards)

1
Q

What determines the color of pepper?

A

The interaction of several genes

This illustrates the complexity of gene interactions in determining phenotypic traits.

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2
Q

What is gene discovery?

A

Studying a set of mutants for a trait that exhibits single-gene inheritance can identify genes involved in the trait’s development.

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3
Q

What are the key questions regarding gene interactions?

A
  • How do the alleles for a gene interact?
  • What are multigene pathways?
  • How do separate genes interact in these pathways?
  • What is the genetic test for gene interaction?
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4
Q

What is an allelic series?

A

A collection of genetic mutations for a particular gene.

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5
Q

Define complete dominance.

A

A condition where homozygous dominant (A/A) cannot be distinguished from heterozygotes (A/a).

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6
Q

What is an example of complete dominance?

A

PKU disease, where one good allele is haplosufficient.

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7
Q

What does haplosufficient mean?

A

One good allele is sufficient for normal function.

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8
Q

What is an example of a mutation that is recessive?

A

Achondroplasia, where a single wild type FGFR3 allele is haploinsufficient.

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9
Q

Define null allele.

A

An allele that produces a non-functional protein.

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10
Q

What is the dominant negative effect?

A

A situation where one bad allele interferes with the activity of the other wild type allele.

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11
Q

What is incomplete dominance?

A

A condition where an intermediate phenotype is observed in the heterozygote.

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12
Q

Provide an example of incomplete dominance.

A

Flower petal phenotype in four-o’clocks, resulting in pink flowers (c+/c).

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13
Q

Define codominance.

A

A condition where the heterozygote expresses both allele phenotypes.

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14
Q

What determines human ABO blood groups?

A

Three alleles for the same gene: I^A, I^B, and i.

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15
Q

What are recessive lethal alleles?

A

Alleles that cause an organism to die prematurely.

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16
Q

What is a pleiotropic gene?

A

A gene that contributes to several traits of an organism.

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17
Q

What is the one-gene-one-enzyme hypothesis?

A

A hypothesis proposed by Beadle and Tatum stating that each gene encodes a single enzyme.

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18
Q

What is the purpose of a complementation test?

A

To determine whether mutations are in separate genes.

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19
Q

What does it mean if two mutations complement each other?

A

The mutations are in different genes.

20
Q

What is gene interaction?

A

When the phenotype of a double mutant is different from the sum of the two individual phenotypes.

21
Q

What is epistasis?

A

Gene interaction where the double mutant has the same phenotype as one of the single mutants.

22
Q

What phenotypic ratio suggests no gene interaction?

A

9:3:3:1 ratio.

23
Q

What does a 9:7 phenotypic ratio indicate?

A

The double mutant has the same phenotype as the two single mutants, suggesting they control different steps in the same pathway.

24
Q

What is a heterokaryon?

A

A fungal cell with two or more genetically different nuclei sharing the same cytoplasm.

25
What happens when two independently derived recessive mutant alleles fail to complement?
They must be alleles of the same gene.
26
What is the genotype ratio for recessive epistasis?
9:3:4 ## Footnote This ratio indicates the interaction between two genes where one gene masks the expression of another.
27
Define epistasis.
Gene interaction where the double mutant has the same phenotype as one of the single mutants.
28
What is the term for the overriding mutant in epistasis?
Epistatic
29
What is the term for the overridden mutant in epistasis?
Hypostatic
30
What color is represented by the B/B or B/b genotype in fur color?
Black
31
What color is represented by the b/b genotype in fur color?
Brown
32
In the context of fur color, which allele is epistatic to the B and b alleles?
e
33
What is the phenotype ratio for dominant epistasis due to a white mutation in Foxgloves?
12:3:1
34
What does a suppressor mutation do?
Reverses the effect of a mutation in a second gene.
35
What is a modifier in genetics?
A type of mutation/allele at a second locus that changes the degree that a mutant phenotype is expressed.
36
What is synthetic lethality?
When two individually viable single mutants are intercrossed, resulting in lethal double mutants.
37
Define penetrance.
The proportion of individuals in a population who carry a specific gene and express the related trait.
38
What is complete penetrance?
When all individuals with a mutant genotype have the mutant phenotype.
39
List three causes of incomplete penetrance.
* Influence of the environment * Influence of other genes * Subtle mutant phenotype
40
What is expressivity?
A measure of the degree to which a given allele is manifested at the phenotypic level.
41
What factors influence expressivity?
* Influence of the environment * Influence of other genes
42
True or False: Variable expressivity means individuals with the same genotype can show different degrees of the same phenotype.
True
43
What genetic condition is associated with a dominant mutation in COL1A1 or COL1A2?
Osteogenesis imperfecta (OI)
44
Fill in the blank: The majority of people with Osteogenesis imperfecta have a dominant mutation in one of the two genes that produce type 1 collagen, __________ or __________.
COL1A1, COL1A2
45
What syndrome is caused by a mutation in the FBN1 gene?
Marfan Syndrome
46
List three symptoms of Marfan Syndrome.
* Tall and slender build * Disproportionately long limbs * Heart murmur