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Genetics Class > Exam 2 > Flashcards

Exam 2 Flashcards

(54 cards)

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1
Q

What is incomplete dominance

A

Only one allele is expressed; the other allele is nonfunctional, such as creating a pink flower from red and while

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2
Q

What is codominance?

A

Both alleles are expressed such as blood types

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3
Q

What is penetrance?

A

The percentage of individuals having a particular genotype that express the expected phenotype

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4
Q

What is expressivity

A

The degree to which a character is expressed

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5
Q

What is a lethal allele?

A

Causes death at an early stage of development, and so some genotypes may not appear among the progeny

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6
Q

What is epistasis?

A

One gene masks the effect of the other gene

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7
Q

What is the masking gene and the masked gene called for epistasis

A

Epistatic gene: gene that does the masking

Hypostatic gene: gene whose effect is being masked

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8
Q

What is recessive epistasis?

A

Epistatic gene is recessive (only masks when there are two copies of the epistatic allele)

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9
Q

What is dominant epistasis?

A

Only a single copy of the epistatic allele is required to mask the phenotype of the hypostatic gene

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10
Q

What is duplicate recessive epistasis?

A

Two recessive alleles at either of two loci are capable of suppressing a phenotype

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11
Q

What is complementation

A

Test that determines whether mutations are at the same locus or at different loci

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12
Q

What are sex influenced characteristics?

A

Autosomal genes that are expressed differently in males vs female
- higher penetrance in one of the sexes

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13
Q

What are sex-limited characteristics

A

Autosomal gene only expressed in one sex

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14
Q

What is cytoplasmic inheritance

A

Usually one gamete (egg) contributes all the cytoplasm to progeny. Can lead to phenotypic variation since no mechanisms ensure mitochondria are evenly distributed

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15
Q

What is LHON?

A

Leber Hereditary Optic Neuropathy

  • Mitochondrially inherited
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16
Q

What is the pedigree for mitochondrial disease?

A

The mother infects all children, but the father doesn’t infect anyone

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17
Q

What are maternal effect genes

A

Phenotype of the offspring is determined by the genotype of the mother

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18
Q

What are temperature sensitive alleles

A

An allele whose product is functional only at certain temperatures

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19
Q

What is continuous characteristics ?

A

Exhibit continuous distribution of phenotypes, the phenotype is usually determined by interaction between many genes

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20
Q

What is pleiotropy

A

One gene affects multiple characteristics.

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21
Q

How do I determine the frequency of one allele?

A
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22
Q

What is the allele frequency for XA and Xa

23
Q

What are the Hardy-Weinberg law assumptions

Study These Flashcards
A
  1. Infinity large population
  2. Mating is random
  3. No natural selection
  4. No mutations
  5. No migration
24
Q

What are effect of non random mating

Study These Flashcards
A

positive assortative mating

negative assortative mating

25
What is positive assortative mating
Mating with someone who is phenotypically similar Reduces frequency of heterozygotes
26
What is negative assortative mating
Mate with someone who is phenotypically dissimilar Increases frequency of heterozygotes
27
What is inbreeding
Mating with an indiviudal who is genetically related
28
What is outcrossing?
Avoidance of mating with a genetically related individual
29
What is allele by the same descent
Two copies of the allele are descended from the same copy in a common ancestor, so they are identical by descent (inbreeding)
30
What is alleles are identical by state
Two copies of the A allele are the alike in structure and function but are descended from two different copies in different ancestors
31
What is the inbreeding coefficient
A measure of the probability that two alleles are identical by descent - ranges from 0 to 1 - 0 is random mating - 1 is identical descent
32
How does the proportion of homo and heterozygosity change with inbreeding
33
What is inbreeding depression?
Increase of lethal and deleterious traits caused by inbreeding
34
What is genetic drift?
Change in allele frequency due to sampling error
35
What are the causes of genetic drift
1. SAmpling error in small populations: only few gametes are used for reproduction. Can skew data 2. Founder effect: establishment of a population by a small number of individuals 3. Bottleneck: occurs when most of the population is destroyed
36
How is fitness calculated
To calculate fitness for each genotype, we take the mean number of offspring produced by a genotype and divide it by the mean number of offspring produced by the most prolific genotype
37
What is genetic recombination?
The sorting of alleles into new combinations
38
What are linkage group
Genes that are close together on a chromosome and often get inherited together. Genes that are farther apart are more likely to recombine due to crossing over.
39
What is complete linkage
Genes on the same chromosome that are so close that there is no crossing over between the two genes
40
What is incomplete linkage
Genes on the same chromosome that are far enough away that crossing over can happen between the two genes
41
What is coupling conformation
Where a wild type allele is found on one chromosome and mutant alleles are found on the other chromosome
42
What is the repulsion conformation
Each chromosome contains one wild type and one mutant allele
43
How do you determine if its coupling or repulsion?
You have to look at the nonrecombinants progeny, which is the highest number progeny. Look at their genotype
44
Who confirmed the chromosomal theory of inheritance
Barbara McClintock using maize
45
What are Genetic maps
based on recombination frequencies between different gnee on a chromosome
46
What are physical gene maps
Does not reply on recombination frequencies. Often correlation between phenotype and a chromosomal landmark (deletion)
47
If a linkage group's recombination frequency is greater than 50% what does that mean?
They belong to different linkage groups either on different chromosomes or far apart on the same chromosome
48
What are the 3 point testcross?
1. Single crossover 2. Single crossover 3. Double crossover (creates the least progeny)
49
How do we determine how many classes of progeny are possible
2^n | n = number of genes
50
How do you determine gene order?
1. Identify the recombinant progeny 2. Identify the double crossover progeny 3. Compare the two, they should be different in one 4. The one that differs is the middle
51
How do you determine map distance
After determining the gene order, find the progeny that are recombinant for the first segment and divide by the total progeny, then do it for the second segment.
52
What is interference
One crossover physically interferes with the formation of a second crossover Interference = 1 - CofC
53
How do you determine coefficient of coincidence?
Determine the probability of crossover occuring by multiplying the probability of the two segments happening time the total progency. This give you the expected. C of C = observed/expected
54
Why is the recombination frequency vs actual map distance not linear
Recombination rates underestimate the true physical distance between genes at higher map distances

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