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Genetics Class > Exam 2 > Flashcards

Exam 2 Flashcards

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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

A
23
Q

What are the Hardy-Weinberg law assumptions

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

A

positive assortative mating

negative assortative mating

25
Q

What is positive assortative mating

A

Mating with someone who is phenotypically similar

Reduces frequency of heterozygotes

26
Q

What is negative assortative mating

A

Mate with someone who is phenotypically dissimilar

Increases frequency of heterozygotes

27
Q

What is inbreeding

A

Mating with an indiviudal who is genetically related

28
Q

What is outcrossing?

A

Avoidance of mating with a genetically related individual

29
Q

What is allele by the same descent

A

Two copies of the allele are descended from the same copy in a common ancestor, so they are identical by descent (inbreeding)

30
Q

What is alleles are identical by state

A

Two copies of the A allele are the alike in structure and function but are descended from two different copies in different ancestors

31
Q

What is the inbreeding coefficient

A

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
Q

How does the proportion of homo and heterozygosity change with inbreeding

A
33
Q

What is inbreeding depression?

A

Increase of lethal and deleterious traits caused by inbreeding

34
Q

What is genetic drift?

A

Change in allele frequency due to sampling error

35
Q

What are the causes of genetic drift

A
  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
Q

How is fitness calculated

A

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
Q

What is genetic recombination?

A

The sorting of alleles into new combinations

38
Q

What are linkage group

A

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
Q

What is complete linkage

A

Genes on the same chromosome that are so close that there is no crossing over between the two genes

40
Q

What is incomplete linkage

A

Genes on the same chromosome that are far enough away that crossing over can happen between the two genes

41
Q

What is coupling conformation

A

Where a wild type allele is found on one chromosome and mutant alleles are found on the other chromosome

42
Q

What is the repulsion conformation

A

Each chromosome contains one wild type and one mutant allele

43
Q

How do you determine if its coupling or repulsion?

A

You have to look at the nonrecombinants progeny, which is the highest number progeny. Look at their genotype

44
Q

Who confirmed the chromosomal theory of inheritance

A

Barbara McClintock using maize

45
Q

What are Genetic maps

A

based on recombination frequencies between different gnee on a chromosome

46
Q

What are physical gene maps

A

Does not reply on recombination frequencies. Often correlation between phenotype and a chromosomal landmark (deletion)

47
Q

If a linkage group’s recombination frequency is greater than 50% what does that mean?

A

They belong to different linkage groups either on different chromosomes or far apart on the same chromosome

48
Q

What are the 3 point testcross?

A
  1. Single crossover
  2. Single crossover
  3. Double crossover (creates the least progeny)
49
Q

How do we determine how many classes of progeny are possible

A

2^n

n = number of genes

50
Q

How do you determine gene order?

A
  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
Q

How do you determine map distance

A

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
Q

What is interference

A

One crossover physically interferes with the formation of a second crossover

Interference = 1 - CofC

53
Q

How do you determine coefficient of coincidence?

A

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
Q

Why is the recombination frequency vs actual map distance not linear

A

Recombination rates underestimate the true physical distance between genes at higher map distances

Genetics Class (10 decks)

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