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VS 307 > Test 3 > Flashcards

Test 3 Flashcards

1
Q

How many types of melanin found in hair?

A

Black and red

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2
Q

What is the genotype for a chestnut colored horse?

A

e/e

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3
Q

What is the genotype at E for a horse with black hair?

A

E/-

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4
Q

What is the relationship between MC1R and Extension?

A

MC1R is the molecular responsible for Extension

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5
Q

How does MC1R variation cause variation in coat color?

A

MC1R is a receptor for a molecule (MSH) that initiates the pathway leading to conversion of pheomelanin to eumelanin

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6
Q

Which approach was used to discover the variation responsible for extension colors?

A

Candidate gene sequencing

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7
Q

Why can’t we tell the genotype for Agouti in chestnut horses?

A

The agouti gene only acts on black

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8
Q

What is the gene action of ASIP?

A

ASIP blocks binding of MSH to MC1R

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9
Q

What is the candidate gene approach to discovery of genetic variants?

A

Scientists notice that genes with the same effect in other species and sequence that gene

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10
Q

How are family studies used for gene variant discovery?

A

Linkage maps are used to study families and localize variants

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11
Q

Genetic variants MC1R causing red hair color occur in many species. In each species, the red color is due to a change in exactly the same base in the DNA sequence.

A

False

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12
Q

Stephan Marklund noted that the genotype for MC1R precisely predicted the phenotypes of horses in different breeds.

A

True

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13
Q

How did Melissa Locke identify the chromosome location of the Cream locus (C)?

A

Family Studies

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14
Q

Why aren’t palominos true breeding?

A

Palomino only occurs in heterozygotes

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15
Q

What is the effect of variants at the Cream locus?

A

Cream alleles are codominant

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16
Q

Which pigment does the Cream locus affect?

A

pheomelanin

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17
Q

What is the genotype of a Bay?

A

E/-, A/-

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18
Q

What is the genotype of Black

A

E/-, a/a

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19
Q

What is the genotype of a Chestnut?

A

e/e, -/-

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20
Q

What is the genotype of a Palomino?

A

e/e, -/-, CR/-

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21
Q

What is a likely genotype of a Dun?

A

E/-, A/-, CR/cr

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22
Q

Which of the following proteins is affected by the mutation causing black pigment?

A

MC1R

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23
Q

Which protein is responsible for the distribution of black pigment on a horse?

A

Agouti

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24
Q

Which pigment is affected by the C locus?

A

pheomelanin

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25
Q

Which pigment is affected by the D locus?

A

both pheomelanin and eumelanin (but not point)

26
Q

Which pigment is affected by the Z locus?

A

just eumelanin

27
Q

Which pigment is affected by the CH locus?

A

Both pigments, including points

28
Q

PMEL17 variants cause dilution of black pigment in several species. But, what additional information led it to be considered a candidate for Silver dilution (Z) in horses?

A

Family studies

29
Q

Why is the Dun dilution allele, D, considered ancestral and the non-dun allele (d2) considered the result of a mutation?

A

Dun is the most common allele among horses

30
Q

Why was KIT considered a candidate for dominant white?

A

KIT variants caused similar white spotting in mice

31
Q

Why are there so many W-alleles (W1-W33, so far) for the KIT gene?

A

Each W allele repesents a different variant that can cause white

32
Q

What types of variants are most likely to cause embryonic lethal Dominant White in horses?

A

White variants caused by frameshifts and nonsense mutation

33
Q

Why is Roan thought to be a variant of KIT?

A

linkage disequilibrium with variants of KIT

34
Q

This image is from the publication about Dun dilution. What does the lower panel show?

A

Differences in distribution of pigment granules in hair shafts

35
Q

Horse scientists were inspired by examining color in mice. What is this approach called for discovery of genetic variants?

A

Candidate Gene approach

36
Q

What is the mode of inheritance of Tobiano?

A

dominant

37
Q

What is the mode of inheritance for Sabino1?

A

partial dominant

38
Q

What kind of DNA variant is responsible for Tobiano?

A

inversion

39
Q

What kind of variant is responsible for Sabino1?

A

Splice Site Variant

40
Q

Sabino Clydesdales look like Sabino1 heterozygotes. How do we know the cause of Sabino phenotype in Clydesdales is different?

A

The DNA variant for SB1 is not present in sabino Clydesdales

41
Q

What would we expect to see if Sabino1 was the cause of Sabino in Clydesdales?

A

Some white offspring when mating Sabino stallions to Sabino mares

42
Q

Why does an inversion result in conservation of linkage relationships among alleles?

A

The inverted chromosome cannot form viable gametes

43
Q

Why do we consider Sabino1 has a codominant mode of inheritance?

A

Horses that are heterozygous for SB1 have a different phenotype from horses that are homozygous for SB1.

44
Q

what does this diagram demonstrate?

A

mechanism for Alternate splicing

45
Q

what does this diagram demonstrate?

A

the nucleotides that participate in the controlled splicing out of introns

46
Q

what is the color pattern of this horse called?

A

Frame Overo

47
Q

What is the mode of inheritance of Gray?

A

Dominant

48
Q

What is the nature of the genetic variant for Gray

A

Intronic Duplication

49
Q

What is the mode of inheritance for Frame Overo?

A

Partial Dominant

50
Q

How was overo discovered?

A

Candidate gene

51
Q

What is the difference for the genetics of these two Roans?

A

The top panel is roan due to LP while the bottom is associated with KIT

52
Q

How does the phenotype for Frame Overo differ from Tobiano?

A

Tobiano crosses the back while Overo does not
Tobiano has solid head, white legs while Overo may or may not have white head and legs
Overo radiates up from the belly while Tobiano is more centered on the body

53
Q

What is a phenocopy?

A

A phenotype that can have multiple genotypes

54
Q

Why did early breeders think that a single locus was responsible for the 7-8 patterns associated with Appaloosa?

A

Breeders noted that mating horses of any pattern could produce offspring with any pattern

55
Q

What are characteristics for appaloosa?

A

verticle stripes on hooves, mottled noses and wide sclera on eyes

56
Q

Why is the gene for appaloosa called Leopard?

A

One of the most popular patterns was called Leopard.

57
Q

Why is Splashed White a good example for phenocopies?

A

Splashed White is a phenotype produced by different genotypes

58
Q

These traits are associated with which color pattern?

A

Panels A, B, C show “characteristics” that appear on all horses with LP

59
Q

This panel shows…

A

Different phenotypes associated with the LP locus

60
Q

What do the phenotypes of these two foals tell us about their genotypes?

A

The top horse is homozygous LP/LP while the lower is LP/lp

61
Q

What does the PATN1 locus do?

A

It is epistatic to LP and determines the extent of white on the horse

VS 307 (5 decks)

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