Test 3

Question 1

How many types of melanin found in hair?

Answer 1

Black and red

Question 2

What is the genotype for a chestnut colored horse?

Answer 2

e/e

Question 3

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

Answer 3

E/-

Question 4

What is the relationship between MC1R and Extension?

Answer 4

MC1R is the molecular responsible for Extension

Question 5

How does MC1R variation cause variation in coat color?

Answer 5

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

Question 6

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

Answer 6

Candidate gene sequencing

Question 7

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

Answer 7

The agouti gene only acts on black

Question 8

What is the gene action of ASIP?

Answer 8

ASIP blocks binding of MSH to MC1R

Question 9

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

Answer 9

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

Question 10

How are family studies used for gene variant discovery?

Answer 10

Linkage maps are used to study families and localize variants

Question 11

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.

Answer 11

False

Question 12

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

Answer 12

True

Question 13

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

Answer 13

Family Studies

Question 14

Why aren’t palominos true breeding?

Answer 14

Palomino only occurs in heterozygotes

Question 15

What is the effect of variants at the Cream locus?

Answer 15

Cream alleles are codominant

Question 16

Which pigment does the Cream locus affect?

Answer 16

pheomelanin

Question 17

What is the genotype of a Bay?

Answer 17

E/-, A/-

Question 18

What is the genotype of Black

Answer 18

E/-, a/a

Question 19

What is the genotype of a Chestnut?

Answer 19

e/e, -/-

Question 20

What is the genotype of a Palomino?

Answer 20

e/e, -/-, CR/-

Question 21

What is a likely genotype of a Dun?

Answer 21

E/-, A/-, CR/cr

Question 22

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

Answer 22

MC1R

Question 23

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

Answer 23

Agouti

Question 24

Which pigment is affected by the C locus?

Answer 24

pheomelanin

Question 25

Which pigment is affected by the D locus?

Answer 25

both pheomelanin and eumelanin (but not point)

Question 26

Which pigment is affected by the Z locus?

Answer 26

just eumelanin

Question 27

Which pigment is affected by the CH locus?

Answer 27

Both pigments, including points

Question 28

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?

Answer 28

Family studies

Question 29

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

Answer 29

Dun is the most common allele among horses

Question 30

Why was KIT considered a candidate for dominant white?

Answer 30

KIT variants caused similar white spotting in mice

Question 31

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

Answer 31

Each W allele repesents a different variant that can cause white

Question 32

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

Answer 32

White variants caused by frameshifts and nonsense mutation

Question 33

Why is Roan thought to be a variant of KIT?

Answer 33

linkage disequilibrium with variants of KIT

Question 34

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

Answer 34

Differences in distribution of pigment granules in hair shafts

Question 35

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

Answer 35

Candidate Gene approach

Question 36

What is the mode of inheritance of Tobiano?

Answer 36

dominant

Question 37

What is the mode of inheritance for Sabino1?

Answer 37

partial dominant

Question 38

What kind of DNA variant is responsible for Tobiano?

Answer 38

inversion

Question 39

What kind of variant is responsible for Sabino1?

Answer 39

Splice Site Variant

Question 40

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

Answer 40

The DNA variant for SB1 is not present in sabino Clydesdales

Question 41

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

Answer 41

Some white offspring when mating Sabino stallions to Sabino mares

Question 42

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

Answer 42

The inverted chromosome cannot form viable gametes

Question 43

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

Answer 43

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

Question 44

what does this diagram demonstrate?

Answer 44

mechanism for Alternate splicing

Question 45

what does this diagram demonstrate?

Answer 45

the nucleotides that participate in the controlled splicing out of introns

Question 46

what is the color pattern of this horse called?

Answer 46

Frame Overo

Question 47

What is the mode of inheritance of Gray?

Answer 47

Dominant

Question 48

What is the nature of the genetic variant for Gray

Answer 48

Intronic Duplication

Question 49

What is the mode of inheritance for Frame Overo?

Answer 49

Partial Dominant

Question 50

How was overo discovered?

Answer 50

Candidate gene

Question 51

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

Answer 51

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

Question 52

How does the phenotype for Frame Overo differ from Tobiano?

Answer 52

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

Question 53

What is a phenocopy?

Answer 53

A phenotype that can have multiple genotypes

Question 54

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

Answer 54

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

Question 55

What are characteristics for appaloosa?

Answer 55

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

Question 56

Why is the gene for appaloosa called Leopard?

Answer 56

One of the most popular patterns was called Leopard.

Question 57

Why is Splashed White a good example for phenocopies?

Answer 57

Splashed White is a phenotype produced by different genotypes

Question 58

These traits are associated with which color pattern?

Answer 58

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

Question 59

This panel shows...

Answer 59

Different phenotypes associated with the LP locus

Question 60

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

Answer 60

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

Question 61

What does the PATN1 locus do?

Answer 61

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