Biology 138 Name ____~~~--r--------Genetics Review 2 - Genetics Has Gone To The Dogs

1. In the English Mastiff, a condition called PRA leads to blindness that develops between the ages of 12 and 18 months. Two English Mastiffs with PRA had several litters of puppies. Out of 37 puppies, 25 of them had PRA and 12 were normal.

a. What is the most likely type of inheritance for PRA? c\___ _()... n .....__-=:.....O~ \_t\ _ --:......____

b. What were the genotypes of the parents? R y____~__:...=_=___----''---_=_ )( 1ty_______

c. If 2 of the normal puppies were bred together, what are the chances that they would have an offpring with PRA? 0"/0

2. Cavalier King Charles Spaniels sometimes inherit a disorder called episodic falling. Episodic falling is a neurological condition, induced by exercise, excitement or frustration, in which muscle tone increases. This means the dog is unable to relax its muscles, becomes rigid and falls over.

In addition, the Cavalier King Charles Spaniel may also suffer from a disorder known as dry eye'0 .... ~ 'L\~ly coat syndrome, where the coat of the animal is unusually curly and feels rough to thetl ,.. ~'1,,,.\\v louch, and the eyes are unable to produce enough tears to keep the cornea moistened. This

leads to very painful dryness and redness of the eyes.

A completely normal Cavalier King Charles Spaniel was bred with a Cavalier King Charles Spaniel with dry eye, curly coat syndrome and episodic falling. All of the F1 offpsring were normal. The F1 offspring were then bred with another dry eye, curly coat dog with episodic

falling. F, ::: ee D~ ~ ulAe( a. What is the mode of inheritance for episodic falling? _..L.""""" ..:-- e____'tt:.....;(._~~S \ "_b. What is the mode of inheritance for dry eye, curly coat syndrome? ttl~~~·' Ve."

c. What is the expected phenotypic ratio in the F2 offpsring of the cross described in the reading?

\ Yl"~lW\.\ "" \ t.t>'<od"'(' fA\\1~ _WMl : 1d\'liey, C\A.~I"I hort'l'VAl: , e.O'c;bA"c t(AXh~

d. What type of cross was done betwe~n fne r; offspring and·thd dry eye, curly coat dog with episodic falling? ! e~-t l.-~~'5

3. In Great Danes, the coat color is controlled by a pair of genes known as the "Merle" genes. If a merle colored Great Dane (blue/gray) is bred with another merlF colored Great Dane, the the offspring are found in a 1 :2:1 ratio of black: merle: double merle (almost white) . What type of inheritance does this demonstrate?

What phenotypic ratio would you expect in a cross between a double merle Great Dane and a

merle Great Dane? M I ~ I ~ ~ ,M' \ vw..V,t ·· \ clOU\?~ ~W M' ",jif I~

~' ~tAt ~~( 4. Use the following pedigree tracing the inheritance of coat color as described in Great Danes in

problem 3 to answer the questions below:

a. What is the most likely phenotype of the parents? W\e~\e

b. If these two parents had another puppy, what are the chances it would have the same phenotype as them? M M I

a. 0% AA ~A "", b. 25% ,- • f'\~ ,...,

@ 50% ... A ~~I ~/~I d. 100% tv~

'

c. If the third puppy were bred with a female whose symbol was completely shaded in on the pedigree, what are the chances that puppy would have the same phenotype as its father? a. 0% b. 25%

@ 50% d. 100%

- -

~~~~£~Je&~:v 5. In addition, in Great Danes a condition exists called OCM (dilated cardiomyopathy) where the

wall of the left ventricle of the heart enlarges, becomes very thin, and cannot pump enough blood to the body, so the dog eventually dies. The gene for this trait is located on the X chromosome,

and is recessive. "" t'A ,e.., H ' X'O."T>t. A male Great Dane with a black coat and OCM is bred with a female with mer~oat, but who did not inherit a gene for OCM from either of her parents. What are the expected genotypic and phenotypic ratios from this cross?

Genotypic Ratio: \ MtAJ\fJ )(~ : I MtA' XDxd ~ \ V\M '(P\i ~ \ Mv!~ 1> 'I Phenotypic Ratio: \ 'o\~Qf l'<l~h' : \V\!..Q.XlL bor~pJ ~: I 'P' doC-1l \1\0 V~ :

6. In Labrador Retrievers, gum c~lora~~~e~!m~d~~!n!'~~ of~les. Gums can either be pink, black, or pink with black spots. What type of inheritance does this trait demonstrate? r-., aJ ' cn dOWl\raVl~

Use the following symbols for the rest of this problem: cP CB= Pink = Black

You have a spotted gummed Labrador Retriever that just had 8 pups. 4 of the puppies have spotted gums like your dog, and the other 4 have pink gums. What is the likely genotype of your dog and of the sneaky neighbor dog?

Your dog: Sneaky Neighbor dog: eVee, CPc P

What is the phenotype of the sneaky neighbor dog? __-\L-l\L....:V\ ==--~~ .:...:...--'S ____\2 :...L..S'k 'jv:....\'Y\ _

7. In Oobermans, coat color is controlled by two pairs of genes (B,b and O,d) that interact with one another to produce 4 different coat colors. The following combinations of alleles produce the coat

colors listed: 'at> bc;\ B_O_ = black dog ~t) ~1) • g bbO_ = red dog "t:> ~bW . ,,~ B_dd = blue (faded black) dog \,JJ bbdd =fawn (faded red) dog J'Oj. X 10\0 ..~ 1)\;1\1 ' tl

If a black dog (produced from the mating of a red dog with a blue dog) is mated with a red dog (produced from the mating of a fawn dog with a black dog), then: What is the expected phenotypic ratio in the offspring?3B\()Ck: '3 vrd: \ \J\v..f.... \~t,\."-,,nto

If the parents have more puppies, what are the chances the puppies will have the same phenotype as either of the parents? ______

8. Knowing that dogs have 39 pairs of chromosomes, answer the following questions:

a. How many chromosomes would be in the cell of one of the dog's eyes? _4_...::Ie~__ I

b. What is the diploid number of chromosomes in a dog? 11S c. How many chromosomes would be found in a sperm cell of the dog? __3::.....-<::1___

I d. What is the haploid number of chromosomes in a dog? '3"\