Three Little Ladies Rabbitry, Jersey Wooly
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Genetics Practice Problems

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Testcross:

In rabbits, the self coloring is caused by a recessive gene, “a.” A breeder has a buck that she wants to use for breeding purposes if possible. The rabbit is Agouti, so the owner knows his genotype is either AA or Aa. If the rabbits’s genotype is Aa, the owner does not wish to use him for breeding so that the self gene will not be passed on. This can be tested by breeding the buck to a self doe (aa). Draw the Punnett squares to illustrate these two possible crosses. In each case, what percentage/how many of the offspring would be expected to be Agouti? self? How could you tell the genotype of this male dog? Also, using Punnett square(s), show how two Agouti rabbits could produce a self offspring.


A doe is genotype aa. What type of alleles can she produce?
and/or

If a buck has a genoype of AA, what kind(s) of alleles can he produce?
and/or

If he is Aa, what kind(s) of alleles can he produce?
and/or


Now lets place some possibilities into a Punnett square to see if we can successfully determine the genotype of the offsprings. For both Punnett squares we will assume the doe has a genotype of aa.

If he is AA:



Step 1: Put the doe's alleles in the correct locations,
by placing one allele in each of the boxes at the far left.

Step 2: Put the male alleles in the correct locations,
by placing one allele in each of the boxes at the very top.

Step 3: Put the genotypes of the offspring in
the correct locations
by carrying on from the left and one from the top.

All (100%) of offspring are Agouti

If he is Aa:



Step 1: Put the doe's alleles in the correct locations,
by placing one allele in each of the boxes at the far left.

Step 2: Put the male alleles in the correct locations,
by placing one allele in each of the boxes at the very top.

Step 3: Put the genotypes of the offspring in
the correct locations
by carrying on from the left and one from the top.

½ of offspring are Agouti
½ of offspring are Self

If any of the kits are self when we breed a self doe to an Agouti buck,
we can assume that the buck, carries the self gene.


If two agouti rabbits were both Aa, what kind(s) of alleles could each produce?
and/or

If they are bred with each other:



Put the female alleles in the correct locations

Put the male alleles in the correct locations

Put the genotypes of the offspring in the correct locations

We would expect ¾ of the rabbits to be Agouti and ¼ self.


Monohybrid Cross:

In rabbits, black (B) dominant over chocolate (b). A black rabbit is bred to a chocolate doe and they have three kits, two of whom are black and one of whom is chocolate. Draw the Punnett square that illustrates this breeding. What is the buck’s genotype? What are the genotypes of the kits?


If chocolate is recessive, what must the doe’s genotype be?

If that’s her genotype, what kind(s) of alleles can she produce?
and/or

If the buck is black, but has kits that are chocolate what must his genotype be?
(if you don’t understand why, review #1)

If that’s his genotype, what kind(s) of alleles can he produce?
and/or

If they have kits:



Put the doe's alleles in the correct locations

Put the buck's alleles in the correct locations

Put the genotypes of the offspring in the correct locations

½ of their kits would be expected to be heterozygous black
and ½ homozygous chocolate.


Dihybrid Cross:

Lets say a chocolate doe has two Agouti alleles which can be represented by AA. Lets say a buck has an agouit and a self allele, so we say they are Aa. Draw the Punnett square for the previous problem also keeping track of the A Lotus of the various individuals.

If the buck is both Aa and Bb, he would be AaBb and so could produce gametes with
either A or a and either B or b (one allele for each gene). There are two choices for
the first trait (A or a). No matter which of those go into an offspring, there are still two
choices for the second trait (B or b). Therefore, a total of 2 × 2 = 4 possible types of
gametes may be produced. What kind(s) of gametes can he produce?
and/or and/or and/or

The does would be AAbb. What kind(s) of gametes can she produce?
and/or and/or and/or

We could put four rows of doe's gametes, but to simplify things,
since they’re all the same, we can get by with one row.

*   * *

Put the female gametes in the correct locations

Put the male gametes in the correct locations

Put the genotypes of the offspring in the correct locations

50% of the kits would be black agouti,
1/2 of the children (6 out of 12) would be expected to be chocolate agouti.


What kind(s) of gametes can a Chocolate (carrying self) homogenous Agouti doe produce?
and/or and/or and/or

A heterozygous buck would be AaBb. What kind(s) of gametes (sperm) can he produce?
and/or and/or and/or

If they have children:



Put the female gametes in the correct locations

Put the male gametes in the correct locations

Put the genotypes of the offspring in the correct locations

Notice that the children will be 100% agouti;
75% of the kits will be black and 25% chocolate;


Trihybrid Cross:

In rabbits, Agouti hair (A) is dominant over self (a), Black (B) is dominant over chocolate (b), and non-dilute (D) is dominant over dilute (d). Assuming these genes are on separate chromosomes, draw the Punnett square for a cross between a homozygous Black Agouti Nondilute and a Dilute Chocolate Agouti. What would the phenotype(s) of the offspring be? If two of the F1 offspring were crossed, draw the Punnett square for this cross. Hint: first make a list of the possible gametes, making sure each has exactly one copy of each of the genes (one allele for each gene). What would the genotype and phenotype ratios be for the F2 generation?

In the parental generation,
if we arbitrarily let the doe be AABBDD, what kind(s) of gametes can she produce?
and/or and/or and/or and/or and/or and/or and/or

If we arbitrarily let the buck be aabbcc, what kind(s) of gametes can he produce?
and/or and/or and/or and/or and/or and/or and/or

Thus, all of the F1 will have the same genotype. What will that be?

What will they look like--what will their phenotype be?
(Hint: to keep the computer happy, use a comma and space to separate multiple words.)

What kind(s) of gametes can the kits produce?
and/or and/or and/or and/or and/or and/or and/or

If they are bred with each other:









Put the female gametes in the correct locations

Put the male gametes in the correct locations

Put the genotypes of the offspring in the correct locations

genotypes: phenotypes:
AABBDD 1     AaBBDD 2     aaBBDD 1
A-B-D- 27
AABBDd 2     AABBDd 4     aaBBDd 2 A-B-dd 9
AABBdd 1     AaBBdd 2     aaBBdd 1 A-bbD- 9
AABbDD 2     AaBbDD 4     aaBbDD 2 A-bbdd 3
AABbDd 4     AaBbDd 8     aaBbDd 4 aaB-D- 9
AABbdd 2     AaBbdd 4     aaBbdd 2 aaB-dd 3
AAbbDD 1     AabbDD 2     aabbDD 1 aabbD- 3
AAbbDd 2     AabbDd 4     aabbDd 2 aabbdd 1
AAbbdd 1     Aabbdd 2     aabbdd 1

To double check, number of squares = 64,
sum of genotypes = 64,
and sum of phenotypes also = 64.

Ok so how did you do? To do this for all the five major Loti of the lops color genetics would require a punnett square of 1024 squares (16 x 16) Now that would be complicated. Most rabbitry management software include genetics modules that will calculate this for you. If you don't have that software then you can visit Welsh Rabbitry or Mama Rabbit and try out their free online calculators.