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CHAPTER 2 Patterns of Inheritance
LL8
genotype bb. (a) In crosses between dihybrid short-haired, black and homozygous short-
haired, brown rabbits, what genotypic and phenotypic ratios are expected among their pro-
geny? (b) Determine the expected genotypic and phenotypic ratios in progeny from the cross
LIBb x Llbb.
2.52.
2.52. The genetic information for the following eight parts is found in Problem 2.51. (a) What
phenotypic ratio is expected among progeny from crosses of LIBb x LIB6? (6) What percen-
tage of the F1 genotypes in part (a) breéds true (i.e., what percentage is of homozygous
genotypes)? (¢) What percentage of the Fi genotypes is heterozygous for only one pair of
genes? (d) What percentage of the Fi genotypes is heterozygous at both loci? (e) What
percentage of the F1 genotypes could be used for testeross purposes (.e., homozygous
double-recessive)? (f) What percentage of the Fi progeny could be used for testcross purposes
at the B locus (i.e., homozygous recessive bb)? (g) What percentage of all short-haired F
individuals is expected to be brown? (h) What percentage of all black F individuals will breed
true for both black and short hair?
am0 af ahickens is due to a dominant allele Fand clean legs to
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Related questions

4. Short hair in rabbits is governed by a dominant gene (L) and long hair by its recessive allele (l). Black hair results from the action of the dominant genotype (B-) and brown from the recessive genotype (bb).

a). In crosses between dihybrid short, black and homozygous short, brown rabbits, what genotypic and phenotypic ratios are expected?

b). Determine the expected genotypic and phenotypic ratios in progeny from the cross LlBb x Llbb.

Hi, Can you please explain clearly. Thank you.

1. (8 points) Anhydrotic ectodermal dysplasia is an X-linked recessive disease in cattle, causing tooth abnormalities and hairlessness. Arachnomelia is an autosomal recessive condition that causes spider legs in newborn calves. Use ‘D’ to indicate the dominant, normal teeth and hair in cattle and ‘d’ for the dysplasia. Use ‘L’ for normal legs and ‘l’ for spider legs. Suppose a heifer having normal teeth and hair and normal legs but whose sire had dysplasia and spider legs is backcrossed to her sire.

a. What are their genotypes?

b. What are the genotypes, phenotypes, and genotypic and phenotypic proportions we expect in their progeny?

2. (6 points) In German Shepherds, hemophilia A is an X-linked recessive disease, affecting the blood clotting times in dogs having the disease. Use ‘+’ to indicate the normal, normal blood clotting time allele and ‘a’ for the hemophilia allele. A bitch (female) who has normal blood clotting times and whose sire (male) had hemophilia A is mated with a sire with normal blood clotting times but whose sire also had hemophilia A.

a. What are the genotypes of the 4 dogs described in the problem?

b. What are the genotypes, phenotypes, genotypic and phenotypic proportions you would expect to observe in the puppies produced from this cross?

3. (8 points) In turkeys, inhibited feathering is a sex-linked dominant gene (F). Use ‘f’ to denote the normal feathering allele. Suppose a bald hen (female) is crossed with a normally feathered rooster.

a. What are the genotypes of the two birds described?
b. What are the genotypes, phenotypes, genotypic and phenotypic proportions expected in the F1 progeny? c. What will be the genotypes, phenotypes and proportions produced when the F1 males are backcrossed?

4. (8 points) In guinea pigs, short hair (H) is dominant to long hair (h) and the heterozygous condition when you cross a yellow coat (CY) and white coat (CW) gives you a cream coat. These two loci are located on different chromosomes. A heterozygous short-haired cream guinea pig is crossed to a long-haired white guinea pig.

a. What are the genotypes, phenotypes and proportions of the pups (baby guinea pigs) produced?

b. What are the genotypes, phenotypes and proportions expected if we crossed the heterozygous short- haired cream guinea pig with a heterozygous short-haired yellow guinea pig?

Diagram a cross between a true breeding pea plant that produces yellow seeds (G/G) with one that produces green seeds (g/g). Carry the cross out to the F2 generation. Answer the following questions:

What was the F1 genotype and phenotype?

What kinds of gametes could the F1 individuals produce?

What were the F2 genotypes and phenotypes, and in what ratios would you expect each to occur?

Diagram a cross between a true breeding pea plant that produces round seeds and purple flowers, with one that produces wrinkled seeds and white flowers. (Round and purple are the dominant traits.) Carry the cross out to the F2 generation. Answer the following questions:

What are the P1 genotypes?

What is the F1 genotype and phenotype?

What kinds of gametes will the F1 individuals produce?

What are the F2 genotypes and phenotypes?

What genotypic and phenotypic ratios are expected in the F2 progeny?

Diagram a cross between a true breeding pea plant that produces yellow seeds (G/G) and purple flowers (W/W) with one that produces green seeds (g/g) and white flowers (w/w). Carry the cross out to the F2 generation. Answer the following questions:

What was the F1 genotype and phenotype?

What kinds of gametes could the F1 individuals produce?

What were the F2 genotypes and phenotypes, and in what ratios would you expect each to occur?

Diagram a test cross of the F1 individuals from the question above, with the homozygous recessive parent strain. What genotypes and phenotypes would you expect in the testcross progeny, and in what ratios?

If you had a fruitfly with phenotype A, what test would you make to determine if it was Aa or AA? Explain the different outcomes expected if the fly in question is AA or Aa.

If individuals of genotype AaBbCc are intercrossed:

How many different genotypes can occur in their progeny? How many different phenotypes can occur in the progeny?

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