genetics

Assignment 3B

1. Curly petals in carnations are dominant to straight petals. A true-breeding curly petaled plant is crossed with a true breeding straight-petaled plant. What are the genotypes and phenotypes of the offspring plants? What are the ratios of genotypes? What are the ratios of phenotypes?

2. Red color in carnations shows incomplete dominance to white color. Heterozygotes are therefore pink. A pink plant is self-pollinated. What are the genotypes and phenotypes of the offspring plants? What are the ratios of genotypes? What are the ratios of phenotypes?

3. In a two factor cross of carnations, with the traits described in #1 and #2: If a doubly heterozygous, pink and curly carnation is self-fertilized, what is the chance of:

A: a pink, curly offspring?

B: a white, curly offspring?

C: a red, straight offspring?

D: a red, curly offspring?

E: a pink, straight offspring?

F: a white straight offspring?

For questions 4-8

Sickle cell anemia is an autosomal recessive disease. A normal couple (both parents are healthy) have 4 children: a healthy girl, a boy with sickle cell anemia, a healthy boy and a girl with sickle cell disease.

4. Draw the pedigree, using appropriate symbols for males and females and indication of healthy or affected (indicate the phenotype).

5. in the diagram above, label the generations (Roman numerals I, II, III, etc) and individuals (Arabic numerals- 1,2,3, etc).

6. in the diagram for question 1, show the genotypes of each person at the hemoglobin locus below their symbol. Use HbS for the sickle cell allele (the recessive allele) and HbA for the normal allele. If you cannot determine the person’s genotype, show a blank line for any allele that is not determined.

7. If the parents in question 1 have a fifth child, what is the chance that the child will be: (fill in the Punnett square

A. healthy (a phenotype)

B. have sickle cell disease (a phenotype)

C. be homozygous for the normal allele (a genotype)

D. be heterozygous (a genotype)

E. be homozygous for the disease causing mutation (a genotype)

8. How do the ratios of the phenotypes (7A and 7B) and the ratios of the genotypes (7C,7D and 7E) compare the ratios that Mendel’s experiments showed?