Reference no: EM133722837

Assignment: Genetics Problems- Biology the Genotype of the Color Blind Father

Read the chapter about Genes and Inheritance in What is Life? A Guide to Biology before beginning this lab.

The purpose of this lab exercise is to gain experience working monohybrid and dihybrid crosses. This will provide a greater understanding of how genes are passed from parents to offspring.

For this lab exercise, work the following genetics problems and answer the questions. A Punnett square may be needed for some of the problems. You may answer the questions electronically on this Word document. You may also work the problems on paper, scan or photograph the paper pages, and submit these pages electronically. Read the questions clearly since all information needed to work the problems and answer the questions is provided in the question. Use the uppercase (capital) letter to indicate a dominant allele. Use the lowercase letter to indicate a recessive allele. We will also assume that mutations are not occurring in the genetics problems.

I. Albinism (lack of skin pigmentation) is caused by a recessive autosomal allele. Autosomal alleles are those found on chromosomes other than the sex chromosomes. This would be chromosome number 1-22 in humans. A man and woman, both normally pigmented, together have an albino child. P = allele for pigmentation, p = allele for albinism.

i. For this trait, what is the genotype of the albino child? Can you be certain? Why?
ii. For this trait, what is genotype of the mother? Can you be certain? Why?
iii. For this trait, what is the genotype of the father? Can you be certain? Why?

II. In peas, tall(T) is dominant over the allele for short(t). What would you expect in the F1generation if you crossed a homozygous tall plant with a short plant? Why?

III. In peas, tall (T) is dominant over the allele for short (t), and smooth(S) seed is dominant over the allele for wrinkled(s) pea seeds. What would you expect in the F1generation if you crossed a homozygous tall, wrinkled seed plant with a short, homozygous smooth-seeded plant? Why?

IV. Cystic fibrosis is an autosomal recessive condition. A couple who are both carriers (heterozygous) for the gene for cystic fibrosis have two children who have cystic fibrosis. N = noncystic fibrosis allele, n = cystic fibrosis allele

i. For this trait, what is the genotype for the two children with cystic fibrosis? Why?
ii. What is the probability that their next child will have cystic fibrosis? Why?

V. In snapdragons, heterozygotes have pink flowers, whereas homozygotes have either red or white flowers. This is an example of incomplete dominance. A plant with red flowers (RR) is crossed with one that has white(rr) flowers.

i. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring will have pink flowers? Why?
ii. When two plants with pink flowers are crossed, what is phenotypic ratio and genotypic ratio of the offspring.

VI. Roan color in cattle is the result of absence of dominance between red and white color genes and the cattle are red and white in color. This is another example of incomplete dominance.

i. If a homozygous red bull is breed to a homozygous red cow, what are the possible phenotypes and genotypes of the calf?
ii. How would one produce a herd of roan-colored cattle?

VII. A recessive allele on the X chromosome is responsible for red-green color blindness in humans. This means that females have two copies (since human females are XX) and males have one copy (since human males are XY). This is called a sex-linked trait. A red-green color blind male is genotype XnY. A normal vision male is genotype XN Y. For this problem, anormal vision woman (Sue) whose father (Mike) is color-blind marries a color-blind male (Sean). N= not color blind allele, n = color blind allele. Y = Y chromosome.

i. What is the genotype of the color-blind father (Mike)? Why?
ii. What is the genotype of the color-blind husband (Sean)? Why?
iii. What is the genotype of the normal vision woman (Sue)? Why?
iv. What is the probability that this couple (Sue and Sean) will have a son that is color-blind?
v. What is the probability that this couple (Sue and Sean) will have a daughter that is color-blind?

VIII. A man who carries an X-linked allele will pass it on to which of his children?

IX. What is associated with Down's syndrome at the chromosomal level?

X. What genetic material do all male humans inherit from their mother?