BIO 201 Short Essay Practice

Exam IV

1. a) A unicorn is homozygous dominant for the horn length gene (H) and heterozygous for the color gene (W); she has a very long horn and is red. She mates with a male who is homozygous recessive for horn length (h), and homozygous recessive for color (w); he has a short horn and is blue. Assuming these genes are on separate chromosomes, predict the genotype and phenotype ratios of the F1 generation. Show your work, list all F1 genotypes and phenotypes produced, and indicate the percent of offspring you expect to show each genotype and phenotype.

b) Now, let's say the color alleles show incomplete dominance. Describe the phenotype of an hhWw individual.

c) Now, let's say there is another trait for tail color, which is sex-linked. Pink is recessive and purple is dominant. The unicorn parents mate. Their first-born is a male, and he has a pink tail. i)Do you know the genotype of the mother? ii)Of the father? Their second-born is a female, and she also has a pink tail. iii)Do you know the genotype of the mother? iv)If not, can you narrow it down to two possibilities? v)Do you know the genotype of the father? vi)Do you know his phenotype?

d) i) If 75% of F1 offspring were red with long horns, could you make any predictions about whether these genes were on the same or on different chromosomes? Why? ii) What if 50% of the offspring were red with long horns? iii) restate the F1 phenotypes from part a), using the terms "parental" and "recombinant."

e) Why do type AB people have both A and B proteins on their red blood cells?

2. Describe and/or define each of the following. In doing so, explain how they are all related to each other: a)chromosome, b)chromatin, c)gene, d)allele, e)dominant and recessive alleles, f)heterozygous and homozygous, g)genotype, h)phenotype, i) incompletely dominant alleles, j) x and y chromosomes, k) Barr bodies.

3. Briefly describe how Mendel's principles of Segregation and Independent Assortment relate to meiosis. When do we NOT expect genes to assort independently?

4. Provide an example disease/condition caused by each of the following: a) a recessive autosomal allele, b) a dominant autosomal allele, c) a sex-linked allele, d) a non-disjunction mutation, e) an incompletely dominant allele, f) a chromosomal deletion. Briefly compare the evolutionary role of mutations of DNA replication with the role of chromosomal mutations. In which gender are sex-linked recessive conditions more common, and why?

5. Galen and Doris are the parents of Terry, Connie, and Galen Jr. Galen Sr. has blue eyes, Doris has brown. Terry has blue, Connie and Galen Jr. have brown. Galen Jr. marries Jean. Jean has blue eyes. Her father, Norm, has blue eyes and her mother, Sally, has brown eyes. Galen Jr. and Jean produce Terri, who has brown eyes. Terri marries John. John has brown eyes. His mother, Nellie, has brown eyes and his father, Rich, has blue eyes. John has a sister, Donna. Donna has brown eyes. Donna's husband Matt has blue eyes. Donna and Matt's first child, Ashley, has brown eyes. Their second child, Marlene, has blue eyes. Create a pedigree based on this information (remember the circles and squares show gender and phenotype only, not genotype). Now, identify the genotypes of these family members. Which of the brown-eyed members are definitely carriers (heterozygotes)? What is the chance (if any) that Terri and John could produce a blue-eyed child?

6. Explain regulation of bacterial operons using the trp operon as an example. What IS an operon?

7. A hormone called Growth Factor has just been released from a gland in the brain into the blood of an animal. Growth Factor is a water-soluble signal molecule, and will tell certain cells to divide more. It will bind a receptor on a cell, for example a cell lining the intestines. That binding will activate a G-protein. Via signal transduction, a specific activator transcription factor will be activated. This specific activator targets genes that code for enzymes involved in cell division (so, the cell cycle will go faster). It also enhances the activity of the gene that codes for the G-protein mentioned above. Using only the level of detail covered in class, a) Describe how this activator will activate its genes, b) Describe how the histones around the genes will be affected, and why that is important, c) why is more than one gene activated, and why is that important?,

d) (same question) Let's focus on the gene that codes for the G-protein. This cell has been encouraged to divide by Growth Factor. During DNA replication, it experiences a mutation to this gene (the G protein gene). Name a specific G-protein gene, and explain why a mutation to this gene can be especially harmful. In doing so, also use the terms "proto-oncogene" and "oncogene." This is the only mutation the daughter cell has (on coding regions); is this cell a cancer cell? Why or why not? What if mutations occured on some of the genes coding for cell division enzymes and the p53 gene?