Genetics. First Test.
Return to Denome's Home Page Return to Old Tests Genetics Syllabus
September 28, 2000
Write your name at the top of each page. Name
This test consists of 9 short answer questions (4 points each), 9 multiple choice questions (4 points each) and two problems (14 points each).
For the short answer questions, keep your answers short and clear. You must answer the question in the space provided. There is partial credit for short answer questions.
For the multiple choice, choose the best answer from those available. Write your answer in the space provided. Only unambiguous answers written in the correct space will count. There is not partial credit for multiple choice questions.
For the problems, you may use a calculator, but make sure that you write out your calculations so that I can see the math. Make sure that you answer the questions that are asked clearly, concisely, completely. Partial credit will be given on problems. However, a correct answer that contains additional incorrect material will not receive full credit.
If you need a clarification on a question or problem, raise your hand. I will clarify Standard English, but I will not define genetics terms for you.
Short answer questions. 4 points each.
1. In birds, females are heterogametic. In sparrows, the C/c gene is sex-linked. The C allele causes color production and is dominant to the c allele, which causes albinism (no color). An colored female is crossed with an albino male. Predict the color of male and female offspring.
2. In mice, the tail length gene is autosomal. There are two alleles that show incomplete dominance. One allele causes long tail, the other causes short tail. A short-tailed female is crossed with a long-tailed male to produce both male and female offspring. These offspring mate to produce yet another generation. Predict the phenotypes of all offspring. Makes sure that you include the frequencies that you expect to see these offspring and their sex.
3. A human cell is in middle of prophase I of meiosis. Fill out the information requested below.
Number of chromosome sets = Number of homologous pairs =
Number of chromosomes = Number of chromatids =
4. Define additive inheritance and epistasis. Please make sure you distinguish between the two concepts.
5. A geneticist working on leaf shape in oaks has discovered the gene that causes oak leaves to have “fingers”. All of the alleles of this gene cause fingering to some extent. However, occasionally, the geneticist will find a perfectly oval leaf on a tree where all of the rest of the leaves have fingers. How do you explain this phenomenon. (Hint: don't just give it a name. Give the name for the phenomenon and explain a mechanism that might cause it.)
6. In mice, the midget phenotype is caused either by maternal effect or maternal inheritance. How would you determine which it was, using crosses between mice. (This is a “design an experiment” question. Give the experiment and predict what would happen if the phenomenon is caused by maternal effect and how that is different from what would happen if it was caused by maternal inheritance.)
7. What is dosage compensation? Describe two different mechanisms used to achieve dosage compensation.
8. What is pleiotropy and what sort of general mechanism causes it?
9. Describe 4 basic sex determination mechanisms.
Multiple choice. 4 points each.
10. Which of the following is true of dominant lethal alleles? #10 answer
A. They are never passed from one generation to the next.
B. In heterozygotes, they sometimes cause a separate, non-lethal phenotype, and only kill as homozygotes.
C. They only kill individuals after they have had a chance to breed.
D. They always have their phenotypes centered on the central nervous system.
E. None of the above is true.
11. The purebred female white mice that a geneticist was going to use for experiments escaped and mated with the “wild” grey mice living in the building. The white females were recovered. They gave birth to lots of mice. All the males progeny were white. The female progeny were many different colors. Which of the following explains these results.
A. The gene controlling color is autosomal, the white allele is dominant to all other alleles.
B. The gene controlling color is autosomal, the white allele is recessive to all other alleles.
C. The gene controlling color is X linked, the white allele is recessive to all other alleles.
D. The gene controlling color is X linked, but the rules of expression cannot be determined from these data.
E. The gene controlling color is mitochondrial. #11 answer
Use the following data for questions 12 and 13.
Purebred Female mink (long, dark fur) X Purebred male (short, light fur)
Progeny 7 females (medium length, light fur) 8 males(long, light fur)
12. What are the rules of expression for the fur length and fur color genes?
A. Fur length: “long allele” dominant to the “short allele”.
Fur color: “light allele” dominant to the “dark allele”. #12 answer
B. Fur length: “long allele” recessive to the “short allele”.
Fur color: “light allele” recessive to the “dark allele”.
C. Fur length: “long allele” and “short allele” are codominant.
Fur color: “light allele” dominant to the “dark allele”.
D. Fur length: “long allele” and “short allele” and incompletely dominant.
Fur color: “light allele” dominant to the “dark allele”.
E. None of these explains the data.
13. What is the mode of transmission for each of these genes?
A. Fur length: Autosomal gene. B. Fur length: Autosomal gene.
Fur color: Autosomal gene. Fur color: X-linked gene.
C. Fur length: X-linked gene. D. Fur length: X-linked gene.
Fur color: Autosomal gene. Fur color: X-linked gene.
E. This cannot be determined from these data. #13 answer
Use the following data for questions 14 and 15.
In Drosophila melanogaster (fruit flies), the body color, wing vein, eye color and bristle shape genes are all X-linked and have the following map.
Body color 10 m.u. wing vein 10 m.u. eye color 10 m.u. bristle shape
A Purebred yellow body, veined, red eyed, forked bristle female is crossed with a brown bodied, unveined, white eyed, unforked bristle male. The female offspring of this cross are allowed to make gametes. Question 14 and 15 refer to these gametes.
14. How many different gamete genotypes will be produced? #14 answer
A. 2 B. 4 C. 8 D. 16 E. 32
15. What proportion of the gametes will have the following genotype?
Brown body allele, unveined allele, red eye allele, unforked allele. #15 answer
A. 1/8 B. 1/16 C. 0.001 D. 0.009 E. 0.0045
16. In mice the A/a and B/b genes are autosomal and 10 m.u. apart. A purebred female showing the “a + b” phenotype is crossed with a purebred male showing the “A + B” phenotype. All of the offspring have the “A + B” phenotype. The offspring are allowed to mate to make an F2 generation. What proportion of the F2 will have both the “a + b” phenotype?
#16 answer
A. 0.1 B. 0.01 C. 0.9 D. 0.81 E. 0.2025
17. A geneticist has found 4 genes that together determine the ability of petunias to withstand cold. Each gene has two alleles (a “hot” and a “cold” allele). Plants with more “cold” alleles survive cold temperatures better, regardless of which genes have the cold alleles. This is an example of:
#17 answer
A. epistasis B. pleiotropy C. additive inheritance
D. variable expressivity
E. incomplete penetrance
18. The allele in humans that causes achondroplastic dwarfism (extremely short stature) also increases the risk of heart disease and gastrointestinal problems. This is an example of:
A. epistasis B. pleiotropy C. variable expressivity
D. incomplete penetrance
E. More than one of the above. #18 answer
Problem #1. 14 points
In Mice, the size locus is 25 m.u. from the color locus on the 2nd autosome. The tail length locus is X-linked. The following cross is done.
Parents
Purebred female (small, black, long tail) X purebred male (large, white, short tail)
Progeny
Females 23 (large, grey, short tail) males (large, grey, long tail).
Please answer the following questions.
A. What are the rules of expression for these three genes?
B. The progeny females are allowed to make gametes. List all possible gamete genotypes. Make sure that you define your symbols clearly (I can't read your mind, so write it out.)
C. Give the frequency of four classes of gametes (you can choose any 4). Write out the calculations.
Problem #2. 14 points
A purebred blue eyed, silky, black furred female rhesus monkey is crossed with a purebred pink eyed, rough, white furred male. They have twins (male and female). The male is blue eyed, rough and grey furred. The female is pink eyed, rough and grey furred. The female offspring is crossed with a pink eyed, silky, black male. Over a span of ten years they have the following offspring.
Females Males
8 Pink eyed silky black 4 Pink eyed silky black
8 Pink eyed rough grey 4 Blue eyed silky black
2 Pink eyed silky grey 4 Pink eyed rough grey
2 Pink eyed rough black 4 Blue eyed rough grey
1 Pink eyed silky grey
1 Blue eyed silky grey
1 Pink eyed rough black
1 Blue eyed rough black
Determine rules of expression, mode of transmission and linkage relationships for the three genes controlling these phenotypes. Draw a map (with map distances), if appropriate. You don't have to work out your calculations. Just right them out.