GENETICS TEST 1 - FALL 2012
Pirate Genetics!
Ahoy, mateys! This test has two parts. In Part 1, answer 5 of the 6 questions (15 pts each). Please indicate the questions you want me to grade. If there is any uncertainty I will grade the first five. All students must complete Part 2 (25 pts). Part 3 will be team-based, and will be completed in class on Wednesday. Parts 1 and 2 together will make up 85% of your test grade, Part 3 will be worth 15%.
NAME:
Test 1 Background Information.
Pirates, due to their shipboard lifestyles and their need to harbor in isolated areas (far from the law) have accumulated a variety of unusual mutations over the years. These mutations are not generally seen in non-pirate populations, except in the rare cases in which pirates have managed to have families in non-pirate harbors.
Pirate Joke: A pirate was standing on the crow's nest and then he slipped and fell. He fell through the first deck, then he fell through the second deck, then he fell through the third deck and hit the bottom deck of the ship!
The first mate comes up to him and asks "Are ye all right matey?"...... (The punch line can be found at end of the test)
PART 1: Short Answer. Answer 5 of the following 6 questions.
Question 1: Many pirates (see picture on first page) are blind in one eye. The assumption has always been that pirates have this trait due to unfortunate accidents as a result of their risky lifestyles. However, recent evidence has indicated that these might well be inherited traits. A female pirate with one eye marries a male pirate with one eye and they have eight children. Two have full vision, four are blind in one eye, and two are blind in both eyes.
a) What is the most likely mode of inheritance?
b) Using appropriate gene symbols, give the genotypes of both parents and of each phenotypic class of child.
c) If a pirate who is blind in both eyes mates with a pirate who has full vision, what would you expect the phenotype of their first child to be?
Question 2: Pirates’ parrots come in a variety of beautiful colors. One enterprising young pirate decides to give up his nefarious ways and go into parrot breeding. He obtains two true-breeding bright green parrots. To his surprise, when he crosses them, all of their offspring are dark green. When these dark green parrots are interbred, the following ratios are seen:
9/16 dark green
6/16 bright green
1/16 yellow
Providing appropriate gene symbols, propose a genetic mechanism to account for these observations, clearly indicating the genotypes of each individual in the P, F1 and F2 generations (generalized genotypes are fine).
Question 3: In pirates, the alleles for peg legs (N), curly hair (H) and gruff voices (G) (ARRRRRGH!) are dominant to the alleles for normal legs (n) straight hair (h) and smooth voices (g). The genes for these traits are located on separate autosomes.
If two pirates with the genotypes NnHhGg and nnHhgg mate:
a) What is the probability that they will have either a peg-legged, curly-haired child with either a smooth voice or a peg-legged, curly-haired child with a gruff voice?
b) What gametes will the nnHhgg individual make?
c) Draw how the chromosomes of the NnHhGg individual will look during metaphase of meiosis I in the nucleus below. I have included arrows to indicate the direction of separation from the equator. Be sure to include sister chromatids (if appropriate) in your drawing and to show alleles on each chromosome. An example of a single chromosome from in individual with an AA genotype is shown below:
Question 4: Black cinnamon and brown cats are common on pirate ships. These phenotypes are due to multiple alleles of the same gene (B). The results of matings between three different pairs of cats is shown below.
Mating Progeny
1. Black x Black. 3/4 black:1/4 cinnamon
2. Black x Brown. 1/2 black: 1/4 cinnamon : 1/4 brown
3. Brown x Brown. 3/4 brown : 1/4 cinnamon
a) Based on these results, and using the gene symbols Bb for black, Br for brown and Bc for cinnamon, write the genotypes of all of the individuals into the spaces provided the table above.
b) If you cross one of the brown progeny from cross number 2 with one of the cinnamon progeny, what phenotypic ratio would you expect in the progeny?
Question 5: Fluorescence microscopy is a technique that allows you to label practically any cell part with a specific colored flourochrome that you can then visualize microscopically (even if you are a pirate).
a) Describe how a chromatic beam splitter plays a role in this process.
b) You are able to differentially label a recessive allele (a) with a red fluorochrome and its dominant allele (A) with a blue fluorochrome, so that when viewed using a fluorescence microscope the homolog with the recessive allele is bright red and the homolog with the dominant allele is bright blue. Describe or draw (with color labels) what you would expect to see if you visualized a heterozygous (Aa) individual's nuclei during 1) anaphase of meiosis I versus 2) that same individual's nuclei during anaphase of mitosis. Assume that you can only visualize the labeled chromosome(s) the rest would be unlabeled, and therefore dark.
Question 6: A pirate with a hooked hand marries a woman with normal hands. All of their sons have normal hands and all of their daughters have hooked hands. Assuming that this ratio is an accurate reflection of the mode of inheritance, rather than an artifact due to small numbers of offspring or incomplete penetrance, propose a mode of inheritance for this trait, using correct gene symbols, and giving the genotypes of all the parents and offspring. (Note...there are two correct answers to this question. Only describe one of them).
PART TWO: All students must answer this question.
Question 1: Alcohol dehydrogenase is an enzyme that everything from pirates to fruit flies uses to metabolize alcohol. Not surprisingly, its expression is particularly important in rum-drinking pirate cultures. A very rare phenotype arises in a particular pirate band in which the activity of alcohol dehydrogenase is decreased and the affected pirates, to their horror, get drunk after a single mug of rum. The local genetic counselor decides to see how this trait is inherited, and generates the following family tree.
a) Based on this pedigree, which of the following modes of inheritance is most likely? For each mode, say likely, unlikely or impossible, giving clear genetic reasons for each of your answers.
1. X-linked dominant
2. X-linked recessive
3. Autosomal dominant
4. Autosomal recessive
5. Sex-influenced, recessive in men
a) Let's say that your most likely mode of inheritance is the correct one. Based on that mode of inheritance, if individual III-8 marries an unaffected male and has 5 children:
1. What is the probability that any three of them will be carriers of this trait?
2. What is the probability that all five of their children will be carriers?
3. What is the probability that their first two children will be affected?
Punch Line to Pirate Joke: The pirate replies, "Arrr, yes... I've been through hardship before!"
Genetics Test, Part III: Fall, 2012
Names:
Oh no! You have been given some pirate DNA samples to analyze for a genetic counselor and the writing has come off of three of the tubes! You have no idea which sample is which. You decide to load all of the samples on an agarose gel, anyways, hoping that you will be able to deduce which sample came from which family member once you see all of the data. The pedigree of the family member is shown below (yes, this is the same pedigree that you had for Part II of the test), followed by the results of the agarose gel that you ran. Each family member is designated by a number that corresponds to the well in which their DNA sample was loaded. (So individual I-1 is loaded in well 1, etc.) Question marks are located underneath the family members with missing labels, and these three samples are loaded into the last three wells (unknowns).
1) The unknown individuals are in lanes 8-10. Identify the individual in each of the lanes using the correct pedigree numbering system (I-1, etc.)
2) Give the genotypes of all of the individuals in the pedigree.
I-1 II-6 III-7
I-2 III-1 III-8
II-1 III-2
II-2 III-3
II-3 III-4
II-4 III-5
II-5 III-6
3) Is this disease more likely to be Tangier Disease, Hypercarotenemia and Vitamin A deficiency or Bazex Syndrome? Justify your answer using both the mode of inheritance you deduce from the pedigree and molecular data, as well as any online information you deem to be helpful. Computers will be provided.