Homework 4 ANSWERS 1.(1) Lydia and Reggie grew up poor in New York city. They now have two children, Jamal and Tanya. Jamal, taking a genetics class, wonders why for some traits he and Tanya do not resemble each other, or their parents. The family is African American. Lydia and Reggie are short, 5 2 and 5 7 respectively, and each has medium brown eyes and skin, and dark brown hair. Tanya and Jamal, on the other hand, are tall 5 8 and 6 1 respectively. Jamal has very dark skin, darker than his parents skin, while Tanya s skin is noticeably lighter than either parent. Give a short explanation for how Jamal and Tanya s skin color and height can be so different from their parents. Both of these traits are multifactorial, involving both multiple genes and the environment. 2. (.5) A study of 1500 twin pairs showed that female identical twins are six times as likely as female fraternal twins to both have alcoholism. Does this finding suggest a larger genetic or environmental component to alcoholism? a. genetic b. environmental A 3. (.5) The concordance for Alzheimers was calculated in sets of fraternal twins to be .3. What is the heritability (H) of Alzheimers? a. .15 b. .3 c. .6 d. 1.2 C 4. (.5) In class last week we discussed assaying polar bodies to determine whether an oocyte has a disease allele. You are looking to avoid implanting an embryo that has the disease allele a . You have assayed polar body #1, and see that the polar body has alleles Aa for this gene. What should you do next? a. discard the egg; a nondisjunction event has occurred. b. discard the egg; you know that it will have the a allele c. implant the egg; you know it will not have the a allele d. test the next polar body produced, after fertilization of the oocyte. D 5. (.5) DNA replication occurs: A. before mitosis and meiosis B. during mitosis and meiosis C. before mitosis; both before and during meiosis D. during mitosis; before meiosis A 6. (1) Order the following 5 terms on the basis of smallest size to largest size. a.Gene b. Chromosome c. Cell d. Nucleotide e. Base (A,T,C,G) E,d,a,b,c 7. (1) DNA polymerase moves along each of the original strands of DNA to create two new strands of DNA. On both strands, the polymerase moves in a _____ to ____ direction, so that the newly created strand has a directionality of _____ to _____. 3 to 5 , 3 to 5 5 to 3 , 5 to 3 3 to 5 , 5 to 3 5 to 3 , 3 to 5 C 8. (1) RNA polymerase moves along one of the original strands of DNA to create a strand of RNA. It moves along the ____ to _____ strand to create a new strand of RNA that is ____ to ____. 3 to 5 , 3 to 5 5 to 3 , 5 to 3 3 to 5 , 5 to 3 5 to 3 , 3 to 5 C 9. (1) You are a hematologist and one day a boy named Jared comes into your office. Jared is having episodes of intense pain and initial laboratory tests show that he is anemic. Based on a family history, you think it is possible that Jared may have <a href="/keyword/sickle-cell-anemia/" >sickle <a href="/keyword/cell-anemia/" >cell anemia</a> </a> . In order to determine this, you order a genetic test to compare the DNA sequence of Jared s beta hemoglobin gene to the sequence of the beta hemoglobin gene in a non-diseased person. Here is part of the coding strand DNA sequence of a portion of the beta hemoglobin gene from an individual that does not have <a href="/keyword/sickle-cell-anemia/" >sickle <a href="/keyword/cell-anemia/" >cell anemia</a> </a> : 5 - C T G A C T C C T G A G G A G A A G T C T-3 Here is the same part of the coding strand DNA sequence of Jared s beta hemoglobin gene: 5 - C T G A C T C C T G A A G A G A A G T C T-3 After transcription, what is the mRNA sequence for the normal individual (assume the transcript includes all of the nucleotides shown above)? A. 3 - CUG ACU CCU GAG GAG AAG UCU- 5 B. 5 - CUG ACU CCU GAG GAG AAG UCU- 3 C. 3 - GAC UGA GGA CUC CUC UUC AGA- 5 D. 5 - GAC UGA GGA CUC CUC UUC AGA- 3 Answer: B 10. (1) Next you want to determine if Jared has a mutation. The sequence above is towards the beginning of the hemoglobin gene, so use the first 3 nucleotides for the first codon. Use the codon table in your book. You conclude that Jared has: A. No mutation B. A missense mutation C. A silent mutation D. A nonsense mutation E. A frame shift mutation Answer: C 11. (1) <a href="/keyword/sickle-cell-anemia/" >sickle <a href="/keyword/cell-anemia/" >cell anemia</a> </a> is most commonly caused by a missense mutation in the human beta hemoglobin gene that changes a glutamic acid (Glu) to a valine (Val) in the beta hemoglobin protein. Jared s aunt and uncle would like to have a baby. They are worried about their child developing <a href="/keyword/sickle-cell-anemia/" >sickle <a href="/keyword/cell-anemia/" >cell anemia</a> </a> , so they decide to use preimplantation genetic diagnosis. Below is the DNA sequence (coding strand) from a potential implantation embryo in the same part of the beta hemoglobin gene as shown above. Note the (A/T) shows a mixed base sequence, which means that in this embryo, one parental chromosome has an A in this position of the nucleotide sequence and the other parental chromosome has a T in this position of the nucleotide sequence. The mixed base sequence does not affect the nucleotide sequence of any other codon. Also, like above, this sequence is towards the beginning of the hemoglobin gene, so use the first 3 nucleotides for the first...