Module6_Problem_Set(1)

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El Paso Community College *

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3320

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Biology

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Dec 6, 2023

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Genetics (BIOL 3320), Section 1 Module 6 Problem Set This problem set is due 7 November 2023 at 1:30pm. It will be graded for completion. You should work individually or in groups on these problems, both in class and out of class. 1. Look at the key for Problem Set 5 (posted as a separate item under Module 5). Identify one question you got wrong and explain why you got it wrong and what the right answer is. If you didn’t get a question wrong, which question do you think was the hardest and why? 2. What still confuses you about the information we have covered so far? If nothing confuses you, what do you this is most interesting and why? 3. If you had $100K to spend on a GWAS study, which species and which trait would you study and why? - Perhaps it has been studied before, but I’m rather interested in seahorses and why they have snout, the benefit of having its mouth shaped like that and if it works like a vacuum or does it have teeth. 4. When does crossing-over occur? Does it occur between sister chromatids or homologous chromosomes? - During prophase I, for homologous chromosomes

5. As genetic distance increases, does the likelihood of crossing-over increase or decrease? Why? - The greater the distance, the greater the probability of crossing over. 6. What is physical distance? What is genetic distance? - Physical location: how many base pairs along a chromosome a gene is. - Physical distance: how far apart (in base pairs) the two genes are. 7. Why should we care if two genes are linked? - Data collection for recombination frequency 8. A unicorn species is 2N = 4; i.e., it has two pairs of chromosomes. Chromosome 1 is 100,000 bp long. It has gene Alpha (alleles A and a) at 10,000 bp and gene Beta (alleles B and b) at 20,000 bp. Chromosome 2 is 50,000 bp long. It has gene Delta (alleles D and d)) at 20,000 bp and gene Epsilon (alleles E and e) at 45,000 bp. Suzy the Unicorn is heterozygous at all genes. Alleles A and B travel together and alleles D and e travel together. Draw her chromosomes (just the chromosomes, not the cells) both before and after DNA replication (remember, DNA replication occurs before mitosis/meiosis). 9. A parent is AB ab . a. Draw what anaphase I looks like in this individual if no crossing-over occurs between these genes. b. Draw what anaphase II looks like in this individual if no crossing-over occurs between these genes.

c. Draw what anaphase I looks like in this individual if crossing-over occurs between the genes (involving one chromatid on each homologous chromosome). d. Draw what anaphase II looks like in this individual after the above crossing-over event between these genes. 10. In a new species of wolf, genes Epsilon and Beta make the proteins Epsilon and Beta, which affect fur color as shown below. Wild-type color is brown; E and B are wild-type alleles. e and b are lof alleles. Genes Epsilon and Beta are linked; they are 30 cM apart. Mama Wolf is EeBb ; her mom was eeBB . Mama Wolf mates with Papa Wolf ( eebb ). a. What are the phenotypes of Mama and Papa Wolf? - Mama: Brown (eB) (Eb) - Papa: Yellow b. Assuming normal crossing-over, what will be the genotypic and phenotypic proportions of the offspring from this cross? - EeBb, Eebb, eeBb, eebb - Parental: Eb, eB =70%  Eb (35%) tan, eB (35%) yellow

- Recombinant 30%  Eb (15%) Brown, eB (15%) yellow c. Let’s say both Mama & Papa Wolf have a mutation that prevents crossing-over from occurring. If so, what will be the genotypic and phenotypic proportions of the offspring from this cross? - 50 % of the offspring would be tan with Eebb - 50% of the offspring would be Yellow with eeBb 11. In the Heliconius butterfly, the gene wingless determines if butterflies are white (due to dominant allele: Y ) or yellow (recessive, y ). An unnamed gene has two alleles B and b that determines what color the butterflies like to mate with. The dominant allele B leads to preference for white butterflies; b for yellow butterflies. a. Assume wingless and the unnamed gene are unlinked, what gametes will a YyBb butterfly make and in what proportions? - YB, Yb, yB, yb- 25% b. If you cross the butterfly in part (a) with a yybb butterfly, what will be the frequencies of offspring genotypes and phenotypes? c. Assume wingless and the unnamed gene are linked and 0 cM apart, what gametes will a YyBb butterfly make and in what proportions? The butterfly’s mom was YYBB . - YB, yb 50 % each d. In real life, wingless and the unnamed gene are linked and 4 cM apart. What gametes will a YyBb butterfly make and in what proportions? The butterfly’s mom was YYBB .

- YB, yb - 48% each Yb, yB. – 2 % each e. If you cross the butterfly in part (d) with a yybb butterfly, what will be the frequencies of offspring genotypes and phenotypes? 12. What is the genetic distance between A and B if we see the following gametes from a parent that is Ab aB : 59/74 AB 15 Ab 44 aB 43 ab 17 13. In silkmoths, eye color and wing pattern are encoded by two linked genes. The eye color gene has mutant allele r that produces red eyes and wild-type allele R . The wing pattern gene has mutant allele w that produces white-banded wings and wild-type allele W . A moth homozygous for red eyes and white-banded wings is crossed with a moth homozygous for the wild-type traits. The F1 offspring have wild-type eyes and wild-type wings. The F1 are crossed with moths that have red eyes and white-banded wings. The progeny are:  wild-type eyes, wild-type wings – 418  red eyes, wild-type wings – 19  wild-type eyes, white-banded wings – 16  red eyes, white-banded wings – 426 a. Which phenotypes are dominant: wild-type or red eyes, white-banded or wild- type wings? How do you know? - Wild type: RrWw - Because these are the phenotypes observed in the F1 b. What phenotypic proportions would be expected if the genes for red eyes and for white-banded wings were located on different chromosomes? - 25% each Rw Rw rw rw r w Rrw w Rrww c. What is the distance between the gene for red eyes and the gene for white-banded wings?

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