BIOL234 Mock Final Exam 2023 (1) 2

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Biology

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Jan 9, 2024

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Mock Final Exam Please refrain from sharing this exam outside of the review session. Question 1: In a distant future, there is an interaction between a nuclear locus (eyebrow) and the mitochondrial genome which contributes to the eyebrow colour in humans. Males and females who have the wild-type mitochondrial genotype (mt-wt) and two copies of the normal eyebrow allele (eb-n) have green eyebrows. Those with the pink mitochondrial genotype (mt-p) have pink eyebrows, unless they have a restorer allele for eyebrows (eb-r), in which case they have green eyebrows a) Draw a punnett square of a cross between eb-n / eb-r mt-p female and an eb-n / eb-n mt-wt male. Specify the genotypes and phenotypes of potential progeny. b) Given this pedigree below (which is unrelated to the cross done in 1a.), specify the most likely nuclear and mitochondrial genotypes for each individual below, and explain. i. A1 ii. A2 iii. B1 c) The eb-n allele is a loss of function mutation of eb-r. Explain if each of the mutations below could result in the eb-n mutation phenotype.

i. A 6bp deletion at the start of the intron ii. A single nucleotide substitution for a missense mutation iii. A 7bp insertion Question 2: Researchers are interested in studying weight in mice. They have been examining obese (ob) mutants. You’re a geneticist that studies genes affecting this phenotype. You treat several mice with a mutagen and in the F 2 you isolate several animals with alterations in weight. You establish five true-breeding lines that have the ob phenotypes. Mice in each line exhibit obesity but you notice some lines have mice that are more obese than others. You perform crosses between all five lines as well as with a wild-type line, establishing a complementation matrix and this is what you observe. (+) indicates wild-type weight. There are three obese phenotypes: mild obesity, obesity, and severe obesity. Wildtype M1 M2 M3 M4 M5 Wildtype + + + + + Obesity M1 Severe obesity + + Severe obesity Obesity M2 Severe obesity Severe obesity + Obesity M3 Mild obesity + Obesity M4 Severe obesity Obesity M5 Obesity a) Using the complementation matrix above, what can you conclude about the number of genes you have identified through your screen? Which mutations map to which complementation group (in other words, which mutations are in the same gene and which are in different genes)? Explain how you came to this conclusion.

b) What can you say about the types of mutations you have identified in each of the genes, i.e. are they loss-of-function, gain-of-function, dominant, recessive? Describe what type of alleles you think each mutation illustrates, and why. Question 3: The petals of the plant Collinsia parviflora are normally blue, giving the species its common name, blue-eyed Mary. Two pure-breeding lines were obtained from color variants found in nature; the first line had pink petals, and the second line had white petals. The following crosses were made between pure lines, with the results shown: a) Explain these results genetically. Define the allele symbols that you use, and show the genetic constitution of the parents, the F1, and the F2 in each cross. b) A cross between a certain blue F2 plant and a certain white F2 plant gave progeny of which 3/8 were blue, 1/8 were pink, and 1/2 were white. What must the genotypes of these two F2 plants have been?

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