Docsity
Docsity

Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity


Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan


Guidelines and tips
Guidelines and tips

Molecular Genetics Exam 3 - Summer 2009: Questions and Answers - Prof. Allen C. Gathman, Exams of Molecular biology

Questions and answers from an exam in molecular genetics held during the summer of 2009. The exam covers various topics such as mutations, gene expression, rna splicing, and transcription regulation. Students are expected to understand concepts related to gene mutations, their effects on protein production, rna processing, and transcription.

Typology: Exams

Pre 2010

Uploaded on 08/08/2009

koofers-user-0u8
koofers-user-0u8 🇺🇸

10 documents

1 / 6

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Molecular Genetics
Exam 3 Summer
2009
i. Relax.
ii. Write your name on the back of the last page only.
1. (10 points) You have a mutant strain of E. coli that produces β-galactosidase in large galactosidase in large
quantities whenever lactose is present in the medium, even if glucose is present also. Propose
two mutations that could produce this effect. For each, tell what gene or site is mutant and how
this mutation would produce the observed phenotype.
2. (10 points) In humans, the gene coding for obliviase is transcribed at high levels in response
to the steroid hormone testosterone. An XY human produces normal levels of testosterone, but
produces little or no obliviase. The coding region of his obliviase gene is normal. Propose two
mutations that could be responsible for this phenotype. For each, tell what gene or site in the
DNA is mutant and explain how the change produces the phenotype.
pf3
pf4
pf5

Partial preview of the text

Download Molecular Genetics Exam 3 - Summer 2009: Questions and Answers - Prof. Allen C. Gathman and more Exams Molecular biology in PDF only on Docsity!

Molecular Genetics

Exam 3 Summer

i. Relax. ii. Write your name on the back of the last page only.

  1. (10 points) You have a mutant strain of E. coli that produces β-galactosidase in large galactosidase in large quantities whenever lactose is present in the medium, even if glucose is present also. Propose two mutations that could produce this effect. For each, tell what gene or site is mutant and how this mutation would produce the observed phenotype.
  2. (10 points) In humans, the gene coding for obliviase is transcribed at high levels in response to the steroid hormone testosterone. An XY human produces normal levels of testosterone, but produces little or no obliviase. The coding region of his obliviase gene is normal. Propose two mutations that could be responsible for this phenotype. For each, tell what gene or site in the DNA is mutant and explain how the change produces the phenotype.
  1. Rosenfeld et al. found two types of thyroid tumors. “High-galactosidase in large producing” tumors produced large amounts of the peptide hormone calcitonin, and of course produced the 1050 bp calcitonin mRNA. “Low-galactosidase in large producing” tumors produced small amounts of calcitonin, but also produced a new mRNA. This new mRNA had sequences found in the calcitonin RNA but was longer (1250-galactosidase in large 1350 bp), and they referred to it as the pseudo-galactosidase in large calcitonin mRNA. They made a cDNA probe from calcitonin mRNA (Cal) and a second cDNA probe that contained only sequences unique to the pseudo-galactosidase in large calcitonin mRNA (psCal). The figure below shows a Northern blot of RNA from low-galactosidase in large producing or high-galactosidase in large producing tumors probed with either Cal or psCal cDNA (see markings in lanes).
  1. Consider the primary RNA transcript shown below. Exon 1 Intron A Exon 2 Intron B Exon 3 5’ XXXXXXX-galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large XXXXXXXX-galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large -galactosidase in large XXXXXXX 3’ Required factors Regulators U U U2AF U2AF hnRNP SR protein In liver tissue, the mRNA produced from this transcript contains exons 1 and 3 only. In brain tissue, the mRNA produced contains exons 1, 2, and 3. (10 points) Explain how the two different splicing products might be produced in the two different tissues, including the roles of the required factors and appropriate splicing regulators as listed in the table above.
  1. (15 points) You have altered the leader sequence in the trp operon in E. coli so that region 1 contains three TRP codons instead of two. What will be the effect of this mutation on tryptophan concentration in the cells of this mutant, compared to wild type? Justify your answer based on the mechanism of attenuation.