Molecular Biology Exam 4

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Questions and Answers

How does region A differ from region B in terms of gene transcription?

Genes in region A will be transcribed at a lower rate

Region A has an open conformation (correct)

Region A has a closed conformation

Genes in region B will be transcribed at a higher rate

What is the correct nucleotide sequence of the tRNA anticodon for tryptophan?

3' – UGG – 5' (correct)

5' – ACC – 3'

5' – UGG – 3'

3' – ACC – 5'

Which strand does RNA polymerase read during transcription?

RNA coding strand

DNA template strand (correct)

Polypeptide strand

DNA coding strand

What are the current environmental conditions of the cell based on the lac operon?

Low glucose, high lactose Signup and view all the answers

If the cell is exposed to high levels of glucose, how does it affect the operon?

The expression of the operon will remain unchanged Signup and view all the answers

What is the role of the repressor in the lac operon under low glucose conditions?

It remains inactivated allowing gene expression Signup and view all the answers

Which of the following best describes the function of tRNA?

It carries amino acids to the ribosome Signup and view all the answers

What happens to the lac operon when both glucose and lactose are present?

The operon remains inactive due to glucose inhibition Signup and view all the answers

How will the XLM1 gene differ in skin and muscle cells with respect to mRNA processing?

The gene and the mRNA will be the same length in both types of cells. Signup and view all the answers

What is the anticodon sequence for the exposed codon in the A-site according to standard base pairing?

3' – AGU – 5' Signup and view all the answers

What will be the final polypeptide sequence post-translation?

Met – Gly – Pro – Leu Signup and view all the answers

A cluster of genes controlled by one promoter is known as what?

An operon Signup and view all the answers

What does a segment of a chromosome becoming attached to a different chromosome exemplify?

Chromosomal translocation Signup and view all the answers

During the translation process, which phase follows initiation?

Elongation Signup and view all the answers

In transcription, RNA polymerase synthesizes mRNA based on which template?

Non-coding DNA strand Signup and view all the answers

The process through which ribosomes decode mRNA to produce polypeptides is termed?

Translating Signup and view all the answers

Which factor plays an important part in RNA polymerase binding to DNA?

Sigma factor Signup and view all the answers

Which of the following sequences are transcribed by RNA polymerase in prokaryotes?

Promoter, coding region, and terminator Signup and view all the answers

What is the significance of the formation of a stem-loop in prokaryotic cells?

It promotes termination of transcription. Signup and view all the answers

Which enzyme belongs to Gene S in the described metabolic pathway?

Enzyme 1 Signup and view all the answers

Based on the growth results with media supplemented with A, B, C, D, or E, which enzyme is likely affected by Gene Q's mutation?

Enzyme 3 Signup and view all the answers

If Gene P has a mutation, which media supplement could still allow the cell to grow?

Only media E Signup and view all the answers

Which statement about the roles of the enzymes in the metabolic pathway is correct?

Enzyme 4 is encoded by Gene L and is essential for converting compound D to E. Signup and view all the answers

In the context of enzymatic reactions, what does each arrow in the metabolic pathway denote?

A catalyzed enzymatic reaction Signup and view all the answers

What effect does proline have on the operon?

Proline binds to DNA and inhibits transcription. Signup and view all the answers

What is the outcome of having mutation #1 in the RNA sequence?

The protein will be shorter due to a premature termination. Signup and view all the answers

Identify the type and effect of mutation #2.

Nonsense mutation; the resulting protein will be shorter. Signup and view all the answers

Where do transcription, translation, and splicing occur in a prokaryotic cell?

Transcription and translation both occur in the cytosol; splicing does not happen. Signup and view all the answers

What is the role of proline as an effector in relation to the operon?

Proline causes a repressor protein to bind to the operon. Signup and view all the answers

What happens to the encoded protein if mutation #2 is a frame shift?

The protein will be shorter due to a shift in the reading frame. Signup and view all the answers

In gene expression, which of the following correctly describes the input and output?

DNA, protein Signup and view all the answers

What occurs immediately after transcription factors bind to the promoter?

RNA polymerase recognizes the start codon. Signup and view all the answers

What does the small ribosomal subunit recognize in eukaryotic cells?

5’ cap, tRNAMet will recognize the start codon. Signup and view all the answers

What can be inferred from a deletion mutation 250 bases upstream of the transcription start site of the VRN4 gene resulting in lower transcription levels?

It deletes an enhancer sequence. Signup and view all the answers

The KRAS gene, which is mutated in colorectal cancer to increase activity, is classified as what?

Oncogene Signup and view all the answers

What effect does adding methyl groups to the core promoter region of a eukaryotic gene have on gene expression?

Transcription will decrease, resulting in less protein. Signup and view all the answers

Which mechanism primarily regulates the translation process in eukaryotic cells?

Recognition of the 5’ cap by the ribosome. Signup and view all the answers

Which of the following statements is correct regarding transcription in eukaryotic cells?

Transcription takes place in the nucleus. Signup and view all the answers

What is the potential consequence of a mutation that decreases the stability of mRNA?

Decreased protein synthesis. Signup and view all the answers

Which mutation is expected to produce the largest change to the structure and function of a protein?

A nonsense mutation in the 5’ end of the gene. Signup and view all the answers

Under what condition will the trp operon be expressed?

Absence of tryptophan with an inactive repressor. Signup and view all the answers

Is it possible to determine a person’s hair color from the DNA of cheek cells?

Yes. Signup and view all the answers

What is the normal function of the chocolate gene when it is not mutated?

To stop the cell cycle when DNA damage is detected. Signup and view all the answers

Which statement is NOT TRUE of the proteins synthesized by a polysome?

They will contain different functional groups. Signup and view all the answers

Which mutation would likely NOT affect the protein function significantly?

A silent mutation. Signup and view all the answers

What mechanism regulates the trp operon's expression?

Feedback inhibition when tryptophan levels are high. Signup and view all the answers

How do missense mutations affect protein function?

They can lead to the incorporation of a different amino acid. Signup and view all the answers

Study Notes

Exam 4 - Answer Key

Full Name/Discussion Section/TA Name: Record these on the scantron.
Codons Table: The codon table is on the last exam page. Consult it as needed.
Genetic Code: Turn in the genetic code with your answer sheet.

Question 1 - Nucleosomes

Region A vs Region B Differences: Region A is an open configuration, making genes in Region A more likely to be transcribed at a higher rate than B.

Question 2 - Anticodon for Tryptophan (trp)

Nucleotide Sequence: The anticodon for tryptophan (trp) is 3'-UGG-5'.

Question 3 - RNA Polymerase

Strand Read During Transcription: RNA polymerase reads the DNA template strand.

Question 4 - Lac Operon Environmental Conditions

Current Conditions: High glucose, low lactose.

Question 5 - Glucose and Lac Operon Expression

Glucose Effect: Yes, the repressor would become inactive in increased glucose levels.

Question 6 - XLM1 Gene Differences

mRNA and DNA Length Differences: The gene will be the same length in both skin and muscle cells. However, the mRNA will be longer in the muscle cells.

Question 7 - Ribosome and A-site Anticodon

A-site Anticodon Sequence: The sequence of the anticodon for the exposed codon in the A-site is 5'-UCA-3'.

Question 8 - Final Polypeptide Sequence

Sequence After Translation: Met-Gly-Pro-Leu-Ser-Arg-Val-Ser

Question 9 - Cluster of Genes

Definition: A cluster of genes under the control of one promoter is called an operon.

Question 10 - Chromosome Segment Attachment

Example: Chromosomal translocation

Question 11 - RNA Polymerase & DNA Sequence

mRNA Sequence: (The required sequence depends on the specific region depicted in the diagram, which isn't explicitly shown in the provided text).

Question 12 - Mutation and Lac Operon Expression

Effect of Operator Mutation: The operon will be expressed in the presence of lactose, with lactose able to be metabolized by the cell.

Question 13 - Mutation Location and Gene Expression

Least Likely Impact: Intron

Question 14 - Scenario 1 and 2 Gene Regulation

Cause in Scenario 1: Repressor, negative control, prokaryotic cell
A in Scenario 2: Regulatory transcription factor

Question 15 - Proline and Operon Expression

Hypothesis: Proline binds to the enzymes in the operon, inactivating them; thus, the operon is not expressed in high proline levels.

Question 16 - Mutation and Amino Acid Change

Mutation #1: A point mutation (C to G) in this situation would potentially lead to a change at the amino acid level.
Mutation #2: An insertion of a uracil (U) nucleotide will cause a frame-shift mutation.

Question 17 - Mutation 1 and Protein Change

Change in Protein: The encoded protein will be shorter than the wild-type protein due to premature termination of translation.

Question 18 - Mutation 2 and Protein Change

Change In Protein: Mutation #2 changes the amino acid sequence and will likely result in a protein of different length than the wild-type. More specifically, the frame shift is in play.

Question 19 - Eukaryotic Transcription Events

Correct Order: III, I, IV

Question 20 - Prokaryotic Transcription Splicing Location

Location: Transcription and translation in the cytosol. Splicing doesn't occur.

Question 21 - Gene Expression Input and Output

Input/Output: DNA/mRNA

Question 22 - Small Ribosomal Subunit Function

Target in Eukaryotes: The 16s rRNA, the small subunit of the ribosome will recognize the tRNA.

Question 23 - VRN4 Gene Mutation and Transcription Levels

Mutation Effect: Deletion of an enhancer sequence negatively affecting transcription and mRNA levels.

Question 24 - KRAS Gene and Cell Proliferation

KRAS Gene Description: An oncogene

Question 25 - Methylation of Gene and Transcription

Effect of Methylation: Transcription decreases.

Question 26 - mRNA Transcript Sequence from DNA

mRNA Sequence: 5'-AAUCGUGGGUGAUACUUUGUAAUUUAU-3'

Question 27 - Polypeptide Sequence

Amino Acid Sequence: Met-Phe-His-Ser-Gly-Cys

Question 28 - Methionine-tRNA Mutation

Likely Effect: Translation will not be initiated, and no protein will be made.

Question 29 - Eukaryotic Ribosome Components

Component Absent: DNA

Question 30 - DNA Coding Strand mRNA

mRNA Transcript: 5'-AUG TAC UCA TGT GGT CGT TAG-3'

Question 31 - Missense and Nonsense Mutations

Largest Change: Nonsense mutation (in the 3′ end).

Question 32 - TRP Operon Expression Conditions

Conditions for TRP Expression: Absence of tryptophan with an inactive repressor.

Question 33 - Hair Color from Cheek Cells

Possibility: No, cheek cells contain specific genes related to function as opposed to hair color genes.

Question 34 - Function of Chocolate Gene

Normal Function of Chocolate Gene: To stop the cell cycle when DNA damage is detected.

Question 35 - Polysome Protein Properties

False Statement: Polysome proteins will differ in length and amino acid sequence.

Question 36 - Prokaryotic Gene Sequences

Important Sequences: TATA box, coding region, and terminator.

Question 37 - Stem-loop Formation

Process: Termination of transcription (in prokaryotes).

Question 38 - Enzyme Order in Metabolic Pathway

Correct Enzyme Order: (This would require the provided data from the diagram). The correct enzyme order can be deciphered from the knockout data given.

Question 39 - Rescuing Mutated Cell with Supplement

Supplement for Rescue: D or E

Question 40 - Gene Regulation Differences in all Organisms

Inaccurate Statement: Mutations in DNA sequences can alter transcription levels and all other statements are true regarding gene regulation.

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Description

This document serves as the answer key for Exam 4 in Molecular Biology. It covers key concepts such as nucleosomes, the genetic code, RNA transcription, and the Lac operon. Use this key to guide your understanding of the exam materials and assess your answers.

Molecular Biology Exam 4 - Answer Key

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