Molecular Biology Core Concepts Practice Test Practice Tests

Question 1

A DNA sequence contains 30% adenine. What percentage of guanine is present?

Accepted Answer

20%

Answer

30%

Answer

40%

Answer

60%

Question 2

During DNA replication, a mutation occurs where a single base pair is inserted into the coding region of a gene. If the original gene coded for a protein with 100 amino acids, how many amino acids would you expect the mutated protein to have before a stop codon is encountered, assuming the insertion causes a frameshift?

Accepted Answer

It is impossible to determine the exact number of amino acids without knowing the specific insertion point and the new reading frame. The frameshift could lead to a premature stop codon, resulting in a protein shorter than 100 amino acids, or it could extend the protein beyond 100 amino acids until a new stop codon is encountered.

Question 3

Okazaki fragments are synthesized on the leading strand during DNA replication.

Accepted Answer

True

Answer

False

Question 4

Which enzyme is primarily responsible for unwinding the DNA double helix during replication?

Accepted Answer

Helicase

Answer

DNA polymerase

Answer

Ligase

Answer

Primase

Question 5

Which of the following are involved in mRNA processing in eukaryotes?

Answer

Addition of a 5' cap

Answer

Replication

Answer

Splicing

Answer

Addition of a poly-A tail

Answer

Translation

Question 6

A particular tRNA molecule has the anticodon 5'-IAG-3'. What codon on the mRNA would it recognize? Note: 'I' represents inosine, which can pair with A, U, or C.

Accepted Answer

5'-CUU-3'

Question 7

If a gene has the sequence 5'-ATG-CGT-GAC-3', what is the sequence of the mRNA transcribed from this gene?

Accepted Answer

5'-AUG-CGU-GAC-3'

Answer

5'-ATG-CGT-GAC-3'

Answer

5'-TAC-GCA-CTG-3'

Answer

5'-UAC-GCA-CUG-3'

Question 8

RNA polymerase requires a primer to initiate transcription.

Accepted Answer

True

Answer

False

Question 9

In the lac operon, if the concentration of lactose is high and the concentration of glucose is low, what is the expected level of transcription of the lac operon genes?

Accepted Answer

C. High transcription due to the presence of lactose and low glucose levels.

Answer

A. No transcription due to the presence of lactose.

Answer

B. Low transcription due to the presence of glucose.

Answer

D. Moderate transcription regardless of lactose and glucose levels.

Question 10

The rate of tryptophan synthesis is regulated by the trp operon. If the intracellular concentration of tryptophan is 10 $\mu$M and the dissociation constant (Kd) for the tryptophan-repressor complex is 1 $\mu$M, calculate the fraction of repressor bound to tryptophan using the equation: Fraction Bound = [Tryptophan] / (Kd + [Tryptophan]).

Accepted Answer

Fraction Bound = 10 $\mu$M / (1 $\mu$M + 10 $\mu$M) = 10/11 ≈ 0.91

Question 11

Which of the following eukaryotic gene regulation mechanisms can lead to multiple different proteins being produced from a single gene?

Answer

A. Alternative RNA splicing

Answer

B. DNA methylation

Answer

C. Post-translational modification

Answer

D. Histone deacetylation

Question 12

DNA methylation generally leads to increased gene expression by promoting chromatin accessibility.

Accepted Answer

False

Answer

True

Question 13

A researcher introduces a synthetic siRNA that perfectly matches a specific mRNA sequence in human cells. If the initial concentration of the mRNA is 1000 molecules and the siRNA effectively degrades 95% of the target mRNA, how many mRNA molecules are expected to remain?

Accepted Answer

50 mRNA molecules

Question 14

A mutation in a Hox gene in a developing Drosophila embryo results in the transformation of the third thoracic segment (T3) into a second thoracic segment (T2). Which of the following best describes the likely function of the mutated Hox gene?

Accepted Answer

B. Specifies the identity of the T3 segment.

Answer

A. Represses the development of all thoracic segments.

Answer

C. Promotes the development of the T2 segment.

Answer

D. Regulates the overall size of the embryo.

Question 15

A cell with a diploid number of 24 chromosomes undergoes mitosis. How many chromosomes will each daughter cell have?

Accepted Answer

24

Answer

12

Answer

48

Answer

6

Question 16

A cell with a diploid number of 20 chromosomes undergoes meiosis. How many chromosomes will each daughter cell have?

Accepted Answer

10

Answer

5

Answer

20

Answer

40

Question 17

If a plant cell starts mitosis with 20 chromosomes, how many chromosomes will be present in each of the two new nuclei after telophase?

Accepted Answer

20

Question 18

Meiosis results in genetically identical daughter cells.

Accepted Answer

True

Answer

False

Question 19

Which of the following events occur during meiosis but NOT during mitosis? (Select all that apply)

Answer

DNA replication

Answer

Crossing over

Answer

Reduction in chromosome number

Answer

Separation of sister chromatids

Question 20

A diploid cell has 2n = 36 chromosomes. How many chromatids are present in the cell during prophase I of meiosis?

Accepted Answer

72

Molecular Biology Core Concepts Practice Test Practice Tests

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Molecular Biology Core Concepts Practice Test

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