Question 1

Which of the following best explains why tigons (offspring of a female lion and a male tiger) are typically the same size as their parents or smaller, rather than larger like ligers (offspring of a female tiger and a male lion)?

Accepted Answer

Genomic imprinting leads to reduced expression of growth factor genes from the paternal tiger.

Question 2

The Dutch 'Hunger Winter' study found that children born to mothers who experienced malnutrition during the first 10 weeks of pregnancy had increased risk of obesity, diabetes, and cardiovascular disease as adults. What is the molecular basis for this observation?

Accepted Answer

Reduced methylation of IGF2, resulting in an imprinting error and altered gene expression.

Question 3

Which statement about the genetic code is correct?

Accepted Answer

An amino acid can be encoded by more than one codon.

Question 4

A mutation changes the DNA sequence 5'-TGG-3' to 5'-TGA-3'. What is the consequence of this mutation at the protein level?

Accepted Answer

A nonsense mutation introducing a premature stop codon.

Question 5

Which of the following is a real-world example of an epigenetic effect caused by environmental factors?

Accepted Answer

Increased risk of disease in adults whose mothers experienced famine during pregnancy due to altered DNA methylation.

Question 6

Which of the following codons is a start codon in the standard genetic code?

Accepted Answer

$$\mathrm{AUG}$$

Question 7

What is the 'wobble hypothesis' and how does it relate to the degeneracy of the genetic code?

Accepted Answer

It explains that relaxed base-pairing at the third position of the codon allows a single tRNA to recognize multiple codons.

Question 8

Which of the following is an exception to the universal genetic code?

Accepted Answer

$$\mathrm{UGA}$$ codes for tryptophan in human mitochondria.

Question 9

A section of mRNA reads 5'-AUGCCGACUGCUAACCG-3'. If translation begins at the first AUG, what is the sequence of amino acids produced?

Accepted Answer

Met-Pro-Thr-Ala-Asn-Arg

Question 10

Why do some viruses have overlapping genes in their genomes?

Accepted Answer

To increase the number of proteins encoded without increasing genome size.

Question 11

Which of the following statements about promoters is correct?

Accepted Answer

Promoters determine which strand of DNA is used as the template for transcription.

Question 12

If a mutation introduces a stop codon in the middle of a gene, what type of mutation is this and what is its likely effect?

Accepted Answer

Nonsense mutation; results in truncated, nonfunctional protein.

Question 13

Which of the following best describes the genetic code?

Accepted Answer

It is commaless, meaning there are no breaks between codons during translation.

Question 14

A tRNA with the anticodon 3'-UAC-5' will pair with which mRNA codon?

Accepted Answer

$$\mathrm{AUG}$$

Question 15

Which of the following is true regarding codon-anticodon base pairing at the wobble position?

Accepted Answer

The third base of the codon can pair with multiple bases in the anticodon.

Question 16

Which of the following is a consequence of the degeneracy of the genetic code?

Accepted Answer

Multiple codons can specify the same amino acid.

Question 17

A mutation in the mitochondrial genome changes the codon AGA from coding for arginine to a stop codon. What is the effect of this mutation?

Accepted Answer

Premature termination of protein synthesis at AGA codons.

Question 18

Which of the following best describes the process of transcription?

Accepted Answer

mRNA is synthesized from the DNA template strand, with uracil replacing thymine.

Question 19

If the mRNA sequence is 5'-UAGCUGGUCCCGAU-3', what amino acids are encoded in the third reading frame?

Accepted Answer

Gly-Ser-Arg

Question 20

Which of the following is NOT a feature of the standard genetic code?

Accepted Answer

It is ambiguous, with some codons specifying more than one amino acid.

Genetic Code, Epigenetic Memory, and Hybrid Genetics: Oct 22

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