Question 1

Which of the following best describes a protein family?

Accepted Answer

A group of proteins that share similar amino acid sequences, structural features, and often related functions due to a common evolutionary origin.

Question 2

A mutation in the sixth position of the beta chain of hemoglobin results in sickle cell anemia. Which amino acid substitution occurs in this disease?

Accepted Answer

Glutamic acid is replaced by valine.

Question 3

Why do some proteins, such as cytochrome c, show highly conserved amino acid sequences across different species?

Accepted Answer

Because mutations in critical residues would disrupt essential functions, leading to non-viable organisms.

Question 4

Which experimental technique is depicted in the first image (top two panels) and is used to distinguish between normal and sickle cell hemoglobin?

Accepted Answer

Two-dimensional paper chromatography of digested peptides.

Question 5

Refer to the second image (red blood cells). What is the primary structural difference between the cells shown in (a) and (b)?

Accepted Answer

Cell (a) is a normal, disc-shaped red blood cell, while cell (b) is a sickle-shaped red blood cell due to a mutation in hemoglobin.

Question 6

Which of the following statements about gene duplication is correct?

Accepted Answer

Gene duplication provides raw material for evolutionary innovation by allowing one copy to mutate and acquire new functions.

Question 7

Cytochrome c is a member of a protein family involved in which cellular process?

Accepted Answer

Electron transport chain and apoptosis.

Question 8

The phylogenetic tree of cytochrome c (see fifth image) shows similar evolutionary distances between mammals, insects, and plants. What does this suggest about mutation rates?

Accepted Answer

Mutation rates are relatively constant over time, regardless of generation time.

Question 9

Which of the following best explains why sickle cell disease persists in certain populations?

Accepted Answer

Heterozygous individuals are resistant to malaria, providing a selective advantage in malaria-endemic regions.

Question 10

Which of the following is an example of a conserved substitution in protein evolution?

Accepted Answer

Replacing aspartic acid (Asp) with glutamic acid (Glu).

Question 11

Which of the following equations best represents the calculation of the percentage of accepted mutations (PAM) between two protein sequences?

Accepted Answer

$$	ext{PAM} = \frac{	ext{Number of accepted point mutations}}{	ext{Total number of amino acids}} 	imes 100$$

Question 12

Which bioinformatics tool is commonly used to identify protein families based on sequence similarity?

Accepted Answer

BLAST

Question 13

A new protein is discovered and found to be part of the serine protease family. What can you infer about its likely function?

Accepted Answer

It likely cleaves peptide bonds using a serine residue at its active site.

Question 14

Which of the following statements about the globin family is correct?

Accepted Answer

Hemoglobin and myoglobin are both members of the globin family, but hemoglobin is specialized for oxygen transport while myoglobin is specialized for oxygen storage.

Question 15

Which of the following best describes 'neutral drift' in protein evolution?

Accepted Answer

A process where amino acid changes do not affect protein function and accumulate over time.

Question 16

Which of the following is a real-world application of understanding protein families in medicine?

Accepted Answer

Designing kinase inhibitors that specifically target cancer cells while minimizing effects on other kinases.

Question 17

Which of the following statements about protein evolution and organismal evolution is correct?

Accepted Answer

Protein evolution can occur rapidly with few mutational changes, often due to changes in gene expression rather than protein sequence.

Question 18

Which of the following best explains why some regions of a protein sequence are highly variable while others are conserved?

Accepted Answer

Conserved regions are critical for protein function, while variable regions are less important for activity.

Question 19

Which of the following is a likely outcome of gene duplication in evolution?

Accepted Answer

The duplicated gene may acquire mutations and evolve a new function.

Protein Families: Structure, Evolution, and Functional Implications

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