▶️ Answer/Explanation
Question
Which statement correctly describes genome and proteome?
Only the genome but not the proteome can be analysed using gel electrophoresis.
The genome and the proteome are the same in all tissues in an organism.
In cells of different tissues, the genome is the same while the proteome varies.
Only mutations in the proteome but not in the genome cause any variability.
▶️Answer/Explanation
Answer: C. In cells of different tissues, the genome is the same while the proteome varies.
Explanation:
Let’s break down the key terms first:
- Genome = The complete set of DNA (genetic instructions) in an organism.
It is identical in almost every cell of the same organism. Proteome = The full set of proteins made by a cell or tissue.
It can change depending on the cell type, environment, or conditions.
Now, let’s evaluate each option:
A. Not true. Both DNA and proteins can be separated and analyzed using different types of gel electrophoresis (e.g., SDS-PAGE for proteins).
B. The genome is the same, but the proteome is not. Different tissues express different proteins.
C. Correct. Every cell has the same DNA, but different cells produce different proteins depending on their function.
D. This is incorrect because mutations occur in the genome, not in the proteome. The proteome reflects changes in the genome or environmental conditions.
Question
What is a proteome?
The genes that code for all the proteins in the ribosome
The group of proteins that generate a proton gradient in mitochondria
The entire genome of a prokaryote
The entire set of proteins expressed by an organism at a certain time
Answer/Explanation
Answer: D. The entire set of proteins expressed by an organism at a certain time.
Explanation:
The proteome is the full range of proteins that are produced or expressed by a cell, tissue, or organism.
Unlike the genome (which is mostly constant), the proteome can change depending on:
- The type of cell
- The stage of development
- Environmental conditions
- Time of day, etc.
Why the other options are incorrect:
A. The genes that code for all the proteins in the ribosome → That describes a subset of the genome, not the full proteome.
B. The group of proteins that generate a proton gradient in mitochondria → That’s referring to the electron transport chain, not the entire proteome.
C. The entire genome of a prokaryote → That’s the genome, not the proteome.
Question
The number of protein-coding genes in the human genome is estimated to be about 20 000, which is much less than the size of the proteome. What is one reason for this?
A. Exons are removed from RNA before translation.
B. There are more types of amino acids than nucleotides.
C. mRNA can be spliced after transcription.
D. Base substitutions occur during transcription.
Answer/Explanation
Answer: C. mRNA can be spliced after transcription.
Explanation:
The human genome has about 20,000 protein-coding genes, but the proteome (total number of different proteins we can make) is much larger possibly hundreds of thousands.
Why?
Because of a process called alternative splicing.
- After DNA is transcribed into mRNA, that mRNA can be spliced in different ways.
- Different exons (coding regions) can be included or skipped.
- This allows one gene to produce many different protein versions (called isoforms).
Let’s review the options:
A. Incorrect – It’s the introns that are removed, not exons. Exons stay in and get translated.
B. Incorrect – There are 20 amino acids and 4 nucleotides, but that’s not related to proteome size.
C. Correct – This allows multiple proteins to be made from a single gene, increasing the size of the proteome.
D. Incorrect – While mutations can happen, they don’t explain the large increase in proteome size.