Question

what shuts down the agouti gene in the thin mouse?
a the brown mouse has a different dna sequence
b a mutation that deletes the gene
c the removal of the chromosome that contains that gene
d a small chemical tag called a methyl group attached to the gene
question 19
what is a methyl groups role in epigenetics?
a it copies dna during replication
b it turns every gene on at once
c it attaches to genes and reduces their expression
d it increases the number of chromosomes
question 20
what is the epigenome?
a the part of dna that changes daily
b the total number of chromosomes in human cells.
c a system of chemical tags that controls when genes are used
d a collection of all mutations in an organism.

Explanation:

First Question (What shuts down the AGOUTI gene in the thin mouse?)

To determine the correct answer, we analyze each option:

• Option a: The brown mouse having a different DNA sequence is not related to shutting down the AGOUTI gene in the thin mouse.
• Option b: A mutation that deletes the gene would remove it rather than shut it down, and this is not the mechanism for AGOUTI gene in thin mice.
• Option c: Removing the chromosome containing the gene is not the way the AGOUTI gene is shut down in thin mice.
• Option d: Epigenetic modifications, specifically methylation (adding a methyl group), can silence genes. In the case of the thin mouse, a methyl group attached to the AGOUTI gene shuts it down.

• Option a: DNA replication is done by DNA polymerase, not methyl groups.
• Option b: Methyl groups do not turn every gene on at once; they typically have a silencing effect.
• Option c: Methyl groups attach to genes and generally reduce (silence) their expression, which is a key role in epigenetics.
• Option d: Methyl groups do not increase the number of chromosomes.

• Option a: The epigenome is not the part of DNA that changes daily; it's a stable but modifiable set of chemical tags.
• Option b: The total number of chromosomes in human cells is 46, and this is not related to the epigenome.
• Option c: The epigenome is a system of chemical tags (like methyl groups, histone modifications) that control when genes are used (expressed or silenced).
• Option d: The epigenome is not a collection of all mutations in an organism.

Answer:

d. A small chemical 'tag' called a methyl group attached to the gene

Question 19 (What is a methyl group’s role in epigenetics?)