D1.3 HL

What is gene knockout?

A technique that makes a gene inoperative to investigate its function.

How can gene knockout reveal a gene's function?

Scientists compare an organism with the inactive gene to a normal organism and observe differences.

What can a phenotype change after gene knockout suggest?

The gene normally contributes to the affected characteristic or process.

What is CRISPR?

A gene-editing system adapted from a bacterial defence mechanism against viruses.

What is the role of guide RNA in CRISPR-Cas9?

It directs Cas9 to a specific DNA sequence through complementary base pairing.

What is the role of Cas9?

An enzyme that cuts DNA at a target sequence directed by guide RNA.

How can CRISPR-Cas9 be used to edit a gene?

Guide RNA directs Cas9 to a target sequence, where DNA is cut and then repaired, allowing the sequence to be changed.

Give an example of CRISPR-Cas9 gene editing.

It can be used to disrupt a disease-associated gene or correct a faulty DNA sequence.

What are conserved gene sequences?

DNA sequences that have changed very little during evolution.

What are highly conserved gene sequences?

DNA sequences that remain almost identical across different species.

What does conservation of a gene sequence suggest?

The sequence is likely important for survival or normal biological function.

What is one hypothesis explaining conserved sequences?

Mutations in the sequence may be harmful, so natural selection removes them.

What is another hypothesis explaining conserved sequences?

The sequence may have an essential function that must be maintained across generations.

Why might non-essential DNA sequences show less conservation?

Changes in these sequences may have little effect on survival or reproduction, so they can accumulate.