Gene function

Question 1

Homology

Answer 1

The similarity between 2 objects, due to a common ancestry

Question 2

orthologous genes

Answer 2

Genes present in two different species, arising from a common ancestor that underwent speciation

Question 3

Paralogous genes

Answer 3

Genes present in the same organism, arising from the duplication of an ancestral gene

Question 4

sequence alignment

Answer 4

Looking in databases for known genes sharing substantial similarity
Both nucleotide and amino acid sequences
More sophisticated for amino acids

Question 5

approaches to inactivate a gene

Answer 5

Homologous recombination
RNA interference
CRISPR

Question 6

Homologous recombination (for gene inactivation)

Answer 6

• Endogenous portion of DNA is replaced by exogenous DNA segment
• The exogenous DNA (deletion cassette) is comprised between 2 homology arms. Having the same sequence of the DNA flanking the gene that has to be deleted
• The deletion cassette usually encodes for a selectable marker gene (bijv. antibiotic resistance)
• The exogenous gene will be expressed, allowing selection of knockout cells

Question 7

RNA interference

Answer 7

Silences a gene, in stead of disturbing it.
- Based on the use of short RNA molecules that are complementary to the target RNA
- they are produced starting from a longer double-stranded RNA procursor
- These short RNAs (siRNAs) are loaded inside a protein called argonaute (Ago) that is part of the RNA-induced Silencing Complex (RISC)
- Ago, guided by the siRNA, introduces a cut in the target RNA, inducing its degradation

Question 8

Gene knockdown

Answer 8

The number of RNA molecules for the gene of interest will be drastically reduced, but some residual RNA will still be present