Gene regulation in eukaryotes

Question 1

what is the structure of chromatin?

Answer 1

DNA wrapped around histones and joined together to form nucleosomes which join together to from chromatin

Question 2

describe features of heterochromatin

Answer 2

amino acids in histones give off positive charge so the negatively charged DNA tightly binds making it inaccessible for transcription
methylated DNA

Question 3

describe features of euchromatin

Answer 3

lightly packed chromatin
acetyl group neutralises histones positive charge
unmethylated DNA

Question 4

what is the inactive state of transcription?

Answer 4

RNA polymerase isn’t bound to the tightly packed chromatin - no phosphorylation

Question 5

what is the paused state of transcription?

Answer 5

RNA polymerase and transcription factors are bound to promotor but remain inactive - single phosphorylation

Question 6

what is the active state of transcription?

Answer 6

more transcription factors bind and RNA polymerase becomes phosphorylated

Question 7

what is RNA processing?

Answer 7

the addition of caps turns pre-mRNA into mature mRNA and introns are spliced out

Question 8

what are 2 types of small RNA?

Answer 8

• small interfering RNA

- micro RNA

Question 9

what does siRNA do?

Answer 9

Repression of gene transcription via chromatin remodelling and DNA methylation

Question 10

what does miRNA do?

Answer 10

• repression of gene translation

- promotes mRNA degradation

Question 11

describe the process of protein degradation?

Answer 11

• ubiquitin molecules attach to a protein
• proteasome responds and unfolds the protein
• enzymes cut the protein into small peptides which cam be further degraded by other enzymes in the cytosol