regulation of transcription and translation

Question 1

in eukaryotes

Answer 1

1. transcription factors move from cytoplasm to nucleus
2. bind to specific DNA sites on target gene (genes they control expression of)
3. control rate of transcription
4. activators stimulate/increase rate of transcription
5. repressors inhibit or decrease rate of transcription

Question 2

how oestrogen affects expression of genes

Answer 2

1. hormone, binds to transcription factor called oestrogen receptor.
2. forms oestrogen - oestrogen receptor complex
3. moves from cytoplasm into nucleus where it binds to specific DNA sites near start of target gene
4. can acts as activator of transcription

Question 3

RNA interference RNAi

Answer 3

RNA molecules (siRNA or miRNA) stop mRNA being translated into proteins

Question 4

siRNA (smal interfering RNA) in mammals

miRNA (microRNA)in plants

Answer 4

1. in cytoplasm double stranded siRNA unwinds due to proteins.
2. single strand binds to target mRNA (base sequence complimentary to target mRNA
3. proteins associated with siRNA cut mRNA into fragments - no longer be translated
4. fragments move into processing body where theyre degraded
5. similar process with miRNA in plants

Question 5

miRNA in mammals

Answer 5

1. not usually fully complimentary to target mRNA - less specific than siRNA so targets more than 1 mRNA
2. unwinds dues to proteins and binds to target mRNA in cytoplasm
3. blocks translation or target mRNA
4. mRNA moved into processing body -> stored (for translation later) or degraded