Gene Expression

Question 1

Effect of oestrogen on gene transcription

Answer 1

Oestrogen activates the transcriptional factor of a gene by changing the shape of the DNA binding site.
Transcription of gene then occurs and gene is constantly activated

Question 2

How does siRNA work?

Answer 2

Double stranded RNA broken into siRNA by an enzyme.
siRNA combines with an enzyme
siRNA pairs complementary to bases on mRNA strand
Enzyme cuts mRNA into small sections

Question 3

What is base methylation?

Answer 3

Addition of methyl group to bases in DNA. Inhibits transcription of genes by preventing binding of transcriptional factors or by condensing DNA-histone complex

Question 4

What is acetylation?

Answer 4

An acetyl group is donated from acetylcoenzymeA. Decreased acetylation increases attraction between histones and phosphate groups of DNA so DNA is not accessible to transcription factors

Question 5

Result of hyper methylation?

Answer 5

Leads to tumour suppressor genes being inactivated

Question 6

What are oncogenes?

Answer 6

Mutations of Proto-oncogenes. Proto oncogenes stimulate a cell to divide when activated. Oncogenes cause a cell to become permanently activated

Question 7

How are DNA fragments produced?

Answer 7

reverse transcriptase forms cDNA from mRNA
restriction endonucleases cut the DNA double strand at specific base sequences.
gene machine makes gene from oligonucleotides

Question 8

How does in-vivo gene cloning work?

Answer 8

DNA and plasmids are combined then inserted into the cell which then divides

Question 9

How does in-vitro gene cloning work?

Answer 9

mixture containing DNA, primers, free nucleotides and DNA polymerase is heated then cooled and heated again to create copies of the DNA