GENE EXPRESSION

Question 1

types of variation (2)

Answer 1

• difference in DNA sequence i.e diff alleles

- physiological effects of environment i.e light intensity on plant growth

Question 2

Epigenetic

Answer 2

• affect how genes are expressed without changing nucleotide sequence

Question 3

DNA methylation (3)

Answer 3

• a methyl/hydroxymethyl group is added to a base
• still read and paired at transcription
• heavily methylated cells are less likely to be transcribed

Question 4

Histone modification

Answer 4

• Attaching acetyl groups to bases
• alters how histone proteins interact
• DNA is more/less coiled making it harder/easier to transcript.

Question 5

how does this relate to cell differentiation

Answer 5

epigenetic changes causes cells to differentiate i.e skin cells produce menalin

Question 6

proof of epigentic changes

Answer 6

• in monozygotic twins they show changes

- as the get older and DNA damage is repaired incorrectly they become less similar

Question 7

consequences of epigenetic changes (2)

Answer 7

• genomic imprinting

- X inactivation

Question 8

What is genomic imprinting (2)

Answer 8

• if genes are inactivated in gametes they can be transferred to the next generation
• so if a certain gene is turned off, only one chromosome will be expressed (either maternal or paternal) leaving individual vulnerable to certain conditions

Question 9

x inactivation (3)

Answer 9

• a whole chromosome is switched off
• becomes mass of densely staining chromatin called Barr body
• random inactivation causes tortoiseshell cats