Epigenetics LAC OPERON LEFT

Question 1

How does the genotype interact with the phenotype?

Answer 1

• External factors can cause genetic changes
• UV light may cause changes in production of melanin (skin pigmentation)

Question 2

Explain epigenetic changes

Answer 2

The changes in gene expression by factors, apart from the DNA sequence

Question 3

What are the 2 factors causing epigenetic changes?

Answer 3

• Acetylation of histones
• DNA Methylation

Question 4

Explain the acetylation of histones

Answer 4

• Acetyl groups attach to lysine amino acids
• Lysine’s R groups (+), and the phosphate backbone of DNA (-)
• This helps DNA to coil tightly around histones
• Addition of acetyl groups means + ions are removed
• So the DNA is less tightly coiled, the RNA polymerase and transcription factors can bind more easily and gene expression occurs

Question 5

Explain the affect of deacetylation of histones

Answer 5

• Removal of acetyl groups inhibits transcription
• gene stops being expressed

Question 6

Explain DNA methylation

Answer 6

Methyl groups are added to cytosine bases

Question 7

Explain the affect of methylation of DNA on genes

Answer 7

• This causes suppression of transcription in the affected gene by inhibiting the binding of transcription factors
• Methylation of DNA causes genes to be in the permanent ‘off’ position
• This is called repression/inactivation

Question 8

What are the causes of DNA methylation?

Answer 8

This can be caused by environmental, age, lifestyle factors

Question 9

What is polygenic?

Answer 9

Characteristics that are controlled by multiple gene
eg. mass, height etc

Question 10

How does environment affect phenotypic variation?

Answer 10

Plants that are grown in the dark may grow yellow, even if the genes make it green

Question 11

Why aren’t environmental factors inherited?

Answer 11

Because they do not impact DNA unlike genetic variation

Question 12

Explain how a phenotype affected by many different genes will show continuous variation?

Answer 12

1 gene impacts Variation; May affect a small area of a person’s phenotype
Multiple genes impact Variation; A significant impact because of a

Question 13

How do bacteria like E.Coli utilise lac operon?

Answer 13

E.coli require a source of energy like glucose. If this is not available but lactose is available then this is transported and metabolized using the lac operon.

Question 14

How does lac operon work in the absence of lactose?

Answer 14

The lac repressor will bind to the operator and prevent RNA from transcribing the Lac operon sequence