20.3,4+5

Question 1

Active transcriptional factors

Answer 1

• TF site binds to specific complementary base sequence of DNA in nucleus
• Binding causes DNA to stimulate RNA polymerase
  -Transcription of Gene occurs
  -mRNA is produced, causing translation to occur
  -Protein is produced

Question 2

Transcription factor

Answer 2

-Specific molecule that moves from cytoplasm to nucleus
-Regulated expression of genes
-Regulates transcription

Question 3

Inactive TF

Answer 3

• Gene isn’t expressed
  -Site that binds to DNA isn’t active
  -Transcription can’t occur

Question 4

Oestrogen

Answer 4

• Diffuses through phospholipid layer on csm
  -In cytoplasm, binds with complementary site on oestrogen receptor TF
  -Binding causes oestrogen to change shape of DNA binding site on TF(activating it)
  -TF now enters nucleus and binds to specific complementary DNA base sequence
  -Stimulates RNA polymerase
  -transcription of gene occurs

Question 5

Epigenome

Answer 5

Chemical tags that cover histones in DNA
Determines shape of DNA-histone complex, affecting gene expression
Affected by environmental changes

Question 6

Epigenetic silencing

Answer 6

Keeps inactive genes in tightly packed arrangement
Ensures genes cannot be read(not expressed)

Question 7

Decreased acetylation of histones

Answer 7

Increases positive charge on histone
Increases attraction to phosphate groups on DNA
Association between DNA and histone is stronger
DNA isn’t accessible to TF
Gene isn’t expressed

Question 8

Increased methylation of DNA

Answer 8

• Added to cytosine base of DNA
• prevents binding of TF
  -attracts proteins that condense DNA-histone complex, so DNA is inaccessible

Question 9

Epigenetic diagnostic tests

Answer 9

detect early stages of cancer
- identify level of DNA methylation and histone acetylation

Question 10

Epigenetic cancer treatments

Answer 10

drugs inhibit enzymes involved in histone acetylation or DNA methylation

Question 11

siRNA

Answer 11

• enzyme cuts large double-stranded molecules of RNA into small interfering RNA
• one of 2 sIRNA strands combines with enzyme
  -siRNA molecule guides enzyme to mRNA by pairing up bases with complementary ones
• enzyme cuts mRNA into smaller sections
  -mRNA no longer able to be translated
  -gene hasn’t been expressed

Question 12

Malignant

Answer 12

Cancerous
uncontrolled rapid growth
spread around the body(metastasis)
Systematic effects
cells become undifferentiated

Question 13

Benign tumors

Answer 13

Non-cancerous
Stays in one place
Applies pressure to organs
Localised effect
Cells are specialised

Question 14

Proto-oncogenes

Answer 14

Has protein receptor on csm which growth factor attaches to
Activates genes that cause DNA to replicate and cell to divide

Question 15

Oncogene

Answer 15

• proto-oncogene mutates
• receptor on csm is permanently activated
  -uncontrolled cell division occurs even without growth factor
  or
  -can code for growth factor that is produced in excessive amounts
  -uncontrolled cell division occurs

Question 16

Tumour suppressor gene

Answer 16

slow down cell division
repair mistakes in DNA
controls apoptosis(programmed cell death)

Question 17

Mutated tumour suppressor gene

Answer 17

Becomes inactivated
Stops inhibiting mitosis
Uncontrolled cell growth occurs
Tumour is produced

Question 18

Hypermethylation of tumour suppressor genes

Answer 18

• increased methylation in promoter region of tsg
• tumour suppressor gene becomes inactivated
• no longer inhibits mitosis
  -uncontrolled cell division occurs

Question 19

Hypomethylation of proto-oncogenes

Answer 19

-decreased methylation causes them to act as oncogenes
-stimulated uncontrolled cell division

Question 20

Oestrogen causing cancer

Answer 20

• oestrogen binds to receptor which promotes transcription in gene that controls cell division/growth
• gene is expressed and uncontrolled growth occurs
  -causes proto-oncogenes to turn into oncogenes

Question 21

epigenetics

Answer 21

Heritable changes in gene function without changes to the base sequence of DNA