8.2 Gene Expression

Question 1

What are totipotent cells?

Answer 1

Cells which can mature into any body cell

Question 2

How do totipotent cells differentiate?

Answer 2

Translate only part of their DNA

Question 3

What are pluripotent stem cells?

Answer 3

Stem cells which can differentiate an unlimited number of times into a limited number of specialised cells
-e.g bone marrow stem cells

Question 4

What are unipotent stem cells?

Answer 4

Stem cells which can only differentiate into a single type of cell
-e.g cardiomyocte

Question 5

How are induced pluripotent stem cells produced?

Answer 5

Unipotent stem cells and the appropriate protein transcription factors

Question 6

What do transcription factors do?

Answer 6

Control the transcription of genes

Question 7

How do transcription factors function?

Answer 7

• Move from cytoplasm to nucleus
• Bind to specific DNA site (promoter region) of the target gene (upstream)
• Activator or repressor for RNA polymerase activity

Question 8

How does oestrogen affect transcription?

Answer 8

• Binds to oestrogen receptor ( transcription factor) outside of the nucleus
• Forms oestrogen - oestrogen receptor complex which moves into nucleus
• Binds to promoter region
• Activator / repressor

Question 9

What are epigenetic changes?

Answer 9

Inheritable chemical changes to DNA that alter DNA’s interaction with other proteins without altering the base sequence

Question 10

Effect of increased methylation?

Answer 10

• More methyl groups attach to DNA

- Prevents transcriptional machinery to interact with the gene

Question 11

Effect of increased acetylation?

Answer 11

• Acetyl groups bond to histone proteins
• More acetyl groups = chromatin less condensed around histones ∴ less coiling
• Allows transcriptional machinery to access

Question 12

Why can epigenetic changes cause disease?

Answer 12

Increased/ decreased transcription of genes e.g. t.s.g or oncogenes

Question 13

What is RNAi

Answer 13

RNA interference is when small, double stranded RNA molecules can prevent the translation of mRNA

Question 14

What are the molecules involved with RNAi

Answer 14

siRNA - small interfering
miRNA - micro
Associated proteins/enzymes
Processing bodies

Question 15

Describe the action of siRNA

Answer 15

1) Double stranded siRNA associate with proteins and winds
2) Single strand binds to complementary target mRNA
3) Proteins cut mRNA into fragments
4) Fragments move to a processing body to be degraded

Question 16

Describe the action of miRNA

Answer 16

1) Single stranded miRNA associate with proteins and binds mRNA
2) Complex blocks translation
3) Complex moved to processing body to either store or degrade

Question 17

Differences between siRNA and miRNA

Answer 17

• miRNA isn’t fully complementary ∴ can target multiple mRNA molecules
• miRNA binds with proteins and mRNA together

Question 18

Tumour definition

Answer 18

Abnormal mass of tissue formed of excess cells

Question 19

Malignant tumour definition

Answer 19

• Tumours which grow quick and invade and destroy surrounding tissue

Question 20

What contains benign tumours?

Answer 20

Fibrous tissue which prevents cell invasion

Question 21

Tumour suppressor gene function

Answer 21

Produce proteins which control cell division and apoptosis to control cell life cycle

Question 22

Proto-oncogene function

Answer 22

Produce proteins which stimulate cell division

Question 23

Are oncogenes more active than proto-oncogenes?

Answer 23

Yes hence cancer

Question 24

What can contribute to breast cancer?

Answer 24

Increased oestrogen exposure