Stem cells (D)

Question 1

What is stem cell?

Answer 1

A cell able to differentiate into other cell types

Question 2

What is a totipotent cell?

Answer 2

• SCs can differentiate into any type of cell including extra-embryonic cells (cells that make up placenta and umbilical cord)
• found in embryo, placenta, umbilical cord
• found a few days after fertilisation (outer layer of the blastocyst)

Question 3

What is a pluripotent cell?

Answer 3

• SCs can differentiate into many cell types such as embryonic ones but not extra-embryonic cells
• Found in the inside mass of the blastocyst a few days after fertilisation

Question 4

Explain the uses of embryonic stem cells

Answer 4

• they make use of waste embryos so this is an ethical objection
• ethical alternatives such as embryo from IVF
• can be used to test treatments

Question 5

Explain the discussion of adult stem cells

Answer 5

• Immune system may reject the stem cells as foreign
• They are good for replacement and repair
• These have limited capabilities
• low number of donors

Question 6

Explain differential gene expression

Answer 6

Where certain genes from the identical genomes are inactivated or inactivated causing different genes to be expressed

Question 7

How does differential gene expression occur?

Answer 7

The activated genes are translated in mRNA to form proteins, as proteins form the cell modifies more and the stem cell is differentiated into another cell type in this way

Question 8

How do transcription factors promote/inhibit differentiation?

Answer 8

They bind to certain sections of DNA to transcribe genes or stop genes from being expressed
(this is how brain cells are made despite having the same DNA as every other cell)

Question 9

Explain the role of an activator?

Answer 9

Activators are transcriptions factors which activate RNA polymerase to DNA at the start of the gene and begin transcription

Question 10

Explain the role of a repressor?

Answer 10

They prevent RNA polymerase from binding to the gene and beginning transcription

Question 11

Explain the concept of an operon?

Answer 11

A cluster of genes with the same promoter region to control the production of LACTASE

Question 12

What is the structure of the lac operon?

Answer 12

Promoter
Repressor
Operator
Genes
POG is from DNA
R is an external protein
It occurs to transport and metabolise lactose in E.coli

Question 13

What happens when lactose is present

Answer 13

• Lactose attaches to the repressor and changes its shape
• ## This allows the RNA polymerase to attach to the promoter and begin transcription

Question 14

Explain the role of the promoter in operon

Answer 14

To begin the transcription sequence

Question 15

Explain the role of the operator and repressor

Answer 15

It is an on/off switch of the operon and the repressor turns the operator off

Question 16

What is lacL?

Answer 16

lacL and its promoter transcribe genes to produce the repressor