stem cells and epigenetics

Question 1

definition of stem cells

Answer 1

cells that can divide by mitosis into 2 genetically identical daughter cells. one remains as daughter cells and the other differentiates into a specialised cell by translating part of their dna

Question 2

definition of totipotent

Answer 2

divide and differentiate into any cell type.
found in embryos

Question 3

definition of pluripotent

Answer 3

dive and differentiate into most type of cells

Question 4

definition of multipotent

Answer 4

divide and differentiate into a limited number of cells

Question 5

definition of unipotent

Answer 5

divide a limited amount of times and can differentiate into one type of cell

Question 6

suggest how molecule increasing gene expression works

Answer 6

molecule is a transcription factor
binds to promoter region in dna as complimentary
stimulates rna polymerase
transcription

Question 7

describe how oestrogen works as a transcription factor

Answer 7

oestrogen is lipid soluble and diffuses through phospholipid cell surface membrane
oestrogen is complimentary to oestrogen receptor so binds
this changes tertiary structure of protein receptor
releasing the transcription factor
transcription factor is complimentary to the promoter region
stimulates rna polymerase to transcribe the gene increasing transcription so mature mrna is produced

Question 8

how do interfering RNA work

Answer 8

Single strand of miRNA or siRNA binds to a protein in the cytoplasm to form a complex - RISC
miRNA or siRNA has a complimentary base sequence to part of a specific mRNA molecule
RISC inhibits gene expression by binding to the complementary mRNA this..
1 mRNA is hydrolysed by and enzyme
2 inhibits the initiation of ribosomal translation , ribosome is prevented from attaching to the mRNA
Translation does not take place the polypeptide is not produced and the expression of the gene has been silenced

Question 9

why some protein could still be made even if there is interfering RNA

Answer 9

not all mRNA destroyed so some translation still takes place

Question 10

define epigenetics

Answer 10

heritable changes in gene function without changes to base sequence of DNA

Question 11

tumour suppressor genes

Answer 11

codes for polypeptides that stop cell division

Question 12

proto onco genes

Answer 12

codes for polypeptides that start cell division

Question 13

what is a tumour

Answer 13

a mass of cells from uncontrolled cell division

Question 14

difference between malignant and benign tumour

Answer 14

m = cells can metastasise and can spread around the body
b = cells cant metastasise and will not spread around the body

Question 15

How does increased methylation of dna inhibit transcription

Answer 15

Methyl group added to carbon 5 of a cytosine base catalysed by methlytransferase
This silences the affected gene by preventing transcription factors bind to the promoter region
Prevents activation of rna polymerase and inhibits transcription

Question 16

How does decreased acetylation inhibit transcription

Answer 16

Chromosomal dna of eukaryotes is wrapped around histones
Wrapping can be tight or loose
Decreased acetylation results in histones moving closer together and tightly packed
Promoter regions are not exposed and transcription factors cannot bind
RNA polymerase cannot bind and target gene cannot be transcribed

Question 17

Changes to a tumour suppressor gene

Answer 17

Increased methylation , rate of cell division increases
Increased acetylation, rate of cell division decreases

Question 18

Changes to an oncogene

Answer 18

Decreased methylation , rate of cell division increases
Decreased acetylation , rate of cell division decreases