Gene expression

Question 1

What is cancer

Answer 1

Mutations in genes that cause uncontrolled mitosis resulting in a tumour

Question 2

Properties of a benign tumour

Answer 2

Can grow large but at a slow rate

cannot spread by metastasis

surrounded by a capsule

contain adhesion molecules to remain compact

localised

Question 3

properties of malignant tumour

Answer 3

grow large rapidly

can spread by metastasis

develop their own blood supply

need supplementary treatment, chemo or radiotherapy

Question 4

Three causes of tumour formation

Answer 4

Hypermethylation of tumour supressor genes

hypomethylation of oncogenes

increased oestrogen conc in by fat cells in breast tissue

Question 5

What do oncogenes do and how can they cause cancer

Answer 5

code for a protein that causes DNA replication + mitosis

can be permanently switched on causing excessive cell division

hypomethylation increases expression as chromatin is less condensed

Question 6

What do tumour suppressor genes do and how can they cause cancer

Answer 6

code for a protein that inhibits cell division and causes apoptosis

mutation can inhibit apoptosis and stimulate cell division

hypermethylation limits genes transcription so tumours can form as cell division can become uncontrolled and apoptosis is inhibited

Question 7

How does oestrogen lead to cancer

Answer 7

production stops at menopause

fat cells in breast tissue produce oestrogen

oestrogen activates transcription factors which can cause transcription of oncogenes

formation of tumour leads to increased oestrogen product and increases tumour size and attracts white blood cells

Question 8

What are the types of silent mutations

Answer 8

Where a base substitution does not change the amino acid sequence as the genetic code is degenerate

a mutation that occurs in non coding regions of DNA will not be translated into the amino acid sequence so no change in sequence

a mutation that causes a change in the tertiary structure of the protein, but has no major effect on the organism

Question 9

What is an insertion and deletion mutation in DNA sequence what does it cause

Answer 9

one or more nucleotide pairs are inserted into the DNA sequence

one or more nucleotide pairs are deleted from the DNA sequence

both cause frameshifts in the DNA base sequence
(insertion right)
(deletion left)

this will change the amino acid sequence of a polypeptide

Question 10

What is a duplication mutation

Answer 10

One or more bases are repeated and will cause a frameshift

same effect as insertion

Question 11

What is an inversion mutation

Answer 11

a group of bases become separated from the dna base sequence and rejoin in reverse order

this changes the amino acid sequence and therefore primary + tertiary structure of protein

Question 12

What is a translocation mutation

Answer 12

when a group of bases become separated on one chromosome and are inserted into the DNA sequence on another chromosome

leads to a significant effect on phenotype as different genes on different chromosomes

Question 13

Causes of the DNA mutations

Answer 13

Spontaneous errors during DNA replication

chemical mutagens such as alcohol, tobacco, asbestos

ionising radiation - UV, x rays, alpha, beta

Question 14

What are stem cells

Answer 14

undifferentiated cells that can continually divide and become specialised

Question 15

4 types of stem cells

Answer 15

totipotent
pluripotent
multipotent
unipotent

Question 16

What are totipotent stem cells and how do they specialise

where do they occur

Answer 16

stem cells that can differentiate into any type of body cell

during development, they can only translate part of their DNA resulting in specialisation

only occur for a limited time in early mammalian embryos

Question 17

What are pluripotent stem cells and where do they occur

what are they used for

Answer 17

Stem cells that can divide in unlimited numbers and can differentiate into almost any type of cell

found in embryos

used for treating human disorders, re growing damaged skin cells, beta cells ( for type 1 diabetes)

Question 18

Issues with pluripotent stem cells

Answer 18

they can continue to divide which can produce a tumour

have to be extracted from embryos, so killing life - unethical

Question 19

Where are multipotent and unipotent stem cells found

Answer 19

in mature mammals

Question 20

What are multipotent stem cells

Answer 20

stem cells that can differentiate into a limited number of cells, e.g. bone marrow, white blood cells, red blood cells

Question 21

What are unipotent stem cells

Answer 21

stem cells that can only differentiate into one type of cell, e.g. cardiomyocytes

Question 22

What are iPS cells and how are they created

Answer 22

induced pluripotent stem cells

created from somatic stem cells (adult unipotent) that are treated with transcription factors to switch on genes that induce pluripotency so they can differentiate into other types of cell

Question 23

Advantages of iPS cells

Answer 23

Don’t cause embryonic destruction, less ethical issues

once created they can divide indefinitely to give a limitless supply

can be used in medical treatment as a replacement of embryonic stem cells