Mutations and Gene Expression

Question 1

what are identical twin studies useful for?

Answer 1

determin whats due to enviro factors and whats due to genetic factors

Question 2

if twins are identical, what must any difference in phenotype be due to?

Answer 2

enviro factors

Question 3

TF are important in the synthesis of particular proteins.

describe how?

Answer 3

• bind to promotor regions
• stimulate gene expression by helping RNA polymerase to bind

Question 4

explain what causes siRNA to attach only to one sort of mRNA molecule?

Answer 4

has complementory base sequence

Question 5

describe and explain how expression of target gene is affected by siRNA?

Answer 5

• no longer able to make specific protein
• because mRNA been cut into pieces

Question 6

scientists have suggested that siRNA may be useful in treating some diseases.

suggest why siRNA may be useful in treating disease?

Answer 6

• prevents gene expression by cutting up mRNA before translated
• siRNA stops product of that gene

Question 7

explain how activated oestrogen receptor affects target cell?

Answer 7

• receptor binds to promotor
• stimulates RNA polymerase
• transcribes gene

Question 8

how does endoxifen reduce the growth rate of these breast tumours?

Answer 8

• similar shape to oestrogen
• binds to receptor - prevents oestrogen binding
• no transcription

Question 9

the black mambas toxin kills prey by preventing their breathing.

it does this by inhibiting the enzyme acetylcholinesterase at neuromuscular junctions.

explain how this prevents breathing?

Answer 9

• acetylcholine not broken down
• Na+ continue to enter
• ICM cannot relax

Question 10

what is meant by epigenetics?

Answer 10

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

Question 11

explain how increased methylation could lead to cancer?

Answer 11

• methyl groups added to TSG
• transcription of TSG inhibited
• leading to uncontrolled cell division

Question 12

a mutation of a TSG can result in the formation of tumour.

how?

Answer 12

• gene incactivated
• uncontrolled rate of cell division

Question 13

some cancer cells have a receptor protein in their cell surface membrane that binds to a hormone called growth factor.

this stimulates the cancer cells to divide.

scientists have produced a monoclonal antibody that stops this stimulation.

use your knowledge of monoclonal antibodies to suggest how this antibody stops growth of tumour?

Answer 13

• antibody has specific TS
• comp shape to receptor protein
• prevents growth factor from binding to receptor

Question 14

how would you explain evidence from a table that cells from a stem tip are totipotent?

Answer 14

• gives rise to new plants
• must be able to develop into diff tissues

Question 15

papaya plants reproduce sexually by means of seeds.

papaya plants grown from seeds are variable in their yield.

why?

Answer 15

• meiosis/crossing over/independent assortment
• random fertilisation

Question 16

explain the advantages of growing papaya plants from tissue culture rather than from seeds?

Answer 16

will be genetically identical

Question 17

suggest why the plasmids were injected into the eggs of silkworm, rather than into the silkworms?

Answer 17

• gene gets into most cells of silkworm
• gets into cells that make silk

Question 18

suggest why scientists used a marker gene and why they used the EGFP gene?

Answer 18

• not all eggs will successfully take up plasmid
• silkworms that will have taken up gene glow

Question 19

suggest TWO reasons why it was important that the spider gene was expressed only in the silk glands of the silkworms?

Answer 19

• so protein can be harvested
• fibres in other cells could cause harm

Question 20

give 2 characteristic features of stem cells?

Answer 20

• can differentiate into any type of cell
• keep dividing

Question 21

SCID is a severe inherited disease. people who are affected have no immunity. doctors carried out a trial using gene therapy to treat children with SCID. the doctors who carried out the trial obtained stem cells from each childs umbilical cord.

some of the children in a trial developed cancer.

how might the insertion of DNA have caused cancer?

Answer 21

• inactivates TSG
• tumour cells divide uncontrollably

Question 22

Answer 22

• attaches to DNA
• to stimulate RNA polymerase

Question 23

using all the info provided, evaluate the use of iPS cells to treat type 1 diabetes in humans?

Answer 23

• results of group A similar to group C
• glucose levels of group A lower than glucose levels of group B
• investigation tested on mice not humans
• short time - only 12 week period - long term effects unknown

Question 24

why does the antibody bind to TF?

Answer 24

• has comp shape to TF
• has specific TS

Question 25

what does precipitated DNA consist of?

Answer 25

DNA, TF and antibody

Question 26

how can single stranded cDNA prevent transcription of p34 gene?

Answer 26

binds to p34 gene

Question 27

describe role of 2 names types of enzymes used to insert DNA fragments into plasmids?

Answer 27

• DNA LIGASE
• joins DNA to plasmid vector
• RESTRICTION ENDONUCLEASE
• cut plasmid

Question 28

2 features of structure of diff proteins that enable them to be separated by gel electrophoresis?

Answer 28

• charge
• R groups
• diff length polypeptides

Question 29

how ips cells could correct red-green colour blindness?

Answer 29

• ips cells divide
• ips cells differentiate into cones

Question 30

advantage of ips over gene therapy?

Answer 30

• long term uses of ips
• less risk of rejection
• single treatment
• harm/side effects from using viruses in gene therapy

Question 31

use all info to suggest how the mutation of NOTCH1 led to the difference in percentage of B cells destroyed by Rituximab?

Answer 31

• changes tertiary structure of protein (TF)
• TF not comp to CD20 gene
• little mRNA for CD20 produced

Question 32

Answer 32

• few faulty mitochondria

OR

• has mostly lots of normal mitochondria
• egg has genes of affected woman

Question 33

Answer 33

• siRNA binds to mRNA for CENP-W
• prevents translation of CENP-W
• CENP-W reduces so does tubulin production

Question 34

the scientists put the same number of skin tumour cells in each dish at the start of this investigation.

explain why it was important to put the same number of cells in each dish

Answer 34

ensure colour at start = same

Question 35

an article in a newspaper claimed that these data show that bromelain can be used to treat cancer.

give reasons why we should be careful about accepting this claim?

Answer 35

• only tests on one type of cancer
• use of mice cells rather than human
• not possible to predict effect on humans as no data collected

Question 36

rate of cell division is important in investigations into cancer

suggest why

Answer 36

• faster rate of cell division, faster cancer grows
• by measuring rate of cell division, you could see ow effective treatment was

Question 37

scientists have investigated the effects of bromelain on cancer growth in humans

suggest why they gave bromelain in addition to, rather than instead of, usual treatment

Answer 37

• not ethical to replace conventional treatment
• as life of patient at risk

Question 38

Answer 38

• no cadmium
• other conditions same as cadmium treated groups

Question 40

Answer 40

• RNA polymerase cannot bind to dna
• no transcription of p16 gene

Question 41

Answer 41

• cadmium causes expression of methyl transferase enzyme
• methyl groups onto p16 gene
• p16 normally suppresses tumour growth
• p16 expression falls afer 4 weeks
• tumour formation occurs after 10 weeks AFTER p16 falls