Mutations, gene expression and cancer

Question 1

Universal definition

Answer 1

the same 3 bases on a codon code for the same amino acids in all organisms

Question 2

non-overlapping definition

Answer 2

each base is only read once in a triplet

Question 3

degenerate

Answer 3

more than one triplet codes for an amino acid

Question 4

what is a gene mutation

Answer 4

change to a single base in the DNA base sequence- occur randomly and spontaneously, can result in the change of primary structures of polypeptides. Can therefore alter secondary structure through changing the position of weak hydrogen bonds which affect alpha helices and beta pleated sheets. May alter tertiary structure by changing position of bonds- leading to a non-functional protein

Question 5

substitution mutations

Answer 5

of 3rd base would not alter the amino acid coded for- silent mutation.

Question 6

what happens if mutation cases the production of a stop codon

Answer 6

polypeptide becomes truncated

Question 7

addition/deletion mutations

Answer 7

results in a frame shift, the earlier the mutation occurs, the more of the amino acids altered

Question 8

chromosomal mutation

Answer 8

daughter cells may contain too many chromosomes, pair of homologous chromosomes may fail to separate. results in chromosome non-disjunction

Question 9

inversion mutations

Answer 9

when a segment of bases or a chromosome are reversed end to end

Question 10

duplication mutation

Answer 10

doubling part of or an entire chromosome

Question 11

translocation mutation

Answer 11

groups of base pairs relocate from one area of the genome to another, usually between non-homologous chromosomes. philodilphia chromosome is always found in bone marrow of myelogenous leukemia

Question 12

Mutagenic agents

Answer 12

increase the rate of spontaneous mutation
Includes: High energy ionizing radiation such as x rays, gamma rays, alpha and beta particles and ultra violet
DNA reactive chemicals such as benzene. bromine and hydrogen peroxide. nitrous acid can remove an NH2 group from the cytosine in DNA
biological agents such as some viruses and bacteria

Question 13

process of stem cells

Answer 13

cell division by mitosis- to make new genetically identical daughter cells, then differentiation when stem cell becomes a specialized cell. Knows what to do: through the expression of some genes and not others. Most of a cell’s DNA is not translated and these genes are not expressed

Question 14

totipotent stem cell

Answer 14

zygote and early embryo- occur for a limited time

Question 15

pluripotent

Answer 15

embryonic and fetal stem cells

Question 16

multipotent

Answer 16

adult stem cells

Question 17

unipotent

Answer 17

used in the formation of single cells such as Cardiomyocytes

Question 18

application of stem cells to medical research

Answer 18

producing tissues for skin grafts
research into producing organs for transplant
research into how cells become specialized
research into cancer and other serious diseases
cure diseases such as parkinson’s

embryonic are more useful as they can divide into many more cell types.

Question 19

promotor region

Answer 19

one or more base sequences found upstream of a gene that control the expression of that gene

Question 20

transcription factors

Answer 20

proteins which, when activated, bind to the promotor region of a gene stimulating RNA polymerase to begin transcription on target gene.

Question 21

describe RNA polymerase role in transcription factors

Answer 21

enzyme that first binds to the transcription factor on the promotor, brings RNA polymerase near the allele to start transcription.

Question 22

Oestrogen control of transcription

Answer 22

Oestrogen diffuses through the phospholipid cell membrane because it’s lipid soluble
Diffuses through nuclear envelope
binds to the oestrogen receptor
changes tertiary structure
releases the transcription factor
transcription factor binds to the DNA at the promotor region
stimulates RNA polymerase to transcribe the gene
this increases transcription so mature mRNA produced.

Question 23

control of translation- RNA interference

Answer 23

reduced by the action of micro rRNA and small interfering siRNA

protein synthesis requires vast quantities of ATP, if cell has synthesises enough of a specific protein, short regulatory RNA molecules are transcribed from a cell’s DNA
this rNA is microRNA and small interfering RNA
A singe strand of this rna binds to a protein/enzyme in the cytoplasm to form an RNA induced silencing complex
the rna has a complementary base sequence to part of a specific mRNA molecule

Question 24

what does RISC do

Answer 24

it inhibits gene expression by binding to the complementary mRNA this means that:
The mRNA is hydrolysed by an enzyme- RNA hydrolse (mRNa cut into fragments) or inhibits the initiation of ribosomal translation- ribosome is prevented from attatching to the mrna so is hydrolysed

Question 25

consequence of RNAi interferrence

Answer 25

translation does

Question 26

what is RNAi used to do and what may happen if mrna is not all destroyed

Answer 26

used to reduce and silence translation of a protein. If a specific protein is still produced, this means that mrna has not been destroyed. and some translation can still occur.

Question 27

epigenetics definition

Answer 27

involves inheritable changes in gene expression without changes to the DNA base sequences.

Question 29

What inheritable changes inhibit transcription

Answer 29

increased methylation of DNA, decreased acetylation of histones

Question 30

methylation of DNA

Answer 30

a methyl griup is added to carbon 5 of cytosine base.
methyltransferase is the catalyst.
methylation of CpG islands ‘silences’ the affected genes by preventing transcription factors from binding to the promotor region. This prevents the activation of RNA polymerase and inhibits transcriotion.

Question 32

acetylation of histones

Answer 32

results in the histone molecules becoming lossely packed/DNA is less condensed. when unwound the promotor regions are exposed and transcription factors can bind. This then allows RNA polymerase to bind and the target gene can be transcribed.

if reduced- dna becomes more tightly packed aroung histones, promotor region hidden and can’t bind so no transcription and gene expression as can’t be accessed by RNA polymerase

Question 33

increase acetylation and methylation vs decrease

Answer 33

increase methylation: silences gene, can stop TF binding to the promotor region and so RNA polymerase is blocked
Increase acetylation: activates gene, chromatin packed less tightly.

decrease methylation- activates gene, TF binding to the promotor region allowing transcription.
decrease acetylation- silences gene, chromatin packed more tightly.

Question 34

define a malignant tumour

Answer 34

tumour that is fast growing, non-capsulated and they metastasise

Question 35

define a benign tumour

Answer 35

slow growing, surrounded by capsule and do not metastasise.

Question 36

proto-onco genes

Answer 36

stimulate cell division (code for proteins that increase the rate of cell division)

Question 37

tumour supressor gene

Answer 37

slows cell division- code for proteins that decrease the rate of cell division. they also code for proteins that repair mistakes in DNA and instruct cells to die (apoptosis). Mutations in these genes increase the rate of cancer

Question 38

what is it called when a mutation occurs within a protoonco gene

Answer 38

oncogene- results in over-stimulation of cell division- permenantly switched on

Question 39

increased methylation of a tumour suppressor gene

Answer 39

rate of cell division increases

Question 40

increased acetylation of tumour suppressor gene

Answer 40

the rate of cell division decreases

Question 41

decreased methylation in onco gene

Answer 41

rate of cell division increases

Question 42

decreased acetylation of oncogene,

Answer 42

rate of cell division decreases.

Question 43

new cancer drugs

Answer 43

could inhibit methyltransferases. this could reduce methylation of a promotor and therfore allow transcription factors to bind- this could activate RNA polymerase and lead to the expression of the tumour suppressor gene which codes for a protein that slows the rate of cell division.

Question 44

oestrogen and breast cancer

Answer 44

cancer cells have ER receptor on the cell surface membrane or within the nucleus, oestrogen stimulates them to divide uncontrollably.