6.1 cellular control

Question 1

when during the cell cycle do mutations occur

Answer 1

during cell replication before cell division

Question 2

define mutagen

Answer 2

physical or chemical agent that increases the chance of mutation above the spontaneous rate of 1 in 10^8 base pairs

Question 3

define somatic mutation

Answer 3

mutations associated with mitotic division

Question 4

what is point mutation

Answer 4

one base pair replaces another

Question 5

define insertion or deletion mutation

Answer 5

one or more nucleotides are inserted or deleted from a DNA sequence this may cause a frame shift

Question 6

what are the 3 types of point mutation

Answer 6

silent
missense
nonsense

Question 7

what is a silent mutation

Answer 7

a point mutation involving a change to the base triplet code, where that triplet still codes for the same amino acid

Question 8

what is a missense mutation

Answer 8

a change to the base triplet sequence that leads to a change in the amino acid sequence in a protein

Question 9

what is a nonsense mutation

Answer 9

a point mutation where there is a change to the triplet sequence, so that it becomes a termination triplet

Question 10

define exon

Answer 10

the coding, or expressed, region of DNA

Question 11

define intron

Answer 11

the non-coding region of DNA

Question 12

define operon

Answer 12

a group of genes that function as a single transcription unit; first identified in prokaryote cells.

Question 13

define transcription factor

Answer 13

protein or short non-coding RNA that can combine with a specific site length of DNA and inhibit or activate transcription of the gene.

Question 14

expanding triple nucleotide repeat

Answer 14

mutated gene contains more triplets than the original gene, this increases at meiosis and again from generation to generation

Question 15

give an example of a disease caused by expanding triple nucleotide repeats

Answer 15

Huntington disease,
if the number of CAG sequences goes above a certain critical number, then a person with that phenotype may experience the symptoms of Huntingtons disease later in life

Question 16

what causes the enzymes that metabolise lactose to be produced

Answer 16

the presence of lactose

Question 17

what is the role of the regulatory gene

Answer 17

codes for a repressor protein that, when expressed, binds to the operator region preventing the binding of RNA polymerase to the promotor region.

Question 18

how are the enzymes for lactose metabolism regulated in bacteria

Answer 18

when lactose is added, molecules of lactose bind with LacI repressor protein molecules so they can’t bind to the operator.
RNA polymerase can bind to the promotor region.
enzymes can be transcribed from lacZ and lacY

Question 19

what do transcription factors do

Answer 19

they slide along a part of the DNA molecule, seeking and binding to their specific promotor regions.
they may then aid or inhabit the attachment of RNA polymerase

Question 20

examples of transcription factors that regulate cell division

Answer 20

proto-oncogenes and tumour supressor genes

Question 21

what percentage of genes in there human genome encode transcription factors

Answer 21

8%

Question 22

post translational level gene regulation

Answer 22

a signalling molecule binds to a receptor on plasma membrane
this activates a transmembrane protein which then activates a G protein
G protein activates adenyl cyclase enzymes
activated adenyl cyclase enzymes catalyse the formation of cAMP and ATP
cAMP activates PKA
activated PKA catalyses the phosphorylation of various proteins hydrolysing ATP in the process
PKA may phosphorylate another protein
this then enters the nucleus and acts as a transcription factor

Question 23

define apoptosis

Answer 23

programmed cell death

Question 24

what is a homeobox sequence

Answer 24

sequence of 180 base pairs (excluding introns) found within genes that are involved in regulating patterns of anatomical development in animals, fungi and plants.

Question 25

what is a hox gene

Answer 25

subset of homeobox genes, found only in animals; involved in formation of anatomical features in correct locations of body plan.