cellular control

Question 1

why is it important that genetic information is conserved accurately when replicating DNA

Answer 1

3 bases code for an AA

sequence of triplets determines the sequence of amino acids for proteins

Question 2

how does an allele form

Answer 2

change to base sequence of a gene

produces no change if the mutation is silent or takes place in an intron

Question 3

why can changed codons still code for the same AA

Answer 3

more than more triplet codon can code for the same AA

changed codon can still code for the same AA

because the code is degenerate

Question 4

define degenerate code

Answer 4

more than one triplet can code for the same AA

Question 5

if there are four bases in DNA and these code for 20 AA, what is the basis for the genetic code

Answer 5

if three bases code for one AA

possible AA = 4x4x4 = 64

Question 6

define mutation

Answer 6

change in base sequence in DNA

Question 7

how does genetic variation occur

Answer 7

random, spontaneous mutations

Question 8

what types of mutations pass onto successive generations

Answer 8

only in gametes

Question 9

why is there is no effect when mutation occurs

Answer 9

mutation occurs in non-coding part of DNA (intron)

Question 10

define mutagens and the different types

Answer 10

changes the rate at which mutations occurs

ionisation – break one/both DNA strands
alkylating agent – adds methyl/ethyl groups
de-aminating agent – alters bases
viruses – insert viral DNA into host genome

Question 11

when does genetic mutation and chromosomal mutation occur

Answer 11

genetic – during DNA replication

chromosomal – during cell division

Question 12

what are the types of point mutations

Answer 12

silent – no change to primary sequence
(degenerate code)

nonsense – changes a codon into stop-codon leading to truncated protein

missense – change to primary sequence
changes the properties to their opposite ones

Question 13

what are the types of chromosomal mutations

Answer 13

deletion – section lost

translocation – substition of a section of chromosome

duplication – of a section

inversion – section of DNA from chromosome breaks off and reversed joined back

Question 14

what is rate of cell division controlled by

Answer 14

proto-oncogene – stimulates cell division

tumour suppressor gene – slows/inhibits cell division

Question 15

what happens when the proto-oncogene undergoes point mutation

Answer 15

turns into oncogene

stimulates excessive cell division

forms tumour

Question 16

what happens when tumour suppressor gene undergoes point mutation

Answer 16

inactivated

rate of cell division increases unregulated

Question 17

what is gene expression important for

Answer 17

responding to receptors

growth

Question 18

how is chromatin formed

Answer 18

DNA is negative
histones are positive

they associate –> coil

Question 19

describe the processes involved in development of an organism

Answer 19

fertilisation –> form zygote (pluripotent)

mitosis (responsible for the quantity of cells in an organism = 37.2 trillion)
differentiation (responsible for the organisms having 200+ different specialised cels)

Question 20

describe the cell signalling mechanism in glucose to move from the intestines to the blood

Answer 20

glucose binds to receptor

causes gene expression in nucleus

to produce proteins (carriers on the c.s.m)
which transports glucose through cell to blood

Question 21

what happens if a gene turns ‘on’ and ‘off’

Answer 21

‘on’ = more of a protein produces

‘off’ = less of a protein produces

Question 22

what is transcription controlled at

Answer 22

transcriptional level

post-transcriptional level

translational level

post-translational level

Question 23

how does chromatin remodelling occur at the transcriptional level

Answer 23

remodel chromatin into:

heterochromatin – tightly wound (present during c.division) –> down regulates transcription

euchromatin – loosely wound (during DNA replication interphase) –> up regulates transcription

Question 24

how does histone modification occur at the transcriptional level

Answer 24

makes histone more or less positive

more => heterochromatin
adding methyl groups to become more hydrophobic or removing acetyl groups

less => euchromatin
adding acetyl groups by phosphorylation

Question 25

what is a transcriptional factor

Answer 25

protein

Question 26

how does a transcriptional factor work at the transcriptional level

Answer 26

cell signal –> activates TF –> links to promoter sequence (non-coding) –> recruits RNA polymerase –> increasing the rate of transcription

Question 27

how does oestrogen affect the rate of transcription

Answer 27

binds to site on TF

changing shape of the TF molecule

inhibits the protein from binding to a promoter sequence

Question 28

define lac operon

Answer 28

group of genes under the control of same regulatory mechanisms expressed at the same time

Question 29

what are two features of lac operon

Answer 29

common to prokaryotes

efficient because if a certain protein isn’t needed, all the genes involved in production can be turned off

Question 30

what does the lac operon consist of

Answer 30

3 genes:

Lac2 – codes for beta-galactosidase –> breaks down lactose

LacY – codes for permease –> binds to membrane for lactose to be pumped into cell

LacA

Question 31

what is the function of LacI

Answer 31

codes for a repressor protein

which is constantly produced and binds to operator region

Question 32

what is the function of repressor protein

Answer 32

binds to the operator region

prevents the RNA polymerase from binding to DNA (down regulation)

Question 33

what happens when lactose is present

Answer 33

lactose binds to R-protein

causing change in T.structure

so the R-protein can no longer bind to DNA

RNA polymerase binds to promoter uninhibited

Question 34

how do we have more cAMP

Answer 34

high lactose

more glucose will be produced

so more undergo respiration synthesising more ATP

so more cAMP is made

Question 35

what is the function of cAMP in lac operon

Answer 35

binds to CRP (cAMP receptor protein)

CRP binds to DNA and acts as a TF