cellular control Flashcards
why is it important that genetic information is conserved accurately when replicating DNA
3 bases code for an AA
sequence of triplets determines the sequence of amino acids for proteins
how does an allele form
change to base sequence of a gene
produces no change if the mutation is silent or takes place in an intron
why can changed codons still code for the same AA
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
define degenerate code
more than one triplet can code for the same AA
if there are four bases in DNA and these code for 20 AA, what is the basis for the genetic code
if three bases code for one AA
possible AA = 4x4x4 = 64
define mutation
change in base sequence in DNA
how does genetic variation occur
random, spontaneous mutations
what types of mutations pass onto successive generations
only in gametes
why is there is no effect when mutation occurs
mutation occurs in non-coding part of DNA (intron)
define mutagens and the different types
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
when does genetic mutation and chromosomal mutation occur
genetic – during DNA replication
chromosomal – during cell division
what are the types of point mutations
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
what are the types of chromosomal mutations
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
what is rate of cell division controlled by
proto-oncogene – stimulates cell division
tumour suppressor gene – slows/inhibits cell division
what happens when the proto-oncogene undergoes point mutation
turns into oncogene
stimulates excessive cell division
forms tumour
what happens when tumour suppressor gene undergoes point mutation
inactivated
rate of cell division increases unregulated
what is gene expression important for
responding to receptors
growth
how is chromatin formed
DNA is negative
histones are positive
they associate –> coil
describe the processes involved in development of an organism
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)
describe the cell signalling mechanism in glucose to move from the intestines to the blood
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
what happens if a gene turns ‘on’ and ‘off’
‘on’ = more of a protein produces
‘off’ = less of a protein produces
what is transcription controlled at
transcriptional level
post-transcriptional level
translational level
post-translational level
how does chromatin remodelling occur at the transcriptional level
remodel chromatin into:
heterochromatin – tightly wound (present during c.division) –> down regulates transcription
euchromatin – loosely wound (during DNA replication interphase) –> up regulates transcription
how does histone modification occur at the transcriptional level
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
