6.1-cellular bontrol Flashcards
what is a mutation?
random change to genetic material.
what is a gene mutation?
random change to DNA
what are mutations associated with mitotic division called?
somatic mutations
can mutations during mitosis be passed to offspring?
no
what might mutations during mitosis be associated with?
tumours
what are the 2 main classes of DNA mutation?
point mutation
indel
what do indel mutations cause?
frameshift
what are the 3 types of point mutation?
silent
missense
nonsense
what happens during a point mutation?
one base pair is substituted for another
what happens during a silent mutation?
point mutation changes base triplet but it still codes for the same amino acid.
what enables silent mutations to happen?
genetic code is degenerate: all amino acids (apart from methionine) have more than 1 base triplet code.
what is a missense mutation?
change in the base sequence that leads to a change in amino acid sequence in a protein.
what is an example of a disease caused by a missense mutation?
sickle cell anaemia
what causes sickle cell?
valine instead of glutamic acid added to b polypeptide chain.
what happens to the blood cells of someone with sickle cell?
deoxygenated haemoglobin crystallises in them, causing them to be sickle shaped, blocking capillaries and depriving tissues of o2.
what happens during nonsense mutations?
a point mutation alters a base triplet so it becomes a stop triplet.
what happens to the proteins that are results of nonsense mutations?
truncated and dysfunctional-likely degraded within cell.
what is an example of a disease caused by a nonsense mutation?
Duchenne muscular dystrophy
what is an example of a disease caused by deletions of bases?
thalassaemia
what happens during expanding triple nucleotide repeats?
in genes which contains a repeating triplet, the number of that triplet increases.
what’s a disease caused by expanding triple nucleotide repeats?
huntingtons-repeat of CAG
what is a disadvantage of having blue eyes?
in areas with high sun: could lead to lens cataracts
what is an exon?
the coding,or expressed,region of dna
what is an intron?
the non coding region of dna
what is an operon?
a group of genes that function as a single transcription unit
what is a transcription factor?
protein or short non-coding RNA that can combine with dna and inhibit or activate transcription of a gene.
what is E.coli’s normal respiratory substrate?
glucose
what does the lack of glucose and presence of lactose cause E.coli to produce?
lactose permease
b-galactosidase
what does lactose permease do?
allows lactose to enter cell
what does b-galactosidase do?
hydrolyses lactose to glucose and galactose
in the lac operon what is lacO?
operator region
in the lac operon what is lacZ?
structural gene that codes for b-galactosidase
in the lac operon what is lacY?
structural gene that codes for lactose permease
what happens at the promoter region (P)of the lac operon?
RNA polymerase binds to begin transcription of lacZ and lacY.
what does the regulatory gene (I) code for in the lac operon?
a repressor protein, LacI
what does the repressor protein do in the lac operon?
binds to the operator, preventing RNA polymerase from binding to the promoter region
when lactose is present what happens to the LacI repressor protein?
molecules of glucose bind to it-its shape gets altered-it’s prevented from binding to the operator
are introns and exons both transcribed?
yes
what is primary mRNA?
mRNA with both introns and exons transcribed.
what happens when primary mRNA is edited?
RNA introns are removed+ the remaining exons joined together (endonuclease enzyme may be involved in this process)
how are many enzymes activated?
by being phosphorylated
what is the homeobox sequence?
sequence of 180 base pairs found within genes involved in regulating patterns of anatomical development in animals, fungi and plants
what are hox genes?
subset of homeobox genes found only in animals-involved in the formation of anatomical features in correct locations of body plan.
what is a homeodomain sequence?
60 amino acid sequence within a protein coded for by the homeobox sequence.
what does the homeodomain sequence do?
folds into a specific shape and binds to dna, regulating transcription of adjacent genes.
what is the shape of a homeodomain containing protein?
HTH: two a helixes connected by a turn
what is an enhancer region?
region that initiates or enhances transcription.
what does it mean when a gene is conserved?
it has remained in an descendent species throughout evolutionary history.
what is colinearity?
a phenomenon where the temporal and sequential order of the gene expressions corresponds to the sequential and temporal development of various body parts. (like the gene at the end codes for the tail)
what can homeodomain proteins do in the nucleus?
switch on cascades of activation of other genes that promote mitosis, apoptosis, cell cycle regulation.
what are hox genes regulated by?
other genes called gap genes and pair-rule genes
what signal molecules are involved in stimulating apoptosis?
cytokines
hormones
growth factors
nitric oxide (NO)
what are 2 examples of apoptosis being useful in humans?
causes separation of toes
removes ineffective or harmful t-lymphocytes when immune system is developing
