6.1 cellular control Flashcards
when during the cell cycle do mutations occur
during cell replication before cell division
define mutagen
physical or chemical agent that increases the chance of mutation above the spontaneous rate of 1 in 10^8 base pairs
define somatic mutation
mutations associated with mitotic division
what is point mutation
one base pair replaces another
define insertion or deletion mutation
one or more nucleotides are inserted or deleted from a DNA sequence this may cause a frame shift
what are the 3 types of point mutation
silent
missense
nonsense
what is a silent mutation
a point mutation involving a change to the base triplet code, where that triplet still codes for the same amino acid
what is a missense mutation
a change to the base triplet sequence that leads to a change in the amino acid sequence in a protein
what is a nonsense mutation
a point mutation where there is a change to the triplet sequence, so that it becomes a termination triplet
define exon
the coding, or expressed, region of DNA
define intron
the non-coding region of DNA
define operon
a group of genes that function as a single transcription unit; first identified in prokaryote cells.
define transcription factor
protein or short non-coding RNA that can combine with a specific site length of DNA and inhibit or activate transcription of the gene.
expanding triple nucleotide repeat
mutated gene contains more triplets than the original gene, this increases at meiosis and again from generation to generation
give an example of a disease caused by expanding triple nucleotide repeats
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
what causes the enzymes that metabolise lactose to be produced
the presence of lactose
what is the role of the regulatory gene
codes for a repressor protein that, when expressed, binds to the operator region preventing the binding of RNA polymerase to the promotor region.
how are the enzymes for lactose metabolism regulated in bacteria
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
what do transcription factors do
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
examples of transcription factors that regulate cell division
proto-oncogenes and tumour supressor genes
what percentage of genes in there human genome encode transcription factors
8%
post translational level gene regulation
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
define apoptosis
programmed cell death
what is a homeobox sequence
sequence of 180 base pairs (excluding introns) found within genes that are involved in regulating patterns of anatomical development in animals, fungi and plants.
