8. control of gene expression Flashcards
MUTATIONS
what’s a mutation?
alteration to the DNA base sequence, often arising spontaneously during DNA replication
MUTATIONS
what’s a addition mutation?
one extra base added to the sequence.
means all subsequent are altered in a FRAMESHIFT
so diff amino acid coded for, can lead to a non-functioning protein.
TAC TTC AGG TGG
TAC ATT CAG GTG G
———————>
MUTATIONS
what’s a deletion mutation?
deletion of a base in a sequence
FRAMESHIFT TO LEFT
diff polypeptide chain produced as diff AA coded for.
TAC TTC AGG TGG
TAC TCA GGT GG
———————>
MUTATIONS
what’s a substitution mutation?
replacement of a base by a different base in DNA- no frameshift.
Only one codon changes and as the genetic code is degenerate it may still code for the same AA (no impact)
TAC TTC AGG TGG
TAC ATC AGG TGG
MUTATIONS
what’s an inversion mutation?
section of bases detach from DNA and when rejoin they are inverted. Diff AA coded for in this region.
FRAMESHIFT
TAC TTC AGG TGG
TAC GGA CTT TGG
MUTATIONS
what’s a translocation mutation?
Section of bases on one chromosome detached and inserted into the DNA of a diff chromosome.
MUTATIONS
what’s a duplication mutation?
where one or more bases duplicate and repeat
FRAMESHIFT
MUTATIONS
which mutations are most like out to have a significant impact and why?
insertion, deletion, duplication, translocation because they produce a frameshift meaning the entire amino acid sequence produced will be diff.
MUTATIONS
what is a mutagenic agent? give examples
factors that increase the rate of gene mutation.
chemical mutagens such as tabasco smoke and alcohol.
Ionising radiation such as UV and X-ray
STEM CELLS
What is a stem cell?
undifferentiated cells that continually divide to become specialised in differentiation
STEM CELLS
name the types of stem cells
totipotent
pluripotent
multipoint
unipotent
STEM CELLS
describe totipotent stem cells
divide to produce any type of body cell including placenta and embryo.
certain parts of the DNA are selectively translated so only some genes are switched on to differentiate the cell into a specific type.
STEM CELLS
describe pluripotent cells
can divide into any type of cell other than placenta and embryo.
can divide into unlimited numbers so can be used to repair or replace damaged tissues.
STEM CELLS
describe multipoint cells
can only divide into a limited number of diff cell types.
found in mature mammals, e.g. in bone marrow
STEM CELLS
describe unipotent cells
A cell that can only differentiate into one type of cell.
only found in mature mammals
STEM CELLS
which type of cells are found in embryos?
totipotent, pluripotent
STEM CELLS
give some uses of stem cells
Medical therapies, e.g. bone marrow transplants, treating blood disorders.
drug testing on artificially grown tissues
REGULATION OF TRANSCRIPTION
what is a transcription factor?
a protein that controls the transcription of genes so that only certain parts of the DNA are expressed (turns on/off gene)
what are induced pluripotent stem cells (IPS)
reprogramming unipotent cells into pluripotent using transcription afford in a lab
REGULATION OF TRANSCRIPTION
how do transcription factors work?
- move from the cytoplasm into the nucleus
- bind to promoter region upstream of target gene
- makes it easier or more difficult for RNA polymerase to bind to gene. This increases or decreases the rate of transcription.
REGULATION OF TRANSCRIPTION
Give an example of a hormone that affects transcription and explain how it works
Oestrogen
can initiate transcription by binding to a receptor site in the cytoplasm
Changes shape so it’s complementary to DNA and can bind and initiate transcription (initiates binding of RNA polymerase)
REGULATION OF TRANSCRIPTION
what are epigenetics?
a heritable change in gene function without change to the base sequence of DNA
REGULATION OF TRANSCRIPTION
how does increased methylation of DNA affect gene transcription?
methyl groups added to DNA, attach to cytosine bases.
This prevents transcription factors binding, so gene transcription is suppressed.
REGULATION OF TRANSCRIPTION
how does decreased acetylation of histones affect gene transcription?
inhibits transcription