8a (mutations/gene expression) Flashcards
what is a mutation?
what can they be caused by?
a change in the DNA base sequence
random errors in DNA replication, rate increased by mutagenic agents
what are the types of mutation?
substitution- one or more bases swapped for another
deletion- one or more bases removed
addition- one or more bases added
duplication- one or more bases repeated
inversion- sequence of bases is reversed
translocation- sequence of bases is moved from one location in the genome to another (within chromosome or to a diff chromosome)
what could happen if a mutation occurs in a gene?
amino acid seq in polypeptide that it codes for changes
may change tertiary structure of protein so doesnt work anymore
can increase likelihood of certain cancers/ genetic disorders
what is a hereditary mutation?
gamete containing mutation for type of cancer or genetic disorder is fertilised, mutation will be present in new foetus
why might a mutation not cause a change in amino acid sequence?
the genetic code is degenerate
what is a frameshift mutation?
number of bases in DNA code changes so shift occurs in base triplets that follow so triplet code is read in diff way.
occurs in additions, duplications, deletions
what are mutagenic agents
increase rate of mutations
(they occur anyway spontaneously)
eg UV, ionising radiation, some chemicals, some viruses
what are the ways in which mutagenic agents can increase rate of mutations?
- acting as a base- chemicals called base analogs can substitute for a base during DNA replication, change base seq in ne DNA
- altering (/deleting) bases- caused by some chemicals
- changing structure of DNA- caused by some radiation causes problems in DNA replication
what are stem cells?
undifferentiated cells that can become specialised or produced more copies of themself
what is totipotent?
multipotent?
pluripotent?
unipotent?
totipotent- can become specialised into any type of body cell- present in embryo for first few divisions
pluripotent- specialise into most cells (not placenta)
multipotent- can become few specialised cells- adult stem cells
unipotent- can become one type of specialised cell eg skin cells
where are stem cells found?
embryo (become specialised to form foetus), adult tissue (become specialised to replace other cells)
how do stem cells become specialised?
during development they can only transcribe and translate part of their DNA
stem cells all contain same genes but not all are expressed
under certain conditions, certain gene are switched on and off
genes that are expressed get transcribed into mRNA which is transcribed into proteins which modify the cell, they determine cell structure and control cell processes
why do cells tend to stay specialised?
changes to cell produced by proteins that cause cell to become specialised
these changes arent reversed
what is a cardiomyocyte?
heart muscle cells that make up a lot of the tissue in our hearts
why did people believe we arent able to regenerate our own heart cells?
what does recent research suggest?
in mature mammals, its though cardiomyocytes cant divide to replicate themselves- problem if heart become damaged
hearts do have some regenerative capabilities, old/ damaged cardiomyocytes replaced by new ones derived from small supply of unipotent stem cells in heart.
some think this constantly occurs but dk how fast. some think its really slow and its possible some arent replaced in someones life. some think its really fast and each is replaced multiple times in a life
