gene mutation Flashcards
what is a unipotent stem cell
can only differentiate into one other cell
what is a totipotent stem cell
can differentiate into any adult stem cell
where are totipotent stem cells found
in the early stages of embryo development
where are unipotent stem cells found
mature mammals
what is a multipotent stem cell
can differentiate into most cells but not all, blood cells are common
where are multipotent cells found
mature mammals
what are pluripotent stem cells found
early stages of embryo
what is a pluripotent stem cell
can differentiate into any tissue in the body
what is a mutagenic agent
a mutagen is a physical or chemical agent that changes the genetic material this will increase the frequency of mutations
what is an oncogene
a gene that has the potential to cause cancer
what are induced multipotent cells
skin or blood cells that have been reprogrammed back to their embryonic-like pluripotent state therefore can differentiate into any tissue cell
what are three tissue layers called
ectoderm
endoderm
mesoderm
what happens in an insertion mutation
one or more bases are added
what happens in a deletion mutation
one or more bases are removed
what happens in a substitution mutation
where one or more bases are swapped for another
what happens in an inversion mutation
a sequence of bases is reversed
what happens in a duplication mutation
one or more of the bases are repeated
what is the effect of a duplication mutation
can cause a frame shift but can also an increase in repeating subunits and causes genetic disease
what is the efefct of a deletion mutation
can cause frame shift
what is the effect of an insertion mutation
can cause frame shift
what is the effect of a substitution mutation
can result in no change as amino acid sequence could stay the same
what is the effect of an inversion mutation
can result in no chnage because amino acid sequence could stay the same
what is interference RNA
a biological process to which RNA molecules inhibit gene expression or translation by neutralising traget mRNA molecules
what is degenerate code
some amino acids are coded for by than more than one codon
what can be the cause of mutations
- high energy ionising radiation ( short wave X-rays and ultra violet rays)
- chemicals such as nitrogen dioxide may directly alter the structure of DNA . or benzopyrene a constituent of tobacco smoke is a powerful mutagen that inactivates a tumour supressor gene
what is an ips produced from
unipotent stem cells
what is an ips
unipotent stem cells that are genetically modified in the laboratory to make them acquire characteristics of an embryonic stem cell which are similar to pluripotent stem cells
how does an ips actually form
transcriptional factors and inducing genes to turn genes on that were otherwise turned off
what is a function of ips that is pretty cool
they are capable of self renewal — this means that they could potentially divide to a limitess supply
what is an ethical advantage of ips
in drug trials embryonic cells are not required just use ips instead!!!
what is a transcriptional factor
specific molecules that move from the cytoplasm to the nucleus to cause a gene to be switched on
how does a transcriptional factor work
- each transcriptional factor has a site that binds to specific bases sequence in the DNA. this binding causes transcription to occur
what happens when a gene is not being expressed
the site on the transcriptional factor that binds to the DNA is not active.
ALL the transcriptional factors fault
how does oestrogen act as transcriptional factor
oestrogen is lipid soluble so can diffuse through the phospholipid bilayer easily
- oestrogen binds to a receptor
-oestrogen causes the transcriptional factor to change shape. - transcriptional factor binds with DNA and begins the process of transcription begins
what is epigenetics
that environmental factors can cause heritable changes in gene function without changing the base sequence of DNA
what is the epigenome
a second layer of chemical tags wrapped around the chromosomes ( this is DNA wrapped around histones)
what is the function of the epigenome
determines the structure of the DNA-histone complex
what is epigenetic silencing
where the epigenome will keep inactive genes tightly packed and ensure that the inactive code will not be read
what can the epigenome also do
it can unwrap active genes so that they can be more easily transcribed
how does epigenome differ from DNA
DNA is fixed whereas the epigenome is flexible
why can the epigenome be described as flexible
because the chemical tags respond to their environment - factors like diet and stress can cause the wrapping and unwrapping function to be adjusted and so switch genes on and off
what can the epigenome change
- acetylation of histones leading to activation or inhibition of a gene
- methylation of DNA by attracting enzymes that can add or remove methyl groups
what is RNAi
small lengths of non-coding RNA that stops mRNA that has already been transcribed to being translated
does RNAi regulate transcription or translation
translation
is RNAi double or single stranded
double - which is weird
what are the two types of RNAi
siRNA - only in animals
miRNA - in plants and animals
how does siRNA and miRNA work in plants xxxxx
double stranded siRna associates with proteins in the cytoplasm and unwinds
- one of the siRNA strands is chosen and the other degrades
- single strand of siRNA binds to the target mRNA ( as it is complementary to the base sequence in a section)
- the proteins associated with the siRNA cut the mRNA into small fragments so it can no longer be translated
- the mRNA fragments then move into a processing body which degrades them
what can siRNAs and miRNAs be used for
gene silencing - treats genetic disorders ( faulty genes are eliminated)
describe how miRNAs work in animals
miRNAs are not fully complementary to the target mRNA so they are often less specific and can target more than one mRNA molecule. miRNA has to go through processing stages in the cytoplasm to be two single strands.
once miRNA is bound to mRNA it will block translation by preventing the ribosome from binding. the mRNA is then moved to a processing body where it can be stored to either be translated at another time or to be degraded
what is the enzyme used to degrade siRNAs and miRNAs
dsRNA
