Gene expression Flashcards
what does substitution of bases mean?
a nucleotide in a section of a DNA molecule is replaced by another nucleotide that has a different base
what are the three possible consequences of substitution?
– formation of stop codons could occur that mark the end of a polypeptide chain
– formation of a codon for a different amino acid
– formation of a different codon but one that produces a codon for the same amino acid as before
what could deletion of bases cause?
frame shift
what are the other types of gene mutations?
– addition of bases
– duplication of bases
– inversion of bases
– translocation of bases
what are two kinds of mutagenic agents?
– high energy ionising radiation
– chemicals
what are totipotent cells?
cells which can mature into any body cell
what are two ways in which genes are prevented from expressing themselves?
– preventing transcription and so preventing the production of mRNA
– preventing translation
what are the 4 sources stem cells can originate from in mammals?
– embryonic stem cells
– umbilical cord blood stem cells
– placental stem cells
– adults stem cells
what are 4 types of stem cells?
– totipotent stem cells
– pluripotent stem cells
– multipotent stem cells
– unipotent stem cells
what does pluripotent mean?
found in embryos and can differentiate into almost any type of cellw
hat does multipotent mean?
found in adults and can differentiate into a limited number of specialised cells
what does unipotent mean?
can only differentiate into a single type of cell
what are induced pluripotent stem cells?
a type of pluripotent cells that is produced from unipotent stem cells taken from almost any body cell and is genetically modified to acquire characteristics of embryonic stem cells
what are the general principles involved in controlling the expression of a gene by controlling transcription?
– gene is switched on by transcription factors
– each transcriptional factor has a site that binds to a specific base sequence of the DNA on the nucleus
– when it binds it causes the region of DNA to begin transcription
– messenger RNA is produced and info it carries is translated into a polypeptide
– when a gene is not being expressed the site on the transcription factor that binds to DNA is not active
– cannot cause transcription and polypeptide synthesis
what is epigenetics?
a new scientific field that provides explanations as to how environmental influences can subtly alter the genetic inheritance of an organisms offspring
