PACK 21: GENE EXPRESSION Flashcards
(22 cards)
describe the regulation of transcription
transcriptional factors are found in the cytoplasm of the cell and they move into the nucleus. each transcriptional factor has a site that binds to the promoter region of the DNA molecule. binding of the transcriptional factor to the promoter region allows RNA polymerase to attach and transcotopn is initiated
describe the role of oestrogen
oestrogen enters the cell by simple diffusion and binds to a specific transcriptional factor. the transcriptional factor changes shape releasing a inhibitor molecule and exposing the DNA binding site on the transcriptional factor. this allows RNA polymerase to bind and transcription is initiated
describe RNAi
double stranded RNAi moves into the cytoplasm, it here becomes single stranded and associates with an enzyme and it binds to specific mRNA molecules by complimentary base pairing . the enzyme cuts the mRNA in two and the mRNA can no longer be translated
what are two feautures of stem cells
they are undifferentiated but can differentiate into specialised cells, they can replace themselves
what are totipotent stem cells
found in early mammalian embryos, and they can differentiate to produce any type of body cell (even placental cells)
what are pluripotent stem cells
found in embryos and can differentiate into all types of tissue cell- except placental cells
what are multipotent stem cells
found in many tissues of mature mammals and can differentiate into a limited number of cell types (e.g. bone marrow)
what are uni potent stem cells
found in mature mammals, can only differentiate into one type of cell or tissue
what are induced pluripotent stem cells
pluripotent stem cells produced from differentiated adult body cells by transcriptional factors reprogramming the body cells
what stem cells do mature plants have
many totipotent stem cells
what is epigenetics
heritable changes in gene function without changes in the base sequence of DNA
what occurs in increased acylation and what effect does this have
acetyl groups bind to histone proteins, this causes DNA to be less tightly wrapped around the histones, hence reducing the condensation of chromatin. this makes promoter regions more accessible and transcriptional factors can bind to promoter regions and initiate transcription
what occurs during increased methylation and what effect does this have
methyl groups are added to cytosine bases in DNA, this results in decreases aceylation of histones so DNA is more tightly wrapped and chromatin becomes more condensed. promoter regions are inaccesible and transcription is inhibited
what is cancer
the rapid uncontrolled division of cells by mitosis
what is a tumor suppressor gene
inhibits cell division and instructs the cell death of faulty cells (apoptosis)
what happens when a tumor suppressor gene becomes inhibited
a change in base sequences inactivates the tumour suppressor gene and the cell divides uncontrollably
what happens during increased methylation of a tumour suppressor gene
methyl groups are added to the cytosine bases in the DNA of the gene, and this inhibits transcription
what are proto-oncogenes
they stimulate cell division
what happens when a proto-oncogene becomes mutated
a change in the base sequence of the DNA on the gene causes the proto-oncogene to become an oncogene. the oncogene is permanently active and cells divide continuously by mitosis
what happens during increased acetylation
acetyl groups bond to histone proteins and transcriptional factors can bind to promoter regions and initiate transcription
what is the genome
the complete set of genes (or all the DNA) in an organism or cell
what is a proteome
the full range of proteins produced by a cell
