the control of gene function Flashcards
describe the in vitro technique of DNA amplification- PCR
- DNA heated to 90 to 95c
- strands separate
- cooled
- primers bind
- nucleotides attach
- by complementary base pairing
- temperature 70 to 75c
- DNA polymerase joins nucleotides together
- cycle repeats
describe the in vivo technique of amplification
- DNA fragments isolated
- DNA fragments inserted in vectors
- vectors transported into bacterial host cells
- bacteria multiply
- marker genes used to identify the successfully transformed bacteria
- remaining bacteria are cultured
totipotent cells-
pluripotent cells-
unipotent cells-
induced pluripotent cells-
totipotent cells- divide into any type of cells and during development, totipotent cells translate only part of their DNA resulting in cell specialisation
pluripotent cells- can divided in unlimited number and can be used to treat human disorders
unipotent cells- eg heart muscle cells which differentiate into their own lineage
induced pluripotent cells- transcriptional factors cause specific genes to be expressed which differentiate a cell back to pluripotent state
describe the role of transcriptional factors
- bind to specific base sequences of the DNA in the nucleus (promoter region)
- causing the DNA to start transcription
- mRNA is produced and the information carried onto a polypeptide
- when a gene is not expressed the binding site will be inactive
- therefore inhibits transcription
describe the role of oestrogen on the gene transcription
- oestrogen enters through the cytoplasm thru the cell surface membrane
- it is lipid soluble so can pass through the phospholipid bilayer
- oestrogen binds to receptors on transcription factors in the cytoplasm
- causing transcription factors in the cytoplasm to change shape
- transcription factors form a receptor hormone complex that can now enter the nucleus
- this then bind to a promoter region which activates transcription and protein synthesis
describe the process of RNA interference
RNAi complimentary to mRNA binds and breaks down the mRNA before its information can be translated
inhibits translation of mRNA
acetyl addition
removal of bond between histone and DNA resulting it from being less tightly wrapped and therefore gene expression is stimulated
methylation
attracts proteins to bind to DNA causing it to be more tightly wrapped and therefore inhibiting gene expression
epigenetics
involves heritable changes in gene function without changes to the base sequence of DNA- caused by changes in the environment and inhibit transcription
tumour suppressor genes-
oncogenes-
tumour suppressor genes- signals apoptosis, controls cell division, causes cell cycle to stop the damage is detected, when switched off causes unregulated cell cycle
oncogenes- permanently switched on causing controlled cell division because they stimulate cell division by producing triggering proteins
abnormal methylation of tumour suppressor genes and oncogenes
hypermethylation causes tumour suppressors to not be coded= uncontrolled cell division
increased oestrogen concentration causes…
binds to TF activating the genes promoting cell division
Role of DNA probes
single strand of DNA that has known base sequence complementary to specific base sequence of a known allele. this binds to sample strand by complementary base pairing and can be detected either by x rays or will glow
DNA hybridisation
two complementary single stranded DNA molecules combine through base pairing to form a double stranded DNA molecule
process of gel electrophoresis
- DNA mixture is places in a slab of gel
- and covered in buffer solution that conducts electricity
- an electrical current is passed through the gel
- DNA fragments are negatively charged so they move towards the positive electrode at the far end of the gel
- small DNA fragments move faster and travel further through the gel
- so the DNA fragments separate according to size
