pack 21 gene expression Flashcards
(27 cards)
1
Q
regulation of transcription
A
- transcriptional factors are found in the cytoplasm of the cell
- they move into the nucleus
- each transcriptional factor has a site the binds to a specific base sequence of the DNA - the promoter region
- binging of the transcriptional factor to the promoter region allows the attachment of RNA polymerase to the DNA and transcription is stimulated
- mRNA is produced and subsequently translated to a polypeptide.
2
Q
what is oestrogen
A
a lipid soluble steroid hormone released into the bloodstream
3
Q
role of oestrogen
A
- oestrogen enters the cell by simple diffusion
- it binds to a specific transcriptional factor
- transcriptional factor to change shape
- an inhibitor molecule to be released which exposes the DNA binding site on the transcriptional factor
- the transcriptional factor now binds to a specific sequence of bases on the promotor region, enabling the RNA polymerases to bind and initiate transcription
4
Q
what is the function of the inhibitor molecule
A
prevents the transcriptional factors binding to the DNA promotor region and initiating transcription and therefore synthesis of protein when protein is not required
5
Q
the effect of RNAi on gene expression
A
- double stranded RNAi is coded for by special regulatory genes
- it moves into the cytoplasm where it becomes single stranded and associates with nuclease enzyme
- it binds to specific mRNA molecules with a complementary base sequence by complementary base pairing
-the enzyme cuts the mRNA in two - the mRNA can no longer be translated so protein synthesis stops
6
Q
when is RNAi important in a cell
A
- stops the translation of viral RNA in a cell infected by virus
7
Q
RNAi used to identify the role of genes
A
- a specific sequence of RNAi which binds to the mRNA transcribed from a particular gene is added to cells
- this prevents translation of that gene so protein is not produced.
- by observing the effect of lack of protein, the role of the blocked gene can be determined
8
Q
RNAi prevention of a genetic condition
A
- it may be possible to use RNA to prevent faulty protein from being produced and so prevent a condition which is caused by faulty genes
9
Q
what are the two features of stem cells
A
- they are undifferentiated but can differentiate into specialised cells
- they can replace themselves
10
Q
what is a totipotent cell
A
- occur for a limited time in early mammalian embryos
- can differentiate to produce any type of body cell, including placental cells
11
Q
what is a pluripotent cell
A
- found in embryos
- can differentiate into all tissue types, except placental cells
12
Q
what is a multipotent cell
A
- found in many tissues of mature mammals
- can differentiate to form a limited number of different cell types
13
Q
what is a unipotent cells
A
- also found in mature mammals
- can only differentiate into one type of cell or tissue
14
Q
what is induced pluripotent cells
A
- these are pluripotent stem cells produced from differentiated adult body cells
- specific protein transcriptional factors are used to reprogramme the body cells
- iPS cells are able to divide to produce new iPS cells or differentiate into any type of body cell
- they could replace the use of embryonic stem cells in medical research and treatments
15
Q
the potential uses of stems cells in treating human disorders
A
- stem cells are grown in cultures in the laboratory
- certain chemical stimuli are added which trigger the cells to differentiate into specialised body cells of a particular type
- these can then be used to replace damaged cells or tissues in a patient
16
Q
plant stem cells
A
- mature plants have many totipotent cells
- under the correct conditions these can differentiate into any other cell.
17
Q
what does epigenetics mean
A
involves heritable changes in gene function, without changes to the base sequence of DNA
18
Q
what is epigenome
A
- dna is wrapped around histone proteins in the nucleus to produce chromatin
- the dna and histones have chemical tags attached to them
- the epigenome comprises all the chemical tags which have been added to a persons genome
the chemical tags are either an acetyl group or methyl group
19
Q
acetylation of histones
A
- acetyl group bind to histone proteins
- this causes the DNA to be less tightly wrapped around the histones - reduces condensation of chromatin
- this makes promotor regions accessible
- transcriptional factor can bind to promotor regions and initiate transcription
- genes are switched on
20
Q
what is decreased acetylation
A
- acetyl groups are removed from histone proteins
- this causes DNA to be more tightly wrapped around the histones which increase condensation of chromatin
- this makes the promotor region inaccessible
- transcriptional factors cannot bind to the promotor regions to initiate transcription
- gene are switched off
21
Q
methylation of DNA
A
- methyl groups are added to cytosine bases in DNA
- this results in decreased acetylation of histones
- DNA wraps more tightly round histones - chromatin becomes more condensed
- promotor regions become inaccessible to transcriptional factors
- transcription is inhibited
- gene are switched off
22
Q
benign tumours and treatment
A
- mass of cells that has no spread into neighbouring tissues
- one part of the body
- do not invade surrounding tissues
-potential to develop into cancers - surgery to remove
23
Q
cancerous tumours and treatments
A
- uncontrollably dividing cell groups that may spread to other parts of the body
- surgery combine with
- chemotherapy - kill fast growing cancer cells
- radiation therapy - uses ionising radiation to damage the DNA of the cancer tissues to kill the abnormal cells
24
Q
tumour suppressor gene
A
- p53 this protein stops the cell cycle moving from g1 to s phase in mitosis
- p53 protein is encoded by the p53 gene
- if the gene mutates the p53 protein is unable to halt the cell cycle and cells divide uncontrollably.
this is cancer
25
proto-oncogene
- permanent activation of the gene becomes an oncogene
- continuous transcription and translation produce protein continuously
- protein stimulates cell to divide too quickly by mitosis
26
what is a genome
the complete set of genes in a cell/ organism
27
what is a proteome
the full range of proteins produced by a give cell
