Control of Gene Expression Flashcards
define mutation
a change to the nucleotide sequence of DNA
what does a Mutogenic Agent do?
increases the rate of mutation
What is a Base Analogue?
a chemical that can substitute for a normal nucleotide base —-> substition mutation
what does radiation cause?
change to the structur of DNA eg) UV
describe substitution
one base swapped for another one
describe addition, and what it causes
one base added this causes frame shift
describe deletion
one base is removed
decribe inversion and what it can cause
sequence of bases are reversed, can cause no change (degenerate) ,change a few, doesn’t cause frame shift
describe duplication
one or more bases are repeated
describe translocation
DNA is moved from one part of a genome to another part of a genome
what could be the impact of the alteration of one AA?
changes primary structure, changing H bonds, changing tertiary structure (could have negligable change)
what does change to many AA cause?
frame shift= change to primary/H bonds —> tertiary
describe stem cells
capable of diffferentiating into specialised cells, can divide for the organisms lifetime (no apoptosis)
what is a totipotent stem cell?
can differentiate into any specialised cell, found in early mammalian embryos
describe a pluripotent cell
can differentiate into many types of cells, but cannot make placental cells
describe a multipotent stem cell
can differentiate into a few types of specialised cells
describe a unipotent stem cell
stem cells that can differentiate into one type of cell
what happens when a cell becomes specialised?
conditions inside the cell control which genes are expressed (eg) transcription factors) cells become irreversibly specialised
How can we obtain induced pluripotent stem cells (iPS)
use a modified virus as a vector, virus inserts transcription factors from pluripotent —-> unipotent, transcription factors are expressed
how can we obtain embryonic stem cells?
IVF embryos, pluripotent stem cells are removed after a few days, pluripotent cells can differentiate into all types of body cell
how can we obtain Adult Stem Cells?
taken by consenting adults in an operation (eg) bone marrow) Adult stem cells are multipotent
how can bone marrow be used in medicine?
contain multipotent stem cells, can differentiate into WBCs and RBCs, donor bone marrow can be used to treat leukemia
how can stem cell grown organs be used in medicine?
no donor required, use iPS cells, no rejection
what are the advantages of stem cells in medicine?
improve quality of life, prevent suffering, save lives
what are the disadvantages of stem cells in medicine? (how can some of these be combatted)
embryos could develop into a foetus, fertalised —> right to life ( use an unfertalised egg that has been triggered to multiply, or develop iPS cells)
define transcription factor
proteins that control the rate of transcription by switching genes on and off
define promotor region
short sequence of DNA at the start of the gene that the ribosome attaches to
decribe the process of a transcription factor
TF moves from the cytoplasm to the nucleus, binds to the promotor region, activate/ repress transcription by helping/ preventing RNA ploymerase binding to DNA
describe using the example of oestrogen how transcription factors can be controlled
steriod hormone, binds to receptor, foring oestrogen - oestrogen receptor complex, alters shape to make transcription factor
define cancer
uncontrolled cell division resulting in a tumour
what is the role of a tumour suppressor gene?
make genes which slow down mitosis or trigger apoptosis
what may result from a mutation of a tumour suppressor gene?
a non functional protein
what is the role of a proto-oncogene?
speed up mitosis
what is a proto-oncogene called if it mutates?
oncogene
how does mutation of a proto -oncogene cause cancer?
oncogene can be over expressed, over increasing the rate of mitosis, resulting in a tumour
define epigenetics
changes to gene expression caused by the environment (without changing the base sequence of DNA)
can epigenetics be inherited?
yes
how does epigenetics control gene expression?
by preventing transcription
Methylation?
More Methylation —-> Terminates Transcription
describe methylation
methyl group attaches to cytosine (CpG site) and prevents transcription, methylated CpG sites prevent transcription enzymes
Acetylation?
Less Acetylation —–> Terminates Transcription
describe acetylation
acetyl group make histones space out, and DNA less tightly coiled, allows transcription enzymes to attach
How does RNA interferance control gene expression?
prevents translation
describe siRNA
short, double stranded
describe how siRNA prevents translation
combines with protein to form siRNA - protein complex, becomes single stranded, unpaired bases are complementary to target mRNA, siRNA protein complex breaks down mRNA, preventing translation
what is formed when microRNA joins with protein?
microRNA-protein complex
how does microRNA prevent translation?
binds to mRNA by complementary base pairing, prevents translation by stooping the ribosome attaching
Describe hypermethylation
affects tumour suppressor genes (think why), proteins are not transcribed, leading to uncontrolled cell division (cancer)
describe hypomethylation
affects proto-oncogenes (think why?), more proteins are transcribed, leading to uncontrolles cell division
how can we uses mitosis to identify a tumour?
more cells dividing
how can we use nuclei to identify a tumour?
appear large, irregular, multiple per cell
how can we use the shape of cells to identify a tumour?
irregular appearance
how would the arrangement of cells in a tumour appear?
disorganised
what is a benign tumour?
non cancerous
describe a benign tumour
slow growing, harmless, can become malignant
what is a malignant tumour?
cancerous
describe a malignant tumour
fast growing, harmful, can spread
what hormone may cause breast cancer?
oestrogen
how may oestrogen cause cancer?
oestrogen- oestrogen receptor complex acts as a transcription factor to increase rate of cell division, increasing cell divisin increases risk of mutations, leading to cancer
why has the chain termination method of gene sequencing been replaced with high throughpat pyrosequencing?
automated, faster, cheaper
why is it easier to sequence the genome of simple organisms such as prokaryotes?
few regulatory genes, little non coding DNA
how is the genome project used?
understand evolutionary relatedness (phylogeny), medicine applications such as finding antigens for vaccines
