Control of Gene Expression Flashcards by Abi Akerman

define mutation

a change to the nucleotide sequence of DNA

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what does a Mutogenic Agent do?

increases the rate of mutation

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What is a Base Analogue?

a chemical that can substitute for a normal nucleotide base —-> substition mutation

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what does radiation cause?

change to the structur of DNA eg) UV

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describe substitution

one base swapped for another one

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describe addition, and what it causes

one base added this causes frame shift

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describe deletion

one base is removed

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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

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describe duplication

one or more bases are repeated

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describe translocation

DNA is moved from one part of a genome to another part of a genome

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what could be the impact of the alteration of one AA?

changes primary structure, changing H bonds, changing tertiary structure (could have negligable change)

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what does change to many AA cause?

frame shift= change to primary/H bonds —> tertiary

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describe stem cells

capable of diffferentiating into specialised cells, can divide for the organisms lifetime (no apoptosis)

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what is a totipotent stem cell?

can differentiate into any specialised cell, found in early mammalian embryos

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describe a pluripotent cell

can differentiate into many types of cells, but cannot make placental cells

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describe a multipotent stem cell

can differentiate into a few types of specialised cells

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describe a unipotent stem cell

stem cells that can differentiate into one type of cell

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what happens when a cell becomes specialised?

conditions inside the cell control which genes are expressed (eg) transcription factors) cells become irreversibly specialised

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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

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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

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how can we obtain Adult Stem Cells?

taken by consenting adults in an operation (eg) bone marrow) Adult stem cells are multipotent

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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

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how can stem cell grown organs be used in medicine?

no donor required, use iPS cells, no rejection

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what are the advantages of stem cells in medicine?

improve quality of life, prevent suffering, save lives

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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