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SEMESTER 1 > BIOCHEM stem cells,epigeneitcs > Flashcards

BIOCHEM stem cells,epigeneitcs Flashcards

1
Q

what are stem cells?

A

undifferentiatated cells that can divide by mitosis + differentitate into different cells depending on their orign

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2
Q

described totipotent cells

A

-occur for LIMITED Time in early mammalian embryos

  • differentiate into ANY type of cell
  • during development they translate only PART of their DNA ( cell specialisation
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3
Q

describe pluripotent stem cells

A
  • founf in embryos, develop from totipotent
  • differentiate into ALMOST ANY type of cell
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4
Q

describe multipotent stem cells and give an example

A
  • found in matura mammals
  • differentiate into few LIMITED TYPES
    eg found in bone marrow + can make any blood cell
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5
Q

describe unipotent stem cells and give an example

A
  • can differentiate into ONE TYPE of specailised cell
    eg cardiomyocytes can differentiate into heart muscle cells
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6
Q

what do ogranisms develop by?

A

mitosis so all body cells of organism have same genes.

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7
Q

during development some genes transcribed and expressed how is this achieved?

A

protein transcription factors in cytoplasm

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8
Q

when a transcription factor is activated what occurs?

A

-attaches to promoter reigon close to target gene which the attachment activates RNA polymerase

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9
Q

what dies expression of different genes mean?

A

different proteins being coded for + so different specialised cells being made eg cell differentiation

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10
Q

what is IPS, what is it made from and how is it used?

A

induced pluripotent cells- made from unipotent using appropriate protein transcription factors which are used to express/inhibit genes so cells develop similar chracterisitics embryonic stem cells

ips stem cells used to develop wide range of tissues

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11
Q

what type of stem cells are used to treat human disorders and how?

A

pluripotent stem cells - can divide into unlimited numbers when used to differentiate into speciifc cell they provide source of replacment to cells+tissues

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12
Q

what does epigentics means?

A

heritable changes in gene function without changes ti base sequence of DNA

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13
Q

what do epigenetics control and when does it occur, what by? and how does it reduce expression of genes?

A

whether gene is transcribed or expressed

happens when changes in gene function caused by aspects of environment
eg stress, diet,exposure to toxins

so may reudce exoression of genes by inhbiting transcription

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14
Q

how does epigenetics inhbit transcription?

A

-increased methylation of DNA
- decreased actylation of associated histones

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15
Q

how does increased methylation occur and what does it do?

A

-occurs when methyl group (CH3) attaches to DNA sequence of gene
- methyl attaches to C next to G (CPG SITE)
-inhbits transcription by preventing binding of transcription factors to promoter reigon so gene is not expressed

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16
Q

how does decreased acetylation happen and why?

A
  • DNA wrapped around proteins (histones) to form chromatin and this can be epigenetically modified by removing actyl groups or addition
  • when histones more actylated(less condensed) transcription of genes most likely

when histones are less actylated they are more condensed so transcription is inhibited as genes arent accessible to transcription factors

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17
Q

what may epigenetics lead to and how can it be reversed and how?

A

-lead to disease by causing ABNORMAL activation or inhibition of genes

-can be reversed by drugs being made to counteract and target speciifc cells eg cancer

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18
Q

how does gene expression link to cancer?

A

group of diseased caused by damage to genes regulating mitosis + cell cycle. develop from tumours but not all are cancerous

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19
Q

what are the differences between maligant and benign tumours?

A

maliganant
- grow faster
- cancerous cells can break off and spread as tumoir isnt enclosed
-cells can become un-differentiated
( not specialised)
- cells nucleus large and dark

benign
-grow slower
- on-cancerous cells dont spread to othet tissues as tumours enclosed by fibrous tissue
- cells often remain differentiated
- cells nuclus normal appearnace

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20
Q

how do tumours develop?

A

-by tumour supressor genes + oncogenes
- increased oestrogen concentration (brest cancer)
- abnormal methylation of tumour supressor genes

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21
Q

why is methylation of genes important and what are the ffects of abnormal process?

A
  • control gene expression
  • abnormal process can lead to cancers+ develop from

-hypermethylation of tumour supressor genes so genes arent transcribed

  • proteins that slow cell division down are not made leading to uncontrollable cell division

-hypomethylation of protons-oncogenes so these genes continually transcribed

-increased production of proteins that control cell dviision+ lead to uncontrollable cell division

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22
Q

what does recombiant DNA technologu involve and do and what is a transgenic organism?

A

-involves transfer of genes from one organism to another

transgenic organism= organism recieveved trasffered DNA

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23
Q

genes can be obtained by many methods what are they?

A

-reverse transcriptase
- using restriction enzymes
- using gene machine

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24
Q

describe steps of reverse transcriptase?

A

rather than obtaining speicifc gene the mRNA thats TRANSCRIBED from gene removed from cells + used

  1. mRNA used as template to make equired gene or fragment DNA eg to make gene for insulin production, mRNA complementary to insulin gene isolayed from pancrease cells

2.mRNA mixed with free DNA nucleotides + enzyme reverse transcriptase

  1. free DNA nucleotides allign + attach next to complementary base pairs on mRNA template
  2. reverse transcriptase joins DNA nucelotides together to make frgament of DNA (Gene) for insulin this DNA is complementary (CDNA)
  3. double stranded DNA made from this using DNA nucleotides + DNA polymerase
25
describe steps of using restriction enzymes for required gene/fragment?
needed gene/fragment removed by restriction endonuclease enzyme 1. this enzyme cuts DNA at speciifc base sequence, /recognition site enzyme cut DNA to make sticky end more useful 2. cut DNA at specific recognition sequences 3. sticky DNA enables DNA to be joined onto different piece of DNA more easily due to the staggered cut . complementary base pairing ca occur between sticky ends 4. so restriction enzymes make straight cut of blunt end=less useful
26
describe steps of using a gene machine
this enables production of fragments of DNA/genes without needing pre-existing DNA/mRNA as template 1. mostly use sequence of amino acids of protein for templaye to determine sequence of DNA nucleotides for speciifc gene 2. automatted process where required nucleotide sequences is inputed into data base of gene machine 3.absence of introns means these genes can be transcribed by bacteria
27
what are bacteria used as in genetically modified microorganisms?
bacteria widely used as HOST cell to CLONE gene genes inside lviing organisms eg in vivo
28
what does genetically modified microrganisms involve use of which enzymes?
- restriction endonucleases + ligases to insert gene into vector which can be transffered into bacterium
29
what does the rapid reproduction role of bacteria enable genes to do?
quickly copied so large amount of gene product can be obtained
30
describe what happens and is involved in genetic modification
-plasmids ofted used as vectors - plsmid cut using same restriction endonuclease used to remove gene -plasmid DNA + foriegn gene then join together using ligase enzyme that fits together the overlapping complementary base pairs (sticky ends) -plasmid + foriegn DNA reffered to as recombiant plasmid - these plasmids vectors are added to culture of bacteria some of which take up recombiant plasmid by process known as transformation
31
what happens hen bacteria takes up the transffered gene?
replicates it during cell division produces COLONY which contains clones of genetically engineered bacteria
32
are bacteria cells cultured and do they make large amount ?
yes cultured+ male large amount eg hormones like insulin + antibiotics eg virus + liposomes can also b used as vector
33
what are promoter+terminator regions?
sections of DNA which must be added to gene/fragments for successful transcription of transffered genes in transformed cells
34
what is a promoyer region what does it do?
initiates transcription of gene by stimulating mRNA polymerases
35
what does the terminator region?
stops transcription by inhibiting mRNA polymerase
36
recombiant plasmids arent always guaranteed to work what are 3 outcomes?
1. bacteria may not take up plasmid at all 2. bacteria may take up plasmid but has joined back together without foriegn gene taken up 3-bacteria may take up recombiant plasmid ( plasmid with inserted gene?
37
how can sceintists identify bacteria for cloning which genes are used?
marker genes that anbles GM bacteria/eukaryotic cells to be detected and isolated for subsequent use
38
what is the GFP gene and what does it do?
marker gene that codes for production of green fluroscent protein and is added to gene transffered - successfully transformed bacteria/eukaryotic cells can be identifiied as they fluroese wnen viewed under micorscope + UV Light
39
what are humantarian beenfits useing GM organisms ?
- reducing famine + malnutrition by developing GM plants/animals that make high yield + resistent to diseases - make vaccines + drugs -treat genetic diseases(gene therapy)
40
why migjt environmentalists and anti-globalisation activists disagree with using GM organisms ?
-possible ransfer of genes to non-target organisms including humas - irreverisble process so no economic benefits - ethical consideration p- permanently altering genome -long term ecological + evolutionary conseuqence unknown -large companies to lack of choice + forcing smaller companies out of business
41
what is the polymerase chain reaction (PCR) and when is it useful?
this enables in VITRO can be used multiplication of identiical copies of DNA fragments/genes to be made from small sample best useful to make clones of isolated genes when only small DNA sample obtained eg from crime scene
42
what does the PCR reaction require?
-DNA sample to be copied - DNA primers (short single strands of DNA with nucelotide bases complementaru to first few bases of DNA sample) - free DNA nucleotides -heat stable DNA polymerase
43
what is the procedure for PCR
1. reactants mixed together and heated to 95 degrees for 5 mins(brekas Hbonds in DNA) 2. mixture cooled to 50-60 for 2 mins allowing primers to join to speciifc target sequence , DNA primers provide starting sequecne for DNA polymerase + her- to prevent DNA strands joining back together 3. free DNA nucleotides allign to DNA starnds by complementary base pairing 4. temp increased to 72 degees (optimum for polymerase). enzyme joins indiivudal nucelotides of strand togeether to make new complementary strand, many cycles of heating + cooling make expotential numbers of DNA molecules
44
does PCR double number moleciles each cycle?
yes 2^n
45
what is gene therapy what does it use, and help?
uses recombient DNA tech for treatment of geneitc diseases, involves introduction of functional copies of an allele into an organism which possesses defective alleles of same genes
46
what are the stages for gene therapy?
1. identifying gene causing disease 2. obtaining+ cloning copies of functional allelle 3.transffering these function alleles into pateint by VECTOR 4. ensuring alleles reach target genes + function normally
47
what is cyctic fibrosis how is it caused and what issues does it cause ?
inherited disorder homozygous recessive, carriers hetrozygous arent affected by disease gene codes for chloride channel protein which controls chlorine ions in + our cell after secretion of large amounts abnormal thick+ sticky mucus by epiethelial cells in lungs + pancrease have severse consequences - clinical trials use gene therpahy successful in altering epithelial cells in lungs of affected individuals
48
what is the DNA sequencing project?
involves determining sequence of DNA nucleotides bases in organism (genome) -sequencing projects have read genome of wide range of organisms eg humans - determining genome of simple organisms allows sequences of proteins that derive from genetic code (proteome) of organsims to be determined - may have applications inlcuding identification of potential antigens for use in vaccine production -
49
why is that most complex organsims you cant get knowledge of genome easily translated into proteome?
as they have non-coding DNA + regulatory genes
50
What is gel elctrophrosis?
DNA fragments can be seperated by this, smaller DNA fragments travle further through gel when electric charge applied -neg charfed DNA fragments move towards pos charge terminal
51
whats the procedure for gel electrophrosis?
1. 3 DNA samples places seperate wells top of gel 2.DNA fragments in each sample seperated according to size as smaller move further when electric charge applied 3. after electrophoresis, DNA fragmenets trasffered to NYLON memebrane + radioactively labelled DNA PROBES are added 4. places on X-ray/photogrpahic film (autoradiography) or can be identified using fluroscent labelled probes
52
what are DNA probes what do they detect?
detect specific sequences -single short stranded fragment of DNA complementary to known frequence of DNA eg particular allele - probe labelled by fluroscent tag -target allelel can be detctected using wavelength emitted by probe
53
what does the use of labelled DNA probes + DNA hybridisation help with?
locating speciifc allelles of genes which enables patient to be screened for Heritible conditions eg CF , sickleCA, HD -indiividualdrug responses- people respond differently to different drugs due to differences in alleles so can lead to personalised medicine health risk is BRCA1 gene increases risk of breast camcer 50-80?
54
what is genetic fingerprinting ( variable number trandem repeats)?
genome of organism has many repeating non-conding sequences of nucleotide bases known as VNTRS with exception of twins, probability of any individuals having same number + length of repatative sequences is very low more related people are more common they will be anlalysis of these VNTRS can be used to determine relatedness between individuals + identify DNA sample from crime scene
55
describe procedure for VNTR
1. PCR used to amplify sample 2. cut into fragments (restriction endonuclease) sites close to VNTRS gives large number of DNA fragments 3. fragemets separated (gel electrophoresis) 4. fragments treated (using alkali) to form single strands 5. single strands transffered in positions they have moved to onto nylon membrane 6. radioactive DNA probes added, complementary to repeated sequences + allow posiition of fragmenys identified lots probes used, bind with VNTRS by DNA Hybridisation 7. radioactive probes allow position of fragments identified when membrane placed onto an x-ray film ie geentic finger print obtrained
56
what do position of fragments depend on in gentic fingerprinting?
number of nucleotides (corresponds to number of repetitve sequences in each fragment) fragments with smaller number nucleotides travel further
57
how can 2 genetic fingerprints be compared?
if both fingerprints have smae position on gel means same number of nucleotides so same number of repetative sequences apart from identical twins geneitc fingerprints wont be the same
58
why is genetic fingerprinting useful + important ?
-forensic science - medical diagnosis -animal + plant breeding (genetic diversity prevents inbreeding)

SEMESTER 1 (8 decks)

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