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Biology > 8 control of gene expression > Flashcards

8 control of gene expression Flashcards

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1
Q

what does each mutation do:
. substitution
. deletion
. addition
. duplication
. inversion
. translocation

A

. sub- swapped
. del- removed (frame shift)
. add - added (frame shift)
. dupli - repeats (frame shift)
. inv - reversed
. trans - removed to same or another chromasome

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2
Q

why might base mutations not effect tertiary structure of proteins

A

. genetic code is degenerate
. mutation is in an intron
. occurs in recessive allele

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3
Q

how might mutations effect tertiary structure

A

. changes amino acid sequence
. may affect h, ionic or disulfide bonds between r groups
. can change shape of active site to change
. no longer able to form es complexes

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4
Q

what are stem cells

A

. unspecialised cells that continually divide that can differentiate into other types of cells
. found in embryos - form foetus
. some adult tissues - bone marrow

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5
Q

what are the different types of stem cells and where are they found

A

. totipotent - develop into any body cell, present in mammals in first few divisions of embryo
. pluripotent - can specialise into anything BUT placenta, from 4-5 day old embryos, used to treat human disorders
. multipotent - present in adult mammals, can differentiate into few cells
. unipotent - can only differentiate into one type of cell, cannot regenerate

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6
Q

why do stem cells become specialised

A

. different genes are expressed
. mRNA only transcribed from specific genes
. this mRNA tranlsted into proteins
. proteins modify the cell and cause cell to specialise, irreversible

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7
Q

how are induced pluripotent cells made and what are they used for

A

. used in medicine and research
. take somatic adult specialised cells and infect them with modified virus with gene coding ofr transcription factors so cells become pluripotent
. transcription factors attach to promoter regions of dna and stimulate RNA polymerase to stimulate transcription

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8
Q

what are the disadvantages of using somatic cells

A

. gathered from adults
. found in bone marrow
. very uncomfortable to obtain
. multipotent not pluripotent

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9
Q

what are the pros and cons of stem cells in research

A

. pro - can be used to grow organs to save lives or replace tissues
. cons - obtaining embryonic stem cells requiers the destruction of an embryo

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10
Q

how do transcription factors work

A

. move from the cytoplasm to the nucleus
. bind to specific DNA sites nesr start of target gened
. activators - increase rate of transcription, help mRNA polymerse to bind to target gene
. repressors - decrease rate of transcription, can prevent mRNA polymerase from binding to target gene

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11
Q

how does oestrogen initiate transcription

A

. oest is small and hydrophobic, diffues through phospholipid bilayer into cells
. binds to transcription factor oest recep alpha oestrogen receptor in cyto which is held in protein complex, changes the shape and releases er ALPHA
. the er ALPHA oest receptor can now enter nucleus and bind to promoter region of one target gene, stimulating RNA polymerase to transcribe target gene

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12
Q

how does RNA interference inhibit the translation of mRNA

A

. small interfering RMA is a double stranded rna found in cyto
. associates with proteins and unwinds to single strands
. strand binds to target mRNA by comp b pairing
. proteins associated with siRNA cut mRNA into pieces so doesnt translate, fragments move to body and are degrqaded

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13
Q

what does mirna do in mammals

A

. microRNA
. is not fully complimentary to target mrna so may target multiple molecules
. associates with the protein and binds to target mrna in cyto
. miRNA protein complex blocks translation od target mrna
. mRNA moved to a processing body to be stored or degraded

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14
Q

what is epigenetics

A

. heritable changes in gene function without the base sequence of dna changing

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15
Q

how does epigenetics control gene expression in eukaryotes

A

. in eukaryote, dna associated with histone
. if dna tightly wound, genes arent transcribed
. chemicals may attach to histones/dna to affect winding and thus transcription
. no changes in base sequence of dna
. epigentic changes can be inherited

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16
Q

how can changes in environment inhibit transcription

A

. hyper-methylation (increased) of dna - caused by diet, stress, smoking, food availability
. can cause growth of tumours by supressing tumour suppressor resulting in uncontrollable cell division
. methyl group attaches to dna, if promotor region slightly methylated, transcription factor cannot bind, so RNA polymerase not stimulated and transcription doesnt occur

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17
Q

what happens if acetylation decreases

A

. acetyl groups being removed causes chromatin to condense so can be transcribed and dna uncoils

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18
Q

what does histone deacetylase do

A

. catalyses the removal of acetyl from histones leading to increased transcription, can be used to reduce epigenetic factors

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19
Q

why are epigenetic changes good targets for drugs

A

. epigenetic changes are reversible
. drugs can be developed to reduce highly methylated tumour suppressor genes

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20
Q

what is a tumour

A

. a mass of abnormal cells caused by uncontrollable cell division

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21
Q

what effects use of tumour suppressor genes

A

. can be inactivated by mutations, or by increased methylation
. reduced function of these genes causes cancer

22
Q

what are proto-oncogenes

A

. stimulate cell division
. effect can be increased by mutations or by decreased methylation becoming oncogenes
. too much protein causes uncontrolled cell division

23
Q

describe how altered dna may lead to cancer

A

. dna altered by mutation
. changes base sequence
. of gene controlling cell growth
. of tumour suppressor gene
. change protein structure
. produce proteins that inhibit cell division
. uncontrolled cell division
. leading to a malignant tumour

24
Q

what are benign and malignant tumours

A

. benign - non cancerous growths, often covered in fibrous tissues stopping them form invading other tissues, can become malignant, can cause blockages or put pressure on other organs
. malignant - grow rapidly, invade and destroy surrounding tissues, cells can break off and spread to other parts of body via blood or lymph

25
Q

what is meant by maligannt tumour (eq)

A

. mass of undifferentiated cells
. uncontrolled cell divison
. metastasises and froms new tumours

26
Q

how does increased oestrogen levels lead to breast cancers

A

. inc oest caused by starting menstruation early, or menopause late, or hormone replacement therapy
. results in more cell division so inc cancer risk
. oestrogen causes canc cells to divide rapidly
. causes mutations directly to dna so increases chance of becoming cancerous

27
Q

what are the different ways of making dna fragments

A

. conversion of mRNA to complementary DNA using reverse transcriptase

. using restriction enzymes to cut fragments containing desired gene from dna

. creating the gene in a ‘gene machine’

28
Q

why can genes be transferred between organisms

A

. the genetic code is universal
. transcription is mostly similar in organisms
. transferred genes can code for proteins in the recipient

29
Q

what is recombinant DNA technology

A

. transferring fragments of DNA from one organism or species to another

30
Q

what is a transgenic organism

A

. an organism containing transferred DNA

31
Q

explain how genes can be isolated and copied using reverse transcriptase enzymes

A

. isolate the mRNA
. mRNA is mixed with free DNA nucleotides and reverse transcriptase
. reverse transcriptase uses mRNA as a template to synthesise new DNA strands
. DNA polymerase is added into double stranded DNA

  • this results in intron free dna
  • prokaryotes have intron free dna
  • means it can be transplanted directly into prokaryotes
32
Q

explain how genes can be isolated and removed using restriction enzymes

A

. restriction enzymes recognise specific palindromic DNA and cut DNA at these places
. shape of recognition sequence comp to enzyme active site

33
Q

what does it mean for DNA fragments to have ‘sticky ends’

A

. small tails of unpaired bases
. can easily bind to any other DNA fragments cut using the same restriction enzyme

34
Q

how can genes be synthesised using ‘gene machines’

A

. Dna sequence is designed
. first nucleotide in the sequence is fixed to a support
. nucleotides are added step by step in the correct order
, faster method than enzyme catalysed reactions

35
Q

what do in vitro and in vivo mean

A

. in vitro - outside of a living organism
. in vivo - inside of a living organism

36
Q

what does DNA amplification by polymerase chain reaction do?

A

. in vitro
. makes large number of copies of specific frags of DNA
. allows tests to be carried out on samples
. only requires about 25 repeats to get 1,000,000 copies of dna

37
Q

describe how the polymerase chain reaction is carried out

A

. DNA heated to about 95c causing dtrands to separate as H bonds break
. cooled to 55c so primers bid making nucleotides attach by comp base pairing
. temperature 75c causing dna polymerase to join nucleotides together, cycle repeated

38
Q

what is a primer

A

. short piece of single stranded DNA thats complimentary to DNA

39
Q

how do you set up a mixture for pcr

A

. DNA sample
. free DNA nucleotides
. Primers
. DNA polymerase

40
Q

explain each stage of pcr

A

. 1 - denaturation - heaat to 95c, H bonds between DNA strands break so separate DNA strands, strands become templates for new comp strands
. 2 - annealing - 55c, primers attach to DNA template strands, H bonds reform
. 3 - synthesis - 70c (polymerases optimum), polymerase attaches to primer and adds new comp bases to template

41
Q

summarise dna amplification by transforming host cells

A

. in vivo
. DNA fragment inserted into host cell
. when host cell ,completes DNA replication prior to dividing, it will copy the DNA fragment as well

42
Q

whaat ar evectors

A

. used to transfer DNA
. can be plasmids or viruses

43
Q

a laboratory has oat plants containg resistance gene and a supply of plasmids. describe how bacteria may be produced which have the resistance gene in their plasmids

A

. cut desired gene of oat plant
. use resistance coding mRNA from oat
cut plasmid open
. with restriction endonuclease
. then use dna ligase to attach sticky ends
. return plasmids to cells
. use of ca2+ or electric shock to allow vector to enter host cell

44
Q

explain in depth DNA amplification

A

. in vivo
. isolate gene, cut DNA using restriction endonucleases at specific base sequences leaving exposed sticky ends
. insert gene into a vector, DNA ligase then used to anneal the donor and vector DNA, now called RECOMBINANT DNA
. uptake of new plasmids into bacteria , only about 1% will uptake successfully, use marker genes to identify these e.g. antibiotic resistance, bioluminescence, enzyme causing colour changes
. culture the bscteria and produce many clones with copies of the gene

45
Q

why might not all the bacteria incorperate the new plasmids in DNA amplification

A

. recombinant plasmid doesnt get into the cell
. plasmid rejoins before dna fragment entered
. dna fragment sticks to itself rather than inserting into the plasmid

46
Q

what can be added in DNA amplification to improve liklihood of a vector entering a cell

A

. Ca2+ ions added
. cells heat/electric shocked
. makes cell more permeable for vectors

46
Q

explain how modified plasmids are made by the genetic engineering and how the use of markers enable bacteria containing these plasmids to be detected

A

. isolate wanted gene
. using restriction endonucleases
. use ligase to join wanted gene to plasmid
. this produces sticky ends
. use ligase to join wanted gene to plasmid and include a marker gene
. add plasmid to bacteria to grow then plate onto medium where the marker gen is expressed
. colonies not killed have the wanted gene

47
Q

what si needed for protein production

A

. promoter and terminator regions

48
Q

what sia promoter region

A

. DNA sequences indicating to RNA polymerase when to stop producing protein

49
Q

what is a terminator region

A

. DNA sequences indicating to RNA polymerase when to stop producing mRNA

Biology (6 decks)

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