8 control of gene expression Flashcards
ripping my eyes out
what does each mutation do:
. substitution
. deletion
. addition
. duplication
. inversion
. translocation
. sub- swapped
. del- removed (frame shift)
. add - added (frame shift)
. dupli - repeats (frame shift)
. inv - reversed
. trans - removed to same or another chromasome
why might base mutations not effect tertiary structure of proteins
. genetic code is degenerate
. mutation is in an intron
. occurs in recessive allele
how might mutations effect tertiary structure
. 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
what are stem cells
. unspecialised cells that continually divide that can differentiate into other types of cells
. found in embryos - form foetus
. some adult tissues - bone marrow
what are the different types of stem cells and where are they found
. 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
why do stem cells become specialised
. 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
how are induced pluripotent cells made and what are they used for
. 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
what are the disadvantages of using somatic cells
. gathered from adults
. found in bone marrow
. very uncomfortable to obtain
. multipotent not pluripotent
what are the pros and cons of stem cells in research
. pro - can be used to grow organs to save lives or replace tissues
. cons - obtaining embryonic stem cells requiers the destruction of an embryo
how do transcription factors work
. 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
how does oestrogen initiate transcription
. 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
how does RNA interference inhibit the translation of mRNA
. 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
what does mirna do in mammals
. 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
what is epigenetics
. heritable changes in gene function without the base sequence of dna changing
how does epigenetics control gene expression in eukaryotes
. 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
how can changes in environment inhibit transcription
. 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
what happens if acetylation decreases
. acetyl groups being removed causes chromatin to condense so can be transcribed and dna uncoils
what does histone deacetylase do
. catalyses the removal of acetyl from histones leading to increased transcription, can be used to reduce epigenetic factors
why are epigenetic changes good targets for drugs
. epigenetic changes are reversible
. drugs can be developed to reduce highly methylated tumour suppressor genes
what is a tumour
. a mass of abnormal cells caused by uncontrollable cell division
what effects use of tumour suppressor genes
. can be inactivated by mutations, or by increased methylation
. reduced function of these genes causes cancer
what are proto-oncogenes
. stimulate cell division
. effect can be increased by mutations or by decreased methylation becoming oncogenes
. too much protein causes uncontrolled cell division
describe how altered dna may lead to cancer
. 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
what are benign and malignant tumours
. 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
what is meant by maligannt tumour (eq)
. mass of undifferentiated cells
. uncontrolled cell divison
. metastasises and froms new tumours
how does increased oestrogen levels lead to breast cancers
. 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
what are the different ways of making dna fragments
. 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’
why can genes be transferred between organisms
. the genetic code is universal
. transcription is mostly similar in organisms
. transferred genes can code for proteins in the recipient
what is recombinant DNA technology
. transferring fragments of DNA from one organism or species to another
what is a transgenic organism
. an organism containing transferred DNA
explain how genes can be isolated and copied using reverse transcriptase enzymes
. 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
explain how genes can be isolated and removed using restriction enzymes
. restriction enzymes recognise specific palindromic DNA and cut DNA at these places
. shape of recognition sequence comp to enzyme active site
what does it mean for DNA fragments to have ‘sticky ends’
. small tails of unpaired bases
. can easily bind to any other DNA fragments cut using the same restriction enzyme
how can genes be synthesised using ‘gene machines’
. 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
what do in vitro and in vivo mean
. in vitro - outside of a living organism
. in vivo - inside of a living organism
what does DNA amplification by polymerase chain reaction do?
. 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
describe how the polymerase chain reaction is carried out
. 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
what is a primer
. short piece of single stranded DNA thats complimentary to DNA
how do you set up a mixture for pcr
. DNA sample
. free DNA nucleotides
. Primers
. DNA polymerase
explain each stage of pcr
. 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
summarise dna amplification by transforming host cells
. 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
whaat ar evectors
. used to transfer DNA
. can be plasmids or viruses
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
. 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
explain in depth DNA amplification
. 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
why might not all the bacteria incorperate the new plasmids in DNA amplification
. recombinant plasmid doesnt get into the cell
. plasmid rejoins before dna fragment entered
. dna fragment sticks to itself rather than inserting into the plasmid
what can be added in DNA amplification to improve liklihood of a vector entering a cell
. Ca2+ ions added
. cells heat/electric shocked
. makes cell more permeable for vectors
explain how modified plasmids are made by the genetic engineering and how the use of markers enable bacteria containing these plasmids to be detected
. 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
what si needed for protein production
. promoter and terminator regions
what sia promoter region
. DNA sequences indicating to RNA polymerase when to stop producing protein
what is a terminator region
. DNA sequences indicating to RNA polymerase when to stop producing mRNA
