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AQA A Level biology > control of gene expression > Flashcards

control of gene expression Flashcards

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1
Q

substitution (types of mutations) are…

A

one or more baes are substituted in the base sequence of DNA, may change to amino acid sequence, may not due to degenerate nature of the genetic code (silent)

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2
Q

silent/ neutral mutations (types of mutations) are…

A

mutation occurs in non-coding region of DNA, change in tertiary structure of the protein has no major effect on the organism

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3
Q

duplication (types of mutations) are…

A

one or more bases are repeated and therefore produced a frameshift, same effect as an insertion

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4
Q

inversion (types of mutations) are…

A

a group of bases become separated from the DNA base sequence + re-join at the same position but in reverse order
changes ion the amino acid sequence + therefore primary + tertiary structure of protein

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5
Q

insertion/deletion (types of mutations) are…

A

insertion- one or more nucleotide pairs are inserted into the sequence, frameshift to the right
deletion- one or more nucleotide pairs are deleted from the sequence, frameshift to the left

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6
Q

translocation (types of mutations) is…

A

group of bases become separated from DNA base sequences on one chromosome + are inserted into the DNA sequence on another chromosome

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7
Q

non-sense mutation is…

A

premature stop codon

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8
Q

mis-sense mutation is…

A

different amino acid coded for

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9
Q

causes of mutation are…

A

spontaneous error during DNA replication
chemical mutagens- benzene, alcohol, asbestos, tobacco
ionising radiation- UV, X-ray, alpha, beta

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10
Q

what are stem cells?…

A

unspecialised cells that continually divide and become specialised
differentiation= process when stem cells become specialised
types= totipotent, pluripotent, multipotent and unipotent

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11
Q

totipotent stem cells can…

A

differentiate into any type of body cell, and any cell needed for development
during development, can translate part of their DNA, resulting in specialisation
only occur for a limited time in early mamaliam embryos

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12
Q

pluripotent stem cells are…

A

found in embryos
can divide in unlimited numbers and differentiate into almost any type of body cell
used in treating human disorders
issues= can keep dividing causing a tumour, ethical problem, is it right for humans to be cloned

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13
Q

multipotent and pluripotent stem cells are…

A

found in mature mammals
multipotent= differentiate into a limited number of cells like bone marrow
unipotent= can only differentiate into one type of cell

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14
Q

iPS cells are…

A

created from adult unipotent cells (somatic)
treated with transcription factors to switch on genes that induced pluripotent (undifferentiated)

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15
Q

advantages of iPS cells are…

A

don’t cause embryonic destruction
self-renewal property, so can divide indefinitely to give a limitless supply
used in medical treatment instead of embryonic stem cells

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16
Q

controlling of transcription is when…

A

transcription of target genes can be either inhibited or stimulated when specific transcription factors move from the cytoplasm to the nucleus
controlling of gene expression (turning ‘off’ or ‘on’

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17
Q

transcription factors are…

A

molecules that move from the cytoplasm to the nucleus
bind to DNA in the promotor/operator region, initiating/inhibiting transcription and therefore translation of the protein
without transcription factors, gene is ‘turned off’, so the protein isn’t made

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18
Q

the role of oestrogen in initiating transcription is…

A

enters the cytoplasm through phospholipid bolster as it’s lipid soluble
binds to receptor site on transcription factor
changes tertiary structure, so TF is now complementary to and can bind to the promotor region of DNA initiating transcription

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19
Q

epigenetic control is…

A

epigenetic= environmental changes that cause heritable changes in gene function without changing the DNA base sequence
epigenetic control is mediated by chemical ‘tags’, which are collectively called the epigenome
some inhibit transcription= increased methylation of DNA+decreased acetylation if associated histones

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20
Q

increase methylation of DNA is…

A

methyl groups added to DNA at cytosine bases (sometimes called CpG islands)
prevents transcription factors from binding to promotor region of DNA
attracts proteins that condes de chromatin (DNA-his tone complex), so preventing transcription of RNA polymerase can’t bind

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21
Q

decreased acetylation of histones is…

A

histones become more positively charged, attracting phosphate groups on DNA as phosphate is negatively charged
causes chromatin to condense, so transcription factors + RNA polymerase can’t bind

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22
Q

treatment of disease…

A

increased methylation/decreased acetylation= inhibition of tumour suppressor genes (tumour formation)+ proto-oncogenes (inhibiting tumour formation)
decreased methylation/increased acetylation= increase in expression of tumour suppressor genes, so rumours are less likely to form
increase in expression of oncogenes- tumour formation
drugs can be given to prevent these changes

23
Q

RNA interference (RNAi) is…

A

translation from mRNA of target genes can be inhibited to RNAi
mRNA destroyed before translation to form polypeptide chain
two types= siRNA and miRNA

24
Q

siRNA and miRNA is…

A

enzymes cuts mRNA into siRNA (double-stranded) and one strand binds with an enzyme (DICER)
siRNA-enzyme complex binds to complementary base if mRNA (specific-one type only) (RISC)
cell can’t recognise double-stranded mRNA, so the enzyme degrades mRNA before translation
miRNA acts in the same way but is less specific so can bind to many mRNA types

25
Q

cancer is…

A

result of mutations in genes that control mitosis/ cell cycle
results in the uncontrollable division of cells and therefore the formation of a tumour
tumours can be benign or malignant

26
Q

benign rumours…

A

can grow large but at a slow rate
non-malignant, so can’t spread/metastasis
surrounded by a capsule and contain adhesion molecules, so remain compact and can be removed by surgery

27
Q

malignant tumours…

A

grow large rapidly
have the ability to spread to tiger parts of the body- metastasis
develop their own blood supply
can be life threatening and often need supplementary treatment (chemotherapy+radiotherapy)

28
Q

tumours can develop by…

A

oncogenes, tumour suppressor genes
increased oestrogen concentration

29
Q

oncogenes are…

A

mutated version of porto-oncogenes
encodes proteins involved in DNA replication + mitosis
can be permanently switched on, causing excessive cell division + tumour formation
hypo methylation increased expression as chromatin will be less condensed

30
Q

tumour suppressor genes…

A

encode proteins that inhibit cell division + cause apoptosis (programmed cell death)
if a mutation occurs, apoptosis is inhibited and cell division is stimulated, leading to u controllable cell division + tumour formation
hyper methylation leads to increased expression as chromatin is more condensed, so the genes transcription is limited

31
Q

increased oestrogen concentration…

A

oestrogen production by ovaries stops at menopause
fat cells in breast tissues produce oestrogen
can cause cancer as oestrogen activates transcription factors + consequently the transcription of genes e.g oncogenes
formation of tumour results in even more oestrogen production, increasing tumour size + attracting white blood cells

32
Q

a genome is…

A

full set of genes in each cell
genome can be sequenced

33
Q

sequencing projects are…

A

reading the genomes of a variety of organisms
determining genome of simple organisms allows the sequence of the proteins that are encoded
applications= identification of potential antigens to use in vaccines
in more complex organisms, the presence of introns means that knowledge of the genome can’t be translated into the proteome
proteome= full range if proteins that can be encoded by the genome
allows genome-wide comparison between different species, allowing the determination of evolutionary relationships
beneficial to medical research as genome comparisons between individuals can allow the development of personalised medications

34
Q

human genome projected has…

A

deteniendo the sequence of bases in a human genome
applications= screening for abnormal/ mutated sequences, allowing identification of disorders before symptoms arise, pre implantation screening
however, ethical issues as misuse and discrimination if genetic info/data is possible

35
Q

sequencing methods…

A

are constantly developing + becoming faster/ more efficient to use
have become more computer based
human genome took 15 years to sequence, but nowadays it can take as little as 26 hours

36
Q

recombinant DNA technology is…

A

involves transfer of fragments of DNA from one organism, or species, to another
genetic code, transcription + translation machinery are universal, so transferred DNA fragments can be translated within cells of the recipient organism- transgenic

37
Q

forming/ isolating DNA fragments involves which 3 processes…

A

reverse transcriptase
restriction endonuclease
gene machine

38
Q

process of reverse transcriptase is…

A

make DNA copies from mRNA
naturally occurs in retrovirus
cell that produces the protein that scientists want is chosen, should have a large amount of mRNA for the protein
reverse transcriptase can align + join the complementary DNA based to the mRNA bases
this is single stranded and called complementary DNA (cDNA)
DNA polymerase makes the cDNA double-stranded
cDNA doesn’t have introns

39
Q

restriction endonucleases are…

A

enzymes that ‘cut’ DNA at restriction sites to form DNA fragments
complementary to a base sequence at a specific restriction site
some cut through the same location in the double-stranded DNA to produce a blunt end
some create staggered (sticky) ends with exposed bases, these are palindromic, can join to como lenta tu base pairs

40
Q

a gene machine is…

A

DNA fragments can be created using computerised methods
1. scientists identify amino acid sequence of the protein of interest and the mRNA + DNA sequence from that
2. DNA sequence entered into a computer, which has to pass bio safety and bio security checks
3. computer creates small sections of overlapping DNA strands called oligonucleotides
4. oligonucleotides can then be joined to form the DNA sequence of the entire gene

41
Q

amplifying DNA fragments can be done…

A

in vitro, pcr (polymerase chain reaction)
in vivo, transformation

42
Q

process of in vitro pcr…

A
  1. DNA fragment heated to 95°c so hydrogen bonds between base paris break, producing 2 singles DNA strands
  2. cooled to 55°c to allow primers to anneal to the DNA fragments, primers are short sequences that allow the attachments of DNA polymerase
  3. heated to 72°c as this is optimum temp of DNA polymerase, DNA polymerase nucleotides together to form 2 new double-stranded DNA fragments
    number of DNA fragments produced by a given number of cycles can calculated 2^x x= number of cycles
43
Q

process of in vivo, transformation…

A
  1. DNA is cut using restriction endonucleases to create fragments with sticky ends
  2. a promotor + terminator region are added to allow transcription
  3. same restriction endonucleases are used to cut open the plasmid (DNA loop in bacteria, act as vector) to allow complementary sticky ends
  4. enzymes DNA ligase is used to incorporate the DNA fragment into the plasmid- recombinant DNA is formed
  5. recombinant plasmid is the then transferred into bacteria via heat shock or Ca2+ to increase membrane permeability
    not all plasmids take up the foreign DBA fragments
    not all recombinant plasmids will be taken up by the bacteria cell
    we can identify which bacterial cells have taken up the recombinant plasmids through marker genes
44
Q

marker genes in identifying if the plasmid was taken up…

A

plasmids contain antibiotic resistance genes
bacteria are given and agar plate containing antibodies
if bacteria have taken up the plasmids, they will survive as they will contain antibiotic resistance genes

45
Q

marker genes in identifying if the plasmids are recombinant…

A
  1. DNA fragment is inserted directly in the middle of a marker gene e.g GFP gene, encode fluorescence
  2. GFP no longer be made, so plasmids that don’t fluoresce are recombinant and those do are no -recombinant, so haven’t taken up the foreign DNA fragment
  3. can be done in antibiotic resistant genes too, as recombinant plasmids wouldn’t survive on agar plates with antibodies
46
Q

gene therapy is…

A

mechanism by which genetic disorders can be cured or treated by masking the effect of the faulty allele with the insertion of the functional allele
1. healthy allele isolated into cells using vectors
2. if mutant allele is recessive, a dominant allele is inserted, and if the mutant allele is dominant, DNA with the insertion into the middle of it to silence it
2 main types= somatic- alleles in body cells are altered, and is not passed on to offspring
germline= alleles in sex cells altered, and are passed on to offspring but is considered unethical due to concern over designer babies or safety of gene therapy

47
Q

DNA probes are…

A

short sections of DNA that are complementary to a known DNA sequence e.g a mutated allied
labelled with fluorescent or radioactive tags
mainly used for genetic screening- study if individuals DNA to identify whether they possess a mutated allele that causes a particular gene

48
Q

how do DNA probes work..

A
  1. labelled DNA probe is mixed with denatured DNA samples from and individual
  2. if the individual has the mitigated allele, the probe will bind to the complementary base sequence in on DNA stranded-hybridisation
  3. hybridised DNA is detected using radiation and fluorescence
49
Q

DNA hybridisation is when…

A

DNA sequences from different species that have complementary base pairs are mixed together and therefore hybridise
the more closely related the species are, the higher temperature it takes to break the hydrogen bonds between the 2 strands

50
Q

uses of DNA probes are…

A

genetic screening to see if an individual is the carrier of a recessive mutation or to evaluate their risk of developing diseases such as cancer
allow for personalised medicine specifically tailored to an individual genotype
individual may have genetic counselling after screening, which provided info + support about the results of the screening + how you can lower your risk of getting a particular disease

51
Q

what is genetic fingerprinting…

A

method used to produce a specific pattern of DNA bands from an individual genome

52
Q

what are VNTR’s…

A

variable number tandem repeat
short repeating sequences of DNA in non-coding regions
in every individual, they vary in length + in the no. of repeats, so the probability of 2 individuals having the same VNTR’s is very low

53
Q

process of DNA fingerprinting is…

A
  1. extraction of the DNA of interest + amplification by PCR
  2. digestion using specific restriction endonucleases into DNA fragments
  3. separation of DNA fragments by gel electrophoresis
    -DNA fragments move towards the positive electrode
    -smaller fragments move further down the gel
    -different sized fragments are separated into bonds
  4. VNTR’s are hybridised at specific complementary base sequences with DNA probes
  5. gel is developed- pattern of bands can be visualised by placing the gel on an X-ray film as the probes can emit radiation
  6. reveals the positions
54
Q

DNA profiling can…

A

determine genetic relationships by looking at how similar the binding patterns are
forensics=comparing DNA profile with those founds at the crime scene
medical diagnosis=identify individuals at risk of developing particular diseases
plant+animal breeding=used to prevent inbreeding by not breeding individuals with similar banding patterns.

AQA A Level biology (8 decks)

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