3.8 Control of Gene Expression Flashcards

Question

how do TSF work

Answer 1

Eukaryotic transcription factors move from the cytoplasm to the nucleus via diffusion Each factor has a site which binds to a specific base sequence at the beginning of the gene (promoter) Once bound, transcription of the DNA begins and mRNA is produced so the information can be translated into a polypeptide. TSF control the gene expression by controlling rate of transcription

Answer 2

stimulate or increase the rate of transcription by helping RNA polymerase bind to the promoter region of the target gene

Answer 3

inhibit or decrease the rate by binding to the promoter region preventing RNA polymerase from binding

Answer 4

the site of the TSF specific to that DNA is inactive because an inhibitor is attached. This means it cannot cause transcription or polypeptide synthesis.

Answer 5

Lipid soluble so diffuses easily through the phospholipid bilayer of the cell surface membrane Once in the cytoplasm, it binds to the oestrogen receptor and forms an OE-OER complex This changes the shape of the DNA binding site of the TSF causing the inhibitor to be released The transcription factor is now activated and enters the nucleus through a nuclear pore to bind to the promoter sequence and initiate transcription

Answer 6

Small double stranded RNA molecules stop mRNA from being translated into proteins

Answer 7

Double stranded Taken up by cells via vectors Not in mammals, in lower animal + plant kingdoms Binds perfectly so can only inhibit translation of specific mRNA sequences

Answer 8

Single stranded Made inside the cell within the introns of larger RNA molecules In all animals + plants Pairing is imperfect so can inhibit the translation of many different mRNA sequences

Answer 9

Unwinds in the cytoplasm, one strand is selected and the other is degraded The single selected strand binds to mRNA Proteins cut mRNA so it cannot be translated, the pieces of mRNA are then degraded

Answer 10

The strand is not fully complementary to mRNA so it can target more than one mRNA Creates a long folded strand when first transcribed This is then processed into a double strand then single by enzymes One strand binds to mRNA, blocks translation instead of cutting it into pieces The mRNA is either stored or degraded

Answer 11

heritable changes in gene function without causing changes to the base sequence of DNA

Answer 12

The epigenome is considered flexible, the tags respond to environmental cues It is the accumulation of these tags during a lifetime Most tags are removed in the early fetus so do not get passed between generations Some escape removal so are passed onto offspring, so expression of some genes are affected by environmental changes which affected the parents or grandparents of the offspring

Answer 13

Acetylation makes the chromatin LESS condensed so it’s accessible to enzymes and can be transcribed This switches the gene on

Answer 14

Deacetylation makes the chromatin MORE condensed because of the increased attraction of histones to phosphate groups of DNA so enzymes cannot access it for it to be transcribed This switches the gene off

Answer 15

Addition of a methyl group to the cytosine bases of DNA This prevents the binding of TSF to the DNA It can alternatively attract proteins that condense the DNA-histone complex (inducing deacetylation of the DNA) making DNA inaccessible to TSF This switches the gene off

Answer 16

High levels of methylation on a TSG inactivates the promoter regions so DNA cannot be transcribed and the TSG itself is inactivated, early stages of cancer Increased methylation of protective genes means mutated DNA cannot be repaired and mutations spread, leading to cancers

Answer 17

Use drugs to inhibit enzymes that cause methylation, which can reactivate genes that have been silenced Drugs to inhibit enzymes involved in acetylation as well Genes must be specifically targeted to prevent switching on/off genes being read correctly which will cause a secondary cancer Tests to identify the level of DNA methylation and histone acetylation to indicate an early stage of disease for the patients to seek early treatment and have better chance of cure

Answer 18

Benign tumours Malignant tumours Grow to a large size Grow to a large size Grow very slowly Grow rapidly Cell nucleus appears relatively normal Cell nucleus is often larger and darker (due to abundance of DNA) Cells are often differentiated/specialized Cells become de-differentiated/unspecialized Cells produce adhesion molecules that makes them stick together so they remain within the tissue from which they arise/ primary tumours only Cells do not produce adhesion molecules so they tend to spread to other regions of the body (metastasis)/form secondary tumours Surrounded by dense tissues remain compact Not surrounded by a capsule so grow finger-like projections into surrounding tissue Less likely to be life-threatening, can disrupt a vital organ functioning More likely to be life-threatening as abnormal tissue replaces normal Localized effects Systemic effects such as weight loss and fatigue Removed by surgery alone Needs radio or chemotherapy as well as surgery Rare reoccurrence Frequently recur

Answer 19

If a mutation occurs in a TSG, the protein to stop cell division or cause apoptosis will not be produced. The cells will divide uncontrollably, forming a tumour

Answer 20

If a mutation occurs in a proto-oncogene, more of the protein to make cells divide will be produced so the cells will divide uncontrollably. This is now an oncogene.

Answer 21

the gene is not transcribed or translated so no protein is produced to stop cell division/cause apoptosis

Answer 22

too many proteins will be produced and it now acts as an oncogene

Answer 23

Estrogen stimulates breast cells to divide more frequently which increases the probability of a mutation Helps cancerous cells divide faster so tumour growth is rapid Can add mutations into DNA of breast cells so increases the risk of them becoming cancerous

Answer 24

Polygenetic cancer are triggered by more than one gene so cannot be sure how one gene being present affects risk Can be triggered by environmental factors, in which case the risk genes are not directly correlated to cancer Difficult to know which of the environmental factors have the greatest effect Cannot have a control group of people because it is unethical

Answer 25

Can screen for certain mutations in DNA for certain cancers Knowledge of increased risk means preventative steps can be taken More sensitive tests can diagnosis earlier for a better prognosis Mutations to a proto-oncogene can be treated with a drug which inhibits the enzyme produced by the mutation so the cells stop expressing it and the mutation does not spread so the tumour does not grow

Answer 26

The human genome project created a sequence of the average composite derived of several individuals More samples were collected than used and no names to remain anonymous Sequenced yeast and zebra fish too

Answer 27

cutting the DNA into smaller sections with overlapping ends and using computer programs to assemble them into the entire genome

Answer 28

There are only a small number of introns so determining the genome allows the proteome to be determined. This is useful to determine antigens on disease causing bacteria for vaccine production, also helps determine antibody resistance for better management and disease outbreaks monitored.

Answer 29

comparing to the human genome identifies disease genes common to both so we can then identify how to treat the disease

Answer 30

The presence of large numbers of introns and regulatory genes makes it difficult to find the protein-coding sections among them. This means the genome cannot be easily translated into the proteome.

Answer 31

DNA from 2 different organisms that has been combined transgenic/genetically modified organisms contain recombinant DNA

Answer 32

the genetic code, translation and transcription mechanisms are universal.

Answer 33

mRNA from the cell that produces the desired protein/gene is isolated and mixed with free nucleotides + reverse transcriptase Reverse transcriptase uses mRNA as a template to make complementary DNA (cDNA) To make the other strand of DNA, DNA polymerase is used to build up the complementary nucleotides on the cDNA template The method targets mRNA instead of the gene because it is more abundant so easier to target

Answer 34

Restriction endonuclease enzymes recognise palindromic sequences and digest/hydrolyse the DNA This leaves sticky ends after the cut which are used to anneal the fragment to another DNA fragment with sticky ends with complementary bases Palindromic sequences can also be known as recognition sequences

Answer 35

Desired sequence is made in the machine if it does not already exist The first nucleotide is fixed with support i.e a bead Nucleotides are then added one by one with a protecting group to make sure they are joined at the correct place with no unwanted branching Oligonucleotides are produced by breaking off the support and protecting groups. They are then joined together to form long sections of DNA from each short section. This method allows for DNA fragments to be made from scratch without needing a template

Answer 36

Insert the DNA fragment into a vector Vector DNA cut open by restriction endonucleases to ensure sticky ends will be complementary to the DNA fragments Vector + fragment DNA are mixed together with ligase which joins the ends together via ligation Recombinant DNA is created Either the vector DNA or the DNA fragment must have specific promoter + terminator sequences for the desired particular protein The vector containing recombinant DNA transfers the gene into host cells If a plasmid is used, a change in temperature and use of certain chemicals will encourage the cell to take it in If a bacteriophage is used, it will inject the recombinant DNA into the host cell so target DNA is integrated into the bacterial DNA The host cells taking up the vectors with the gene are transformed Identify transformed cells Marker genes are inserted into the vector with the DNA fragment It will either code for antibiotic resistance or make the transformed genes fluoresce under UV light Only those who are resistant to the specific antibody will be able to survive and replicate so those who grow are transformed

Answer 37

Create a mixture containing the DNA fragment, free nucleotides, DNA polymerase and primers Heat the DNA mixture to 95c in order to break hydrogen bonds Cool the mixture to 50-65c for primers to bind to the strands Heat the mixture to 72c in order for the DNA polymerase to work The DNA polymerase lines up free nucleotides along each template fragment strand to create complementary strands PCR doubles the number of strands in each cycle. 4 strands are created in each one.

Answer 38

Desired gene is inserted into a vector of either a plasmid or bacteria The bacteria infects the plants and inserts its DNA into the genome The plant produces the protein if the correct promoter gene is present Can be used for added nutrients or to cause resistance to pests A bacterial vector can infect the plant and cause it to develop the disease

Answer 39

Desired gene is added into egg cell or early stage embryo Modifying the egg means altering the genes of the germ cells which mature into GM egg + sperm Germline editing is only of reproductive cells This means it is possible to correct disease genes and pass them onto future generations

Answer 40

insert a promoter gene only activated by certain cells present in that area.

Answer 41

Cheaper production of treatments Quicker process Larger quantities

Answer 42

Crops larger and higher yield so prices will fall Crops more resistant to disease Increases shelf life Crops can produce herbicides themselves so cheaper

Answer 43

Food production + cleaning can be done by enzymes made by recombinant DNA Cheap production Large quantities made

Answer 44

Conglomerates will limit use in order to charge higher prices because stock is limited

Answer 45

Plants could be infected with disease from vector Decrease in biodiversity which damages food chains + ecosystem cohabitation Could breed with wild plants to produce superweeds Seeds may blow into nearby farms and contaminate organic products

Answer 46

No choice about eating GM food Large companies control GM technology so small businesses are forced out because they cannot compete with lower prices

Answer 47

few, if any, amino acids they code for will differ and the resultant polypeptide will be normal/near normal

Answer 48

frame shift is 3 bases long so subsequent codons are not affected. The resulting polypeptide will have an additional amino acid but otherwise unchanged.

Answer 49

codons after each duplication will change so polypeptide may have different amino acids but not all different due to degenerate code. After the third duplicate base, the codons will be unchanged.

Answer 50

if the replacement codons are the same as the originals

Answer 51

the second will have comp bases and it is unlikely these will complement a sequence on the miRNA

Answer 52

siRNA that blocks a certain gene could be added to cells, by observing the effect we could determine the role of the blocked gene. Could also be used to prevent disease by blocking the gene that causes it

Answer 53

a change in the sequence of amino acids so a change in the hydrogen bonds which results in an alters tertiary structure

Answer 54

oestrogen with protein + DNA, methyl binds with DNA, acetyl binds with protein

Answer 55

rank all values in ascending order and find the value with the same number of people above and below

Answer 56

the patient will produce healthy blood cells, there will be no cancerous blood cells present. the stem cells will be able to divide and replicate to increase numbers of healthy blood cells.

Answer 57

iPS cells divide and differentiate into green sensitive cones

Answer 58

Greater blood supply (to damaged areas); Bringing more oxygen / glucose for respiration; Brings more amino acids for protein synthesis; For cell repair / mitosis / division;

Answer 59

Mutation in the viral DNA Altered tertiary structure of the viral attachment protein Allows the attachment protein to bind to receptors of other species

Answer 60

gel electrophoresis, DNA fingerprinting, genome sequencing, PCR

Answer 61

mass/number of amino acids charge R groups differ

Answer 62

produces cDNA using mRNA

Answer 63

joins nucleotides to produce complementary strands of DNA

Answer 64

to remove any DNA present because this DNA would be amplified/replicated

Answer 65

there is a limited number of primers + nucleotides

Answer 66

Cut the plasmid with a restriction endonuclease; (So that) both have complementary / sticky ends; (Mix together) and add ligase to join the complementary / sticky ends

Answer 67

the gene gets into all of the cells in the silkworm so gets into the cells that make silk

Answer 68

identified using an X-ray film exposed by radioactivity

Answer 69

fluoresce when bound to the target DNA sequence

Answer 70

Sequence the allele you are screening for Produce a fragment of DNA containing the complementary base sequence to the desired allele using restriction enzymes + separate with gel electrophoresis Use PCR to produce multiple copies of the complementary DNA Attach a marker to the DNA, making it a DNA probe Sample DNA is heated to separate the two strands and cooled in a mixture containing the DNA probes If the desired allele is present, the DNA probes will bind to it causing DNA hybridisation Wash sample clean to remove unattached probes The remaining hybridised DNA will fluoresce

Answer 71

1. Use a microarray with desired DNA probes attached 2. Wash a sample of fluorescently sampled DNA over the microarray and wash again to remove any unattached DNA 3. Detect where fluorescence occurs to see where binding has taken place to know of any genetic disorders (and their alleles) present

Answer 72

Screen a person’s DNA and tailor the drugs they recieve to ones they will respond to best This helps for a quicker recovery time, lesser side effects, and more effective dosages which reduce NHS costs

Answer 73

Oncogene mutations, determines type of cancer and hence the most effective drug/radiotherapy to use Gene changes that predict which patients are more likely to benefit from certain treatments and give the best chances of survival A single cancer cell among millions of normal cells, detecting risk of relapse

Answer 74

inform people who are carriers of genetic disorders the likelihood of their future children having the condition Advice on treatments or preventative treatments if genetic test is positive Options on genes to be screened if people have a history of family illness

Answer 75

The base sequences which don’t code for proteins but repeat over + over Probability of two individuals having the same VNTRs is very low

Answer 76

comparing the VNTRs of two individual's genomes

Answer 77

Extraction - separate the DNA from the rest of the cell sample and use PCR to increase the volume of the VNTRs Digestion - using the same restriction endonuclease enzymes, cut the DNA into fragments Separation - separate the fragments by gel electrophoresis, the agarose gel is immersed in alkali to separate the double strands Hybridisation - DNA probes bind to the VNTRS because they have base sequences complementary to the base sequences of the VNTRs Development - View the gel under UV or X-ray depending on the type of labelled probe, bands are revealed to show where the DNA probes have attached. The gel can contain a DNA ladder to compare lengths of the fragments which appear to alleles of lengths of known value to identify bands present

Answer 78

Shorter, lighter fragments move further and longer, heavier fragments do not move as far in the agarose An electric current is passed through the gel, DNA is negatively charged so will move towards the anode

Answer 79

to determine genetic relationships, determine genetic variability within a population, forensic science, medical diagnosis, and plant/animal breeding

Answer 80

each band on a DNA fingerprint of an individual should have a corresponding band in one of the parents DNA fingerprint

Answer 81

a population with very similar bands in their GFs show little genetic diversity and vice versa

Answer 82

can match the DNA fingerprint of a suspect to that of DNA found at the scene of the crime, however this does not prove they carried out the crime only that they were present at some point. The probability that someone else’s DNA might match that of the suspect (and therefore it may not have been the suspect) needs to be calculated e.g if their culture tend to have partners from within their own small community

Answer 83

can match fingerprints with people who have various forms of the disease or those without the disease to predict the probability of developing symptoms and when

Answer 84

used to identify organisms with a desirable gene so they are selected to reproduce in order to increase the likelihood their offspring have the characteristic the desirable gene produces, also prevents undesirable breeding

Answer 85

use of restriction endonuclease enzymes which cut the DNA at the recognition site

Answer 86

contains fragments of known sizes to compare positions of viral fragments

Answer 87

1. to see if it is resistant to antibiotics in order to prescribe effective ones 2. to see whether any vaccine works against the strain so potential contacts can be vaccinated and the spread stopped

Answer 88

can join two pieces of DNA by complementary binding

Answer 89

mRNA more abundant than DNA so easier to target, mRNA has no introns

Answer 90

to mark a region of DNA to be copied useful because the enzyme needs a starting strand onto which attach nucleotides

Answer 91

change in base sequences due to addition, deletion or substitution changes mRNA transcribed therefore amino acid sequence changed so there is a loss of function in the protein leading to uncontrollable cell division

Answer 92

they cut open the plasmid at the same base sequence

Answer 93

anneal phosphodiester bonds

Answer 94

isolated cells divide by mitosis, there is a rapid production of toxin-producing plants and all cells will produce the toxin