control of gene expression Flashcards

Question

Methylation of DNA

Answer 1

a methyl group is an epigenetic mark and is attached to the DNA coding for a gene the group always attaches at a CpG site which is where a cytosine and a guanine base are next to each other in DNA Increased methylation changes the DNA structure so that the transcriptional machinery e.g. enzymes, proteins can't interact with the gene so the gene is not expressed = SWITCHED OFF

Answer 2

proteins that DNA wrap around to form chromatin which make up chromosomes chromatin can be highly condensed/not condensed how condensed it is affects the accessibility of DNA and whether or not it can be transcribed

Answer 3

when histones are acetylated , the chromatin is less condensed. transcription factors can access the DNA which allows genes to be transcribed acetyl groups removal = chromatin highly condensed= transcription factors have no access = gene switched off histone deacetylase = enzyme responsible for removing acetyl group

Answer 4

decreased metylation can turn on genes that should be switched off e.g. colorectal cancer

Answer 5

epigenetic changes are reversible drugs can counteract these changes Increased methylation= gene switched off = drugs to stop DNA methylation decreased acetylation= gene switched off= HDAC inhibitor drugs work by inhibiting the activity of HDAC enzymes . Genes remain acetylated and the proteins they code for can be transcribed

Answer 6

mutations that occur in cells after fertilisation

Answer 7

1. acquired mutation in a gene that controls cell division . Can cause uncontrolled cell division 2. If a cell divides uncontrollably= tumour (mass of abnormal cells) 3. tumours invade and destroy surrounding tissue = cancer

Answer 8

1. tumour suppressor gene | 2. Proto-oncogene

Answer 9

takes a mutation of BOTH alleles to inactivate this gene when functioning normally, tumour suppressor genes slow cell division by producing proteins that stop cells dividing/cause them to self destruct if a mutation occurs the protein isn't produced. cells divide uncontrollably

Answer 10

a single mutated allele can activate this gene normally they stimulate cell division by producing proteins that make cells divide if a mutation occurs the gene can become overactive and stimulates the cell to divide uncontrollably mutated protooncogene is known as an oncogene

Answer 11

- cancers - grow rapidly and destroy surrounding tissues - can spread - cells nucleus is darker due to an abundance of DNA and often larger - cells become unspecialised - removal involves radio/chemotherapy

Answer 12

- non cancerous - grow more slowly than malignant - covered in fibrous tissue that stop cells invading other tissues - often harmless but they can cause blockages and put pressure on organs - removed by surgery - nucleus has normal appearance

Answer 13

- increased methylation of tumour suppressor genes =gene not transcribed= proteins to slow cell division are not made. uncontrollable growth - decreased methylation of proto oncogenes causes them to act as oncogenes= high production of proteins that encourage cell division= uncontrollable division.

Answer 14

- oestrogen can stimulate certain breast cells to divide and replicate. the fact that more cell divisions are taking place naturally, increases chance of mutations happening so increases chance of cells becoming cancerous - the ability to stimulate division means that if there are cancerous cells then their rapid replication can further be assissted by oestrogen - some research shows that oestrogen is able to directly introduce mutations into the DNA of certain breast cells, increasing chance of cells becoming cancerous.

Answer 15

the complete set of genes in an organism.

Answer 16

require fragments of DNA. if you want to sequence the entire genome of an organism it needs to be divided into smaller pieces. the smaller pieces are sequenced and then put back in order to give the sequence of the whole genome

Answer 17

the full set of protein produced by the genome

Answer 18

- contain large sections of non coding DNA - contain complex, regulatory proteins= determine when the gene for a protein is switched on/off - makes it more difficult to translate their genome into their proteome

Answer 19

produced by inserting the DNA of one organism into the DNA of another - genetic code is universal and transcription/translation mechanisms similar too so transferred DNA used to produce a protein in the cells of the recipient organism. - organisms that contain transferred DNA= transgenic organisms

Answer 20

lots of diseases result from faulty genes that stops production of some essential protein. If healthy gene coding for this protein placed into microbes DNA then this DNA can produce this protein on a large scale.

Answer 21

1. isolation- of DNA fragment that has the gene for the desired protein 2. insertion- of DNA fragment into a vector 3. Transformation- the transfer of DNA into a suitable hot cell 4. identification- if the host cell has successfully taken up the gene 5. cloning- of the host cell and thus protein being made

Answer 22

1. cells produce lots of mRNA for a target gene 2. mRNA used as a template by reverse transcriptase to make complementary DNA= cDNA 3. single stranded cDNA is isolated using enzymes to hydrolyse the mRNA 4. Double stranded DNA formed using DNA polymerase 5. copy of gene produced

Answer 23

- they are enzymes that cut up DNA at a specific base sequence called a recognition site - different RE's cut at different specific recognition sites because the shape of the recognition sequence is complementary to the enzyme's active site. - some cut straight across a strand= blunt end - others cut in a staggered way leaving som bases exposed= sticky end

Answer 24

1. the sequence that is required is designed 2. the first nucleotide is fixed to a support e.g. a bead 3. nucleotides are added in the correct order in a cycle of processes that includes adding protecting groups. Protecting groups make sure the nucleotides are joined at the right points 4. short sections of DNA called oligonucleotides (about 20 nucleotides long) are produced. These are broken off from the support and protecting groups are removed. The oligonucleotides can then be joined together to make longer DNA fragments

Answer 25

transferring the fragment into a vector into a living host cell and then cloning these cells

Answer 26

1. isolate the gene you wish to manufacture and cut it using a restriction endonuclease - producing sticky ends 2. use the same restriction endonuclease for the gene to cut the vector. this produces complementary sticky ends to the sticky ends of the DNA 3. The vector DNA and DNA fragment are mixed together with DNA ligase = joins the sticky ends of the DNA fragment to the sticky ends of the vector DNA= ligation complementary sticky ends increase chance of DNA sticking into vector than blunt ends

Answer 27

using chemicals can encourage the organisms to take up the vector = transformation once successful the organism can reproduce along with it the gene you require e.g. Ca2+ encourages bacteria to take up plasmids

Answer 28

- use a plasmid with 2 different genes that make it resistant to 2 different antibiotics - 1st antibiotic is to find out if bacteria have taken up a plasmid - 2nd antibiotic is to find out if bacteria have taken up the plasmid with the recombinant DNA - a replica plate is made so that we can refer back to which colony has the required plasmid and therefore our inserted DNA fragment

Answer 29

using a green fluorescent protein from jellyfish and inserting this into the plasmid with the DNA fragment you wish to clone insert the DNA fragment into the middle of the GFP gene so that the colonies that produce the genes we require don't show up as green cells don't die = rapid process

Answer 30

enzyme lactase converts a particular colourless substrate blue if inserted DNA fragment is accepted then the bacterial cells will not produce lactase and therefore the substrate will not turn blue

Answer 31

- where copies of a DNA fragment are made outside of a living organism - involves the polymerase chain reaction (PCR) - Method of copying fragments of DNA quickly+Efficiently

Answer 32

- original DNA sample that wants to be replicated - free nuclotides - DNA polymerase= heat resistant= does not denature - primers= short sequences of nucleotide bases that show DNA polymerase where to start - thermocycler= computer controlled machine that varies temp throughout process

Answer 33

1. Original sample of DNA heated to 95 degrees to separate the strands of DNA by breaking h bonds 2. sample is cooled to 55-40 degrees so that primers can bind to the complementary bases on the DNA fragment. provides the starting sequence for DNA polymerase to begin addition of nucleotides 3. temp raised to 72 degrees adding DNA polymerase to copy each strand of DNA adding complementary nucloetides starting from the primer end

Answer 34

2 copies formed of the DNA fragment from one cycle. each PCR cycle doubles the amount of DNA used for crime scenes to produce enough DNA for forensic analysis

Answer 35

``` advantages: - extremely rapid - no living cells required disadvantages - mistakes can happen in copying the sequence ```

Answer 36

modifiying an organism using recombinant DNA

Answer 37

Microbes can be used in in vivo cloning e.g bacteria that produce the insulin protein

Answer 38

inserting the desirable gene into the animal embryo

Answer 39

inserting the desirable gene into a plasmid then put it into a bacteria then the bacteria is used as a vector itself to insert the gene into a plant cell.

Answer 40

- crops can be transformed so they give higher yields/ are more nutritious= decrease risk of famine+ malnutrition - can also be transformed to have pest resistance so fewer pesticides needed= reduces costs+ envo problems associated with pesticides

Answer 41

-industrial processes often use enzymes as biological catalysts. These enzymes can be produced from transformed organisms so they can be produced in large quantaties for less money

Answer 42

- many drugs/vaccines produced by transformed organisms . can be made quickly, cheaply and in large quantities e.g. insulin

Answer 43

- can lead to monoculture= the whole crop could become vulnerable to a certain disease as they are genetically identical - monoculture= reduced biodiversity - if wild plants interbred with transformed crops then there would be an uncontrolled spread of recombinant DNA= unknown consequences

Answer 44

- genetic engineering is controlled by a few large biotech companies= smaller companies forced out of business - lack of proper labelling means people may feel like they dont' have a choice when it comes to choosing to eat foods which involve GM crops

Answer 45

- companies that own genetic engineering technology may limit the use of this technology which could be used to save lives - inappropriate use of tech e.g. designer babies

Answer 46

- who owns genetic info once it has been removd from the body- the donor or the researcher? - small number of large corporations own patent to seeds so can charge high prices - if non GM crops contaminated by GM crops farmers can be sued for breaking patent law

Answer 47

recombinant DNA can be used to treat human diseases

Answer 48

- by altering the defective genes inside cells to treat genetic disorders/cancer - if defective gene is caused by 2 mutated recessive alleles= add a working dominant allele to DNA to make up for them - if defective gene is caused by a mutation in the dominant allele then the gene can be silenced e.g by inserting DNA into the middle of the allele so it doesn't work - both involve inserting DNA fragments into person's original DNA - new allele is transported into cells by vectors e.g. plasmids, altered viruses

Answer 49

involves altering the alleles in body cells, particularly the cells that are most affected by the disorder e.g. CF somatic therapy targets epithelial cells lining the lungs doesn't affect sex cells so offspring can inherit disorder

Answer 50

involves altering the alleles in sex cells= every cell of any offspring produced will be affected by gene therapy and won't suffer from the disease.

control of gene expression Flashcards

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