Control Of Gene Expression Flashcards

Question

How can cardiomyocytes be made form unipotent stem cells?

Answer 1

Cardiomyocytes are heart muscle cells that make up a lot of the tissue of a heart, in mature mammals they cannot replicate themselves - old or damaged cardiomyocytes can be replaced by new ones derived from a small supply of unipotent stem cells. In the heart - some believe it is a really slow process and that its possible that some cardiomyocytes are never replaced - some think its more quickly so every cardiomyocytes is replaced several times

Answer 2

Bone marrow contains stem cells that can differentiate into any blood cells, so bone marrow treats plants can be used to replace faulty bone marrow in patients producing abnormal blood cells. - used to treat leukaemia and lymphoma - and sickle cell disease

Answer 3

- spinal cord injuries = stem cells used to replace nerve tissue - heart disease - bladder conditions = stem cells used to grow whole bladders - respiratory disease = donated windpipes and stem cells used - organ transplants = organs can be grown

Answer 4

- save many lives = organ transplants - improve quality of life for many people - used to replace damaged cells in the eyes of blind people

Answer 5

- obtained from body tissues of an adult e.g. bone marrow - obtained din a simple operation = a lot of discomfort - are not as flexible as embryonic stem cells as they are often multipotent

Answer 6

- obtained from embryos at an early stage of development - embryos are created in a laboratory using in vitro fertilisation - at 4-5 days old the stems cels are removed and the rest of the embryo is destroyed - they can divide a n unlimited number of time s and develop inti all types of body cells = pluripotent

Answer 7

- induced pluripotent stem cells created in a lab by reprogramming specialised adult body cells so that they become pluripotent - adult cells are made to express a series of transcription factors normal for pluripotent cells, so they express genes that are associated with pluripotentency - infected with a specially modified virus = the genes form the virus are passed into the adult cells DNA meaning the cell is able to produce the transcription factors

Answer 8

- could have developed into a foetus in a womb - some people believe that embryos have the right to life

Answer 9

- eukaryotes = transcription factors move from the cytoplasm to the nucleus - in the nucleus they bind to specific DNA site near the start of their target genes - the genes they control the expression of - they control expression by controlling the rate of transcription - some transcription factors called activators stimulate or increase the rate of transcription e.g. help RNA polymerase to bind to the target genes - others are called repressors which inhibit or decrease the rate of transcription e.g. bind to the start if the target genes preventing RNA polymerase for binding

Answer 10

- oestrogen is a steroid hormone that binds to a transcription factor called an oestrogen receptor, making an oestrogen-oestrogen receptor complex - the complex moves from the cytoplasm into the nucleus where it binds to specific DNA sites near the start of the target genes - complex acts as an indicator of transcription e.g. helping RNA polymerase bind to the start of their target genes

Answer 11

RNA interference is where small double stranded RNA molecules stop mRNA from target genes being translated into proteins One type is called siRNA = small interfering RNA and miRNA = microRNA

Answer 12

Once mRNA has been transcribed, it enters the cytoplasm - Where double stranded small interfering RNA associates with several proteins and unwinds, a single strand then binds to the target mRNA, the basic sequence of SI RNA is complimentary to the base sequence in sections of the target mRNA - The proteins associated with SIRA cut the mRNA into fragments = no longer be translated, fragments move into a processing body and are degraded - Similar process happens with MIRNA in plants

Answer 13

In mammals, MIRNA isn’t usually fully complementary to the target mRNA making it less specific than SIRNA and so may target more than one mRNA molecule - It associates with proteins and binds to target mRNA the miRNA-protein complex physically blocked the translation of the target mRNA - mRNA is then moved into a processing body where it is stored or degraded, if stored it can be returned and translated at another time

Answer 14

- lactose present for E.coli it makes an enzyme to digest it, if no lactose it doesn’t waste energy making the enzyme it doesn’t need, the enzyme gene is only expressed when lactose is parent - it is controlled by the transcription factor - Iac repressor - no lactose = Iac repressor bind to the DNA at the start of the gene stopping transcription - yes lactose = lactose binds to the Iac repressor stopping it binding to the DNA so they gene is transcribed

Answer 15

Through the attachment or removal of chemical groups known as epigenetic marks to or from DNA or his stone proteins - Epigenetic marks don’t hold the base sequence of DNA - They alter how easy it is for the enzymes to interact with transcribe the DNA

Answer 16

- Organisms inherit their DNA base sequence from their parents - Most genetic marks on DNA are removed between generations, but some escape the removal process and are passed on - Meaning expression of some genes in offspring can be affected by environmental changes that affected their parents or grandparents E.G.epigenetic changes in plants in response to drought have been shown to be passed to later generations

Answer 17

This is when a methyl group is attached to the DNA coding for a gene - The group always touches a CPG site which is where a site and guanine base next to each other in the DNA - Increased methylation changes the DNA structure so that the transcriptional machinery can’t interact with the gene so the gene is no longer expressed

Answer 18

His stones are proteins that DNA wrapped around to form chromatin which makes up chromosomes, chromosomes can be highly condensed or less condensed how condensed they are affects the accessibility of the DNA and whether or not it can be transcribed: - The addition or removal of acetyl groups, when histones are acetylated the chromatin is less condensed, allowing transcription - When acetyl groups are removed chromatin becomes highly condensed. DNA cannot be transcribed because enzymes and proteins can’t physically access them. - Histone deacetylase enzymes are responsible for removing the acetal groups

Answer 19

Fragile X syndrome is a genetic disorder that can cause symptoms such as learning and behavioural difficulties Caused by a heritable duplication mutation in a gene on the X chromosome called FMR one, the mutation results in short DNA sequence CGG being repeated many more times than usual - Meaning there are lots of CPG sites resulting in increased methylation which switches it off, because the genius switch switched off the protein that codes for it isn’t produced

Answer 20

Genetic changes are reversible - Drugs designed to counteract the genetic changes that caused disease - For example increased methylation is an epigenetic change drugs that stop DNA methylation can be used to treat this - E.G. azacitidine is used in chemotherapy for cancer that is caused by increased methylation of tumour suppressor genes - decreased acetylation of histones can also lead to genes being switched off HDAC inhibiting drugs can be used to treat diseases by inhibiting the activity of histone deactylase - The drugs need to be specific as these changes take place normally in a lot of cells

Answer 21

If the twins are genetically identical, any differences in phenotype must be entirely due to environmental factors If a characteristic is different between the twins, the environment must have a large influence

Answer 22

Mapped the entire sequence of the human genome in 2003 - found where each gene is located - determine the sequences of the 3 million chemical base pairs that make up human DNA - stored the information in a public data base

Answer 23

- proteome is all the proteins made by an organism - Bacteria don’t have non-coding DNA - so it’s easy to determine their proteome from the DNA sequence of their genome - This can be useful in medical research and development

Answer 24

More complex organisms contain large sections of non-coding DNA - Also contain complex regulatory genes, which determine when the genes that cover particular proteins should be switched on or off - Making it more difficult to translate their genome into their protein

Answer 25

Recombinant DNA technology involves transferring a fragment of DNA from one organism to another - Because the genetic code is universal and because is transcription and translation mechanisms are similar to the transfer. DNA can produce a protein in the cells of the recipient organism, which don’t even have to be the same species - Organisms containing transferred to DNA are also known as transgenic organisms

Answer 26

mRNA is easy to obtain as there are many copies which are complimentary to the gene, whereas most cells only contain two copies of each gene - mRNA molecules can be used as template to make lots of DNA, using reverse transcriptase to make DNA from an RNA template, the DNA produced is complementary DNA cDNA - To do this mRNA’s first isolated from cells then mixed with three DNA nucleotides in reverse transcriptase - The reverse transcript uses the mRNA as a template to synthesise in new strand of cDNA

Answer 27

Some sections of DNA have palindromic sequences of nucleotides, these consist of antiparallel basis that read the same and opposite directions - Restriction endonucleases recognise specific palindromic sequences and cut the DNA at these ends - The shape of the recognition sequence is complementary to the enzymes active site - The DNA sample is incubators with the specific restriction endonuclease which cuts the DNA fragment out. There are hydrolysis reaction. - Sometimes the cut leaves sticky ends which are small tales of unpaired bases at each end of the fragment, these can be used to bind the DNA fragment to another piece of DNA with complementary sequences

Answer 28

Fragments of DNA can be synthesised from scratch without needing pre-existing DNA templates - A database contains the necessary information to produce the DNA frag - The sequence that is required is designed - The first nucleotide and the sequence is fixed to some sort of support - Nucleotides are added step-by-step in the correct order that includes adding protecting groups which make sure that the nucleotides are joined at the right points to prevent unwanted branching - Short sections of DNA called oligonucleotides produced, once these are complete they are broken enough from the support and all the protecting groups removed, or oligonucleotides can then be joined together to make longer DNA fragments

Answer 29

Transforming host cells - once DNA fragments are isolated you need to amplify it so you have a sufficient quantity to work with, one way of doing this is to use in vivo cloning which is where copies of the DNA fragment are made inside a living organism

Answer 30

DNA fragment is inserted into vector DNA - a vector is something that’s used to transfer DNA into a cell, they can be plasmids or bacteriophages - the vector DNA is cut open using the same restriction endonuclease that was used to isolate the DNA fragments containing the target gene, so the sticky ends of the vector are complementary to the sticky ends of the DNA fragments containing containing the gene - the vector DNA and the DNA fragment are mixed together with DNA ligase which joins the sticky ends of the DNA fragments to the sticky ends of the vector DNA, called ligation - new combination if bases in the DNA is called the recombinant DNA

Answer 31

- vector with the recombinant DNA is used to transfer the gene into cells - if a plasmid vector is used, host cells have to be persuaded to take in the plasmid vector and its DNA - with a bacteriophage vector, the bacteria phage will infect the host bacterium by injecting its DNA into it, the phage DNA then integrates into the bacterial DNA - host cells that take up the vectors containing the gene of interest are said to be transformed Transformation

Answer 32

Marker genes can be used to identify the transformed cells: - they can be inserted into vectors at the same time as the gene to be cloned, any transformed cells will contain the gene to be cloned and the marker gene - host cells are grown on agar plates, each cell divides and replicates its DNA, creating a colony of cloned cells, transformed cells will produce colonies where all the cells contain the cloned and marker genes - marker gens can code for antibiotic resistance - host cells grown with a specific antibiotic, so only transformed cells that have the marker genes will survive and grow, can also code for fluorescence when agar is placed into UV light - identified cells are allowed to grown more, producing lots of copies of the cloned gene

Answer 33

Make sure the vector contains specific promoter and terminator regions - promoter regions are DNA sequences that tell the enzyme RNA polymerase then to start producing mRNA - terminator regions tell it when to stop - without the right promoter region the DNA fragment will not be transcribed and the proteins wont be made - p and t may be present in the vector DNA or they may have to be added in along with the fragment

Answer 34

- Doesn’t require a specific enzymes to extract or synthesise fragments of DNA - Will not result in blunt ends - Can produce any sequence you like - DNA sequence but no introns so can we put into prokaryotic cells?

Answer 35

Polymerase Chain Reaction: - can clone or amplify DNA samples as small as a single molecule - Useful for producing large quantities of fragments - A form of in vitro cloning

Answer 36

1) reaction mixture is set up containing the DNA sample, free nucleotides, primers and DNA polymerase (Prime as a short pieces of DNA that are complementary to the basis at the start of the fragment you want) 2) the mixture is heated to 95°C to break the hydrogen bonds between the two strands 3) mixer is then included between 50 and 65°C so that the primers can bind (anneal) to the strands 4) mixture is then heated to 72°C so DNA polymerase can work 5) DNA polymer lines up three nucleotides alongside each template strand and joins them together using specific base pairing making complementary strands 6) two new copies of the DNA fragment formed and one cycle of PCR is completed 7) cycle starts again with the mixture being heated to 95° and this time all four strands are used as templates 8) each PCR cycle doubles the amount of DNA E.G.1st cycle = 4 DNA fragments, second cycle = 8 DNA fragments, third cycle = 16 DNA fragments and so on

Answer 37

Microorganisms, plants and animals can all be transformed using recombinant DNA technology Transformed microorganisms can be made using the same technology as in vivo cloning for example for a DNA can be inserted into microorganisms to produce lots of useful proteins such as insulin

Answer 38

- transformed plants can also be produced where a gene for a desirable protein is inserted into a plasmid which is added to a bacterium which is used as a vector to get the gene into the plant cells. If the right promote a region has been added the transformed cells will be able to produce the desired protein.

Answer 39

A gene that codes for a desirable protein can be inserted into an early animal embryo or into the egg cells of a female, if the gene is inserted into a very early embryo all the body cells of the resulting transformed animal end up containing that gene - Inserting it into an excel means when that female reproduce is all the cells of her offspring will contain the gene

Answer 40

Promote Tay Tay regions that are only activated in specific cell types - If the protein is only produced in certain cells it can be harvested more easily producing the protein in wrong cells could also damage the organism

Answer 41

First, the DNA fragment containing the insulin gene is isolated Then the DNA fragment is inserted into a plasmid vector - Then the plasma containing the recombinant DNA is transferred into a bacterium - Transformed bacteria identified and grown - The insulin produced from the cloned gene is extracted and purified

Answer 42

Crops can be transformed so that they have higher yield or a more nutritious They can also have pest resistance so few pesticides are needed reducing costs and environmental problems E.G.golden rice is a variety of transformed rice containing one gene from maize plant and one gene from a soil bacterium which enabled the rice to produce beta carotene. It is used to reduce vitamin a deficiency in areas of shortage.

Answer 43

A lot of industrial processes use biological catalysts which can be produced from transformed organisms in large quantities for less money reducing cost E.g. Chymosin used in making cheese can be produced by transformed organisms

Answer 44

Many drugs and vaccines are produced by transformed organisms using recumbent DNA technology, can be made quickly cheaply and enlarged quantities E.g. Insulin is now made from transformed microorganisms using a clone human and gene.

Answer 45

Can result in monocultures making a whole crop vulnerable to the same disease because the plants are genetically identical. This also reduces biodiversity. - Transformed crops could interbreed with wild plants leading to an uncontrolled spread of recombinant DNA - Organic farmers could have their crops contaminated by wild blown seeds from nearby genetically modified crops therefore can’t sell their crop as organic

Answer 46

Anti-globalisation activists oppose globalisation - As the use of technology increases large multinational companies get bigger and more powerful which may for smaller companies out of business - Without proper labelling some people won’t know if they have a choice about whether to consume genetically engineered organisms - Companies who own genetically engineering technologies may limit the use of technologies that could be saving lives E.G. unethical to make designer babies

Answer 47

Who owns genetic material from humans once it has been removed from the body? The donor or the researcher. Large corporations own patents for particular seeds they can charge high prices and can require farmers to purchase seeds each year If non-genetically modified crops are contaminated by genetically modified crops farmers can be sued for breaching the patent law

Answer 48

- Agricultural crops could be used that help reduce famine and malnutrition - Transformed crops could be used to produce useful pharmaceuticals - Medicines can be produced cheaper - Has potential to treat human diseases

Answer 49

1) involves altering the defective genes inside cells to treat genetic disorders and cancer 2) how this is done depends on whether the disorder is caused by a mutated dominant allele or two mutated recessive alleles - Caused by two mutated recessive alleles you can add a working dominant allele - Caused by a mutated dominant allele you can silence the dominant allele by sticking a bit of DNA in the middle of the allele so it doesn’t work Both processes involve inserting a DNA fragment into a persons original DNA

Answer 50

The allow is inserted into cells using factors just like a component DNA technology Different vectors can be used like viruses, plasma or liposomes

Answer 51

Involves altering the alleles in body cells particularly the cells are most affected by the disorder Somatic gene therapy doesn’t affect the individual sex cells so any offspring could still inherit the disease

Answer 52

This involves altering the alleles in the sex cells meaning that every cell of any offspring produced from these cells will be affected by the genetherapy and they will not suffer from the disease Currently illegal

Answer 53

Worries about using gene therapy for cosmetic effective aging and other people worry there is the potential to do more harm than good by using technology

Answer 54

Functioning gene is isolated and inserted into plasmids Recumbent plasmas are placed back into the bacteria and cloned Plasma is extracted and wrapped in lipid molecules Liposome sprayed into patient’s airways Liposomes fuse with plasma membranes of target cells and into nucleus + package larger DNA + can pass through cell membranes + less likely to trigger an immune response - Less efficient

Answer 55

Adenoivirus can be modified to make it harmless Adenoviruses are grown in cells in vitro recombinant plasma that contain normal gene Recombinant plasmid is taken up by adenovirus and the gene becomes part of the viruses DNA The viruses are isolated and sprayed into the nostrils of a patient Viral DNA inserts into the epithelial cells of a patient’s lungs + good at invading specific cells + easy to modify - could trigger an immune response - small and can’t get large DNA in

Answer 56

DNA probes a short strand of DNA with a specific basic sequence that’s complimentary to the base sequence of a part of a target allele This means the DNA pro bind/hybridise to the target allele if it is present in a DNA sample DNA probes also has a label attached so they can be detected, this could be a radioactive label or a fluorescent label

Answer 57

Example of DNA is digested into fragments using restriction enzymes and separated using electrophoresis Separated DNA fragments and then transferred to a nylon membrane and incubated with the fluorescent labelled DNA probe If The was present, the DNA probe will hybridise to it Membrane is an exposed to UV light and if the genius present there will be a fluorescent band

Answer 58

A DNA microarray is a glass slide with microscopic spots of different DNA probes attached to it in rows - A sample of fluorescent labelled human DNA is washed over the array - If the human DNA contains any DNA sequences that match any of the probes it will stick to the array - The arrays washed to remove any labelled DNA that isn’t stuck - The array is then visualise under the UV light and any label DNA attached to the probe will show up - Any spot that fluorescent means that the persons DNA contains that specific allele

Answer 59

First, you need to sequence the allele that you want to screen for You then use PCR to produce multiple complementary copies of parts of the allele these are the probes

Answer 60

Can help to identify inherited conditions E.G.Huntington’s disease Can help to determine how a patient will respond to specific drugs E.G.breast cancer which can be treated with the drug herceptin screening for the mutation can help to see if the drug will be useful treatment or not Can help identify health risks, inheriting particular mutated alleles increases your risk of developing certain cancers, this could be useful to help prevent it but some people are concerned that it may lead to discrimination by insurance companies and employers

Answer 61

It is advising patients and their relatives about the risks of genetic disorders, it involves advising people about screening and explaining the results of a screening Screening can help identify if someone is the carrier of a mutated allele, the type of allele they carrying and the most effective treatment If the results of a screening are positive then genetic cancelling is used to advise the patient on options of prevention and treatment

Answer 62

Medicines that are tailored to an individuals DNA The theory is that if doctors have your genetic information, they can use it to predict how you respond to different drug drugs and only prescribed the ones that will be most effective for you

Answer 63

VNTR are base sequences that don’t code for proteins and repeat next to each other over and over again - The number of times these sequences are repeated differs from person to person so the length of the sequences in nucleotides differs to - The repeated sequences occur in lots of places in the genome. The number of times the sequence is repeated at different places in their genome can be compared between individuals. This is called genetic fingerprinting. - The probability of two individuals having the same genetic fingerprint is very low because the chance of two individuals having the same number of VNT is at each place they are found in DNA is very low

Answer 64

1) a sample of DNA is obtained 2) PCR is used to make many copies of the areas of DNA that contain the VNTR’s - primers are used that binds to either side of these repeats and so the whole repeat is amplified 3) you end up with DNA fragments where the length corresponds to the number of repeats at each specific position 4) fluorescent tags added to all the DNA fragments 5) DNA fragments undergo electrophoresis where the DNA mixture is placed into a well in a slab of gel and covered in a buffer solution that conduct electricity, an electrical current is passed through the jail. The DNA fragments are negatively charged so they move towards the positive electrode at the far end of the gel. Small DNA fragments move faster and travel further. 6) DNA fragments view as bands under UV light 7) when comparing to genetic fingerprints if both fingerprints have a band at the same location on the gel it means that they have the same number of nucleotides and so the same number of VNTRs making it a match

Answer 65

We inherit VNTR base sequences from our parents, roughly half of the sequences come from each parent Meaning more the bands on genetic fingerprints that match the more closely related to people are The higher the number of places in the G name compared the more accurate the test will be

Answer 66

The greater number of bands that don’t match on a genetic fingerprint the more genetically different people are Meaning you can compare the number of repeats at several places in the genome for a population to find out how genetically varied they are

Answer 67

If a DNA sample is left by possible suspects, it can be used to link them to the crime - The DNA is isolated and each sample is replicated using PCR which is then run on electrophoresis gel and a genetic fingerprint producer compared to see if any match - If the samples match a link a person to the crime scene

Answer 68

- Genetic fingerprinting can refer to a unique pattern of several alleles - It can be used to diagnose genetic disorders and cancer, it’s useful when the specific mutation isn’t known or where several mutations could have caused the disorder as it identifies a broader altered genetic pattern

Answer 69

Genetic fingerprinting can be used on animals and plants to prevent into breeding which decreases the gene pool Interbreeding can lead to an increased risk of genetic disorders leading to health productivity and reproductive problems Genetic fingerprints can be used to identify how closely related individuals are and so the least related individuals will be bred together