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Biology - Year 2 (Eduqas) > Chapter 11 - Application of Reproduction and Genetics. > Flashcards

Chapter 11 - Application of Reproduction and Genetics. Flashcards

1
Q

What were the aims of the human genome project?

A
  • Identify all the genes in the human genome and identify which chromosome each is on.
  • Determine the sequence of all base pairs in human DNA.
  • Store the information on a database.
  • Consider ethical, social ad legal issues that arise.
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2
Q

What were the findings of the human genome project?

A
  • Humans have around 20,500 genes.
  • There are more repeated segments of DNA than had been suspected.
  • Fewer than 7% of the families of proteins were specific to vertebrates.
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3
Q

What are the applications of the human genome project?

A
  • Scan for mutations.
  • Carrier screening.
  • Pre-natal testing.
  • Newborn screening.
  • Screening for adult onset disorders.
  • Forensic and identity testing.
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4
Q

What did the 100k project aim to do?

A
  • Create an ethical, transparent programme based on consent.
  • Set up a genomic service for the NHS to benefit patients.
  • Enable medical and scientific discovery.
  • Develop a UK genomics industry.
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5
Q

What moral/ethical concerns are there regarding the human genome and 100k genome project?

A
  • Who owns the genetic information?
  • Some people don’t wish to have information on future health problems that they may have.
  • Concerns over the idea of ‘designer babies’.
  • Storage and security of genomic data is a concern because of the potential for computer storage to be hacked.
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6
Q

Why was the DNA sequencing of the female anopheles mosquito done?

A

So It can be used to try to develop chemicals that can prevent the mosquito from transmitting malaria by making it susceptible to insecticides.

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7
Q

Why is a genetic fingerprint not the same as DNA sequence?

A

Because it represent only non-coding portions of DNA.

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8
Q

What 2 techniques does genetic fingerprinting rely on?

A
  • The polymerase chain reaction to make large numbers of copies of DNA fragments.
  • Gel electrophoresis, to separate DNA fragments based on their size.
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9
Q

What are STR’s?

A

They’re Short Tandem Repeats, these are sequences of nucleotides within an intron.

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10
Q

What is PCR?

A

It is semi-conservative replication of DNA in a test tube and it greatly amplifies the quantity of DNA.

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11
Q

In PCR, what is the DNA sample mixed with?

A
  • Taq polymerase (DNA polymerase with an optimum of 80’c).
  • Nucleotides containing the 4 DNA bases.
  • Primers, which bind to the start signalling taq to start replication.
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12
Q

What is a primer?

A

A strand of DNA about 10 nucleotides long that base pairs with the end of another longer strand, making a double-stranded section, to which DNA polymerase may attach prior to replication.

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13
Q

What device does PCR occur in?

A

A Thermocycler.

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14
Q

What are the stages of PCR?

A
  • Original DNA is heated to 95’c separating it into 2 strands.
  • Solution cooled to 55’c for the primers to anneal to the complementary base sequences.
  • Solution hated to 70’c and taq catalyses the synthesis of a complementary strand by adding complementary nucleotides and catalysing sugar-phosphate backbone.
  • Sequence repeated multiple times.
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15
Q

What are the limitations of PCR?

A
  • Contamination, any DNA that enters will also be amplified.
  • Error rate, all polymerases sometimes insert the wrong base but taq can’t proofread and correct the error.
  • PCR is most efficient for making DNA 1000-3000 base pairs long but many genes are much longer than this.
  • Limits on amplification, after around 20 cycles it slows down.
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16
Q

Why does the amount of DNA produced in PCR plateau after about 20 cycles?

A
  • Reagent concentrations become limiting.
  • Enzymes denature after repeated heating.
  • DNA in high concentrations causes single-stranded molecules to base pair with each other rather than with primers.
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17
Q

What is the purpose of gel electrophoresis and what is it conducted on?

A

DNA fragments are separated by length on an agarose gel.

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18
Q

What are the steps in gel electrophoresis?

A
  • DNA extracted and cut into fragments using restriction endonucleases.
  • The samples are loaded into wells at one end of the gel.
  • A voltage is applied across the gel (DNA is -) so fragments are attracted to the anode.
  • Smaller fragments move more easily through the pores so they migrate through the gel quicker.
  • Luminescent DNA probes attach to complementary to the STRs.
  • Autoradiograph shows the position of the probe
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19
Q

What are the uses of DNA profiling?

A
  • Paternity testing.
  • Twins, identical or fraternal.
  • Siblings.
  • Immigration.
  • Forensic use to identify and rule out suspects.
  • Phylogenetic studies.
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20
Q

What are the pros of DNA profiling?

A
  • It doesn’t requre an invasive method to obtain a biological sample, as mouth swabs, urine or hair can be used to obtain DNA, rather than blood samples.
  • The technique can be used on samples that would be too small for blood testing.
  • It has reversed wrongful convictions when used with other forensic tools and evidence.
  • DNA profiling can rule out non-matches of DNA samples, the exonerate people who have been falsely accused.
  • Efforts are being made to store genetic material from people around the world, before isolated groups are intermixed and lost.
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21
Q

What are the cons of DNA profiling?

A
  • Some people consider the request for DNA a violation of privacy.
  • DNA profiles in databases are vulnerable to misuse and hacking.
  • Access to and use of data must be carefully regulated so its not used to increase insurance premiums.
  • It may produce wrongful convictions if errors occur in the procedure, untrustworthy people conduct the test, DNA evidence is planted etc.
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22
Q

What is recombinant DNA?

A

DNA produced by combining DNA from 2 different species.

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23
Q

What is transgenic?

A

An organism that has been genetically modified by the addition of a gene or genes from another species.

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24
Q

What does it mean is a cell is transformed?

A

Happens when a cell has incorporated a plasmid containing a foreign gene.

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25
Q

What does the process of producing a protein using genetic engineering technology involve?

A
  • Isolation of the DNA fragments.
  • Insertion of the DNA fragment into a vector.
  • The transfer of the DNA into a suitable host cell.
  • Identification of the host cell that have taken up the gene, using gene markers.
  • Cloning the transformed host cells.
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26
Q

What are the 2 ways the identified and located genes can be isolated?

A

Using one of 2 enzymes,

  • Restriction endonuclease.
  • Reverse transcriptase.
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27
Q

How can you isolated the desired gene using restriction endonuclease?

A
  • They cut at specific nucleotide sequences.
  • The DNA is cut into many small fragments and individual genes can be isolated.
  • These enzymes make a staggered cut which leaves sticky ends.
28
Q

What is a sticky end?

A

A sequence of unpaired bases on a double-stranded DNA molecule that readily base pairs with a complementary strand.

29
Q

What are the main drawbacks with using restriction endonuclease to excise a gene?

A
  • If the recognition sequence occurs within the gene of interest, the gene will be broken into fragments that have no function.
  • Eukaryotic genes contain introns but bacteria do not and so they may not have the appropriate enzymes to process the RNA to remove them.
30
Q

How can you isolate the desired gene using reverse transcriptase?

A
  • There may be many molecules of mRNA that have been transcribed from the desired gene.
  • The enzyme reverse transcriptase synthesises copy DNA.
  • Many copies of cDNA that is complementary to the mRNA can be made.
  • DNA polymerase then catalyses the synthesis of DNA that is complementary to the single-stranded cDNA.
31
Q

What is reverse transcriptase?

A

An enzyme, derived from a retrovirus, that catalyses the synthesis of cDNA from an RNA template.

32
Q

How are plasmids within bacteria isolated?

A
  • EDTA used to destabilise the cell wall.
  • Detergent to dissolve the phospholipid cell membrane.
  • Sodium hydroxide to make an alkaline environment that denatures the membrane proteins.
  • The plasmids can then be separated from the cell debris.
33
Q

What is a plasmid and why are they useful for introducing genes into bacteria?

A

They are small circular loops of self-replicating double-stranded DNA in bacteria. They are much smaller than the bacterial chromosome and can move in and out of cells making them useful.

34
Q

How is a recombinant plasmid made?

A
  • The circular DNA is cut open using the same restriction endonuclease as was used to isolate the gene which means it has the same nucleotide sequence in its sticky ends.
  • The vector and gene are mixed and their complementary base sequences base pair with each other.
  • The gene is now bound to the plasmid with DNA ligase.
35
Q

To make a good vector, what should a structure be?

A
  • Self-replicating.
  • Small.
  • Not be broken down by host cell enzymes,
  • Not stimulate an immune response in the recipient.
  • Be able to be screened to confirm the gene was successfully inserted.
  • Have markers to allow host cells that have taken up the vector to be identified.
36
Q

How is DNA transfered into the host cell?

A

Plasmids are mixed with bacterial cells but very few take up the plasmid and become transformed. This amount can be increased with calcium chloride. DNA passes into the cells with a heat shock.

37
Q

How can you identify which cells have been transformed?

A
  • Plasmids with antibiotic-resistance are used which confer resistance to ampicillin and tetracycline.
  • The cells are cultured in a growth medium containing the antibiotic and if they’ve incorporated the plasmid, they also contain the resistant gene.
38
Q

What are the pros of genetic engineering in bacteria?

A
  • Medical products: large amounts of pure human proteins for use in medicine have been made.
  • Prevention and treatment of disease.
  • Enhancing crop growth.
  • Environmental use: deleting and removing environmental hazards.
39
Q

What are the cons of genetic engineering in bacteria?

A
  • Plasmids are easily transferred so there is potential for antibiotic resistance markers genes to be transferred.
  • cDNA may contain oncogenes that activate proto-oncogenes in recipient cells.
  • A micro-organism with a new gene may become a threat if released into the environment.
  • A newly introduced gene may disrupt the normal function of other genes.
40
Q

What ways are there of introducing a novel gene into plant cells?

A
  • The ‘gene gun’ fires small spheres with the gene at plant cells.
  • Electroporation, enhances gene uptake.
  • Microinjection, gene injected into cytoplasm/nucleus.
  • Using bacterial vector.
41
Q

How does using a bacterial vector transform a plant?

A

The desired gene is inserted into the bacteria and used to infect the plant and insert their DNA with the desired gene into the plants DNA.

42
Q

How have soy beans been genetically modified?

A

They have been made ‘Roundup Ready’ so they’re genetically modified to contain a gene that makes them herbicide-resistant.

43
Q

How have Bt tomatoes been genetically modified?

A

They have had a gene incorporated into own genes that codes for a protein that acts as an insecticide inside their leaves.

44
Q

How have Antisense tomatoes been genetically modified?

A

Tomatoes ripen naturally when they produce an enzyme which breaks down the pectin in their cell walls. The ‘Flavr Savr’ tomato stops this enzyme working so the tomato stays riper for longer.

45
Q

What are the arguments in favour of GM crops?

A
  • Higher crop yield.
  • Pesticide reduction.
  • Improved food; nutritional quality can be improved (e.g. golden rice).
  • Introducing genes that confer resistance to herbicide decreases plant loss in the field.
  • ‘Pharming’,plants with antibodies, vaccines etc.
  • Plants that contain nitrogen fixing bacteria would decrease fertiliser need.
46
Q

What are the arguments against the use of GM crops?

A
  • Pollen from GM plants may transfer genes to wild relatives (superweeds).
  • Pest resistance.
  • Marker genes are often antibiotic resisatnce and there is fears they may pass to the bacteria in the human gut.
  • Reduction of biodiversity.
  • Could compromise organic farming.
47
Q

What does genetic screening have the potential to do?

A
  • Confirm a diagnosis.
  • Indicate appropriate treatment.
  • Allow families to avoid having children with devastating diseases.
  • Identify people at high risk for conditions that may be preventable.
48
Q

What are the concerns with genetic screening?

A
  • Many believe it is an invasion of privacy.
  • Defective alleles identified in prenatal test may increase the number of abortions.
  • Individuals with defects may be placed in a high-risk group for insurance purposes to cover cost of treatment.
49
Q

What are the main uses of genetic testing?

A
  • Carrier screening to identify if someone carries a recessive allele.
  • Pre-natal diagnostic testing.
  • Newborn baby screening.
  • Pre-symptomatic testing for predicting adult-onset disorders (E.g. Huntington’s).
  • Confirmation that an individual has a suspected disease.
  • Forensic and identity testing.
50
Q

What are the limitations of commercialised gene tests?

A
  • They only test a small number of genes in the human genome.
  • Difficult to interpret a positive result/ a mutations effects can’t be predicted.
  • Lab errors may occur.
  • May be no medical options for treating this disease.
  • Tests may provoke anxiety.
  • Risks of discrimination and social stigmatisation.
51
Q

What is gene therapy?

A

A technique in which a defective allele is replaced with one cloned from a healthy individual, providing a treatment or cure.

52
Q

In gene therapy, what are the ways in which the DNA can be introduced into the target cells?

A
  • Using a virus as a vector.
  • Using a plasmid as a vector.
  • Injection of naked plasmid DNA.
53
Q

What are the 2 main approaches to gene therapy?

A
  • Somatic cell, targets body cells.

- Germ-line, introduces the corrective genes into the oocyte so the correction is inherited.

54
Q

What is DMD and what effect does it have on the patient?

A

Duchenne Muscular Dystrophy is a recessive, sex-linked form of muscular dystrophy. People have severe muscle loss.

55
Q

How does drisapersen treat DMD?

A

It is an antisense oligonucleotide and it acts as a ‘molecular patch’; it binds to the mRNA over the exon with the deletion so it can’t be read.

56
Q

How is Cystic Fibrosis caused?

A

The normal allele codes for CFTR, a protein that transports Cl- ions out and so water follows making the extra-cellular mucus watery. Mutant CFTR can’t transport these chloride ions.

57
Q

What areas does cystic fibrosis affect?

A
  • Bronchioles and alveoli become clogged causing difficulty in breathing.
  • Pancreatic duct becomes clogged so digestion and absorption is limited.
  • Reproductive tubes become blocked.
58
Q

What are the main advantages to gene therapy?

A
  • Only a small proportion of the introduced genes are expressed.
  • There may be an immune response in the patient.
59
Q

What is the purpose of tissue engineering?

A

It uses the methods of biochemistry, cell biology, engineering and materials science to repair, improve or replace biological function.

60
Q

What are the different types of cells used in tissue culturing?

A
  • Autologous cells, from the same individual.
  • Allogenic cells come from a donor of the same species.
  • Xenogenic cells are from another species.
  • Syngenic cells are from genetically identical organisms.
61
Q

Cells are seeded onto a scaffold but what features must it have?

A
  • Allows cells to attach and move.
  • Deliver and retain cells and biological molecules.
  • Be porous to allow diffusion of nutrients and waste products.
  • Be biodegradable and be absorbed by the surrounding tissues.
62
Q

What are stem cells?

A

An undifferentiated cell capable of dividing to give rise to daughter cells, which can develop into different types of specialised cells or remain as undifferentiated stem cells.

63
Q

Where can stem cells come from?

A
  • Embryonic stem cells, the blastocyst has ESCs which can form every cell type in the body.
  • Some adult tissue, e.g. bone marrow, contain stem cells.
64
Q

What do stem cells have the potential to do?

A
  • For tissue engineering to regenerate tissues and organs.
  • For cell based therapies to treat disease.
  • To screen new drugs.
  • To develop model systems to study normal growth and identify the causes of birth defects.
  • To investigate the events that occur during human development.
65
Q

What are the advantages of using stem cells?

A
  • Embryonic stem cells can become any type of cell.
  • Embryonic stem cells grow easily in culture and large quantities can be readily produced.
  • The use of stem cells will make the problem of a shortage of organs for transplantation less significant.
  • A patient receiving ESCs is less likely to need immunosupressive drugs.
66
Q

What are the disadvantages of using stem cells?

A
  • Techniques for extracting, culturing and manipulating stem cells are still under development and their behaviour isn’t always predictable.
  • The use of them is very new and so long term studies haven’t yet been conducted.
  • Ethical issues tied to the use of ESCs.
67
Q

What are the ethical issues surrounding the use of embryonic stem cells?

A
  • The source, they used to use ‘left over’ embryos from in vitro.
  • The moral status of the embryo, they don’t have the same human rights as a living individual but some groups argue that ‘life begins at conception.
  • Their potential rights are balanced against the potentially large benefits that other people may gain from the research and treatment it produces.
  • Fears it may lead to humans being cloned which devalues human life.

Biology - Year 2 (Eduqas) (14 decks)

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