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WJEC BIO > Application of Reproduction and Genetics > Flashcards

Application of Reproduction and Genetics Flashcards

1
Q

What is the Human Genome Project?

A

An international research project involving thousands of scientists which used Sanger sequencing to successfully map the entire human genome.

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2
Q

What is DNA sequencing?

A

Identifying the base sequence of a DNA fragment.

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3
Q

What is Sanger sequencing?

A

A method of DNA sequencing that only sequences relatively short sections of DNA at a time. It takes a long period of time.

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4
Q

Outline the potential benefits of the Human Genome Project.

A

Allows for the development of targeted, personalised medical treatments and greater accuracy of diagnosis
Increased opportunities for screening genetic conditions and early detection of disease
Enables the study of incidences of mutation in different genes

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5
Q

What is the 100K Genome Project?

A

A UK Government project that aims to study variation in the human genome amongst 100,000 UK citizens. It uses Next Generation Sequencers (NGS).

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6
Q

Describe Next Generation Sequencing (NGS).

A

A faster, cheaper and more accessible method of sequencing that can sequence an entire genome in a few hours.

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7
Q

Describe genetic counselling.

A

Service that provides information and advice to people affected by or at risk of genetic diseases
* Helps individuals and families to make informed decisions

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8
Q

What is genetic screening?

A
  • Testing individuals for certain faulty alleles
  • Used to detect disorders such as cystic fibrosis, Huntington’s disease and thalassemia
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9
Q

Outline the potential disadvantages of genetic screening.

A

Screening for conditions such as cancer and Alzheimer’s disease only indicates an increased risk - may cause unnecessary stress and anxiety.
What happens to the test result data? Discrimination from employers or insurance companies? Misuse of information?
Risk of false positives or false negatives
Who should be screened? Limited funds and time. Screening embryos could lead to ‘designer babies’

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10
Q

Give some examples of organisms other than humans whose genomes have been sequenced.

A
  • Chimpanzees and other primates
  • Anopheles gambiae, the mosquito
  • Plasmodium parasite
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11
Q

How has sequencing the genome of the mosquito, Anopheles gambiae, been useful to humans?

A

Anopheles has developed insecticide resistance
* Sequencing has enabled the development of chemicals that make Anopheles susceptible to insecticides

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12
Q

Outline the advantage of sequencing the genome of the Plasmodium sp. to humans.

A
  • Plasmodium sp. has developed multi-drug resistance
  • Enables the development of more effective
    drugs
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13
Q

What is genetic fingerprinting? State some applications of genetic fingerprinting.

A
  • A technique used to genetically identify an organism
  • Applications in forensics, screening for hereditary diseases, paternity testing, selection for clinical trials
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14
Q

What are exons?

A

Region of DNA that code for an amino acid sequence.

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15
Q

What are introns?

A

Non-coding sequences of DNA.

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16
Q

What techniques can be used to produce a genetic fingerprint?

A

PCR and gel electrophoresis

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17
Q

What is PCR?

A
  • Polymerase Chain Reaction
  • An in vitro technique used to rapidly amplify fragments of DNA
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18
Q

Describe the reaction mixture in the first stage of PCR.

A

Contains the DNA fragment to be amplified, primers that are complementary to the start of the fragment, free nucleotides to match up to exposed bases, and Taq DNA polymerase to
create the new DNA.

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19
Q

What is Taq DNA polymerase?

A

A thermally stable enzyme that synthesises a double-stranded molecule of DNA from a single template strand using complementary nucleotides.

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20
Q

Summarise the process of amplifying DNA fragments using PCR.

A
  1. Heated (95°C) to break hydrogen bonds between DNA strands
  2. Cooled (50-60°C) to allow primers to bind - annealing
  3. Heated (70°C) to activate Taq DNA polymerase and allow free
    nucleotides to join
  4. New DNA acts as a template for next cycle
21
Q

What is gel electrophoresis?

A

A technique that separates nucleic acid fragments or proteins by size using electric current.

22
Q

How does gel electrophoresis work?

A

DNA fragments of varying lengths are placed at one end of a slab of agarose gel. Electric current applied. DNA fragments move towards the
positive end of the gel. Shorter fragments travel further. The pattern of bands created is unique to every individual.

23
Q

What is genetic engineering?

A

The modification of the genome of an organism by the insertion of a desired gene from another organism. This enables the formation of organisms with beneficial characteristics.

24
Q

What is recombinant DNA?

A

A combination of DNA from two different organisms.

25
Q

Summarise the process of using restriction enzymes to produce DNA fragments.

A

Gene identified using gene probe. Restriction endonucleases cut DNA at specific palindromic sequences producing sticky ends .

26
Q

Summarise the process of using reverse transcriptase to produce DNA fragments.

A

mRNA complementary to the target gene used as a template
Reverse transcriptase synthesises cDNA (complementary)
Mixed with free nucleotides which match up to their base pairs. DNA polymerase joins nucleotides forming second strand.

27
Q

Outline the advantages of using reverse transcriptase to produce cDNA.

A

Don’t have to locate the gene
Gene not cut into non-functional fragments by restriction enzymes
Introns not present in cDNA
* Doesn’t require post-transcriptional processing to produce functional mRNA

28
Q

Summarise the process of inserting a DNA fragment into a vector.

A
  • Plasmid (circular DNA from bacteria) used as the vector
  • Plasmid cut using the same restriction enzymes as the DNA, so that the sticky ends are complementary. DNA ligase joins the fragment and plasmid together
29
Q

Describe how antibiotic-resistance genes are used in the identification of recombinant bacteria.

A

Antibiotic resistance genes can be inserted into plasmids at the same time as DNA fragments. The transformed cells are then placed on a plate with antibiotics. Only the cells that successfully took up the vector will grow.

30
Q

Give an application for genetic modification of bacterial cells.

A

Human gene for insulin production can be inserted into a vector, so that the bacterial cell will produce insulin. Useful in medicine e.g. treatment of diabetes.

31
Q

Outline the disadvantages of using recombinant DNA to make human products.

A
  • Identifying the required gene may be difficult
    Some eukaryotic genes can’t be expressed in prokaryotes
    Antibiotic-resistance genes could be transferred to pathogenic bacteria
  • Expensive
32
Q

What are GM organisms?

A

Organisms that have had their genome
altered.

33
Q

Outline the benefits of GM crop production.

A
  • Improves nutritional value of foods
  • Longer shelf-life of products
  • Greater crop yields
  • Reduces need for pesticides
  • Reduces need for land clearing
34
Q

Outline the risks of GM crop production.

A

Reduction in biodiversity
Unknown effects on health
Cross-pollination could result in herbicide-resistant weeds
May increases costs for farmers

35
Q

What is gene therapy?

A

A therapeutic technique in which a faulty allele is replaced with a functional allele in order to treat or prevent disease.

36
Q

Name the two types of gene therapy.

A

Somatic cell therapy
Germ line therapy

37
Q

Differentiate between somatic cell therapy and germ line therapy.

A

Somatic - allele introduced to target cells only, short-term, must be repeated
Germ line - allele introduced to embryonic cells so it is present in all resultant cells, permanent, passed onto offspring

38
Q

What is a vector?

A

A carrier used to transfer a gene from one organism to another, e.g. plasmid or virus.

39
Q

What is Duchenne Muscular Dystrophy (DMD)?

A
  • X-linked recessive condition
  • Characterised by muscle degeneration and weakness
40
Q

What is the cause of DMD?

A

It is caused by one or more mutations in the dystrophin gene that prevent the production of dystrophin.

41
Q

Outline how DMD can be treated using gene
therapy.

A
  1. Healthy gene inserted into vector (e.g. virus)
  2. Vector inserted into muscle tissue
  3. Virus delivers gene to muscle cells
  4. New gene incorporated into DNA of cell
  5. Transcription and translation of gene produces normal dystrophin protein
  6. Symptoms of DMD alleviated
42
Q

What is drisapersen?

A

An experimental drug that aims to treat DMD by exon skipping.

43
Q

Explain how drisapersen works.

A

It introduces a ‘molecular patch’ over the mutated exon, enabling the gene to be read. A shorter, more functional type of dystrophin is synthesised.

44
Q

Discuss the ethical issues surrounding the use of gene therapy.

A

Health implications - may produce an immune response, activation of oncogenes etc.
Is it right to alter the genotype of an unborn child? What conditions should be treated using gene therapy? Could lead to healthcare inequalities. Expensive - money could be better spent elsewhere.

45
Q

What are stem cells?

A

Cells that are unspecialised and retain the ability to differentiate into a range of cell types.

46
Q

What is tissue engineering?

A

An extension of gene therapy that aims to replace, repair or improve biological function by replacing organs and tissues

47
Q

What is the main advantage of using stem cells?

A

Rapid production of genetically identical cells and organisms.

48
Q

Outline the disadvantages of using stem cells.

A
  • Expensive and unreliable in mammals
    In plants, disease and pathogens can cause issues
  • Inadvertent selection of disadvantageous alleles, unknown long-term effects
49
Q

What are the ethical issues related to the use of stem cells from embryos?

A

Embryos used to provide stem cells are destroyed which is seen as unethical and a waste of potential human life
Could lead to the ‘farming’ of embryos for stem cells
* May lead to the reproductive cloning of humans

WJEC BIO (14 decks)

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