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A Level Biology (Eduqas) > Chapter 11 Application of Genetics > Flashcards

Chapter 11 Application of Genetics Flashcards

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1
Q

When was the human genome project proposed and when did it begin?

A

Proposed in 1985 and began in 1990

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2
Q

When was the human genome project completed?

A

A working draft published in 2000 and completed draft in 2003

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3
Q

What were the aims of the human genome project?

A

To identify all the genes in the human genome and identify which chromosome each is on. To improve knowledge and understanding of genetic disorders and improve their diagnosis and treatment.

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4
Q

What were the findings of the human genome project?

A

Humans have 20,500 genes. They also found that fewer than 7% of the families of proteins were specific to vertebrates, this shows a close relationship between all living organisms.

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5
Q

What method of DNA sequencing was used in the human genome project?

A

Sanger sequencing also known as the chain termination method.

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6
Q

What was the 100k genome project?

A

Launched by Genomics England (department of health) in 2012 to use next generation sequencing to sequence 100,000 genomes from NHS patients with cancer or rare diseases and their families.

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7
Q

What were the aims of the 100k genome project?

A

Aims to:
Create an ethical transparent programme based on consent
Set up a genomic service to benefit NHS patients
Enable medical/scientific discovery
Develop a UK genomics industry

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8
Q

What are the ethical concerns of the genome projects?

A

Ownership of genetic information may be misused to make financial profit, e.g-a sequence perdisposing an individual to heart disease should not be used to raise or deny them health insurance.
Embryos made during the process can be screened for the presence of alleles. This can lead to the potential of choosing alleles to ensure specific characteristics, commonly known as “designer babies”.
Storage and security of data maintaining anonymity, confidentiality and privacy.

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9
Q

Why is DNA sequencing being carried out on non-human organisms?

A

The examination of genomes of closely related organism allow inferences to be drawn concerning evolutionary relationships providing a true phylogenetic classification.

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10
Q

What causes the differences in individuals DNA fingerprints?

A

Within DNA, introns do not code for proteins and form sequences of nucleotides which repeat hundreds of times called short tandem repeats (STR’s). The number of repeats is different for every individual.

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11
Q

How is a genetic fingerprint made?

A

The polymerase chain reaction is used to make large copies of DNA fragments. Gel electrophoresis is then used to separate the fragments based on their size.

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12
Q

What is the polymerase chain reaction?

A

3 stages repeated

  • denature (sample DNA is heated to 95°C, breaking hydrogen bonds)
  • Annealing (sample is cooled to 50°C and primers are added which anneal to the DNA strands to start replication
  • Extension (nucleotides and thermostable DNA polymerase are added, temperature is raised to 72°C)
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13
Q

What are the limitations of using the polymerase chain reaction?

A

Contamination from previous PCR reactions using the same apparatus can enter the system and be accidentally amplified.
Error rate between 1 in 10,000 and 100,000

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14
Q

What are the advantages of using PCR?

A

Does not require living bacteria or cells
Produces millions of copies from a single template
Relatively quick
Specific process that targets the desired DNA to be copied
Amplifies targets up to 35kb in length

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15
Q

How do you carry out a gel electrophoresis?

A

Restriction endonuclease to produce fragments, Short tandem repeats (non-coding regions) are not cut so fragments produced are different for every individual. The mixture of fragments are placed into wells on a gel and a current is applied. DNA is negatively charged and so the fragments move across the gel towards the positive electrode. The smaller fragments move faster. DNA must be stained so that bands form. The gel is pressed against a nylon sheet which is pressed on an x-ray film. The positions of bands are then analysed.

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16
Q

What are the uses of DNA profiling?

A

Paternity tests
Forensic use to identify and rule out suspects
Phylogenetic studies (assess genetic relatedness)
Establish migration patterns

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17
Q

What are the weaknesses of DNA profiling?

A

Some consider that any request for DNA sample is a violation of an individuals right to privacy
Profiles are stored in computer databases which an be vulnerable to misuse and hacking
Profiles give probabilities not absolutes
Errors occur which can have significant consequences such as wrongful convictions

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18
Q

Define recombinant DNA

A

DNA produced by combining DNA from two different species

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19
Q

Define transgenic

A

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

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20
Q

What is the process of genetic engineering a protein?

A 
Isolate genes that code for protein
Insert DNA fragment into a vector
Transfer DNA into suitable host cell
Identify host cell that has taken up the gene using markers
Clone the transformed host cells
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21
Q

How are genes isolated in the genetic engineering of a protein?

A
  • Restriction endonuclease is a restriction enzyme that cut DNA at specific nucleotide sequences. The fragments produced have unpaired bases on both strands so they are readily complementary, so they are called ‘sticky ends’.
  • Reverse transcriptase is an enzyme derived from a retrovirus that catalyses the synthesis of cDNA from an RNA template
22
Q

Give an example of a restriction enzyme?

A

The bacteria E. coli produces a restriction enzyme called EcoR1 and it catalyses the breaking of the DNA backbone in specific nucleotide sequences.

23
Q

How is DNA inserted into a vector?

A

Plasmids act as vectors. Plasmids from bacteria are isolated by destabilising the cell walls and sodium hydroxide is added to denature the membrane proteins. The plasmid is then cut using the same restriction enzyme used to isolate the gene so that it has complementary sticky ends. The vector and gene are mixed and the bases pair with each other. The join is made permanent with DNA ligase by forming phosphodiester bonds between the backbones. It is now recombinant DNA.

24
Q

What characteristics are needed for a vector?

A 
Self replicating
Small
Not be broken down by host cell enzymes
Not stimulate an immune response
Have markers to allow host cell that has taken up the vector to be identified
25
Q

Give examples of vectors

A

Viruses - bacteriophage, lentivirus/retrovirus
Bacteria - Agrobacterium tumefaciens
Plasmid DNA

26
Q

How are genetic markers used?

A

A vector such as the plasmid will contain a marker gene such as antibiotic resistance. This is so that when the host cells are cultured in a medium containing the antibiotic, only the cells that took up the vector and the target gene will grow.

27
Q

What are the pros of genetic engineering?

A

Medical products such as insulin
prevention and treatment of diseases such as modified bacteria producing vaccines
enhancing crop growth

28
Q

What are the cons of genetic engineering?

A

Plasmids are easily transferred, they may exchange antibiotic resistant marker genes to pathogenic species.
cDNA may contain oncogenes that cause cancer
Newly introduced gene may disrupt the normal function of other genes in ways not yet understood.

29
Q

How are GM crops made?

A

Plasmids extracted from Agrobacterium tumefaciens are spliced using restriction enzymes. A section of DNA containing the desired gene is isolated using the same restriction enzyme. The gene is inserted into the plasmid and joined by DNA ligase. Plasmid is reinserted into bacteria and the bacterial cell is introduced into a plant cell. The bacteria cell divides and gene is inserted into plant chromosome. Transgenic plant cells are the cloned and transformed plants grow.

30
Q

Give examples of GM crops

A 
Golden rice (with increased vitamin A)
'Roundup ready' soya beans (herbicide resistant)
31
Q

What are the advantages of GM crops?

A

Higher crop yield to solve crops lost by droughts, disease, floods,etc
Pesticide reduction
Improved food with enhanced nutritional quality

32
Q

What are the disadvantages of GM crops?

A

Pollen from GM crops might transfer to wild relatives which can produce superweeds
Reduction in biodiversity because it reduces the range of useful genes
Pollen from GM crops can compromise organic crops

33
Q

What are the 2 types of gene therapy?

A
  • Somatic cell therapy that targets body cells in the affected tissues
  • Germ line therapy introduces corrective genes into gamete producing cells (ethical concerns as they can have unpredictable effects in future generations)
34
Q

How is Duchenne muscular dystrophy (DMD) treated using gene therapy?

A

DMD is caused by deletions in the dystrophin mRNA altering the reading frame. The ribosome then meets a stop codon too soon and the protein is not made. The drug drisapersen is a nucleotide complementary to the mutated sequence. It acts as a molecular patch by binding to the mRNA over the exon with the deletion making it double stranded so the ribosome doesn’t translate it, restoring the reading frame

35
Q

How are symptoms of Cystic Fibrosis (CF) managed using gene therapy?

A

The gene coding for the cystic fibrosis transmembrane regulator (CFTR) is isolated and cloned and placed in viruses or liposomes (hollow phospholipid spheres). They are then inhaled with an aerosol and the DNA enters the lung epithelial cells making the CFTR protein relieving CF symptoms. However, lung cells are replaced and so the treatment must be repeated. This does not relieve mucus build up in the pancreatic duct or vas deferens

36
Q

What are the healthcare benefits to genomics?

A

Accurate diagnosis of genetic disorders
Better prediction of the effectiveness of drugs such as warfarin an anticoagulant to prevent stroke is effected by 2 gene variants. Genomics made it possible to recommend doses depending on the individuals genotype
New and improved treatments

37
Q

What is tissue engineering?

A

Using the methods of biochemistry, engineering and material sciences to repair, improve or replace biological functions by producing bio artificial tissues and organs.

38
Q

Give an example of tissue engineering

A

An artificial skin is called an apligraf which is used to treat burns in place of skin grafts.

39
Q

What types of cells are used for tissue engineering?

A

Autologous cells - cells from the same individual
Allogenic cells - cells from a donor of the same species
Xenogenic cells - cells from another species

40
Q

What are scaffolds?

A

An artificial structure that can support a 3D tissue. It must allow cells to attach and move, deliver and retain cells and biological molecules, porous to allow diffusion, be biodegradable and be absorbed by the surrounding tissue.

41
Q

Define stem cell

A

An undifferentiated cell capable of dividing indefinitely and can develop into different types of specialised cells.

42
Q

What are totipotent stem cells?

A

Embryonic stem cells within the first couple of cell divisions after fertilisation, capable of forming all the cell types in a body.

43
Q

What are pluripotent stem cells?

A

Embryonic stem cells that can give rise to all cells of the body, except placental cells

44
Q

What are multipotent stem cells?

A

Adult stem cells that have less potential for differentiation

45
Q

Where are adult stem cells present?

A

Bone marrow, blood, brain and umbilical cord

46
Q

What are induced pluripotent stem cells?

A

Adult stem cells genetically reprogrammed to behave as embryonic stem cells

47
Q

What are the advantages of using embryonic stem cells?

A

Blastocysts contain 100 stem cells so they can be isolated in large numbers
Stem cells solve the acute problem of a shortage of organs for transplantation

48
Q

What are the disadvantages of using embryonic stem cells?

A

Expensive
Ethical concerns
Pluripotent cells risk teratoma (cancer) formation

49
Q

What are the advantages of using adult stem cells?

A

Less ethical concerns than embryonic
Solves acute problem of shortage of organs for transplantation
Stem cells from the same individual are less likely to provoke immune rejection

50
Q

What are the disadvantages of using adult stem cells?

A

Expensive
Less potential for differentiation than embryonic
Induced pluripotent stem cells have low reprogramming efficiency
Induced pluripotent stem cells have higher risk of tumorigenesis (cancer)

A Level Biology (Eduqas) (23 decks)

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