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Biology > Gene technology > Flashcards

Gene technology Flashcards

1
Q

Define genome

A

all the DNA in a cell/ organism

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2
Q

Define proteome

A

full range of proteins a cell/ organism can produce

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3
Q

Explain what a genome project is and how it be used to determine an organisms proteome

A
  • Genome projects determine the DNA base sequence of an organisms genome
  • Determining the genome of an organism allows the amino acid sequences of the proteins to be determined (the proteome)
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4
Q

Explain why it is easier to determine the genome and proteome of simpler organisms compared to more complex organisms

A

It is easier to determine the proteome of prokaryotic DNA because its shorter and doesn’t contain introns. In more complex organisms (e.g. eukaryotes) the non-coding DNA and regulatory genes mean that the genome cant easily be translated into the proteome

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5
Q

Name one medical use of genome projects

A

Identifying the proteome of microorganisms allows the identification of antigens for use in vaccine production

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6
Q

Define recombinant DNA

A

DNA made up from 2 or more different organisms

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7
Q

Explain how complementary DNA is produced using reverse transcriptase and the advantages of this method

A
  • mRNA coding for insulin is extracted
  • mRNA acts as a template on which a cDNA is formed using reverse transcriptase
  • Single stranded DNA
  • Double stranded DNA is formed using DNA polymerase and DNA nucleotides
  • Starting with mRNA means the DNA won’t have introns so can be expressed by prokaryotes (don’t have the enzymes for splicing)
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8
Q

Explain how DNA is cut into fragments and what enzyme is used

A
  • Restriction enzymes hydrolyse phosphodiester bonds at recognitions sites to form sticky ends
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9
Q

Explain the advantages of the gene machine method

A
  • Faster as no need to isolate DNA/ RNA from the cell
  • Any sequence of nucleotides can be made
  • No introns, so can be expressed by prokaryotes
  • Very accurate, no errors
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10
Q

Explain how a DNA fragment can be inserted into a vector including the importance of sticky ends

A
  • add a promoter and terminator
  • plasmids cut open using the same restriction enzyme as was used to cut out the gene from the DNA
  • the sticky ends of the plasmid and gene are complementary so form hydrogen bonds between CBPs
  • DNA ligase forms phosphodiester bonds to join the nucleotides of the plasmid and gene
  • This is recombinant DNA
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11
Q

Define the term vector in terms of making recombinant DNA

A

carries the gene into the cell

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12
Q

Explain how the DNA of the vector is introduced into host cells by transformation

A
  • Calcium ions
  • Electric shock
  • Heat shock
  • Using a virus e.g. bacteriophage
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13
Q

Explain what a gene marker is ad how it can be used to identify which cells have taken up the recombinant vector/ gene

A
  • the marker gene identifies which cells have taken up the plasmid
    It does this by;
  • e.g. bacteria are grown on a medium containing the antibiotic the plasmid causes resistance to
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14
Q

Describe one real life use of recombinant DNA in industry or research

A

Human insulin gene is inserted into bacteria and the bacteria express the gene or form human insulin protein

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15
Q

Explain what PCR is used for

A

PCR is carried out to make many copies of a particular DNA base sequence from a small sample i.e. amplify the DNA to make millions of copies

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16
Q

In PCR, explain why the DNA has to be heated to 95 degrees C?

A

This breaks the hydrogen bonds between the complementary base pairs causing the strands to separate

17
Q

In PCR, explain why the DNA is cooled to 55 degrees C?

A

allows the primers to bind to the DNA

18
Q

In PCR, explain why the DNA is heated to 72 degrees C?

A

Optimum temperature for thermostable DNA polymerase

19
Q

In PCR, explain what primers are for and why 2 are used?

A
  • Primers provide a starting sequence for DNA polymerase to bind and stop the original DNA strands re-joining
  • 2 different primers are needed, one of each DNA strand as each strand has a different base sequence
20
Q

Explain how electrophoresis separates DNA and how you can identify unknown lengths of DNA

A
  • Separates DNA fragments according to their length and charge
  • DNA is negatively charged due to its phosphate group so its attracted to the positive electrode
  • The shorter the DNA fragments the further it travels
  • To identify unknow lengths, compare to known lengths of DNA on the gel
21
Q

Describe what a DNA probe is

A
  • short single strand of DNA
  • has a complementary base sequence to the allele
  • bind to the allele and have a radioactive or fluorescent label for detection
22
Q

Describe the step by step method by which DNA probes can be used to identify the presence of the certain allele by genetic screening

A
  1. Extract DNA by homogenisation and ultracentrifugation
  2. Use PCR to make many copies of DNA
  3. Cut DNA with restriction enzymes at recognition sites, making sure not the cut the allele
  4. Use gel electrophoresis to separate the DNA fragments by length
  5. Transfer the DNA from the gel to a nylon membrane. This is Southern blotting
  6. DNA is made single stranded
  7. Add a DNA probe with a complementary base sequence to the allele of interest and a radioactive/ fluorescent label, which binds to allele is present. This is DNA hybridisation
  8. Wash the membrane to remove unbound probe and prevent false positives
  9. Identify if the allele is present using autoradiography (using x-ray film to detect the radioactivity)
    Compare the position of the band to another known DNA sample containing the sample
23
Q

Describe the use of genetic counselling

A

People may be referred for genetic counselling if they;
- have been diagnosed with a genetic condition
- have had a baby with a genetic condition
- are planning a pregnancy but may carry a genetic condition

24
Q

Suggest how gel electrophoresis can separate proteins

A
  • by mass
  • by charge
25
Q

Describe what VNTRs are

A

Variable number tandem repeats are repeating DNA base sequences found between genes
The number of times each VNTR is repeated differs between each person

26
Q

Explain how genetic fingerprinting is carried out

A
  1. Extract DNA using homogenisation and ultracentrifugation
  2. Amplify DNA using PCR
  3. Cut out DNA fragments containing VNTRs using restriction enzymes
  4. Separate DNA fragments by length using gel electrophoresis
  5. Perform southern blotting (Transfer DNA fragments from gel to nylon membrane)
  6. Make DNA single stranded
  7. Add DNA probes which bind to the VNTRs being identified
  8. Wash to remove unbound probes
  9. Identify if VNTRs are present using autoradiography
27
Q

Explain how the results of genetic fingerprinting are interpreted in a paternity test

A

All bands in a child that don’t match the mother must match the father

28
Q

Describe the uses of genetic fingerprinting in terms of medical diagnosis, forensic science and animal and plant breeding

A
  • Medical diagnosis; Certain tumours are known to have certain genetic fingerprints, which are different from normal body cells fingerprints. The genetic fingerprint of a patients tumour can be compared to those of known types of tumours, in order to diagnose the type of tumour
  • Forensic science; Use to match the suspects genetic fingerprint to the DNA found at a crime scene e.g. from hair or blood sample
  • Relationships between species; the greater the number of bands that match on a genetic fingerprint the more genetically similar and therefore more closely related 2 species are
29
Q

Describe and explain how the polymerase chain reaction (PCR) is used to amplify a DNA fragment

A
  • requires DNA fragment, thermostable DNA polymerase, DNA nucleotides and primers
  • Heat to 95 degrees C to break hydrogen bonds between CBPs and separate strands
  • Reduce temperature to 55 degrees C to allow primers to bind
  • Increase temperature to 75 degrees C- optimum temperature for thermostable DNA polymerase, allows DNA polymerase to join DNA nucleotides and form phosphodiester bonds

Biology (26 decks)

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