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A LEVEL BIOLOGY > 11 - Application of Reproduction and Genetics (C2) > Flashcards

11 - Application of Reproduction and Genetics (C2) Flashcards

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1
Q

What did the 100K Human Genome Project find out?

A
  • The order of bases in the human genome

- The identification of some genes, their sequencing and mapping

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2
Q

What is a stem cell?

A

An undifferentiated cell capable of dividing to give rise to cells which can develop into different types of specialised cells

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3
Q

What are advantages of using stem cells?

A
  • Speed of production
  • Large scale production
  • Production of genetically identical cells / organisms
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4
Q

What are disadvantages of using stem cells?

A
  • In mammals the technique is very expensive and unreliable
  • In plant disease, entry of pathogens may cause problems
  • Inadvertent selection of disadvantageous alleles
  • Long term / unforeseen effects such as premature ageing
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5
Q

What are the 2 methods of replacing defective genes?

A
  • Somatic cell therapy

- Germ line therapy - hasn’t yet been performed

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6
Q

What does somatic cell therapy not prevent?

A

Defective genes from being passed on

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7
Q

What is DMD? (Duchenne Muscular Dystrophy)

A
  • A recessive, sex-linked condition, affecting males
  • Sufferers can’t produce functional dystrophin, an important structural component of muscle tissue
  • Causes wasting of the muscles, so sufferers often use wheelchairs by their teenage years
  • Low life expectancy (27)
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8
Q

What are sticky ends?

A

Unpaired bases at the ends of DNA

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9
Q

What problems does producing cDNA help overcome?

A
  • Locating the gene
  • Restriction enzymes cutting the gene into non-functional fragments
  • The presence of introns
  • The need for post-transcriptional processing to produce functional mRNA
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10
Q

What are 2 examples of GM crops?

A
  • Tomatoes

- Soya

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11
Q

What are some benefits associated with the production of GM crops?

A
  • Superior keeping qualities
  • Higher yield
  • Substantial reduction in pesticide use on crops engineered for resistance to fungal pathogens and insect attack
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12
Q

What are some concerns associated with the production of GM crops?

A
  • Dispersal of pollen from crops engineered for herbicide resistance to wild relatives
  • Unknown effects of eating new protein produced in the crop
  • Reduction in biodiversity
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13
Q

What are STRs? (Short Tandem Repeats)

A

Blocks of repeated nucleotides in introns

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14
Q

What does PCR (polymerase chain reaction) do?

A

Amplifies small sections of DNA rapidly to create a large enough sample for extensive research

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15
Q

What does PCR allow?

A

Allows tests to be carried out on very small samples accurately and more rapidly regardless of the age of the sample

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16
Q

What is the process of PCR?

A
  • DNA is heated to 95 degrees
  • Sample is cooled to 50-60 degrees
  • Heated to 70 degrees
  • For each strand of DNA, 2 identical strands are produced
  • The resulting PCR product can be run and visualised on electrophoresis gel
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17
Q

Why in PCR is the DNA heated to 95 degrees?

A

To separate the 2 strands

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18
Q

Why in PCR is the DNA sample cooled to 50-60 degrees?

A

To allow the primers to bind to the DNA strands (annealing)

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19
Q

Why in PCR is the DNA sample heated to 70 degrees?

A

To allow a thermally stable DNA polymerase (Taq) to add complementary nucleotides by forming the phosphodiester bonds in the sugar-phosphate backbone

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20
Q

What does gel electrophoresis do?

A

Separates DNA fragments according to size

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21
Q

What is gel electrophoresis gel made from?

A

Agarose, which contains pores in its matrix

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22
Q

What is the process of gel electrophoresis?

A
  • DNA samples are loaded into wells at one end and a voltage is applied across the gel
  • Add a mixture of DNA fragments of known lengths to build a DNA ladder
  • DNA is attracted to the positive electrode due to its negative charge on the phosphate group
  • Smaller fragments find it easier to migrate through the pores in the gel so they travel further than large fragments in the same time
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23
Q

How can fragment size of DNA be determined in gel electrophoresis?

A

By running a DNA ladder (which contains fragments of known size) alongside samples in the gel

24
Q

What is recombinant DNA?

A

When the DNA within an organism includes one or more genes added by man via genetic engineering

25
Q

What does DNA ligase do?

A

Joins (anneals) sticky ends

26
Q

What is meant by ‘sequencing’ the human genome?

A

Determining the exact order of the base pairs in a segment of DNA

27
Q

What is needed in PCR and why?

A
  • Taq Polymerase - catalyses the synthesis of a complementary strand
  • Buffer - DNA sample is dissolved in this
  • Thermocycler - device which ensures rapid temperature change
  • Primers - bind to the DNA strand, signalling taq polymerase to start replication
  • Nucleotides - mixed with the DNA sample
28
Q

Why would DNA polymerase from human sources not be suitable for use in a PCR machine?

A

As the enzyme would denature at these high temperatures

29
Q

Why can’t species of plants be identifies from xylem material using PCR and DNA profiling?

A

DNA of plants is too different to that of humans so the PCR and DNA profiling methods don’t work

30
Q

What are 2 methods of isolating DNA fragments for genetic engineering?

A
  • Using restriction enzymes

- Using reverse transcriptase

31
Q

What is the process of using restriction enzymes in genetic engineering?

A
  • Gene is cut from genome using restriction enzymes isolated from bacteria, leaving sticky ends
  • The endonuclease catalyses a hydrolysis reaction which breaks the sugar phosphate backbone of the DNA
  • Once isolated the gene will be inserted into an appropriate plasmid that is cut using the same restriction enzymes used to produce complementary sticky ends
  • Ligase forms phosphodiester bonds between sugar phosphate backbones
  • The plasmid is now referred to as recombinant DNA, and will act as a vector to introduce the DNA into an appropriate bacteria cell
32
Q

What is the process of genetic engineering?

A
  • Obtain the required gene in a DNA fragment
  • Insert this DNA fragment into a vector
  • The vector carries the gene into a suitable host cell
  • The recipient expresses the gene through protein synthesis
  • Identification of the host cells that have taken up the gene by the use of gene markers
  • Growth of the transformed host cells
33
Q

What conditions must cells differentiating into specialised tissues have?

A
  • Oxygen, nutrients, growth factors

- Correct pH, humidity and WP

34
Q

Why is tissue engineering done?

A

To produce bio artificial tissues and organs that can be used to replace or repair damaged or defective tissue

35
Q

What cells are used for atuologous tissue engineering?

A

Induced pluripotent stem cells

36
Q

What cells are used for allogenic tissue engineering?

A

Embryonic stem cells

37
Q

Why is using adult stem cells better?

A

There is no risk of the tissue being rejected by the immune system

38
Q

What are some advantages of recombinant DNA technology?

A
  • There’s no limit to the amount of protein that can be synthesised cheaply
  • No need to extract proteins from mammalian organs
  • Quick to change amount to demand
  • Proteins made are identical to those made by humans so no risk of allergic reactions
39
Q

What are some disadvantages of recombinant DNA technology?

A
  • Complicated
  • Difficult to identify genes from entire human genome
  • Not all eukaryotic genes can be expressed in prokaryotic cells
  • Using antibiotic resistance genes to identify transformed cells could accidentally introduce these genes into human pathogens
40
Q

What are some ethical consequences of genetic testing?

A
  • Testing for late onset diseases in presently healthy individuals causes anxiety when there is no cure
  • Risk of social stigmatisation
  • Risk of discrimination by insurers or employers
  • Lab errors could cause misdiagnosis
41
Q

What are weaknesses of PCR?

A
  • DNA is at risk of contamination (in the sample or in the machine)
  • Errors occur during polymerisation
  • Polymerisation may be inhibited by contaminants (e.g. Hb breakdown products, dye from blue denim)
  • After 20 cycles rate slows (as enzymes denature and the conc of primers falls below that of the separated strands, which tend to recombine)
42
Q

What is the process of genetic fingerprinting?

A
  • Multiply DNA from hypervariable regions via PCR
  • Cut with restriction enzymes
  • Separate the fragments by electrophoresis
  • Transfer to a nylon mesh and add radioactive probes
  • Place on photographic film for autoradiography
43
Q

What are advantages of genetic fingerprinting?

A
  • Can readily identify the guilty
  • Can obtain a sample non-invasively
  • Could set up a universal database to rapidly identify suspects
44
Q

What are disadvantages of genetic fingerprinting?

A
  • It’s possible to tamper with a sample to give false results
  • A universal database is an invasion of privacy and could be used by employers or insurers to identify people with health problems
45
Q

What is gene therapy?

A
  • Where a faulty gene is modified or replaced so that a functional protein is produced in humans
  • Helps relieve symptoms associated with a genetic disorder
46
Q

What is somatic cell gene therapy?

A

Replacing faulty genes with correct copies in only certain tissues

47
Q

Why is germ line gene therapy controversial?

A
  • Involves the gene being inserted into an embryo or gamete. All the new cells formed would contain new gene and be passed on
  • Modifying babies for non-medical reasons, playing God
  • No consent from baby
48
Q

What is DMD caused by?

A

Frame shift mutations within the dystrophin gene

49
Q

What are totipotent cells?

A

Cells that can form all other types of cells

50
Q

What are multipotent cells?

A

Cells that have the ability to self-renew by dividing

51
Q

What does allogenic mean?

A

Cells come from a different individual of the same species

52
Q

What are advantages and disadvantages of using embryonic stem cells?

A

+ Totipotent

  • Allogenic - hence may be rejected by immune system
  • Unethical
53
Q

What are advantages of using induced pluripotent stem cells?

A

+ No moral problems
+ Limitless different genomes can be made
+ Autologous - hence no risk of rejection by immune system

54
Q

What are main uses of stem cells?

A
  • Tissue engineering
  • Cell based therapy
  • Screening for new drugs
  • Study of development and differentiation in normal cells compared to those with genetic disorders
55
Q

What happens in tissue engineering?

A

Stem cells colonise a porous scaffolding which later biodegrades leaving replacement tissues
- Scaffold provides nutrients, O2, growth factors to the cells and ensures correct shape of developed tissue

56
Q

What are bacteria treated with in order to isolate their plasmids?

A
  • EDTA to destabilise the cell walls
  • Detergent to dissolve the phospholipid bilayer
  • Sodium hydroxide to make an alkaline environment that denatures the membrane proteins

A LEVEL BIOLOGY (13 decks)

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