chapter 9 - biotechnology

Question 1

what is the genome and human genome project

Answer 1

• G: complete set of genetic information of an organism

- HGP: international research effort aimed at mapping the location of genes in all 46 chromosome in the human genome

Question 2

what is PCR

Answer 2

• technique used to artificially multiply sections of DNA through a series of repeated cycles of duplication

Question 3

explain the process of PCR

Answer 3

• denaturation: separates double helix by heating to 92-96
• annealing: temp. is dropped so primers can anneal to strands at 50-65
• -> primer: segment of DNA complimentary to the sample sequence of DNA which initiates replication by taq polymerase
• elongation: of primers, synthesis of new strands by making a complete copy of templates at 72 degrees
• -> taq polymerase: heat stable polymerase, does not breakdown when heated

Question 4

what is the purpose of PCR

Answer 4

• hereditary disease: sickle cell, cystic fibrosis, amplifies to then sequence gene in question
• forensic science: amplify single drop of blood or semen or strand of hair, can later produce DNA fingerprint
• ancestry: relationships between ancestors, amplification of DNA found in fossils

Question 5

what is gel electrophoresis

Answer 5

• determines ones DNA fingerprint / profile (unique for each individual) by separating DNA fragments according to size

Question 6

explain the process of gel electrophoresis

Answer 6

• make agarose gel and add comb to form wells, allow to set
• DNA samples are died with a tracking die
• bed of semi solid agarose gel is place in an electrophoresis tank with buffer solution (conducts electricity)
• DNA samples are loaded into wells
• electric current is passed through the chamber
• DNA (-) moves through gel via reptation (snaking through pores of gel), towards positive electrode
• shorter migrate faster and are pulled towards +
• pattern of bands separated by size
• ethidium bromide stains DNA (fluoresce when illuminated under UV light)

Question 7

what is DNA profiling

Answer 7

• determining individuals DNA profile via special enzymes that cut DNA at specific base sequences leaving pieces of various lengths

Question 8

explain the process of DNA profiling

Answer 8

• PCR: artificially amplify DNA through repeated cycles of duplication
• profiling: DNA is treated with restriction enzymes to cut DNA at specific sequences
• electrophoresis: separates fragments according to size

Question 9

what is the purpose of DNA profiling

Answer 9

• tracing ancestry, paternity tests, forensic science

- hereditary disease: identify mutated gene, compared to a DNA ladder where length and position of diseases are known

Question 10

what is DNA sequencing and what is involved

Answer 10

• determination of precise order of nucleotides in a sample of DNA
• dNTP: DNA nucleotide, contain OH group acts as ‘hook’ to allow new nucleotide to add to existing chain
• ddNTP: dideoxy-nucleotide, chain terminating, labelled with characteristic fluorescent dye, lack OH, no ‘hook’

Question 11

explain the process of DNA sequencing

Answer 11

• DNA sample, primer, DNA polymerase, dNTP and ddNTP combined in tube
• denaturation, annealing and elongation occur
  DNA polymerase continues adding dNTP’s until a ddNTP is added, synthesis stops and strand ends
• millions of DNA molecules are present, strand terminated at any position
• ends with fragments with labelled dyes indicating final ddNTP
• electrophoresis: DNA is transferred to polyacrylamide gel (more porous and selective)
• gel placed in DNA sequences for electrophoresis, fragments migrate according to size
• detected as it passes a laser beam (bottom)
• ddNTP emits coloured light of characteristic wavelength, recorded as coloured band
• computer inputs raw data and outputs a chromatogram with coloured peaks of a fluorescent intensity representing each letter in sequence

Question 12

what is the purpose of DNA sequencing

Answer 12

• shows whether a person will develop an inherited disease by comparing sequences, changed alleles can be detected
• point mutations and insertions / deletions are readily identified
• sickle cell, cystic fibrosis,

Question 13

what is a hereditary disease

Answer 13

• caused by defective genetic information being transmitted from parents to their children

Question 14

what is a mutation

Answer 14

• particular gene may quite suddenly change from original structure and produce a different characteristic
• change in genetic material and can therefore be passed on to future generations

Question 15

what is a genetic probe

Answer 15

• locates a gene in a chromosome by pairing to specific DNA sequence
• involves pairing a short known segment of DNA or RNA with a matching sequence of bases on a chromosome
• DNA of known structure is marked with radioactive isotope
• used to detect presence of alleles responsible for hereditary disease

Question 16

what is gene therapy

Answer 16

• treats or cures abnormalities by replacing faulty genes with healthy ones
• occurs of single cell gene disorders
• CF: thick sticky mucous in lungs and pancreas, mutation in CFTR gene, modified cold virus acts as vector to transfer healthy genes to CFTR cells
• HD: mutation of chrom. 4 gene IT15, damage to nerve cells, physical, mental and emotional changes, modified virus delivers corrective gene into brain cells to boost natural shield against effects of mutation

Question 17

what is tissue engineering

Answer 17

• restores healthy tissues or organs, eliminates need for tissue / organ transplants or artificial implants
• requires abundant supply of stem cells, induced to grow on scaffold of natural or synthetic material to produce 3D tissue
• scaffold is template for tissue growth, must have high pore sizes that enable cell growth and diffusion of nutrients
• tissue growth must equal degradation of scaffold

Question 18

what is cell replacement therapy

Answer 18

• treatment which makes use of culturing of embryonic stem cells to replace damaged cells with healthy ones
• no scaffold, involves replacement of individual cells not entire organs / tissues

Question 19

what are the ethics concerned surrounding gene therapy and cell replacement therapy

Answer 19

• GP: does not alter genome, can’t pass on healthy gene to offspring as new healthy cells are somatic not gametes, viruses are used as vectors (risk of infection / immune response / side-effects / allergic reaction), unknown long term effects on individual or subsequent generations
• CRP: use of embryos (taking life away), cost / affordability, and unknown long term effects