7. Application of production of genetics

aims of human genome project

work out order or sequence of all the 3 billion base pairs in the human genome
identify all the genes
develop faster methods for DNA sequencing

improve tools for data analysis and related technology

address ethical issues

genome

entire set of DNA instructions found in a cell

main findings of human genome project

humans have about 25,000 genes
many repeated segments
less than 7% of proteins were specific to vertebrates

Genetic screening

testing individuals for certain faulty alleles to determine disorders such as cystic fibrosis and Huntingtons

Sanger sequencing

method of DNA sequencing used in th human genome project, involves formation of DNA fragments, very long process

Genomics

The study of structure, function, evolution and mapping of genomes. It could be used to personalise healthcare.

Stem cells

Undifferentiated cells that can differentiate into different specialised cells.

What is 100K genome project

A new project to study the genomes of 100,000 people in order to study genome variation in the UK. This uses NGS (Next generation sequencing) which is much faster.

Ethical issues with genetic technology

Ownership of data, insurance claims, hacking of data, employment, social stigma, misuse of data, idea of genetically modified babies for chosen characteristics

what enzyme is used to cut DNA?

restriction endonucleases

what are short tandem repeats?

blocks of repeated base sequences in introns which are variable between individuals

difference between introns and exons

exons are going regions for the amino acid sequence, introns are the non-coding regions which contain STRs

what is polymerase chain reaction?

technique used to make many copies of DNA where only small samples are available

steps of PCR

DNA heated to 95 degrees to separate strands, cooled to 50-50 degrees to allow primers to join, temperature raised to 70 degrees and Taq polymerase attaches new necleoxides onto their bases

process repeated no more that 40 times

what is gel electrophoresis

technique that separates DNA fragments by length, used in genetic fingerprinting and Sanger sequencing

steps of gel electrophoresis

DNA cut by restriction endonucleases, put in wells of gel, loading dye added to track progress, current applied to buffer and the negatively charged DNA travels toward the anode, shorter fragments pass through more easily

process of producing a protein using genetic engineering:

isolation and insertion of DNA into a vector
transfer of DNA into a suitable host cell

identification of host cell that have taken up the gene, using gene markers

cloning the transformed host cells

explain the 2 ways of isolating a gene

1) cut gene out of DNA directly with restriction endonucleases - there is a risk of cutting gene in the middle making it

2) using reverse transcriptase - joins complimentary DNA bases to mRNA to make cDNA and then treated with polymerase to make the double helix

what are stick ends?

staggered cuts in the DNA where there are unpaired bases formed by restriction endonucleases

plasmids as vectors

carry the gene into bacteria where the protein will be made, cut with the same endonucleases so that sticky ends are complimentary. DNA ligase joins DNA together and the DNA is recombinant

what is a vector?

a virus or plasmid used as a vehicle for carrying foreign genetic material into a cell

how is the rate of bacterial cells taking up plasmids increased?

adding calcium chloride as the ions have a positive charge which binds to the negatively charged DNA backbone of the plasmid and the membrane polysaccharides

heat shock - chilled cells at 4 degrees are briefly heated to 42 degrees

what is replica plating?

technique of selecting bacteria containing recombinant plasmids because they contain antibiotic resistance called mater genes

what is blue-white printing?

a technique to distinguish between transformed bacterial cells that contain an empty plasmid

benefits of using bacteria to produce human proteins

rapid and large yields produced, insulin treatments for diabetics, less rejection issues compared to animal proteins

concerns around using bacteria to produce human proteins

plasmids used carry antibiotic resistance, worries that this could spread to human pathogens

worry of oncogenes being activated

benefits of GM crops

modified to have superior keeping qualities, resistant to herbicides, eliminates competition from weeds, plants produce their own pesticides and fungicides

concerns of GM crops

Cross-pollination of genetically modified pollen into wild populations could lead to herbicide resistance. Overuse of herbicides harms beneficial insects and reduces biodiversity. People are also concerned about consuming proteins that are not typically found in their food.

what is genetic screening used for?

to confirm diagnosis, indicate appropriate treatment, allow families to avoid having children with devastating diseases, identify people at high risk for conditions

disadvantages of genetic screening

ownership and misuse of genetic data, discrimination and social stigma, designer babies

advantages of genetic screening

genetic counselling, detection of disorders such as CF and Huntington’s, identification of mutated genes

what is gene therapy?

a technique where the defective gene is replaced with a cloned one from a healthy person, for treatment or cure by vectors or injection of naked plasmid DNA

What is germ-line gene therapy?

introduces genes into the oocyte before rapid mitosis occurs, this is controversial as side effects on future generations are unknown

What is somatic gene therapy?

it targets cells in affected tissues for treatment, is not able to be inherited though

Issues around gene therapy

May activate oncogenes
Not permanent - re-treatments are needed
Difficult to get new functional genes into genome of the cells

Duchenne muscular dystrophy - symptoms and what causes it?

Muscle loss to the point where most suffered become wheelchair bound by teenage years and LE is 27

It is recessive and sex linked, caused by one or more deletions in dystrophin genes meaning the protein is not produced

Treatment for Duchenne muscular dystrophy

Dirasapersen is injected and acts as a molecular patch so that the RNA becomes double-stranded so the ribosomes can’t translate the exon

This means a shorter, partially functional dystrophin gene can be synthesised

Cystic fibrosis - symptoms and what causes it

Thick and sticky mucus that causes difficulty breathing, digestion and absorbing nutrients from food, and fertility issues for males as vs deferens become blocked

Homozygous for autosomal recessive allele

Cystic fibrosis - treatment

Gene coding for the mutant CFTR (which can’t transport ions so osmosis does not happen) is isolated, liposomes are inhaled with an aerosol and fuse with phospholipid bilayer

DNA enters the cell and the gene is transcribed - functional at relieving symptoms but needs to be repeated