Application of genetics

• Human Genome Project


  Project to improve knowledge and understanding of genetic disorders and improve their diagnosis and treatment
• The Human Genome Project was completed


  1990-2003
• Sanger Sequencing


  DNA sequencing process that involved reading the base sequence of a length of DNA, telling us the order of DNA bases, the distribution and sequences of introns and exons, and the loci of individual genes
• Next Generation Sequencing (NGS)


  Faster techniques that can sequence the entire genome in a few hours, enabling the study of variation within the human genome
• 100K Genome Project


  Project that used NGS to sequence 100,000 genomes from NHS patients with cancer or rare diseases, enabling the location of genes responsible for rare diseases and cancers, the location of mutated genes, the comparison of genomes of genetic disorder sufferers with the normal genome, and the development of treatments for genetic disorders
• A vast quantity of data has been produced by the HGP and the 100K genome project, and society has yet to decide how it should be treated and where legal and moral responsibilities lie
• Identification of allele sequences

  Enables scanning a patient's DNA sample for mutated sequences and comparing the sequence of DNA bases in a patient's gene to a normal version of the gene
• IVF embryo screening


  Can screen for the presence of alleles which cause conditions including cystic fibrosis, Huntington's disease and thalassaemia
• Genetic screening can be useful in association with genetic counselling, allowing a couple to make informed decisions before having children
• Ethical issues regarding DNA screening

  • Ownership of genetic information that could lead to potential discrimination
  • Concerns over the possibility of routine screening for adult onset disorders such as Alzheimer's disease and some cancers
  • Concerns over embryo screening and the potential for choosing alleles to ensure specific characteristics: 'designer babies'
• Cystic fibrosis


  Sufferers are homozygous for an autosomal recessive allele and lack a functioning CFTR gene, resulting in mucus blocking the airways and symptoms such as difficulty breathing, coughing and recurrent chest infections
• Genetic cross to show probability of inheriting cystic fibrosis


  Draw a genetic cross to show the probability of a child inheriting cystic fibrosis from a carrier father and a mother who suffers from the disease
• Carriers of cystic fibrosis can be identified through epithelial cells
• Genomes have been sequenced for a number of other species including the mosquito Anopheles gambiae and the Plasmodium parasite, as well as chimpanzees and other primates, allowing scientists to look at evolutionary relationships and to conserve species in the future
• Rapid evolution of insecticide resistance in the Anopheles gambiae mosquito is hampering attempts to eradicate the disease, which is responsible for over a million deaths per year</b>
• Pyrethroid resistance is a problem as this is the only insecticide safe for use with the nets which people sleep under
• The malarial parasite, Plasmodium sp. has also developed multi-drug resistance
• The DNA sequence of the Anopheles gambiae genome was completed in 2002 and is allowing scientists to develop chemicals that could render the mosquito susceptible to insecticides again, preventing it from transmitting malaria
• Malaria is transmitted by the mosquito Anopheles gambiae
• The genome of Plasmodium sp. was sequenced in 2002, and it is hoped that a better understanding of genetic control of Plasmodium infection will allow the development of more effective drugs
• Advantages and disadvantages of chemical control (pesticide) of mosquitoes

  • Advantages
  • Disadvantages
• How the mosquito population in Africa became resistant to insecticides like Pyrethroid

  Through natural selection
• Antibody structure


  Describe the structure of an antibody
• Synthesis of antibodies can initiate an immune response in mosquitoes against Plasmodium
• Suggesting how the synthesis of these antibodies could help to reduce malaria outbreaks in humans in the future
• Polymerase chain reaction (PCR)


  Allows the quantity of DNA to be amplified rapidly for analysis
• An individual's DNA profile is different from that of another individual
• Exons


  Regions of DNA that code for proteins
• Introns


  Regions of non-coding DNA between exons, containing blocks of repeated nucleotides
• Short tandem repeats (STRs)

  Repeating blocks of introns found in DNA that produce variation in individuals
• PCR process


  1. Separation

  2. Annealing

  3. Extension
• Separation step


  The target DNA molecule is dissolved in a buffer and heated to break the hydrogen bonds and denature the DNA, causing the two strands to separate and expose the nitrogenous bases
• Annealing step


  The sample is cooled to allow the short DNA primers to bind to the DNA strands and form hydrogen bonds with complementary bases
• Extension step


  Heating allows DNA polymerase (Taq) to add complementary nucleotides by forming phosphodiester bonds in the sugar-phosphate backbone, creating two double-stranded molecules
• After 40 cycles, over a billion copies of the target sequence can be produced from just one piece of DNA
• At the end of one PCR cycle, two molecules of DNA have been produced from each original molecule
• Practical uses of PCR

  Suggest one practical use of this technique
• Separation step


  Complementary DNA strands are separated by heating to break the hydrogen bonds
• Primer


  Short DNA sequence that binds to the DNA template and provides a starting point for DNA synthesis
• Enzyme required in extension step

  DNA polymerase