Unit 1 – Living Cells
The study of the human genome - involves sequencing DNA nucleotides - and relating this to gene functions In 2003, the human genome project (HGP) was completed The entire DNA sequence of the human genome was completed - aided by techniques like DNA sequencing, and cataloguing single nucleotide polymorphisms (SNP’s)
The analysis of data produced by DNA technology - using statistical analysis and computer technology Allows the identification of: - Protein-coding sequences - Start sequences - Stop codons - specific base sequences Can be used for - evolutionary biology - inheritance - personalised medicine
The study of diversity, relatedness and classification in living things Can be used to study origins of humans - and their evolutionary relationships Human DNA only varies by 0.3% - most variation in within Africa Out of Africa theory: Humans originated in Africa Evolved within Africa over millions of years - lots of genetic variation Small groups migrated out of Africa recently - 100,000 years ago
Now possible to determine a DNA sequence for every individual: Personal genomics - becoming cheaper and faster - allows for analysis of mutations - if they are harmful or neutral - links specific genetic sequences to genetic diseases - however, environmental factors still play a role
Studies the effects of drugs on the human population In the future, could be used to customise medical treatment - suitable drugs and dosage could be prescribed for each individual - reduced risk of “side effects”
Possibility to scan individual DNA for predisposition to, and predict risk to, disease - risk could be reduced by specific drug treatment & lifestyle choices Ethical issues: - Who should have access to this info? - Could it affect employability/insurance/fa mily? - Potential for genetic discrimination
Polymerase Chain Reaction (PCR): Creates many copies of a piece of DNA - amplification - outside the body (in vitro) Primers are used - single stranded DNA - complimentary to a specific target sequence of DNA (at the 3’ end) - DNA separated – by heat treatment - primer binds to target sequence - DNA cooled - DNA polymerase then adds nucleotides to the primers Allows many copies of DNA to be extracted from a tiny sample
DNA probes Detect a specific sequence of nucleotide bases in a DNA sample - the target DNA Probes are fluorescent labelled Probes are part of a DNA microarray - arrangement of thousands of different probes Useful for: - identifying genes that are active/inactive (cancers) - genetic identification
PCR allows many copies of DNA to be produced - copies can then be screened for sequences linked to genetic disease - estimate risk of disease onset - confirm diagnosis e.g. cystic fibrosis testing - blood testing can identify a mutant allele for cystic fibrosis
DNA profile: - human genome contains many, repetitive non-coding sequences - differ in number and length between individuals - can therefore construct an individual DNA profile PCR can amplify a small DNA sample from a crime scene - samples from victims and suspects can then be separated by gel electrophoresis, and compared - also used to resolve paternity disputes - child will share 50% of bands in common with each parent