2.7 - application of reproduction + genetics Flashcards
what’s the human genome project
international research project involving thousands of scientists which used sanger sequencing to successfully map the entire human genome
what’s DNA sequencing
identifying the base sequence of a DNA fragment
what’s sanger sequencing
method of DNA sequencing that only sequences relatively short sections of DNA at a time
takes a long time
potential benefits of the human genome project
- allows for development of targeted, personalised medical treatments + greater accuracy of diagnosis
- increased opportunities for screening genetic conditions + early detection of disease
- enables study of incidences of mutation in different genes
what’s the 100K genome project
UK government project that aims to study variation in the human genome amongst 100 000 UK citizens
uses next generation sequencing (NGS)
describe NGS
faster, cheaper + more accessible method of sequencing that can sequence entire genomes in a few hours
describe genetic counselling
- service that provides information + advice to people affected by/at risk of genetic diseases
- helps individuals + families make informed decisions
what’s genetic screening
- testing individuals for certain faulty alleles
- used to detect disorder such as cystic fibrosis, huntingtons + thalassemia
potential disadvantages of genetic screening
- may cause unnecessary stress + anxiety
- what happens to test results, discrimination from employers + insurance, misuse of info
- risk of false positives/negatives
- screening embryos can lead to designer babies
examples of organisms other than humans whose genomes have been sequenced
- chimpanzees + other primates
- mosquito
- plasmodium parasite
how has sequencing the genome of the mosquito been useful to humans
- they developed insecticide resistance
- sequencing enabled development of chemicals making mosquitos susceptible to insecticides
advantages of sequencing the genome of the plasmodium sp to humans
- they developed multi-drug resistance
- enables development of more effective drugs
what’s genetic fingerprinting
- technique used to genetically identify an organism
- applications in forensics, screening for hereditary diseases, paternity testing, selection for clinical trials
what are exons
region of DNA that comes for an amino acid sequence
what are introns
non-coding sequences of DNA
what are STRs
- short tandem repeats
- sections of repeated nucleotides within introns that produce variation in individuals
why techniques can be used to produce a genetic fingerprint
- PCR
- gel electrophoresis
what’s PCR
- polymerase chain reaction
- in vitro technique used to rapidly amplify fragments of DNA
describe the reaction mixture in the first stage of PCR
contains DNA fragment to be amplified, primers complementary to start of fragment, free nucleotides to match up to exposed bases, + taq polymerase to create new DNA
what’s taq DNA polymerase
thermally stable enzyme that synthesises double stranded molecule of DNA from single template strand using complementary nucleotides
summarise the process of amplifying DNA fragments using PCR
- heated (90-95C) to break H bonds between DNA strands
- cooled (55-60C) to allow primers to bind - annealing
- heated (70C) to activate taq DNA polymerase + allow free nucleotides to join
- new DNA acts as template for next cycle
what’s gel electrophoresis
technique that separates nucleic acid fragments/proteins by size using electric current
how does gel electrophoresis work
-1. DNA fragments of varying lengths placed at one end of slab of agarose gel
2. electric current applied, DNA fragments more towards positive end of gel
- shorter fragments travel further
- pattern of bands created unique to every indiviudal
what’s genetic engineering
modification of genome of organism by insertion of desired gene from another organism
enables formation of organisms w/ beneficial characteristics
what’s recombinant DNA
combo of DNA from 2 diff organsims
summarise the process of using restriction enzymes to produce DNA fragments
- gene identified using gene probe
- restriction endonucleases cut DNA at specific palindromic sequences producing sticky ends
summarise the process of using reverse transciptase to produce DNA fragments
- mRNA complementary to target gene used as template
- reverse transcriptase synthesises cDNA (complementary)
- mixed w/ free nucleotides which match up to base pairs
- DNA polymerase joins nucleotides forming second strand
advantages of using reverse transcriptase to produce cDNA
- don’t have to locate gene
- gene not cut into non-functional fragments by restriction enzymes
- no introns in cDNA
- doesn’t require post-transcriptional processing to produce functional mRNA
process of inserting DNA fragments into a vector
- plasmid used as vector
- plasmid cut using same restriction enzymes as DNA, so sticky ends are complementary
- DNA ligaments joins fragment + plasmid together
describe how antibiotic-resistance genes used in identification of recombinant DNA
antibiotic resistance genes can be inserted into plasmids at same time as DNA fragments
transformed cells placed on plate w/ antibiotics
only cells that successfully took up vector will grow
give an application for genetic modification of bacterial cells
human gene from insulin production can be inserted into vector, so bacterial cell will produce insulin
useful in medicine
eg: treatment of diabetes
disadvantages of using recombinant DNA to make human products
- identifying required gene may be difficult
- some eukaryotic genes can’t be expressed in prokaryotes
- antibiotic resistance genes could be transferred to pathogenic bacteria
- expensive
what are GM organisms
organisms that have had genome latered
benefits of GM crop production
- improves nutritional value of foods
- longer shelf life of products
- greater crop yields + reduces crop losses
- reduces need for pesticides
- reduces need for land clearing
- can produce human medicine + vaccines
risks of GM crop production
- reduction in biodiversity
- unknown effects on health
- cross pollination could result in herbicide-resistant weeds
- may increase costs for farmers
- insect eating predators may be damaged by toxins in plant
- transferred gene may spread to wild population + cause problems
what’s gene therapy
therapeutic technique in which faulty allele replaced w/ functional allele in order to treat/prevent disease
name the 2 types of gene therapy
- somatic cell therapy
- germ line therapy
differences between somatic cell therapy + germ line therapy
somatic - allele introduced to target cells only, short term, must be repeated
germ line - allele introduced to embryonic cells so its present in all resultant cells, permanent, passed onto offspring
what’s a vector
carrier used to transfer gene form one organism to another, e.g: plasmid or virus
what is DMD
- X-linked recessive condition
- characterised by muscle degeneration + weakness
what’s the cause of DMD
caused by one or more mutations in dystrophin gene that prevents production of dystrophin
how can DMD be treated using gene therapy
- healthy gene inserted into vector
- vector inserted into muscle tissue
- virus delivers gene to muscle cells
- new gene incorporated into DNA of cell
- transcription + translation of gene produces normal dystrophin protein
- symptoms of DMD alleviated
what’s drisapersen
experimental drug aiming to treat DMD by exon skipping
explain how drisapersen works
introduces ‘molecular patch’ over mutated exon, enabling gene to be read
shorter, more functional type of dystrophin synthesised
ethical issues surrounding use of gene therapy
- health implications, may produce immune response, activation of oncogenes, etc
- is it right alter genotype of unborn child
- could lead to healthcare inequalities
- expensive
what are stem cells
cells unspecialised + retain ability to differentiate into range of cell types
what’s tissue engineering
extension of gene therapy that aims to replace, repair or improve biological function by replacing organs + tissues
main advantage of using stem cells
rapid production of genetically identical cells + organisms
disadvantages of using stem cells
- expensive + unreliable in mammals
- in plants, disease + pathogens can cause issues
- inadvertent selection of disadvantageous alleles, unknown long term effetcs
ethical issues related to use of stem cells from embryos
- embryos used to provide stem cells destroyed
- could lead to ‘farming’ of embryos for stem cells
- may lead to reproductive cloning of humans
ethical issues related to use of stem cells from embryos
- embryos used to provide stem cells destroyed
- could lead to ‘farming’ of embryos for stem cells
- may lead to reproductive cloning of humans
