Biology - dna and gene technologies Flashcards
how is dna contained in eukaryotic cells
contained in nucleus in long, thread-like structures called chromosomes
what is dna
large polymer made up of smaller monomers
what are the monomers of dna made up of
monomer is a nucleotide, made of three components, a sugar (ribose), a phosphate and a nitrogenous base
there are 4 bases: adenine, cytosine, guanine, thymine
nucleotide bases
complementary base pairing
bases bond by hydrogen bonding
structure of dna
made up of 2 polynucleotide chains (strands) that are twisted around each other to form a double helix
protein synthesis
- chromosome consists of millions of bases of dna
- gene is a section of chromosome which codes for a specific protein
- code is read as triplets and each triplet codes for a single amino acid
- there are some triplets that code for the same amino acid
- the sequence of amino acids produces the protein
what is a mutation
change in dna sequence
harmful mutations
- mutations can be harmful if it changes a triplet, which will then code for a different amino acid and therefore change the structure of the protein
- if a mutation occurs within an enzyme, the active site may no longer be complementary to the substrate
what are silent mutations
- large sections of dna do not code for proteins
- mutations are unlikely to affect phenotype
- could happen if a change in a triplet occurs but the new triplet still codes for the same amino acid
what is genetic engineering
- modification of organism’s genetic material
- involves taking a copy of a gene from one organism and inserting that gene into another organism’s dna
- creates GMO or GENETICALLY MODIFIED ORGANISM, which is also called TRANSGENIC
what are the steps of genetically engineering bacterial cells
- useful gene cut from dna using RESTRICTION ENZYME (enzyme cuts dna in staggered way, creates sticky ends)
- BACTERIAL PLASMID DNA cut open using SAME RESTRICTION ENZYME, also creating sticky ends (unpaired bases on ends of plasmids are complementary)
- useful gene and plasmid dna are mixed and gene is inserted into plasmid through hydrogen bonds that form complementary bases in sticky ends
- DNA LIGASE is used to join the plasmid DNA and gene together, creating RECOMBINANT PLASMID
- recombinant plasmid is then inserted into bacterial cell - plasmid acts as a VECTOR, as it carries the gene into the bacterial cell
- bacterial cell can be cultured through cloning, so multiple GENETICALLY MODIFIED bacteria containing recombinant plasmid will be made
examples of proteins produced by genetically engineering bacterial cells and their uses
- hormones e.g. insulin to treat diabetes
- enzymes e.g. rennin for producing cheese
- blood clotting factors e.g. factor VIII in order to treat haemophilia
- antibiotics e.g. penicillin
genetically engineering of plants
- plants dont have plasmids
- plants have bacteria AGROBACTERIUM TUMEFACIENS used to make GM plants (these have Ti PLASMID that is able to enter plant cells and genome when bacteria infect plant)
- plant cells grown in culture and then develop into new plants thatt contain useful gene
examples of GM plants
pest resistance in Bt cotton
disease resistance in bananas
adding nutrients to avoid malnutrition in countries e.g. golden rice infused with carotene to prevent vitamin A deficiency
genetic engineering in producing medicine
e.g. insulin, blood clotting factors
- can produce larger quantities of medicine
- fewer side effects as human proteins
- however, there are concerns about unknown long-term consequences as relatively recent technology
genetic engineering in producing vaccines
e.g. hepatitis B
- can produce more vaccines that are safer and cheaper
genetic engineering in producing human-like organs
e.g. GM pigs
- help to reduce shortage of suitable donor organs
- however, concerns over the spread of disease from pigs to human
- ethical objections of using pigs
genetic engineering in reducing the spread of diseases
e.g. malaria
- modifying ANOPHELES mosquitoes to have a more efficient immune response when infected with parasite so does not survive within them
- concerns over the implications of other wild populations of insects
what is gene therapy?
- use of genes to cure or prevent severe genetic diseases
- done by introducing a normally-functioning gene into a patient’s cells to replace a faulty, mutated gene that causes disease
- however, if the therapeutic gene is accidentally inserted too close to a cancer-causing gene, then it can cause this gene to be switched on
gene therapy on body cells (e.g. cystic fibrosis)
can add a gene to lung cells to enable cells to produce a protein to reduce symptoms
pros/cons of gene therapy on body cells (e.g. cystic fibrosis)
- longer lasting treatment
- increased quality of life
- provides possible cures for genetic conditions such as CF
- reduces need for daily medication
- less controversial
gene therapy on gametes
currently illegal in the UK
pros/cons of gene therapy on gametes
- any therapeutic gene added into a gamete cell will be found in every cell of child formed from gamete, so can prevent offspring developing genetic conditions
- very controversial and currently illegal (designer babies, changes passed onto offspring have unanticipated results on next generation)
gene therapy on stem cells
sickle cell anaemia - GM bone marrow cells can be used to create healthy red blood cells for oxygen transport
pros/cons of gene therapy on stem cells
- provides longer-term cure
- can use patient’s own stem cells so no need to find a suitable donor and no risk of rejection
what are stem cells
- undifferentiated cells - renew themselves through mitosis
- potential to become many different types of cells in body through differentiation
what are totipotent stem cells
at fertilisation, stem cells are totipotent
can differentiate and develop into any of the specialised cells found in an adult
what are pluripotent stem cells
as mitosis occurs, an embryo has stem cells that are pluripotent
can differentiate into almost every specialised cell, except cells that become the placenta
what are multipotent stem cells
adult stem cells found in several organs in the body are multipotent
can only differentiate into a small number of different cells e.g. bone marrow differentiate into types of blood cells
examples of bone marrow stem cells
can be used to treat certain cancers
issues with bone marrow stem cells
risk of rejection
examples of embryonic stem cells
- treat diabetes by replacing insulin-secreting cells in pancreas
- treat burns through replacing damaged skin tissue
- replacing neurons to treat spinal cord injuries
examples of induced pluripotent stem cells (iPSC)
- produced in laboratory using adult body cells (less controversial) so can be used instead of embryonic stem cells
- test effectiveness of drugs before used on patient
- no rejection as from patient’s body
selective breeding
- animals with desirable characteristics are bred together
- animals with most desirable characteristics are selected from offspring, which are then bred together
- cycle repeated over several generations until desirable trait increases in population
examples of animals selectively bred
cows
pigs
dogs e.g. greyhounds for their intelligence, border collies for obedience
