Flashcards in B Test N3 S7 Deck (41):
Purpose of mitosis
Normal cell division and growth, asexual reproduction and repair (i.e. skin repair, hair, zygotes etc.) where there is an increase in the number of cells that are genetically identical to the parent cell.
Purpose of meiosis
In sexual reproduction in order to produce haploid gametes, in general, with half the chromosome number and variation.
Where does mitosis take place?
In animals: everywhere (for example the nails and hair)
In plants: in the tips of the roots and shoots (the meristems)
Where does meiosis take place?
In animals: in the ovaries and testes
In plants: in the anthers and ovaries
Result of mitosis
Two daughter cells that are genetically identical to each other and the parent cell
Result of meiosis
Four genetically different cells with half the number of chromosomes
Where does variation in meiosis occur?
Crossing over at prophase I between homologous chromosomes
Random orientation of homologous chromosomes at metaphase I.
Random orientation of homologous chromosomes containing nonsister chromatids at metaphase II.
The cell cycle
G1 phase: rapid cell growth and the synthesis of organelles
S phase: the amount of DNA in the cell doubles
G2 phase: The centrioles replicate and the microtubules begin to construct the spindle
Cytokinesis in animal cells
The centre of the cell pinches to form a division furrow due to the contraction of a ring made up of actin and myosin.
Cytokinesis in plant cells
Vesicles (containing carbohydrates: pectins and hemicelluloses) produced by the Golgi body collect on the equator and fuse to form a cell plate. This cell plate stretches across the cells to form the middle lamella and cellulose builds on either side of this to form the new cell walls.
What is cancer?
Cancer is uncontrolled mitotic division.
Nondisjunction in anaphase I or II of meiosis will lead to the abnormalities in the offspring if the resulting gamete is fertilised: Down's syndrome and Turner syndrome.
Cut DNA into small fragments at precise sequences.
A gene from one organism that can be inserted into the DNA of another.
DNA that contains genetic material from two or more different sources
Joins the backbone of the sticky ends of donor DNA and the host DNA together
Uses of restriction enzymes
Manipulation of DNA in many ways for many purposes:
Health (insulin and factor 8)
Environmental (pest resistance)
Agricultural (oil spills)
Criminology and heredity (murders and paternity testing)
How is an organism genetically modified
- adding a gene (human insulin used to treat diabetic patients)
- altering the gene (used in gene therapy to treat genetic disorders such as cystic fibrosis)
- deleting or turning off a gene (deactivation of the right ripening gene in tomatoes)
Gene cloning dilemmas
Safety (human health and environmental impact)
Access and intellectual property
Two methods for cloning genes
The PCR: short term such as crime scenes
Vectors: bacteria for long-term such as cystic fibrosis
Cystic fibrosis cause
Inherited recessive disease caused by a defective gene resulting from the deletion of a base triplet. An amino acid is therefore omitted from the coded protein.
Cystic fibrosis consequence
Normal gene codes for protein which transport chloride irons and therefore sodium irons and water out of the cell into mucus.
Chloride irons are not transported and the mucus is thick and sticky: air passages are blocked, the pancreatic duct can become blocked, health deterioration.
Cystic fibrosis genetic treatment
Non-defective gene is isolated and cut out by restriction enzyme and cloned with the PCR.
The genes are encapsulated in tiny spheres of lipids (liposomes).
Aerosol inhaler is used to spray the non-defective gene in the epithet cells of the lungs.
Liposomes fuse with the phospholipid bilayer of the membrane and the DNA enters the affected cells
Genetic fingerprinting process
DNA extracted and purified
Enzymes cut DNA into fragments
Electrophoresis separates DNA fragments
Transfer of DNA to nylon membrane
Radioactive probes bind to DNA fragments
DNA probes exposed to x-ray film
Pattern of bands appear
Genetic fingerprinting use
Used to provide forensic evidence and therefore solve crimes or match heredity.
Transgenic organisms use
AAT: cystic fibrosis
Factor 8: haemophilia
Transgenic organisms misuse
BST: infertile cows, mastitis, susceptibility to disease, effect on mothers, unnatural...
Introduction of foreign genes into plant cells
Transgenic plants use
- resistance to disease: potato leaf root virus
- nitrogen fixation: in wheat and rice
- Improved quality: tomatoes for ripening
Eggs from best cows and sperms from best bulls
Fertilisation in a Petri dish
Eggs grow into embryos
Embryo is split to produce more
Embryos transplanted into surrogate cows
Donor cells from X and cultured to stop division
And fertilised egg removed from Y and egg removed
Dormant donor cell and recipient egg cell placed together
Electric pulse triggers cell division
Embryo implanted into Y
X is born
Gene technology method
- DNA from human cells
- restriction enzyme cuts DNA
- plasmid removed and cut
- DNA ligase attaches gene to plasmid
- recombinant plasmid taken up by treated bacterium
- bacterial cells multiply
Used as factors as they replicate very rapidly
Used to indicate that new genes have been incorporated into the host cells
Used as they can survive at very high temperatures and therefore withstand the PCR
Used embryo cloning
Advantages of modern gene technology as opposed to previous
- economic benefit
- Health benefit (no hepatitis or HIV)
- solving global hunger
- environmental friendly
- consumer benefits
- GM maize (resistance to insect pest)
- GM soya (herbicide tolerant)