Paper 2 Flashcards
(138 cards)
1
Q
What are the stages in spermatogenesis?
A
Germinal Epithelial Cells (Mitosis).
Spermatogonia (Mitosis).
Primary spermatocytes (Meiosis I).
Secondary spermatocytes (Meiosis II).
Spermatids (Differentiation).
Spermatozoan.
2
Q
What do interstitial cells (AKA. Leydig cells) do?
A
They secrete testosterone which has a role in sperm formation and maturation.
3
Q
What are the stages of oogenesis?
A
Germinal epithelial cells (Mitosis).
Oogonia (Mitosis).
Primary Oocytes (Meiosis I).
Secondary Oocyte +Polar body (Meiosis II).
Ovum + 2nd polar body (Only happens after fertilisation).
4
Q
Where does Oogenesis have breaks?
A
-Primary Oocytes start to divide by meiosis but stop at Prophase I. Then, at puberty FSH stimulates one each month to complete Meiosis I and get to Metaphase II where it stops unless its fertilised.
5
Q
How does a Graafian Follicle develop?
A
Some germinal epithelial cells also divide by mitosis to form follicle cells which surround the primary oocytes to form primary follicles. FSH will then cause one each month to develop into a secondary follicle and then forms a Graafian follicle.
6
Q
What is the the temporary gland formed when the graafian follicle ruptures and what hormone does it produce if fertilised?
A
The corpus luteum which produces progesterone that maintains the endometrium.
7
Q
What happens to the corpus luteum is the oocyte isn’t fertilised?
A
It regresses.
8
Q
What in the oocytes prevents the entry of more than one sperm?
A
Cortical granules, they’re secretory organelles.
9
Q
What is a major difference between spermatogenesis and oogenesis?
A
A primary spermatocyte will produce four gametes but a primary oocytes produces only one (Due to the polar body created).
10
Q
What is the process of capacitation in a sperm cells?
A
It’s the removal of cholesterol and glycoproteins from the cell membrane over the acrosome in the sperm head. Over time, it becomes more fluid and permeable to Ca+ ions.
allowing acrosome reaction
11
Q
What is the acrosome reaction?
A
Acrosome enzymes (proteases) digest the corona radiata and the zona pellucida, allowing the sperm and oocytes cell membranes to fuse.
12
Q
What is the reaction that prevents polyspermy and how does it occur?
A
The cortical reaction, when the sperm attaches to the secondary oocyte, the SER releases Calcium ions into the cytoplasm. They make the cortical granules fuse with the membrane and release their contents causing the zona pellucida to expand and harden.
13
Q
What is the sequence called as the embryo moves down the oviduct, dividing many times?
A
Cleavage.
14
Q
What is the process of implantation?
A
The sinking of the blastocyst into the endometrium.
15
Q
What is a trophoblast and what are the villi they form used for?
A
The trophoblast is the name given to the cells forming the outer layer of the blastocyst. The trophoblastic villi penetrate the endometrium and they increase the surface area for the absorption of nutrients from the endometrium.
16
Q
What does the trophoblast develop into?
A
The chorion, these create larger villi and acquire blood capillaries which are connected to the umbilical artery and vein.
17
Q
What are the functions of the placenta?
A
Endocrine organ, producing hormones to support the pregnancy.
Exchange between the blood (Inter-villous spaces surround the chorionic
villi).
A physical barrier, protecting the fragile foetal capillaries.
Provides passive immunity.
Protection against the mother’s immune system.
18
Q
What are the significant hormones in the menstrual cycle?
A
Follicle stimulating hormone (FSH).
Luteinising hormone (LH).
Oestrogen.
Progesterone.
19
Q
During pregnancy, what do each of the hormones do?
A
HCG made by the embryo maintains the corpus luteum maintaining pregnancy.
Progesterone, prevents uterine contractions.
Oestrogen, stimulates the growth of the uterus and mammary glands.
20
Q
What is a period?
A
The shedding of the endometrium wall if a blastocyst has not implanted.
21
Q
What hormones are secreted in the period?
A
GnRH is secreted by the hypothalamus thich stimulates the anterior pituitary gland to secrete FSH which stimulates the development of a primary follicle. This has a positive feedback mechanism as it stimulates the theca cells to produce oestrogen.
22
Q
What does increasing oestrogen levels cause to happen?
A
Triggers the rebuilding of the endometrium, that was shed during menstruation.
Inhibits FSH secretion by negative feedback, which in turn brings its own concentration down.
Stimulates LH production by positive feedback.
23
Q
What does the surge in LH cause to happen?
A
It causes ovulation (release of the secondary oocyte), and has a positive feedback on FSH and levels pick back up again.
24
Q
What does the ruptured graafian follicle develop into and what hormones does it secrete?
A
It develops into the corpus luteum which secretes oestrogen and progesterone.
25
What do the increased levels of oestrogen and progesterone do?
They build and maintain the endometrium lining so that is a secondary oocyte is fertilised,, there with be suitable tissue in which the embryo can implant. These high levels also inhibit FSH and LH production.
26
What does the falling levels of FSH and LH do to the corpus luteum?
It causes it to degenerate so progesterone and oestrogen production declines.
27
What does the drop in progesterone cause to happen?
It causes mensuration so the endometrium is shed and the cycle starts over.
28
Even if the secondary oocyte is fertilised, why may a pregnancy fail?
It may fail to divide.
It may implant in the wrong place.
It may fail to implant.
29
What are the main roles of the main hormones during the menstrual cycle?
FSH, follicle development.
LH, ovulation.
Oestrogen, rebuild endometrium.
Progesterone, maintain endometrium.
30
What is the function of the amniotic fluid?
Maintains the foetus’s temperature.
Provides lubrication.
Contributes to lung development.
Allows movement so muscles and bones function before birth.
Acts as a shock absorber.
31
What does hCG do and when is it secreted?
It is secreted by the embryo and it maintains the corpus luteum.
32
Before birth, what does the decrease of progesterone and oestrogen cause?
They are no longer inhibiting the production of oxytocin and prolactin. Oxytocin causes contractions of the myometrium in the uterus wall. The contractions are mild but they stimulate the secretion of more oxytosin so concentration increases
33
where are prolactin and oxytocin secreted and what is their function?
oxytocin - posterior pituitary gland. stimulates contractions in uterus
prolactin - anterior pituitary gland. stimulates milk production
34
hormones secreted by placenta
HCG
Oestrogen
Progesterone
35
How does sexual reproduction generate heritable variation?
Crossing over between homologous chromosomes during prophase I of meiosis.
The random distribution of chromosomes during metaphase I.
The random distribution of chromatids at metaphase II.
The mixing of 2 different parental genotypes at fertilisation.
36
What does it mean if a variation is non-heritable?
If the variation is imposed by the environment that isn’t a result of epigenetic change and cannot be transmitted to offspring.
37
What are the 2 types of variation?
Discontinuous.
- Continuous.
38
What is discontinuous variation?
For some characteristics, there is only a small number of possibilities. There are no intermediates and the characteristics are discrete. These characteristics are controlled by single genes and so are monogenic.
39
What is continuous variation?
-For some characteristics, there are many possible values e.g. height. The values show a gradation from one extreme to another. These are controlled by many genes and are described as polygenic. The environment has considerable influence on the phenotypes.
40
What are the 2 types of competition?
Inter specific competition, between individuals of different species.
Intra specific competition, between individuals of the same species.
41
What is selection pressure?
An environmental factor that can alter the frequency of alleles in a population, when it’s limiting.
42
What is the gene pool?
All the alleles present in a population at a given time.
43
What is the allele frequency?
The frequency of an allele is its proportion, fraction or percentage of all the alleles of that gene in a gene pool.
44
What is genetic drift?
Chance variations in allele frequencies in a population.
45
What are the three factors which can cause significant changes to the allele frequency of a gene pool?
Mutation.
Natural selection.
Genetic drift.
46
What does the Hardy-Weinberg principle state?
That in ideal conditions, allele and genotype frequencies in a population are constant from generation to generation.
47
What is meant by the term evolution?
Allele frequencies change and phenotypes alter over time.
48
What is speciation?
The formation of a new species. If the change in phenotype is profound enough, organisms with the altered phenotype are unable to reproduce successfully with the initial population.
49
What is the founder effect?
The loss of genetic variation in a new population established by a very small number of individuals from a larger population.
50
What are the 3 types of natural selection?
Stabilising selection.
Directional selection.
Disruptive selection.
51
What is the concept of stabilising selection?
In a stable environment, the average phenotype may provide a greater advantage than either extreme. In this case, the extreme values will be selected against.
52
What is the concept of directional selection?
In a changing environment, an extreme phenotype may become advantageous. Then, other values are selected against and over time, the average phenotype changes.
53
What is the concept of disruptive selection?
In some situations, the average phenotype doesn’t provide an advantage and is selected against (The extremes are selected for at the same time). If these two demes are isolated, a new species may occur.
54
What is a species?
A group of phenotypically similar organisms that can interbreed to produce fertile offspring.
55
What is reproductive isolation?
The prevention of reproduction and, therefore, gene flow between breeding groups within a species.
56
What are the 2 forms of reproductive isolation?
Pre-zygotic, gametes are prevented from fusing so a zygote is never formed.
Post-zygotic, gametes fuse and zygote forms but is sterile and so the genes of the parent species are kept separate.
57
What is the difference between Allopatric speciation and Sympatric speciation?
Allopatric, the evolution of a new species from demes isolated in different geographical locations (Physically split).
Sympatric, the evolution of a new species from demes sharing a geographical location (The barriers are not physical ones).
58
What are the examples of sympatric speciation?
Morphological isolation.
Behavioural isolation.
Gametic isolation.
Seasonal isolation.
Hybrid inviability.
Hybrid sterility.
59
What is the concept of seasonal isolation?
Reproductive organs of different demes are mature at different times of the year. They are therefore unable to hybridise and are genetically isolated.
60
What is the concept of behavioural isolation?
Many animals have mating rituals and courtship displays that are recognised by other members of the same species as a prelude to mating.
61
What is the concept of morphological/mechanical isolation?
This is caused by variation in the sexual organs which can lead to some being unable to mate successfully with one another.
62
What is the concept of Gametic isolation?
Gametes in open environments often meet gametes of other species e.g. in coral reefs,. In about 2/3 of the cases, they’re incompatible. Barriers prevent the fusion of gametes of different species, so populations are isolated.
63
What is the concept of hybrid inviability and sterility?
Inviability, fertilisation occurs but incompatibility between the genes of the parents prevents the development of the embryo.
Sterility, an embryo formed from the gametes of 2 species can develop but if the chromosomes are not sufficiently similar, they are unable to pair at prophase I of meiosis and so gametes can’t form meaning the hybrid is sterile (Odd number of homologous chromosomes).
64
What are the changes in a population brought about by?
Mutation.
Gene flow.
Genetic drift.
Natural selection.
65
Why are low levels of antibiotics left in the environment?
They have been added routinely to animal feeds in intensive farming.
They have been added to handwashes.
People may not finish a prescribed course.
66
Why does some bacteria develop antibiotic resistance?
Bacteria reproduce rapidly and therefore random mutation quickly led to resistant strains.
67
How does a gene for resistance in a species quickly spread to others?
Bacteria can pass plasmids on during binary fision and directly to any other bacterial cell by means of a pilis.
68
In the pollen sacs, what goes under meiosis and what do they form?
Diploid pollen mother cells undergo meiosis, each forming a tetrad containing 4 haploid cells which become 4 pollen grains.
69
What happens to the haploid nucleus inside the pollen grain?
The haploid nucleus undergoes mitosis to produce 2 nuclei, a generative nucleus and a tube nucleus.
70
What are the 2 nuclei formed in the pollen grain and what are their roles?
Generative nucleus, produces 2 male nuclei by mitosis.
- Tube nucleus, creates a tube for the nuclei to pass down in the stigma and style to the ovary.
71
What is dehiscence?
The opening of the anther, releasing mature pollen grains.
72
How does the female gamete develop?
The ovary will contain one or more ovules.
In each ovule, a megaspore mother cell, surrounded by cells of the nucellus, undergoes meiosis making 4 haploid cells.
3 disintegrate.
The remaining cell undergoes 3 rounds of mitosis producing 8 haploid nuclei.
2 of the haploid nuclei fuse to make a diploid nucleus called the polar nucleus.
73
What does the embryo sac in a mature ovule contain?
3 antipodals (haploid).
1 polar nucleus (diploid).
1 oosphere (haploid and the female gamete).
2 synergids (haploid).
74
What is protandry?
The stamens of a flower ripen before the stigmas to prevent self pollination.
75
What are the sequences of germination? (non endospermic, dicot germination)
Seed imbibes water.
Testa splits.
Radicle emerges.
Plumule emerges.
Elongation pushes shoot above ground.
76
What effect does gibberellins have on barley? (endospermic mono cot germination)
The embryo secretes giberellic acid which diffuses to the alurone layer.
This switches on genes in the cells in the aleurone layer producing enzymes including protease and amylase.
Proteases hydrolyse protein to amino acid, to make amylase.
Amylase diffuses into the endosperm and hydrolyses the starch.
The maltose and glucose diffuse back through the endosperm to the plumule and radicle of the embryo.
These are respired for energy which brings the seed out of dormancy.
77
What is a gene?
A sequence of DNA that codes for a polypeptide and which occupies a specific locus on a chromosome.
78
What is an allele?
A variant nucleotide sequence for a particular gene at a given locus, which codes for an altered phenotype.
79
What is Mendel’s 1st law?
The law of segregation; The characteristics of an organism are determined by factors (alleles) which occur in pairs.
80
What does it mean if genes are ‘linked’?
It means that the genes are on the same chromosome and therefore don’t segregate independently during meiosis.
81
What is the difference between complete and incomplete linkage?
Complete - No crossing over has occurred.
Incomplete - Crossing over has occurred.
82
83
What is the null hypothesis in a chi squared test?
It states that there is no difference between the observed and expected results of a cross.
84
How do you work out the degrees of freedom for a chi-squared test?
It is one less than the number of classes of data.
85
What does it mean if a gene is sex linked?
The gene is carried by a sex chromosome so that a characteristic it encodes is seen predominately in one sex.
86
What are the different ways in which mutation can happen?
Gene/point mutation, DNA not copied accurately in interphase.
Chromosome mutation, chromosomes may get damaged and break. They then may repair themselves incorrectly.
Aneuploidy, whole chromosomes lost or added.
Polyploidy, number of chromosomes may double if cells fail to divide after fertilisation.
87
What are the different types of point/gene mutation?
Addition, a base is added.
Duplication, same base incorporated twice.
Subtraction, a base is deleted.
Substitution, a different base in incorporated.
Inversion, adjacent bases on the same DNA strand exchange position.
88
What is it called if the new codon codes for the same amino acid so there is no change to the polypeptide?
A silent mutation.
89
What is down syndrome caused by?
Non-disjunction.
90
What is non-disjunction?
A faulty cell division in meiosis following which one of the daughter cells receives 2 copies of a chromosome and the other receives none.
91
What is the difference between a benign tumour and a malignant tumour?
Benign, usually harmless as it doesn’t invade surrounding tissues or spread to other parts of the body.
Malignant, harmful as they spread around the body and invade other tissues, making secondary tumours.
92
What is an oncogene?
A proto-oncogene with a mutation that results in cancer.
93
How may an oncogene occur?
If a mutation causes chromosomes to rearrange and places the proto-oncogene next to a DNA sequence that permanently activates it.
There is an extra copy of the proto-oncogene resulting in too much of its product being made, causing excessive mitosis.
94
What is epigenetics?
The control of gene expression by modifying DNA or histones, but not by affecting the DNA nucleotide sequence.
95
What is Mendels 2nd law?
Mendel’s second law is also known as the law of independent assortment. The law of independent assortment states that the alleles of one gene sort into gametes independently of the alleles of another gene.
96
What were the aims of the human genome project?
Identify all the genes in the human genome and identify which chromosome each is on.
Determine the sequence of all base pairs in human DNA.
Store the information on a database.
Consider ethical, social ad legal issues that arise.
97
What are the applications of the human genome project?
Scan for mutations.
Carrier screening.
Pre-natal testing.
Newborn screening.
Screening for adult onset disorders.
Forensic and identity testing.
98
What did the 100k project aim to do?
Create an ethical, transparent programme based on consent.
Set up a genomic service for the NHS to benefit patients.
Enable medical and scientific discovery.
Develop a UK genomics industry.
99
What moral/ethical concerns are there regarding the human genome and 100k genome project?
Who owns the genetic information?
Some people don’t wish to have information on future health problems that they may have.
Concerns over the idea of ‘designer babies’.
Storage and security of genomic data is a concern because of the potential for computer storage to be hacked.
100
Why is a genetic fingerprint not the same as DNA sequence?
Because it represent only non-coding portions of DNA.
101
What 2 techniques does genetic fingerprinting rely on?
The polymerase chain reaction to make large numbers of copies of DNA fragments.
Gel electrophoresis, to separate DNA fragments based on their size.
102
What are STR’s?
They’re Short Tandem Repeats, these are sequences of nucleotides within an intron.
103
What is PCR?
It is semi-conservative replication of DNA in a test tube and it greatly amplifies the quantity of DNA.
104
In PCR, what is the DNA sample mixed with?
Taq polymerase (DNA polymerase with an optimum of 80’c).
Nucleotides containing the 4 DNA bases.
Primers, which bind to the start signalling taq to start replication.
105
What are the stages of PCR?
Original DNA is heated to 95’c separating it into 2 strands.
Solution cooled to 55’c for the primers to anneal to the complementary base sequences.
Solution hated to 70’c and taq catalyses the synthesis of a complementary strand by adding complementary nucleotides and catalysing sugar-phosphate backbone.
Sequence repeated multiple times.
106
What are the limitations of PCR?
Contamination, any DNA that enters will also be amplified.
Error rate, all polymerases sometimes insert the wrong base but taq can’t proofread and correct the error.
PCR is most efficient for making DNA 1000-3000 base pairs long but many genes are much longer than this.
Limits on amplification, after around 20 cycles it slows down.
107
Why does the amount of DNA produced in PCR plateau after about 20 cycles?
Reagent concentrations become limiting.
Enzymes denature after repeated heating.
DNA in high concentrations causes single-stranded molecules to base pair with each other rather than with primers.
108
What are the steps in gel electrophoresis?
DNA extracted and cut into fragments using restriction endonucleases.
The samples are loaded into wells at one end of the gel.
A voltage is applied across the gel (DNA is -) so fragments are attracted to the anode.
Smaller fragments move more easily through the pores so they migrate through the gel quicker.
Luminescent DNA probes attach to complementary to the STRs.
Autoradiograph shows the position of the probe
109
What are the uses of DNA profiling?
Paternity testing.
Twins, identical or fraternal.
Siblings.
Immigration.
Forensic use to identify and rule out suspects.
Phylogenetic studies.
110
What are the pros of DNA profiling?
It doesn’t requre an invasive method to obtain a biological sample, as mouth swabs, urine or hair can be used to obtain DNA, rather than blood samples.
The technique can be used on samples that would be too small for blood testing.
It has reversed wrongful convictions when used with other forensic tools and evidence.
DNA profiling can rule out non-matches of DNA samples, the exonerate people who have been falsely accused.
Efforts are being made to store genetic material from people around the world, before isolated groups are intermixed and lost.
111
What are the cons of DNA profiling?
Some people consider the request for DNA a violation of privacy.
DNA profiles in databases are vulnerable to misuse and hacking.
Access to and use of data must be carefully regulated so its not used to increase insurance premiums.
It may produce wrongful convictions if errors occur in the procedure, untrustworthy people conduct the test, DNA evidence is planted etc.
112
What is recombinant DNA?
DNA produced by combining DNA from 2 different species.
113
What is transgenic?
An organism that has been genetically modified by the addition of a gene or genes from another species.
114
What does the process of producing a protein using genetic engineering technology involve?
Isolation of the DNA fragments.
Insertion of the DNA fragment into a vector.
The transfer of the DNA into a suitable host cell.
Identification of the host cell that have taken up the gene, using gene markers.
Cloning the transformed host cells.
115
What are the 2 ways the identified and located genes can be isolated?
Using one of 2 enzymes,
Restriction endonuclease.
Reverse transcriptase.
116
How can you isolated the desired gene using restriction endonuclease?
They cut at specific nucleotide sequences.
The DNA is cut into many small fragments and individual genes can be isolated.
These enzymes make a staggered cut which leaves sticky ends.
117
What are the main drawbacks with using restriction endonuclease to excise a gene?
If the recognition sequence occurs within the gene of interest, the gene will be broken into fragments that have no function.
Eukaryotic genes contain introns but bacteria do not and so they may not have the appropriate enzymes to process the RNA to remove them.
118
How can you isolate the desired gene using reverse transcriptase?
There may be many molecules of mRNA that have been transcribed from the desired gene.
The enzyme reverse transcriptase synthesises copy DNA.
Many copies of cDNA that is complementary to the mRNA can be made.
DNA polymerase then catalyses the synthesis of DNA that is complementary to the single-stranded cDNA.
119
How are plasmids within bacteria isolated?
EDTA used to destabilise the cell wall.
Detergent to dissolve the phospholipid cell membrane.
Sodium hydroxide to make an alkaline environment that denatures the membrane proteins.
The plasmids can then be separated from the cell debris.
120
What is a plasmid and why are they useful for introducing genes into bacteria?
They are small circular loops of self-replicating double-stranded DNA in bacteria. They are much smaller than the bacterial chromosome and can move in and out of cells making them useful.
121
How is a recombinant plasmid made?
The circular DNA is cut open using the same restriction endonuclease as was used to isolate the gene which means it has the same nucleotide sequence in its sticky ends.
The vector and gene are mixed and their complementary base sequences base pair with each other.
The gene is now bound to the plasmid with DNA ligase.
122
To make a good vector, what should a structure be?
Self-replicating.
Small.
Not be broken down by host cell enzymes,
Not stimulate an immune response in the recipient.
Be able to be screened to confirm the gene was successfully inserted.
Have markers to allow host cells that have taken up the vector to be identified.
123
How is DNA transfered into the host cell?
Plasmids are mixed with bacterial cells but very few take up the plasmid and become transformed. This amount can be increased with calcium chloride. DNA passes into the cells with a heat shock.
124
How can you identify which cells have been transformed?
Plasmids with antibiotic-resistance are used which confer resistance to ampicillin and tetracycline.
The cells are cultured in a growth medium containing the antibiotic and if they’ve incorporated the plasmid, they also contain the resistant gene.
125
What are the pros of genetic engineering in bacteria?
Medical products: large amounts of pure human proteins for use in medicine have been made.
Prevention and treatment of disease.
Enhancing crop growth.
Environmental use: deleting and removing environmental hazards.
126
What are the cons of genetic engineering in bacteria?
Plasmids are easily transferred so there is potential for antibiotic resistance markers genes to be transferred.
cDNA may contain oncogenes that activate proto-oncogenes in recipient cells.
A micro-organism with a new gene may become a threat if released into the environment.
A newly introduced gene may disrupt the normal function of other genes.
127
What are the arguments against the use of GM crops?
Pollen from GM plants may transfer genes to wild relatives (superweeds).
Pest resistance.
Marker genes are often antibiotic resisatnce and there is fears they may pass to the bacteria in the human gut.
Reduction of biodiversity.
Could compromise organic farming.
128
What is gene therapy?
A technique in which a defective allele is replaced with one cloned from a healthy individual, providing a treatment or cure.
129
In gene therapy, what are the ways in which the DNA can be introduced into the target cells?
Using a virus as a vector.
Using a plasmid as a vector.
Injection of naked plasmid DNA.
130
What are the 2 main approaches to gene therapy?
Somatic cell, targets body cells.
- Germ-line, introduces the corrective genes into the oocyte so the correction is inherited.
131
What is DMD and what effect does it have on the patient?
Duchenne Muscular Dystrophy is a recessive, sex-linked form of muscular dystrophy. People have severe muscle loss.
132
How does drisapersen treat DMD?
It is an antisense oligonucleotide and it acts as a ‘molecular patch’; it binds to the mRNA over the exon with the deletion so it can’t be read.
133
What are stem cells?
An undifferentiated cell capable of dividing to give rise to daughter cells, which can develop into different types of specialised cells or remain as undifferentiated stem cells.
134
Where can stem cells come from?
Embryonic stem cells, the blastocyst has ESCs which can form every cell type in the body.
Some adult tissue, e.g. bone marrow, contain stem cells.
135
What do stem cells have the potential to do?
For tissue engineering to regenerate tissues and organs.
For cell based therapies to treat disease.
To screen new drugs.
To develop model systems to study normal growth and identify the causes of birth defects.
To investigate the events that occur during human development.
136
What are the advantages of using stem cells?
Embryonic stem cells can become any type of cell.
Embryonic stem cells grow easily in culture and large quantities can be readily produced.
The use of stem cells will make the problem of a shortage of organs for transplantation less significant.
A patient receiving ESCs is less likely to need immunosupressive drugs.
137
What are the disadvantages of using stem cells?
Techniques for extracting, culturing and manipulating stem cells are still under development and their behaviour isn’t always predictable.
The use of them is very new and so long term studies haven’t yet been conducted.
Ethical issues tied to the use of ESCs.
138
What are the ethical issues surrounding the use of embryonic stem cells?
The source, they used to use ‘left over’ embryos from in vitro.
The moral status of the embryo, they don’t have the same human rights as a living individual but some groups argue that ‘life begins at conception.
Their potential rights are balanced against the potentially large benefits that other people may gain from the research and treatment it produces.
Fears it may lead to humans being cloned which devalues human life.
