GENETICS
Everyone receives one set of chromosomes from their mother and one set of chromosomes from their father, ie, half their genetic material comes from their mother and half comes from their father. This explains why you may look more like one or other of your parents.
46 chromosomes 46 chromosomes
meiosis
Egg cell with 23 chromosomes
meiosis
Sperm cell with 23 chromosomes
Fertilization
A child with 46 chromosomes with some
characteristics of his mother and some of his
father.
ALLELES
Paternal
chromosome
Maternal
chromosome
- For eye colour
Alleles – for hair colour
Alleles – for straight or
curly hair
Brown eyes
Homozygous blue
Blue eyes Brown eyes
Homozygous
brownHeterozygous
brown
M P M PM P
Brown eyes is dominant to blue eyes – the gene for brown eyes is
represented by ‘B’.
Blue eyes is recessive to brown eyes – the gene for blue eyes is
represented by ‘b’.
Homozygous blue Homozygous
brownHeterozygous
brown
M MMP PP
bb BbBB
HOW WAS ALL OF THIS DISCOVERED????
Pure breeding tall pea
plantX Pure breeding short pea
plant
All the offspring were tall
Tall offspring X Tall offspring
A ratio of 3 tall plants
to 1 short plant.
P1
meiosis
gametes
Tall x Short
TT tt
T T t t
phenotype
genotype
T T
t Tt Tt
t Tt Tt
F1 Genotype Tt
Phenotype All tall
P2
meiosis
gametes
Tall x Tall
Tt Tt
T t T t
phenotype
genotype
T t
T TT Tt
t Tt tt
F1 Genotype TT; 2Tt; tt
Phenotype 3 Tall : 1 Short
Phenotypic ratio 3 : 1
Mendel’s Findings• Mendel called the characteristic that showed in the F1, the
dominant characteristic.
• He called the characteristic that was hidden the
recessive characteristic
•For each characteristic, there are only two genes which
segregate so that each gamete has only one of these
genes. This is Mendel’s First Law: The Law of
Segregation.
•The various genes are separate entities and do not
influence each other in any way. They sort themselves
out independently during gamete formation. This is
Mendel’s Second Law: The Law of Independent
Assortment
Examples of dominant
characteristics
Hand Clasping
Clasp your hands together (without
thinking about it!). Most people place their
left thumb on top of their right and this
happens to be the dominant phenotype.
Now, for fun, try clasping your hands so
that the opposite thumb is on top. Feels
strange and unnatural, doesn’t it?
Alleles: L,l
Dominant phenotype: left thumb on top
Dominant genotype: L –
Recessive genotype: ll
Bent Little Finger
A dominant allele causes the
last joint of the little finger to
dramatically bend inward
toward the 4th finger. Lay
both hands flat on a table
relax your muscles, and note
whether your have a bent or
straight little finger.
Alleles: B, b
Dominant phenotype: bent
little finger
Dominant genotype: B –
Recessive genotype: bb
Tongue
Try to roll your tongue into a tube.
The ability to roll your tongue is the
dominant phenotype. If you cannot
roll your tongue it does not matter
how much you try you will never be
able to do it.
Alleles: T,t
Dominant phenotype: the ability to
roll your tongue
Dominant genotype: T –
Recessive genotype: tl
Monohybrid crosses with
DominanceThe gene for red flowers is dominant over white. A homozygous red flowering plant is
crossed with a homozygous white flowering plant to produce the F1 generation
1. Determine the genotype and phenotype of the F1 generation. Illustrate your
answer in the form of a diagram.
2. If the F1 generation were allowed to self-pollinate, determine the genotypic ration
and phenotypic ratio of the F2 generation.
3. If 200 seeds were produced in the F2 generation, how many would germinate into
plants with red flowers and how many will germinate into plants with white flowers?
Monohybrid Crosses with Dominance
P1 Red flowers x White flowers
RR rr
R R r r
meiosis
gametes
phenotype
genotype
R R
r Rr Rr
r Rr Rr
F1 Genotype Rr
Phenotype All red
P2
meiosis
gametes
Red x Red
Rr Rr
R r R r
phenotype
genotype
R r
R RR Rr
r Rr rr
F1 Genotype RR; 2Rr; rr
Phenotype 3 Red : 1 White
Phenotypic ratio 3 : 1
When a black rabbit is crossed with a white rabbit, all offspring produced are grey.
X
How does this happen?
Monohybrid Cross without
Dominance
(Incomplete Dominance)
Monohybrid Crosses without Dominance
P1 Black x White
BB WW
B B W W
meiosis
gametes
phenotype
genotype
B B
W BW BW
W BW BW
F1 Genotype BW
Phenotype All grey
P2 Grey x Grey
BW BW
B W B W
meiosis
gametes
phenotype
genotype
B W
B BB BW
W BW WW
F2 Genotype BB; 2BW; WW
Phenotype 1 black; 2 grey; 1 white
Family resemblance
What is variation?People are similar, but not identical, to their
parents and siblings. The differences within a
species are called variation.
People inherit characteristics from both parents
and each person gets a different combination of
features. This is called inherited variation.
Variation can come about for two reasons. What
are they?
Other characteristics are affected by a person’s surroundings. This
called environmental variation.
Dihybrid Crosses
A dihybrid cross involves two pairs of contrasting characteristics, e.g. round, yellow seed crossed with wrinkled green seeds.
X
X
Yellow is dominant
Round is dominant
Green is recessive
Wrinkled is recessive
YYRR X yyrr
YR yr
meiosis
gametes
P1 genotype
RY RY RY RY
ry RrYy RrYy RrYy RrYy
ry RrYy RrYy RrYy RrYy
ry RrYy RrYy RrYy RrYy
ry RrYy RrYy RrYy RrYy
F1 genotype RrYy
phenotype all round, yellow seeds
X
YyRr X YyRr
YR
meiosis
gametes
P2 phenotype
genotype
Yellow , round Yellow , round
yR Yr yr YR yR Yr yr
RY Ry rY ry
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
F1 genotype 1RRYY, 2RRYy,
2RrYY, 4RrYy, 2Rryy,
1RRyy, 1rrYY, 2rrYy,
1rryy
phenotype 9 round, yellow
3 round, green
3 wrinkled yellow
1 wrinkled green
SEX DETERMINATION IN HUMANS
XX XY
X X X Y
X Y
X XX XY
X XX XY
2XX and 2XY
50% chance of having a boy or a girl
GENE
MUTATIONS
During DNA replication, the base pairs maybe altered and
the new DNA formed is slightly different from the original.
This may be caused by X-rays, ultra-violet radiation and
certain chemical agents.
Most gene mutations are harmless but some may cause
problems such as sickle-cell anaemia and haemophilia.
Most people with Marfan Syndrome
are taller than normal. Males can
often reach at least 6’5” and most
females are taller than 6 feet.
Individuals with this disorder usually
have abnormally long arms and legs
that are out of proportion to the rest
of their body. They often have long,
thin fingers and toes and very
flexible joints.
Another characteristic of Marfan
Syndrome is a long, narrow face
and a small jaw. The roof of the
mouth may be high and crowded
teeth are common.
Many individuals have hunched
shoulders, a curved spine or
backbone and flat feet. Their
breastbone is often deformed and
either caves in or sticks out.
Stretch marks on the skin and
hernias are also very common and
almost every person with Marfan
Syndrome experiences eye
problems.
Marfan Syndrome
NATURAL SELECTION
Within a population the individuals show considerable
variation due to crossing over and the random
assortment of genes.
The individuals with the variation which makes them
best adapted to the environment will survive and
reproduce. Their offspring will carry the genes for the
favorable characteristics.
The individuals with variations that make them less
adapted to the environment either die or are unable
to reproduce. As they do not produce offspring the
unfavorable genes disappear from the gene pool
PRACTICAL APPLICATIONS
OF GENETICS
29/03/2020
Selective breeding
I raise cows. Each type of cow is good at a certain job. The Friesian cow produces large quantities of milk, the Jersey cow produces very nice milk
and the Hereford cow produces lot of beef.
If, for example, I want lots of milk I would only breed Friesian cows with each other – this is
SELECTIVE BREEDING.
Friesian
Jersey
Hereford
Selective breedingSelective breeding is a process used to produce different breeds of animals or
varieties of plants that have useful characteristics.
Farmers can choose individual cows to
mate in order to produce a generation of
cows that will yield more milk.
Apple growers want to produce a type of apple that is
tasty and resistant to disease.
This can be done by crossing a variety of apple known
for taste with another variety that shows strong
resistance to disease.
BLOOD GROUPS
BLOOD GROUP
(Phenotype)
GENES
(Genotype)
O ii
AB IAIB
A IAIA or IAi
B IBIB or IBi
Two parents, one heterozygous for A blood group and one heterozygous for B
blood group produce children. Determine the possible phenotypes and
genotypes of the children.
P1 A type blood x B type blood
IAi IBi
IA i IB i
meiosis
gametes
phenotype
genotype
IA i
IB IAIB IBi
i IAi ii
F1 Genotype IAIB; IAi; IBi; ii
Phenotype AB; A; B; O
A mother who is heterozygous for blood group A and a father with blood
group O have two children. The children have different blood groups. What
type of blood do they have?
P1 A type blood x O type blood
IAi ii
IA i i i
meiosis
gametes
phenotype
genotype
IA i
i IAi ii
i IAi ii
F1 Genotype IAi; ii
Phenotype A; O
Mrs Steyn and Mrs Stassen both had babies in the same hospital on 24 May
2007. Mrs Steyn’s baby was born at 03:44am and Mrs Stassen’s baby at
0:45am. The tags with the babies’ names were put around their wrists
straight after birth to identify them. Jana was given to Mrs Steyn and Laura
to Mrs Stassen. However, after 3 days the mothers instinctively felt that the
babies had been switched at birth. They insisted on blood tests to determine
whether this had indeed happened. The results of the blood tests were as
follows.
Mr Steyn - A
Mrs Steyn - B
Mr Stassen - A
Mrs Stassen - AB
Jana - A
Laura - O
Use genetic diagrams to determine whether or not a switch took place.
P1 A type blood x B type blood
IAi IBi
IA i IB i
meiosis
gametes
phenotype
genotype
IA i
IB IAIB IBi
i IAi ii
F1 Genotype IAIB; IAi; IBi; ii
Phenotype A; B; AB; O
The Steyns
Mrs Steyn must be IAi and Mr Steyn must be IBi
The Stassens
Mrs Stassen can be AA or AO and Mr Stassen is AB.
Either cross can produce a child with A type blood but Mr and Mrs
Stassen can never have a child with O type blood.
ANSWER
Yes, a swop did take place. The Steyns are the only couple
that are able to have a child with O type blood. This means
that Laura belongs to the Steyn’s and Jana belongs to the
Stassens.
RHESUS FACTOR
RHESUS DISEASE
PRENATAL
DIAGNOSTIC
TESTING
Percutaneous
umbilical
blood sample
Each abnormality can be classified into one of three levels
LEVEL 1
The mutation causes part of a single gene to be altered.
Colour blindness, Sickle cell anaemia, Haemophilia, Albinism,
Cystic fibrosis, Severe combined immunodeficiency
LEVEL 2
An entire chromosome or large portion of it is missing (deletion), doubled
(duplicated), turned around (inverted) or altered in some way where part of
a chromosome may break off and join a non-homologous chromosome.
Klinefelter syndrome, Down’s syndrome, Cri-du-Chat syndrome, Turner
syndrome, Williams syndrome, Huntington’s disease
LEVEL 3
Mutations occur in multiple genes and is often linked to environmental
causes
Alzheimer’s disease, Colon cancer, Breast cancer, Ovarian cancer,
Hypothyroidism
Cystic Fibrosis Severe Combined
Immunodeficiency
CF is a chronic, progressive and genetic (inherited) disease of the body's exocrine (mucus producing) glands CF primarily affects the respiratory, digestive and reproductive systems, as well as the sweat glands. The mucus secreted is very thick and blocks passageways in the lungs and digestive tracts.
SCID is actually a group of inherited disorders that cause severe abnormalities of the immune system. These disorders lead to reduced or malfunctioning T- and B-lymphocytes, the specialized white blood cells made in the bone marrow to fight infection. When the immune system doesn't function properly, it can be difficult or impossible for it to battle viruses, bacteria, and fungi that cause infections.
Cri-du-Chat syndrome
Cri du chat syndrome (French for cry or call of the cat), is a rare genetic disorder due to a missing part of chromosome 5. The condition affects an estimated 1 in 20,000 to 50,000 live births. The syndrome gets its name from the characteristic of the cry of infants born with the disorder. The infant sounds just like a meowing kitten, due to problems with the larynx and nervous system. Other symptoms of cri du chat syndrome may include:
•feeding problems because of difficulty swallowing and sucking, •low birth weight and poor growth, •severe cognitive, speech, and motor delays, •behavioral problems such as hyperactivity, aggression, tantrums, and repetitive movements, •unusual facial features which may change over time. •excessive dribbling. •constipation.
Huntington’s diseaseWilliams syndrome
A rare neurodevelopmental disordercaused by a deletion of about 26 genes from the long arm of chromosome 7. It is characterized by a distinctive, "elfin" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; mental retardation coupled with unusual (for persons who are diagnosed as mentally retarded) language skills; a love for music; and cardiovascular problems .
The most characteristic physical symptoms are jerky,
random, and uncontrollable movements called
chorea. In a few cases, very slow movement and
stiffness (called bradykinesia and dystonia) occur
instead. As the disease progresses, any function that
requires muscle control is affected, causing physical
instability, abnormal facial expression, and difficulties
chewing and swallowing. Eating difficulties
commonly cause weight loss and may lead to
malnutrition.
Select cognitive abilities are impaired progressively.
Psychiatric symptoms vary far more than cognitive
and physical ones, and may include anxiety,
depression, a reduced display of emotions (blunted
affect), egocentrism, aggression, and compulsive
behavior, which can cause, or worsen addictions,
including alcoholism and gambling.
Hypothyroidism
Hypothyroidism is the disease state in humans and in animals caused by insufficient production of thyroid hormone by the thyroid gland. Cretinismis a form of hypothyroidism found in infants.
Primary hypothyroidism occurs when the thyroid gland does not produce enough thyroxin.
Secondary hypothyroidism occurs when the bodies cells are unable to use the thyroxin even though there is enough present.
The reduced ability of people to distinguish between certain colours. It is
a sex-linked inherited disease that affects mostly men.
There are three types of cone cells in the retina. If one or more types of
cone cells becomes faulty then the person becomes colour blind.
inability to see
the color red or
to distinguish
red and bluish-
green (the most
common kind)
inability to see
the color blue
or to
distinguish the
colors blue
and yellow
inability to see
the color green
or to
distinguish
green and
purplish-red
TYPE OF COLOUR BLINDNESS
Colour blindness can show up as :
1. Different shades of red appear dull and indistinct.
2. Shades of green orange, red and brown all appear as the same hue
and may be distinguished only by their intensity.
In one type all
colours
cannot be
distinguished
and vision is
only black and
white.
In another
very rare type,
yellows and
blues cannot
be
distinguished.
P1Normal female (carrier) x Normal male
XBXb XBY
XBXb
XB Y
meiosis
gametes
phenotype
genotype
XB Xb
XB XBXB XBXb
Y XBY XbY
F1 Genotype XBXB; XBXb; XBY; XbY
Phenotype 2 normal females,
1 normal male, 1 colour blind male
There is no particular treatment if it is inherited. If it is caused by
medication then the medication must be stopped immediately. If
there are underlying eye disorders then those must be treated.
SCA is caused by a mutation in a gene on chromosome 11 which causes the abnormal formation of haemoglobin molecules. This results in RBC’s becoming rigid and having a concave shape like a sickle. These cells cannot transport oxygen efficiently, and they tend to get stuck in blood vessels
Symptoms
1. Damage to organs like heart, liver, lungs, kidneys, spleen due to a lack of oxygen.
2. Low RBC count (anaemia)
3. Episodes of pain called ‘crisis’ due to RBC’s becoming stuck in the blood vessels
4. Strokes
5. Delayed growth
6. Jaundice
Diagnosis
Most newborns are screened for the disease with a simple blood test. If not detected at birth a test called haemoglobin electrophoresis is performed.
Treatment
Babies and children are usually given a daily dose of penicillin to prevent infections. Patients are advised to take folic acid to help build RBC’s, to get plenty of rest, avoid strenuous activity and to drink plenty of water. Blood transfusions can be performed and in the most severe cases patients may be treated with a bone marrow transplant
Symptoms
Blood does not clot well. Internal bleeding, especially at the joints occurs.
Diagnosis
Parents can undergo genetic testing to determine if they are carriers.
Treatment
Haemophiliacs are normally given injections of purified clotting agents that have
been extracted from human blood plasma. Dangers involved include HIV and
rejection. Patients were therefore given drugs to suppress the immune system.
These days, however, most of the clotting factors are harvested from genetically
engineered organisms and therefore produce few side-effects.
P1Normal female (carrier) x Normal male
XHXh XHY
XHXh
XH Y
meiosis
gametes
phenotype
genotype
XH Xh
XH XHXH XHXh
Y XHY XhY
F1 Genotype XHXH; XHXh; XHY; XhY
Phenotype 2 normal females,
1 normal male, 1 haemophiliac male
Albinism is characterized by the inability of the patient to produce melanin of the skin, hair and eyes. There are about 10 different kinds of albinism. The most common is oculocutaneous albinism which affects the eyes, skin and hair. It is caused by a mutation on chromosome 15. The type of albinism that affects only the eyes is called ocular albinism. It is caused by a mutation on the X chromosome.
Symptoms
1. The eyes are usually light brown to pale in colour, sensitive to the sun and may display nystagmus (fast, involuntary back and forth movements) or strabismus (squinting). Vision could also be impaired.
2. The skin is very light in colour and is sensitive to sunlight. Freckles or pigmentation patches could develop.
3. Hair ranges in colour from reddish, light brown, yellow to white with eyebrows and eyelashes also being yellow to whitish.
4. Intelligence is within the normal range although infants may seem a little slower in developing because of their visual problems.
Diagnosis
DNA testing and parents can undergo screening before having children.
Treatment
There is no cure. People with the disorder have to learn to manage it. Many people with the disorder are stigmatised by their communities. Greater effort is required to educate the public about this disorder.
Myths
1. It is caused by the food that the mother ate
2. The mother may have laughed at a person with albinism.
3. The mother had a fright or an accident during pregnancy
4. If the mother is a person of colour then she had a sexual encounter with a white person
5. People with albinism have supernatural powers.
6. People with albinism do not die, they disappear.
A genetic disorder that only affects males. They have an extra X chromosome which gives them a total of 47 chromosomes. It is caused by nondisjunction, i.e. a pair of chromosomes fail to separate during meiosis either during the formation of the egg or the sperm.
Symptoms
1. The extra X chromosome mainly affects the testes. This affects the production of testosterone and sperm. At puberty the males normally grow tall and display subtle male characteristics. They usually, however do not develop male secondary sex characteristics.
2. Males develop more breast tissue than normal and have a less muscular body.
Many males have no idea they have the syndrome until puberty or until they try to have children and they are usually sterile as they cannot produce sperm.
Diagnosis
As an adult DNA testing is done. Prenatal testing can also be performed to screen for the abnormality before birth.
Treatment
Hormone replacement therapy which involves testosterone injections.
Phenotype female x male
Genotype XX XY
meiosis
XXX Y
nondisjunction
XXX
Female
Usually self-aborts
XXY
Male with Klinefelter
syndrome
Phenotype female x male
Genotype XX XY
meiosis
XXY
nondisjunction
XXY
Male with Klinefelter
syndrome
GENERAL INFORMATION
Down’s Syndrome is caused by an extra copy of chromosome 21. It is the most common genetic disorder caused by a chromosomal abnormality and it affects as many as 1 out of every 800 babies. It is caused by nondisjunction during the development of the sperm or the egg where a pair of chromosome 21 fail to separate during meiosis.
(Trisomy 21)
General cont…
In very rare cases it is caused by translocation which occurs when one of the arms of chromosome 21 breaks off and then becomes attached to the centromere of another chromosome. This will lead to the person being a carrier of Down’s but will not display the symptoms.
Symptoms
•A flat face
•Upwardly slanting eyes
•A small broad nose
•Abnormally shaped ears
•A large tongue
Increased risk of developing respiratory infections, heart defects, hearing loss, gastrointestinal tract obstructions, leukaemia, eye abnormalities, hypothyroidism and moderate to severe retardation.
Diagnosis
•Ultrasound
•Alpha-Fetoprotein Plus test and the Triple Screen Test
•Amniocentesis, chorionic villus sampling or precutaneous umbilical cord sampling.
•At birth due to the distinctive features.
Treatment
There is no cure and treatment is supportive and palliative.
GENERAL INFORMATION
This disorder can affect as many as 1 in 2000
babies. It is caused by either a missing X
chromosome or an incomplete X chromosome
and people with this syndrome develop as
females.
It is also caused by nondisjunction where a pair
of sex chromosomes fails to separate during
meiosis.
XX
XXXX -- --
FEMALE
X
+
This child will have 45 chromosomes and
cannot survive
-Y
X
X-
This child will have 45 chromosomes and can
survive
+
General cont…
The syndrome is not an inherited disorder, since women with this disorder are usually sterile.
Symptoms
It affects both growth and sexual development. One of the missing genes on the X
chromosome is responsible for long bone growth so girls who have this disorder are short.
Other missing genes regulate ovarian development and so the ovaries, eggs and sex
hormones cannot develop properly. Girls may be:
1. Short and stocky.
2. They may not start puberty when they should.
3. Have a short webbed neck.
4. Have a receding lower jaw.
5. Their arms may turn out slightly at the elbows
6. Have a low hairline at the back of the neck.
Other symptoms may include lymphedema, heart and kidney defects, high blood pressure and
infertility.
Diagnosis
Diagnosis is made using physical symptoms after the baby is born. Many patients are only
diagnosed in adolescence when they fail to go through puberty. Diagnosis can be
confirmed with a blood sample. Diagnosis can be done before birth but only if the doctor
suspects a problem.
Treatment
Hormone replacement therapy and growth hormone. Low doses of androgens are also given to
promote growth in height and to encourage the normal development of muscles and hair.
20 year old girl who I believe has Turner
syndrome (next to an American medical student who volunteered to help with our mission)
Alzheimer’s causes dementia and affects
those parts of the brain that deal with memory,
thought and language.
The most common form is linked to a gene
known as the apoE gene on chromosome 19.
This form of the disease occurs after the age
of 65
Rarer forms of this disease strike much earlier
in life and are caused by mutations on
chromosome 1, 14 and 21. Scientists don’t
know how this disorder develops but it may be
caused by a combination of genes and
environmental factors.
The forms of Alzheimer’s that strike early in life
are inherited in an autosomal dominant
pattern. This means that the presence of a
single defective gene results in the individual
developing Alzheirmer’s
Symptoms
Patients slowly lose their ability to think clearly. At first they forget names, where they put their
belongings or they may even start to forget words. As the disorder worsens they may forget
how to do simple things like combing their hair. Some patients also feel sad and/or nervous
Treatment
There is no cure for Alzheimer’s. Doctors prescribe medication to treat the symptoms. Patients
often need a caregiver to help them around and to do the things that they are unable to.
Descent Into Alzheimer’s
29/03/2020
Cloning1) Cloning plants:
2) Cloning sheep:
Cloning, however, is not new. Many organisms in
nature reproduce themselves, i.e. asexual
reproduction.
Farmers have also used it for thousands of years to
clone plants, i.e. vegetative reproduction.
During their experimenting with growing different
plants, farmers devised breeding techniques to
reproduce plants that would yield larger fruit or seeds
etc. This was the beginning of selective breeding.
29/03/2020
Selective breeding
I raise cows. Each type of cow is good at a certain job. The Friesian cow produces large quantities of milk, the Jersey cow produces very nice milk
and the Hereford cow produces lot of beef.
If, for example, I want lots of milk I would only breed Friesian cows with each other – this is
SELECTIVE BREEDING.
Friesian
Jersey
Hereford
Eventually scientists combined selective breeding techniques with cloning to produce many plants with desired traits. This later led to genetic engineering in which they manipulate DNA to create a plant with the exact desired traits very quickly and very accurately, e.g. GM foods
Advantages of GM Foods
1. Pest resistant
2. Herbicide tolerant
3. Disease resistance
4. Cold tolerant
5. Drought tolerant/salinity tolerant
6. Enhanced nutrition
7. Production of pharmaceuticals
Other Uses of Genetic Engineering
Controversies
1. ManyGenetically engineered plants to clean up heavy metal pollution from the environment.
2. Producing bacteria to consume pollutants.
3. Genetic modification of animals to give them new characteristics. They can then be used to produce commercial products, eg insulin for diabetics or clotting agent for hemophiliacs
4. people are opposed to the cloning of animals despite scientists arguing that this could lead to great advancements in medicine, the saving of endangered species or the resurrection of extinct species.
5. The fear that transgenic organisms could develop new diseases that could cause widespread epidemics.
6. Premature aging in cloned animals.
Stem Cell Cloning
When an embryo reaches the blastocyst stage the embryo contains cells that can differentiate into any type of cell, i.e. embryonic stem cells.
These stem cells can become any cell in the body but they lose this ability as they age. Adult stem cells from bone marrow seem to be the only stem cells that retain this ability.
SOURCE OF STEM CELLS
• Blood from the umbilical cord of a newborn.
• From embryos in a laboratory.
Pedigrees and Genetic Counselling
A pedigree is a diagram that represents the interrelationships of a family across the generations. A genetic counselor will draw up a pedigree to illustrate how a genetic disorder is inherited within a family. They will then use this pedigree to counsell a coupe about having children.
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