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21 CENTURY…read more

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B1 ­ You and Your Genes.
NUCLEUS ­ Contains Genetic Material
GENE ­ A short length of DNA.
Can exist in different versions
each giving a different
characteristic. ALLELE ­ A
different version of the same
gene e.g Blue and Brown alleles
for the eye-colour gene.
DNA ­ Deoxyrybo Nucleic
Acid. A nucleic acid which
contains the genetic
information of a cell and is
CHROMOSOME ­ Long made up of BASE PAIRS e.g
molecule of DNA that is coiled up G=G and B=A…read more

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- A gene is an instruction/code for making a certain protein
-Having different versions of proteins means we end up with different characteristics
TWO TYPES OF PROTEINS: -STRUCTURAL e.g: skin, hair, blood and
-FUNCTIONAL e.g Enzymes such as amylase and protease
GENOTYPE ­ The genes an organism has.
PHENOTYPE ­ The characteristic/feature displayed by the organism
Some features are controlled by genes only ­ Eye colour. Some features are controlled
by environmental factors only ­ Scars. Some features are controlled by both ­ weight.
DOMINANT and RECESSIVE ALLELES: -DOMINANT: This means that the allele will always
show its feature and only one allele in a pair is needed to produce the feature
-RECESSIVE: The allele will not show its feature when paired with a dominant allele and
therefore requires two of the same alleles in a pair to produce its feature.
HOMOZYGOUS: When two alleles in a pair are HETEROZYGOUS: When two alleles in a
the same. E.g BB or bb pair are different. E.g Bb
Body cells have 23 pairs of chromosomes. The Sex Determining Chromosome is
Sex cells (gametes) only have 23 the Y chromosome ­ it leads to the
chromosomes so they join together to production of ANDROGENS which
make 23 pairs. causes male sex organs to produce…read more

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-Genetic Disorders are caused by faulty alleles
CYSTIC FIBROSIS: Caused by a defective recessive allele, it is a genetic disorder of the cell
SYMPTOMS: - Thick sticky mucus in air passages, gut and pancreas.
-Breathing Difficulties
-Chest Infections
-Difficulty in the digestion of food (causes sufferers to be skinny)
The cystic fibrosis allele is recessive and therefore parents can be symptomless
carriers meaning that their healthy allele over-rides the recessive faulty alleles
but they still have the potential to have a child with cystic fibrosis if BOTH
parents are carriers.
HUNTINGTON's DISORDER: Caused by a single defective dominant allele. There is
currently no cure for the disorder and symptoms appear around the age of 40.
SYMPTOMS: -Tremors (shaking) Since the Huntington's Disorder Allele is
-Clumsiness dominant this means that only one allele is
-Memory Loss required in the parent to produce a 50% chance
-Mood changes of having the disease. All carrier parents are also
-Poor concentration. sufferers.…read more

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When embyros are produced using IVF, they can be tested to determine if they are carrying
any genetic disorders- This is called Pre-implantation Genetic Diagnosis...
...however, only healthy embryos are implanted in the mother's womb and all other
embryos with genetic disorders are discarded and destroyed.
Also, doctors can test fetus's by taking out the fluid around the fetus and testing it.
-Results are NOT 100% accurate due to contamination of samples or misinterpretation of the
results: FALSE POSITIVE: A healthy person is told that he/she has the genetic disorder
FALSE NEGATIVE: A person affected with a genetic disorder is told that he/she is healthy.
-Genetic tests carried out during pregnancy are NOT 100% safe and there is a small chance
(0.5-1%) of a miscarriage occuring. Also, there is a small risk of infection.
-Some people argue that it is NOT right to terminate a pregnancy . Despite the fact that
parents may have a harder time taking care of a sick child, people believe that all embryos have
an equal right to life.
-There is a potential that discrimination may occur if results from tests were to become
available to the public. For example, an employer may refuse an applicant who is more likely
to become ill. Some people argue that employers could use the results in order to ensure that
their employees are not exposed to anything dangerous to them…read more

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DEFINITION: Organisms that are genetically identical to each other
ASEXUAL REPRODUCTION: When there is only one parent and all offspring are gentically
identical to the parent. (Bacteria, some plants and a few animals)
Most bacteria can reproduce ASEXUALLY by simply dividing by two.
Plants can reproduce ASEXUALLY by producing runners that move out from the base of the
plant and form new clones
IDENTICAL TWINS: Identical twins are created when the cells of an
embryo split to create two separate and genetically identical
embryos. Twins are a form of NATURAL CLONES
Egg Cell
Body cell from donor
Nucleus is
Uses this technique in
Nucleus is order to produce
removed embryonic stem cells that
are identical to the
New cell is genetically patient for treating a
identical to donor and is variety of diseases and
stimulated to divide disorders.…read more

Slide 7

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