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Genes are small sections of DNA that are in every single cell
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They tell the cells what to do and when, how to make
your bones, muscles, skin and everything else
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The enzyme then makes a single-stranded molecule of RNA, using the DNA as a
template and then the RNA create the proteins
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Everyone’s DNA is different except for identical twins
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The gene in the
DNA specifies which order the amino acid must be joined together
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These are long strands of molecules
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This occurs
when the chromosomes make identical copies of them and line up along the centre of the cell
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TAQ 2
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He studied
plants in his garden, making notes on how characteristics in plants were passed on from one
generation to the next
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From this he had shown that hereditary units determined characteristics in plants,
they are passed on from each parent and they can be either dominant or recessive
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From this came three rules
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Segregation:
In diploid organisms, chromosome pairs (and their alleles) are separated into individual gametes
(eggs or sperm) to transmit genetic information to offspring
2
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A dominant allele
produces the same phenotype in heterozygote’s and in homozygote’s
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Independent assortment: Alleles on different chromosomes are distributed rand
omly to individual gametes
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RULES OF INHERITENCE
TAQ 3
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EXPLAIN HOW SEX OR GENDER IS DETERMINED
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Gender is determined by the sperm that
fertilises the egg cell
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XX is female and YY is male
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Therefore if the sperm that
carries a X chromosome fertilises the egg first then the baby will be a girl
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This is because the Y chromosome carries a
gene called sex determining region Y or SRY for short
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These produce androgens which are male sex hormones
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3
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ehow
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htm

TAQ 4
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Continuous variation is where there can be a range of values
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http://www
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co
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A mutation occurs when an organism is born with a difference characteristic
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Mutations occur naturally, it can be caused by the Sun, or simply
when the DNA doesn’t copy itself properly
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Certain chemicals can also cause mutations, such as cancer
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The mutations can produce new
Alleles which will not function correctly
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CHD7
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1
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In mammals they arise by several different mechanisms
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
The fusion of two different zygotes, or early embryos, into one
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The tetra parental mouse is a chimera formed this way
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
The sharing of blood supplies by separate embryos
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Blood stem cells of each twin seed the bone marrow of the
other
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
During early development, errors during mitosis can produce stem cells that go on to
populate a tissue or organ with, for example, a chromosomal aberration (e
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, aneuploid)
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This can produce a
leukemia-like illness that, fortunately, often disappears as that cell population declines
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[Discussion]
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Anyone unlucky enough to have a cancer is a genetic mosaic because all cancers are
made up of the descendants of cells carrying a suite of mutations not found in normal
cells
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Early results indicate than even normal cells in an adult have Accumulated a suite
of somatic mutations that differs from cell to cell
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http://www
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nih
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htm

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medicinenet
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asp?articlekey=4992
TAQ 6
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WHAT DOES PROTIEN SYNTHESIS MEAN AND WHERE DOES IT TAKE PLACE?
http://www
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co
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TWO MAIN STAGES OF PROTIEN SYNTHESIS
http://www
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org/NR/rdonlyres/2CD13D36-0C47-4017-A0EDD0287F090708/59183/PROTEINSYNTHESIS1

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