B1 - You and Your Genes

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Sexual Reproduction

Most Animals produce using Sexual Reprodiction. The offspring has two parents but they are not cloned.

In Sexual Reproduction sex cells are roduced. They make copies from the parent chromosomes. The fertilized egg cell has the correct number of chromosomes 23 pairs.

One chromosome came from each pair of egg cells and the other came from the sperm cell. (23 from X) (23 from Y) = 46 in Total

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Male or Female?

There are 23 pairs of chromosomes and 46 in Total

In the sex cells known as Gametes the eggs and sperm contain 23 each

One pair of chromosomes are called the sex cells

A male has XY and Female has ** Chromosomes

Everything to do with the gender of a human is on the Chromosomes

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A Karyotype is the set of chromosomes in every body cell

The difference between the male and female Karyotype is that there are no difference except the last which is ** or XY

The Karyotype is just a map of chromosomes set out in their pairs of 23

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How do genes from our natural parents work?

Every pair of chromosomes have a gene called and allele which is a gene from the mother and one from the father.

There are two different types of genes known as recessive and dominant.

Dominant - The gene which shows on the child

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Huntingtons Condition

Unable to stand up

Restless Legs

Loss of Memory

Wont sit in a chair for long periods of time

Confused about simple things

Prone to accidents

Required to take tablets to control movement

Dominant Gene causes Huntingtons

Tests are taken to see if someone has this condition

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Cystic Fibrosis

Lungs - Become unable to produce mucas (build up of fluid)

Drowning and unable to cough up naturally so they require someone to give back massages to release the mucas

£1.50 for every person to have a test to see if they have this condition

Normally dies at a young age if they have this condition

Able to have a transplant to reduce the risks

A blood test at birth costs only 10p

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Testing the Genes from Embryo's (Amniocentisis Tes

How it works

A needle with a syringe which includes Amniotic Fluid is placed into a the Females skin and placed near the baby to gather up cells and check the chromosomes


Less chance of a misscarriage 0.5%

Recieve results at 15-18 weeks


Small risk of infection

Not 100% reliable

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Testing the Genes from Embryo's (Chronicvillus Tes

How it works

A tube is placed in the womans cervix to gather up cells which are then taken for tests


Recieve results are quicker 10-12 weeks

No risk of infection


not 100% Reliable

Higher chance of a misscarriage 2%

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Key Words

Phenotype - Word that refers to the features that you actually see in an organism

Genotype - Refers to the actual genes that someone has eg. HH,Hh,hh

Homozygous - This is when the genotype has two of the same genes, either two dominant or two recessive eg. HH or hh both Homozygous

Heterozygous - This is when the genotype has one dominant and one recessive eg Hh

Genetic Factors - Dimples, Eye colour

Environmental Factors - Scars, Hair Style

Adult Stem Cells - Taken from areas that are adapted for the replacement and repair of tissues eg Umbilical Chord and Bone Marrow

Embryonic Stem Cells - Taken from a developing embryo to help clone other embryo's and they also have the potential to develop into any kind of specialised cell

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How are Embryo's Selected?

The women takes a fertility drug so she releases several ova's. then the ferlitity drug becomes a hormone.

The doctor collects the ova and a small operation begins where a large needle is injected into the womb.

The males sperm fertilizes the ova in a dish known as a petri dish. this is known as in vitro fertalization

The embryo reaches the 8 cell stage. One cell then gets removed from each of them.

The cells are then tested for Huntington's condition. This stage is called pre-implantation genetic diagnosis

Only Embryo's without the huntingtons allele are implanted into the womens uterus.

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Asexual Reproduction

Bacteria and other single cell organisms can reproduce by dividing to form two "new" clones (genetically identical to the parent)

This is called Asexual Reproduction. Most plants and some animals produce this way.

Variation in organisms that produce Asexually is normally caused by the environmental factors

Animal Clones occur naturally:

The cells of an embryo sometimes separate

The two new embryo's develop into identical twins

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