B1- You and Your Genes

Genes, Chromosomes and DNA
1. Most cells have a nucleus- contains genetic material.
2. Genetic material arranged into chromosomes- 23 pairs.
3. Chromosome- one long molecule of DNA coiled up.
4. Gene- short length of chromosome.
  1. Control development of different characteristics.
5. Genes are instructions for cells.
  1. Gene is code for making certain proteins.
    1. Different versions of proteins gives us different characteristics.
6. Proteins can be structural or functional.
  1. Structural protein- part of things like skin, hair, blood and the cytoplasm in cells.
  2. Functional protein- e.g. enzymes help digestion by breaking down food.
7. Organisms genotype is all genes it has.
8. The characteristics of an organism are the phenotype.
  1. Can be caused by one gene e.g. dimples or several genes working together e.g. eye colour.
  2. Others are due to environmental factors e.g. scars.
Genes and Variation
1. Sperm and egg cells have half the normal amount of DNA.
  1. Contain 23 chromosomes so when sperm fertilises egg have 46.
2. Children resemble both parents but are not identical to either.
  1. Have own set of alleles making each individual unique.
3. Egg and Sperm cells are never identical to others as the alleles are randomly put together.
  1. 8 million combination's each one could be.
  2. Unless identical twins can never be the same.
Inheritance
1. Combination of alleles determines the phenotype.
2. Even though we have 2 copies of a gene usually only one can be expressed in the phenotype.
3. Homozygous- two alleles the same from a gene
4. Heterozygous- two different alleles of the same gene.
5. Alleles can be dominant or recessive.
  1. Dominant- If a characteristic is caused by a dominant allele you will need two dominant alleles or one dominant and one recessive for the characteristic to be shown.
  2. Recessive- both alleles have to be recessive for the characteristic to show.
Sex Chromosomes.
1. You're chromosomes control whether you're male or female.
  1. Determined by 1 gene.
2. There are 23 pairs of chromosomes in every human cell.
  1. The final pair are labelled XY
    1. Sex cells- determine gender.
3. All men have an X and Y chromosome.
  1. Y causes male characteristics.
4. All females have 2 X chromosomes.
  1. Lack of Y chromosome causes female characteristics.
Genetic disorders
1. Caused by Faulty Alleles.
2. Some disorders are inherited.
  1. One or both parents carry a faulty allele and pass it on.
  2. Cystic fibrosis and Huntington's disease are caused by a faulty allele of a single gene.
3. Some are caused by a recessive allele.
  1. Most defective alleles are responsible for genetic disorders are recessive.
    1. Cystic fibrosis is a genetic disorder of the cell membrane caused by a faulty recessive allele.
4. Others caused by Dominant alleles.
  1. Huntington's disease is caused by a dominant allele.
Genetic testing
1. Can be used on embryos, children and adults.
2. Embryos can be produced by IVF and tested for diseases before implanted.
  1. Known as pre-implantation genetic diagnosis.
    1. Only healthy embryos are implanted into womb.
      1. Others just discarded.
3. Children and adults can be checked.
  1. See if carry alleles for specific genetic disorders,
    1. Also can be used to see how different prescription drugs can effect them e.g. effective treatment, adverse effect.
4. Lots of issues.
  1. May not be 100% accurate.
    1. Contaminated or misinterpreted results
  2. Doing genetic tests on the fluid around fetus can cause miscarriage- 0.5-1% of cases.
  3. If your positive should the rest of family be tested- fair on future children.
  4. Should people with genetic disorders be allowed to have children in the future.
  5. If test on embryo is positive is it right to terminate.
    1. Is it the child's right to live a healthy life or to live at all.
    2. Can parents cope.
    3. Abortion is wrong.
  6. Discrimination.
    1. Harder to get a job.
  7. Insurance companies refuse life insurance for wrong alleles.
Clones
1. Genetically identical organisms.
2. Can be made...
  1. Asexually
    1. Only have one parent so genetically identical to them.
    2. Most bacteria reproduce like this- can multiply very quickly.
    3. Plants reproduce asexually as well.
      1. Some animals do e.g. greenfly.
  2. When embryos split.
    1. Identical twins are clones.
  3. Animal clones can be made in a lab.
    1. Nucleus of an egg cell is removed
      1. Nucleus from adult donor cell is inserted.
        Cell then stimulated so starts dividing like normal embryo.
        Embryo produced genetically genetically to donor cell.
Stem cells
1. Can become other types of cells.
  1. Unspecialised cells
2. Two main types
  1. Embryonic
    1. Unspecialised- found in early embryos.
    2. Stem cells removed from embryo- embryo destroyed.
    3. Exciting for doctors and medical researchers- potential to turn into any type of cell.
    4. All different types of cell found in an organism have to come from those few cells in the early embryo.
  2. Adult
    1. Unspecialised- found in adult animals.
    2. Involved in maintaining and rearing old and damaged tissue and can specialise into many (not all) different cells.
    3. Stem cells can be safely removed from adult patients- extract from bone marrow- no embryos have to be destroyed.
3. Treat many illnesses.
  1. Replace faulty cells.
  2. Turn into new blood cells to replace faulty ones instead of bone marrow transplants.

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B1- You and Your Genes

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	Created by Charlotte johnson almost 11 years ago