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Biology 1 ocr 21st century

Genes, Chromosomes and DNA
1. 1. Most cells have a nucleus containing your genetic material
2. 2. Genetic material in the nucleus is arranged into chromosomes of which there are 23 pairs
3. 3. Each chromosome is one long molecule of DNA that is coiled up
4. 4. A gene is a short length of a chromosome
5. 5. Genes control he development of different characteristics
6. 6. Genes exist in different versions called alleles
7. Genotype- the genes an organism has
Genes and Variation
1. Sperm and egg cells have half the normal amount of DNA
2. Children resemble both parents but are identical to neither
3. Genes are shuffled together randomly to make eggs and sperm
4. Half chromosomes are from each parent
Inheritance and Genetic Diagrams
1. Combination of alleles controls phenotype
2. Homozygous- two same alleles of a gene
3. Heterozygous- two different alleles of a gene
4. Alleles can be dominant or recessive
Sex Chromasomes
1. Control whether you are male or female
2. Men have XY
3. Women have XX
4. Determined by one gene
5. Control which hormones and sex organs are produced
6. Y causes protein to be formed- not formed in women
Genetic Disorders
1. Caused by faulty alleles
2. One or both parents carry a faulty allele
3. Huntingtons
  1. Dominant allele
  2. Tremors
  3. Clumsiness
  4. Memory loss
  5. Mood changes
  6. Poor concentration
  7. Symptoms appear after 40
4. Cystic fibrosis
  1. Thick sticky mucus
  2. Breathing difficulty
  3. Chest infections (painful coughing)
  4. Difficulty digesting food
  5. Recessive allele
Genetic Testing
1. Used on embryos children and adults
2. Embryos
  1. Produced in IVF- check for genetic disorders (pre-implantation genetic testing)
  2. Not 100% safe
    1. Miscarriage
  3. Cause people to terminate?
3. Children and adults
  1. Checked if they carry alleles for genetic disorders so they can see if their child would inherit a disorder
  2. Tested before drugs are prescribed to see how it will affect an individual
  3. If one member of the family is tested should others?
4. False positive / false negative
5. If results become available there could be discrimination
  1. Harder to get a job
  2. More expensive insurance
Clones
1. Genetically identical organisms
2. Nature makes clones
  1. Asexual reproduction
    1. Bacteria- divide in two
    2. Plants
      1. Strawberry plants grow new runners
      2. Garlic grow underground fleshy structures (bulbs)
  2. Embryo cells split
    1. Identical twins
      1. Single egg fertilized by a single sperm
        Embryo splits in 2
3. Clone in a lab
  1. 1. Nucleus is removed from an egg cell leaving an egg
    1. 2. nucleus from adult donor inserted in its place
      1. 3. Cell stimulated and divides as normal
Stem Cells
1. Most cells in the body are specialised
2. Embryonic stem cells
  1. Unspecialised and found in early embryos
  2. Removed from the embryo then the embryo is destroyed
  3. Potential to turn into ANY cell
3. Adult Stem Cells
  1. Unspecialised
  2. Involved in maintaining and repairing old and damages tissues
  3. Can specialise into MANY (not all) cell types
  4. Safely removed via bone marrow
4. Uses
  1. Cure Sickle cell anaemia- bone marrow transplants
  2. Replace faulty cells in the sick

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Biology 1 ocr 21st century

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