You and Your Genes

Reproduction and Stem Cells
Genetic Diseases
Genetic Testing
Genetic Information
Genetic Information
1. DNA
  1. The instructions for a cell are within a gene
  2. CHROMOSOMES
    1. These occur in very long DNA molecules called chromosomes
    2. Chromosomes are made of DNA molecules
      1. Each DNA molecule consists of two strands, which form a double helix structure
  3. GENES
    1. Sections of DNA describe how to make proteins
2. VARIATION
  1. Genetic - dimples or not
  2. Environmental - cutting skin may cause a scar
3. ALLELES
  1. Can be either dominant or recessive
    1. TT - Homozygous dominant tt - Homozygous recessive Tt-heterozygous
4. SEX CELLS
  1. Eggs produced in ovaries, Sperm produced in Testes
    1. Each has 23 single chromosomes which will pair up with eachother and fuse together during fertilisation
  2. The pairing of chromosomes is random
    1. This means that the offspring will differ from the parents
      1. The child will share similarites depends on which came from the father or mother, and which ones are dominant or recessive
  3. SEX DETERMINATION
    1. XX = female
      1. XY = male
5. GENETIC DIAGRAMS
  1. Punnet Square
  2. Family Trees
Genetic Testing
1. WHAT IS IT
  1. Can test adults, children and embryos for a faulty allele if there is family history of a genetic disorder
    1. Can also test to see if you can be prescribed a drug without suffering from serious side effects
  2. Embryos can be tested for embryo selection
    1. Healthy ones can be implanted as normal (IVF - In vitro fertilisation )
2. AMNIOCENTESIS TESTING
  1. RISKS
    1. 0.5% (1 in 200) chance of the test causing a miscarraige
    2. Small chance of infection
  2. WHAT IS IT
    1. Carried out 14-16 weeks into pregnancy
      1. Needle inserted into uternus and a small sample of amniotic fluid is extracted
    2. POSITIVE RESULTS
      1. Can be terminated between 16-18 weeks
3. CHORIONIC VILLUS TESTING
  1. WHAT IS IT
    1. Carried out 8-10 weeks into pregnancy
      1. Special catheter inserted into vagina and cervix until it reaches the placenta
        Part of placenta has finger-like protusions called chorionic villi. Samples are removed for testing
    2. POSITIVE RESULTS
      1. If there is a faulty allele the pregnancy can be terminated.
        Can be terminated much earlier at (10 - 12 weeks into pregnancy)
  2. RISKS
    1. Chance of miscarriage at 2% (1 in 50)
    2. Small chance of infection
4. RELIABILITY
  1. True Positive
    1. Test Result: Subject has disorder Reality: Subject has disorder
  2. False Positive
    1. Test Result: Subject has disorder Reality: Subject does not have the disorder
    2. Healthy embryo would be terminated
  3. True Negative
    1. Test Result: Subject does not have the disorder Reality: Subject does not have the disorder
  4. False Negative
    1. Test Result: Subject does not have the disorder Reality: Subject has the disorder
    2. Birth of child with the disorder
  5. If subject was a parent, they may decide not to have children if the result was a false positive
5. ETHICAL CONSIDERATIONS
  1. Should child be terminated?
  2. Tell child of possible Huntington's?
  3. Death of healthy embryos?
Reproduction and Stem Cells
1. ASEXUAL REPRODUCTION
  1. CLONES
  2. When a cell grows and divides into two
2. STEM CELLS
  1. EMBRYONIC
    1. WHAT ARE THEY
      1. Embryonic stem cells are unspecialised that can develop into any type of cell, including more embryonic cells
    2. Both can be used to treat some illnesses or injuries
      1. E.g. Skin can be grown as a treatment for serious burns and sight can now be restored to people who are blind due to damage of their corneas
    3. After the 16 cell stage, they start to become specialised, with some genes switched off and some on
      1. This leads to the production of proteins.
      2. If specialised divide, it can only make the same type of cell
  2. ADULT
    1. WHAT ARE THEY
      1. Adult stem cells are unspecialised cells that can develop into many, but not all, types of cell
3. IDENTICAL TWINS
  1. CLONES
    1. Two organisms with the same genetic information
    2. Artificial clones - taking nucleus from adult body cell and transferring it into an empty, unfertilised egg (Dolly the Sheep)
  2. The developing embryo split into two
Genetic Diseases
1. HUNTINGTONS DISEASE
  1. DISEASE AND CAUSE
    1. Huntington's is a genetic disorder that affects the centrel nervous system. It is caused by a faulty dominant allele on chromosome 4
  2. SYMPTOMS
    1. Late onset, a tremor, clumsiness, ,memory loss, an inability to concentrate and mood changes
2. CYSTIC FIBROSIS
  1. DISEASE AND CAUSE
    1. It affects the cell membranes, causing a thick mucus to be produced in the lungs, gut and pancreas
    2. Caused by a recessive allele (can be a carrier)
  2. SYMPTOMS
    1. Difficulty breathing, chest infections, difficulty digesting food

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	Created by chlamber over 10 years ago