B1 - You And Your Genes

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  • B1 - You And Your Genes
    • 1. Genes, Chromosomes and DNA
      • A nucleus contains your genetic material
      • The genetic material is arranged into chromosomes
      • There are 23 pairs of chromosomes in a human cell
      • 1 chromosome is 1 very long molecule of DNA that's coiled up
      • A gene is a short length of a chromosome
      • Genes control the development of characteristics
      • Different versions of the same gene is called an allele
      • Genes hold the code to make 2 types of proteins;
        • Structural; They're part of things like skin, hair, blood and the cytoplasm
        • Functional; These proteins speed up chemicals. So an enzyme is an example of one.
      • An organisms genotype is all of the genes that it has
      • Eye colour is determined by several genes working together
      • Scars are caused by environmental factors
    • 2. Genes And Variation
      • Sex cells contain just 23 chromosomes
      • When the sperm fertilises the egg, the fertilised egg has 23 pairs of chromosomes
      • The 2 chromosomes in the pair carry the same genes. And the same gene is found in the same place
      • Half of a child's chromosomes are from each parent
      • Siblings look similar but not identical because they have different pair of allele. Some of these alleles they will share.
    • 3. Inheritance and Genetic Diagrams
      • The combination of alleles determine the phenotype
      • Homozygous means that you have 2 alleles the same for that particular gene
      • Heterozygous is when you have 2 different alleles for that particular genes
      • An allele can either be dominant or recessive
      • Family trees is a good way to show how inheritance works
    • 4. Genetic Diagrams and Sex Chromosomes
      • Punnett squares are a good way to work out a genetic cross
      • The 23rd pair of chromosomes determine your sex
      • XY means that you would be male
      • XX means that you would be female
      • The Y chromosome causes a specific protein to be produced. It causes the development of the testes
      • If the male protein is not made, the embryo will develop ovaries
    • 5. Genetic Disorders
      • Caused by faulty alleles
      • Cystic fibrosis is caused by having 2 recessive alleles for the gene
      • Huntington's disease is caused by a dominant allele
      • Symptom of cystic fibrosis include;
        • Thick Sticky Mucus in the air passages, gut and pancreas
        • Breathing difficulty
        • Chest infections
        • Difficulty in digesting food
      • Symptoms of Huntington's disease include;
        • Tremors
        • Clumsiness
        • Memory loss
        • Mood Changes
        • Poor Concentration
    • 6. Genetic Testing
      • PGD is used if the parents are concerned about passing on a genetic disorder
      • Children and adults can be tested before drugs are given to them. This is to see how they might react.
      • There are many issues
        • The results may not be 100% accurate
        • People could get a false positive/negatie result
        • The procedure may not be 100% safe
        • Can be used on Embryos, Children and Adults
        • Risk of a miscarriage
        • Should the pregnancy be terminated?
        • Should other family members be informed
    • 7. Clones
      • Clones are genetically identical organisms
      • There are 2 ways of naturally making clones;
        • Asexual reproduction
        • Embryo splitting
      • Scientists can now make animals in labs
        • 1. The nucleus of an egg cell is removed
        • 2. A nucleus from an adult donor is inserted in its place
        • 3. There is now a fertilised egg
        • 4. The embryo produced is genetically identical to the donor
    • 8. Stem cells
      • They can become other cells
      • Most cells become specialised in early development
      • Stem cells are unspecialised, so they can be given instructions to develop
      • Embryonic stem cells
        • Removed from an early embryo
      • Adult Stem Cells
        • Invoved in maintaining and repairing old tissue
        • Can be taken safely
      • They are able to treat many illnesses

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