B6

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  • Genetics
    • DNA
      • cell - nucleus-chromosome =inherited features
      • chromosomes are made up of deoxyribonucl-eic acid (DNA)
      • double helix structure
      • DNA carries instructions to make the proteins which form most of your cell structures. These cells make up specialised cells which form tissues, organs and organ systems
        • they also carry the instructions to make enzymes
      • The genetic code
        • DNA is made up of 4 different chemical bases
          • these bases are grouped in 3s. Each group of 3 codes for a different amino acid
            • The order of these bases controls the order in which the amino acids are put together so that they make aa particular protein.
              • Each gene codes for a particular combination of amino acids, which makes a specific protein.
        • ATGC
        • A change or mutation in a single group of bases can be enough to change or disrupt the whole protein structure and the way it works.
    • DNA fingerprinting
      • DNA is unique to you, you have your own unique pattern
        • only identical twins have the same DNA
        • The unique pattern in your DNA can be used to identify you. DNA fingerprinting can be used
          • this can be produced from tiny samples of DNA  - blood, saliva etc
        • patterns are more similar between relatives
    • Mendel
      • used peas for experiments because....
        • wide range of varieties available
        • for each trait chosen, differences are sharply defined, with no immediate form
        • fertilisation is easily controlled: a pea plant will fertilise itself or can be cross fertilised
        • Peas are easy to cultivate
        • peas grow and flower, and seed can be collected for sowing he following growing season
      • B. 1822       Austria            poor monk (monk for education (he's clever))
      • never seen chromosomes or heard of genes - ahead of his time. people didn't know about them so didn't understand his theories. he died believing them. he also published is findings in 1866
      • he found that characteristics were inherited in clear and predictable patterns
        • he suggested that there were separate units of inherited material
        • he realised that some characteristics were dominant over others
    • 1900
      • chromosomes seen through a microscope
      • other scientists repeated his experiments
      • credited mendel for what they observed
    • inheritance in action
      • humans have 23 pairs of chromosomes
        • all pairs are made up of similar chromosomes except sex chromosomes
      • ALLELES = different forms of the same gene. Each allele will result in a different protein.
        • DOMINANT = alleles which control the development of a characteristic, even when only present on one chromosome. (CAPITAL LETTER)
        • RECESSIVE = alleles which only control the development of a characteristic when they are present on both chromosomes. no dominant allele is present.    (lowercase)
          • DOMINANT = alleles which control the development of a characteristic, even when only present on one chromosome. (CAPITAL LETTER)
        • most characteristic are controlled by a no. of genes. some are controlled by 1 single gene e.g. dimples
      • ** = female
      • XY = male
      • Family trees = show males and females and can be used for tracing family likeness or tracking inherited diseases, showing a physical characteristic or allele.
    • inherited conditions
      • a disease caused by a problem in your genes  - genetic or inherited disorders
      • polydactyly
        • extra fingers / toes
        • caused by dominant allele
        • some have the extra digit removed
        • if 1 parent has the condition you have a 50% chance of inheriting it. half of their gametes will contain the faulty allele. if they are homozygous, you will definitely have the condition
        • it can be inherited form 1 parent with the condition
      • cystic fibrosis
        • affects lungs and pancreas
          • organs become clogged with sticky thick mucus - stops then working properley
            • the reproductive system is also affected so many people w/ this condition are in fertile
        • treatment: physiotherapy and antibiotics
          • help to keep lungs clear of mucus and infections.
          • enzymes are also used to replace the ones the pancreas cannot produce and to thin the mucus
          • no cure
        • caused by a recessive allele
          • must be inherited from both parents. they can be carriers
        • usually born to people who do not suffer from the condition. the parents usually have a dominant, healthy allele which means there body works normally. they also carry the recessive allele but it gives no symptoms = carriers
      • colour blindness
        • red-green colour blindness = common = confuses red + green
          • a single gene determines whether a person has normal colour vision or is red-green colour blind.
            • a defective allele of this gene means that the cells in the eyes (cones) that detect red and green don't function properly.
              • the gene is on the X chromosome
    • reproduction
      • asexual
        • 1 parent       clones        less energy   loner       many offspring          mitosis
      • sexual
        • 2 parents      variation       enviro change can survive through  natural selection    meiosis
    • embryo screening
      • People who have, or think they have, an allele for a genetic disorder can decide to have their embryo screened at a very early stage of pregnancy.
        • Tests the embryo for specific alleles. If it's certain that the embryo will develop an inherited disorder, the couple can ask for a termination (abottion)
      • ethical issues
        • Screening carries a very small risk of damaging the embryo-should parents take the risk?
        • Does an embryo have the same right to life as a person? If so, is it right to abort an embryo that will develop the disease?
      • social issues
        • If the child needs lots of care, is this fair on other children in the family
        • If the child needs care throughout life, who will do it if the parents can't?
      • economic issues
        • Will it cost parent extra money to support a child with a disorder?
        • Does someone with the disorder need lots of hospital treatment and/or drugs?

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