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  • Created by: Inda1
  • Created on: 07-02-16 16:46
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  • B1
    • Genes, chromosomes and DNA
      • each chromosome is one very long molecule of DNA That is coiled up
      • A gene is a short length of a chromosome
      • Genes  control the development of characteristics
      • Genes exist in different versions
        • Each version gives a different from of characteristic
          • The different versions of the same gene are called alleles
      • Genes are instructions for cells
        • each gene is a code for making a certain protein
        • some proteins are structural proteins. They are part of things like skin, hair, blood and the cytoplasm
        • Other proteins are funtional proteins for example enzymes are proteins that helps with digestion
      • An organism's genotype describes the genes It's got
        • An organsims genotype is all the genes it has
        • Thw charateristics that an organism display are calles its phenotype
    • Gnens and varation
      • so half a childs chromosomes have come from each parent This means that ....
        • Children get some of their alleles from each of their parents
        • this is why children look like theor parebts
        • Every child will have a new, unique , combinationn of allelles taht why there is no two people in the world except for identcal twins
    • Inheritance and genetic diagraks
      • Allelles are the different version of the same gene
      • Homozygous traits are if you have two alleles the same for that particular gene
        • Hetrozygous traits are if you have  twio different alleles for that paricular gene
    • Genetic disorders
      • some disorders are inherited- one or both parents carry a faulty allele and pass it on to their children
      • cystic fibrosis and huntingtons disease are both caused by a faulty allelle of a single gene
      • Cystic fibrosis
        • is a ressisive allele
        • symptoms include : Thick mucus in air ways, Breathing difficulty, Cheast infection,   Difficulty digesting food
      • Huntingtons disease
        • Is a dominant allele
        • This disoder causes shaking, clumsiness, mwemory loss, Rthere is not cure
        • The donimnant allele mwans that there is 50% chance of each child inheriting the disorder
        • The carrier parent will of course be a sufferer too since it is a dominant allele, The symptoms don't usually appear till about 40 years of age
    • Genetic testing
      • When embroyos are produced using IVF, doctors can test the embroyos  to check if they've got a cetain genetic disorder
        • This is known as pre-implantation genetic diagnosis and is especially important if there's concern that one of the parents might carryy alleles for a genetic disorder.
      • Doctors can also test fetuses in the womb for genetic disorders by testing the fluid surounding the fetus
      • Issues surrounding genetic testing
        • The result of genetic testing may not be 100% accurate. There are often errors due tpo misinterpretations and the sample being contaminated
        • Like most medical procedures, tests carries out during pregnancy aren't 100% safe for example doing a genetic test on the fluid around the fetus may cause miscarriages
        • If the result is positive should other family members be tested, Some people may prefer not to know, but is this fair on any partners or futire children
        • Is it right for someone who's at risk of passing on a genetic condition to have  children? is it fair to put them under pressure not to, if they decide they want children?


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