B1 | Mind Map

B1
1. Genetic traits
  1. Passed through genes
    1. Either dominant or recessive
2. Sex deterimination
  1. If a defective gene in found on parts of the X chromosome, it can result in sex-linked diseases
    1. More likely in men
  2. Female has two X chromosomes
    1. Male has an X and a Y chromosome
      1. The Y chromosome triggers the growth of the testes, without it, ovaries develop
3. Gene disorders
  1. Some disorders are caused by faulty or defective alleles
  2. Huntington's disease is a dominant disorder
    1. Occurs in middle age
    2. Symptoms include tremors, memory loss, inability to concentrate and mood changes
  3. Cystic fibrosis is a recessive disorder which means both alleles must be recessive for you to get it
    1. Symptoms includes production of thick gluey mucus that affects lungs and digestion, breathing problems and chest infections
    2. You can be a carrier for this and still be normal
We're all different
1. Characteristics controlled by genes and enviroment
2. Phenotype= physical
3. Genotype= genetic
What genes do
1. Functional proteins enable body to function
2. Structural proteins give the body structure
  1. DNA= packed into chromosomes
    1. Carry instructions= control how develop& function
      1. Tells body what proteins it needs
        Gene=section of DNA
Genes& chromosomes
1. Sex cells= 23 chromosomes
  1. 46 cmromosomes
  2. At fertilisation= Zygote
    1. Combination from parents causes variation
      1. Pairs of chromosomes have genes for the same characteristic
Alleles
1. Different forms of gene
  1. Homozygous= same
  2. Heterozygous= different
Genetic testing
1. Genetic screening is used to check for a disorder even when there is no history
  1. Genetic testingis carried out when a genetic disease runs in the family
    1. Ethical issues include who should know if someone has a disorder like Huntington's
      1. Tests during pregnancy carry risk of miscarriage
        IVF allows doctors to only implant normal embryos
        Ethical issues include playing God however can allow people to plan
Stem cells
1. A human embryo develops from a single cell
  1. Five days= ball of cells containing embryonic stem cells
    1. These are unspecialised and can turn into any cell in body
      1. Adult stem cells have limited uses
      2. Ethical issues
        Usually taken from unused embryos in fertility treatments
        Using them involves destroying embryos
Cloning
1. Have identical genes
  1. In asexual reproduction the offspring is in identical to the parent
    1. Identical twins happen when a fertilised egg splits
      1. Artificial cloning: Nucleus from body cell is inserted into egg cell then implanted into surrogate mother

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	Created by Lisa Cracknell over 8 years ago