B1 (YOU AND YOUR GENES)

VARIATIONS
1. Genetic factors e.g dimples,eye colour
2. Environmental factors e.g scares,hair style
GENETIC INFORMATION
1. DNA or deoxyribonucleic acid
2. Genes carry the information needed for you to develop
  1. Different geans controle diffrent charcteristics
    1. E.g hair and eye colour
3. Chromosomes are made from DNA molecules
  1. made from
    1. to very long strands
    2. to form a double helix
4. DNA molecules are instrctions for
  1. how the organism should be constructed
  2. how each cell should function
5. Genes
  1. are sections of DNA
    1. Control the development of characteristics
      1. by using instruction that produce proteins
        protenins
        structural protenins
        E.G for cell growth or repair e.g collagen
        functional proteins
        E.G enzymes ( to speed up chemical reactions) such as amylase
CHROMOSMES
1. come in pairs
2. different species have different numbers of pairs of chromsomes
3. humans have 23 pairs with 46 in total
  1. 23 from the mother
    1. both x chromosomes
  2. 23 from the farther
    1. there is both x and y chromosomes
      1. y chromosmes is a lot small than x
      2. half and half
4. the sex of an individual is determined by the
  1. sexdetermining region (sry)
  2. iif two x chromosmes are present it will be a girl
  3. if there is an x chromosome it will be a boy
    1. start producing androgen hormone
  4. some times the y chromosme is present but androgen isn detected.
    1. embro has female sex organs but not a uterus
    2. and is infertile
ALLELES
1. You can inherit two alleles that are the same this is called
  1. Homozygous
2. you can inherit tow alleles that are different this is called
  1. Heterozygous
3. brothers and sisters can ramdomly inherit different combinations of alleles
4. The combination of alleles is called your genotype
  1. The actual characteristics you show is your phenotype
5. Dominant allele
  1. controls development
    1. even if it is only one chromosome in a pair
6. Recessive allele
  1. controls development
    1. if a dominant allele is not present
Disease
1. Huntingtons disease
  1. caused by one or more faulty allele
    1. faulty gene on the fourth pair of chromosomes
  2. affecting the central nervous system
  3. damages brain nerve cells
  4. symptoms involuntary movement,clumsiness,memory loss,mood changes and inabiliry to concentrate
    1. seen in adulthood
  5. leading to premature death
  6. only one parent needs to pass on the gene to inherit it
    1. it is a dominant
2. cystic fibrosis
  1. affects the cell membranes causing a thick mucus
    1. problem in the lungs,gut,pancreas
  2. symptoms including weight loss,difficulty in breathing,chest infections and difficulty in digesting food
  3. no cure
  4. allele is recessive
    1. need to of them to get it
    2. one will be a carrier and will pass it on
GENETIC TESTING
1. testing for one faulty allele
2. risks and benefits
TESTING ON ADULTS OR CHILDREN
1. if it is found the adult may not have children
  1. or odopt in sted
2. children can be tested to help with treatment
  1. or tested be for prescribing certain drugs
TESTING ON FETUSES
1. Fluid surrounding the fetus or the placenta can be tested for an faulty alleles
  1. a small risk inculiding a miscarriage and outher implications
2. if a faulty alllele is found the parents have to consider if the pregnancy should be have terminated
  1. other family members might have to be told
    1. they too could pass on the faulty allele
3. RELIABILITY
  1. no test is 100% reliable
  2. may terminate the pregnancy even if there is no problem
  3. see book for table
THE IMPLICATIONS ON GENETIC TESTING
1. some people think that what we can do and what we should do is an important
2. used to screen for
  1. susceptibility to certain diseases or conditions
  2. possible problems with prescribed drugs or treatment
  3. people think it should be used on babies at birth for
    1. to tailor healthcare and prevent problems
    2. to stop genetic disorders from being passed on and eliminating over time
3. one view is that this will mean that there is less suffering and a lower cost spent on treatment
  1. but some people think that it is natural and it will be wrong to eliminate them
4. raises questions about confidentiality should people like employers or insurance people have this information
  1. if they have a higher risk of illness
EMBRYO SELECTION
1. able to pervent babies from haveing genetic disorders
  1. this can be produced in (in vitro fertillsation) or (ivf)
2. harvested ,tested,implanted then the pregnancy proceeds an normal
3. pre-implatation genetic diagnosis (pgd)
  1. the embryos are allowed to divide into the eight cell stage before a single cell is tested
    1. tested to see if they have the allels for the genetic disorder
4. some people do not llike embryo selection
  1. think it is unnatural
  2. concerns that people could chose certain characteristis
    1. so some could die out like brown eyes
Asexual reproduction
1. it is division of single cell organisms and bacteria
  1. this forms 2 new cells from 1
    1. clone
2. most plants and some animals do this
3. variations normally only caused by environmental factors
4. animal clones can occur naturally
  1. an embryo may separate and the 2 embryo's are identical twins
5. animal clones artificially produced by nucleus from one transferred into cell with no nucleus
  1. unethical
  2. see book for diagram
6. plants make clones out of bulbs and runners - daffodils
  1. allow plant survival without male female together. ( sex cells called gametes)
Stem cells, 2 types adult and embryonic
1. yound cells that are not specialised that can quickly develop into different ones.
2. can be used to replaced tissues - Parkinson,s disease
3. adult stem cells
  1. only found in bone marrow or umbilical cord blood
  2. cannot develop into all types of cell
4. Embryonic Stem cells
  1. from embryo
    1. need to clone embryos to get
  2. can develop into any kind of specialised cell
  3. controversial but regulated by gov as can help many people

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B1 (YOU AND YOUR GENES)

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