You Your Genes

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You Your Genes

• B1 Revision Notes

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Individual Characteristics

• Features determined either owing to environment
  or inheritance. Examples?
• Variation amongst individuals
• Organisms made of cells.
• Cells controlled by a nucleus containing
  chromosomes.
• Each chromosome is made of thousands of genes
  which control how you develop.
• Genes tell the cell how to make proteins (50,000
  types in human body).

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Chromosomes

• Put in correct order, largest 1st
• Chromosome, gene, cell, nucleus
• Each body cell contains 46 (23 pairs)
  chromosomes. 23 from each parent.
• Only sex cells (gametes) contain only 23
  chromosomes.

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Genes and Alleles

• Chromosomes pair up and genes for the same
  feature align next to each other.
• Different versions of the same gene are called
  alleles, e.g. eye colour (brown and blue alleles,
  but gene for the same feature).
• One allele is always dominant and means this
  feature shows up. The other allele is recessive.

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Genetic Crosses

• Mum has 2 alleles,
• A and a for hair colour.
• Dad has the same ones.
• A is brown hair
• a is blond hair.
• Both parents have brown hair.
• What is chance of offspring having blond?

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X and Y

• XX is female.
• XY is male.
• Y dominates.
• 5050 chance of either sex
• Sex-linked diseases
• Haemophilia
• Colour-blindness
• Muscular dystrophy

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Inherited Diseases

• Cystic Fibrosis.
• Caused by recessive allele.
• Mainly people are carriers.
• Causes cells to produce sticky mucus. Results in
  lengthy physio and higher infections rates.
• Huntingtons Disease.
• Attacks the nervous system. Symptoms include loss
  of muscle control and memory loss and commence
  later in life.
• Caused by dominant allele.

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Ethical Decisions

• Amniocentesis is a test on an unborn baby to
  detect if it has cystic fibrosis.
• It is not 100 reliable with a 0.5 miscarriage
  risk, small chance of infection, and results only
  between 15-18 weeks.
• Information could be used to decide on a
  termination (abortion). This is an ethical
  decision based on genetic testing

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Reliability of Genetic Tests

• False-negative
• Wrong result which says a person does not have a
  medical condition but they do.
• False-positive
• Wrong result which says a person has a medical
  condition but they do not (this could have been
  aborted so ethics again!)

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Designer babies

• Embryo selection (form of IVF)
• Gametes fertilised in labs, and then the embryos
  tested for genetic disease/s (checking the
  alleles). Healthy ones used for mothers womb.
  What about the others??
• Gene therapy
• Curing an inherited disease by putting correctly
  working alleles into a person.
• Had limited success. Currently illegal for sex
  cells. People worried it could lead to control
  features like eye colour, etc.

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Cloning

• Clone is genetically identical to the organism it
  was made from.
• Happens naturally with identical twins and also
  asexual reproduction (one parents such as
  bacteria).
• Early embryos are made of stem cells which can
  develop into any specialised cell. Scientists
  want to clone using cloned embryos. Ethical
  decisions?

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Arguments

• In favour
• Scientific progress
• Organ transplants
• Legal up to 14 days
• Your relation/friend?
• Against
• Human rights
• Lowers value of life
• Murder of embryos