B1 revision part 2

B1 revision part 2

1. Genetic Disorders

   • The alleles of some genes can be FAULTY.
     • These faults are known as genetic disorders
     • They can be passed down from parent to child.
   • Recessive Alleles
     • CYSTIC FIBROSIS is caused by a faulty recessive allele.
       • For example
         • in this example, the faulty Cystic Fibrosis Allele has the letter 'f'
         • FF=normal
           • No Symptoms
           • People with TWO copies oof the DOMINANT allele WON'T show any symptoms of CF
         • Ff= carrier
           • someone will only have one copy of the recessive allele, so isn't a sufferer
           • No Symptoms
             • No symptoms because they only have one copy of the RECESSIVE allele.
         • ff= Sufferer
           • someone who has the disorder
           • Symptoms
             • difficulty breathing
             • thick mucus
             • difficulty digesting food
             • chest infections
           • Only people with two copies of the RECESSIVE allele are sufferers
     • The mixture of alleles that a person had decides whether they have cystic fibrosis or not
   • Dominant alleles
     • HUNTINGTON'S DISEASE is caused by a faulty DOMINANT allele.
       • Huntington's disease has a LATE ONSET. This means that sufferers only show symptoms later in their lives
     • The mixture of alleles that a person has decides whether they have huntingtons disease or not
     • for example
       • The allele for huntingtons disease will be H in this example
       • HH= sufferer
         • symptoms
           • tremors
           • clumsy
           • memory loss
           • mood changes
           • can't concentrate
       • Hh= sufferer
         • Symptoms
         • People with ONE or TWO copies of the DOMINANT allele have Huntingtons disease
       • hh= normal
         • no symptoms
         • Only people with TWO copies of the RECESSIVE allele are normal

2. Genetic Testing

   • Doctors and scientists can test for genetic disorders but its not always a good thing.
   • Positives
     • Genetic testing is looking at a persons DNA to see what ALLELES they have.
     • There are three main uses of genetic testing
       • When doctors are helping a couple have a baby, they can test the EMBRYOS for genetic disorders.
         • Only HEALTHY embryos are chosen to be put into the mother
       • Couples can have tests before having children.
         • They can find out if their children might inherit a GENETIC DISORDER.
       • People can be tested before they're given DRUGS.
         • This can tell doctors if the drug will work well.
         • It can also tell them if the person will have a DANGEROUS REACTION to it
   • Negetives
     • Genetic tests AREN'T ALWAYS RIGHT.
       • HEALTHY PEOPLE could be told that they have a genetic disorder.
         • FALSE POSITIVE
       • People WITH A DISORDER could be told they are fit and well.
         • FALSE NEGETIVE
     • Tests carried out during pregnancy AREN'T ALWAYS SAFE
       • collecting cells from an unborn baby sometimes causes a miscarriage
     • If a test result is POSITIVE there are lots of important questions to answer.
       • "Do I still want to have my baby"
       • "Should I have a baby?"
       • "Should I tell my family that they might be carriers? What if they don't want to know?
     • If employers and insurance companies get the results it might cause problems
       • Insurance companies might not give out life insurance
       • Job companies might not give out jobs because of sick leave

3. Clones

   • Nature has been making clones for millions of years.
     • ASEXUAL REPRODUCTION
       • lots of organisms can form clones by reproducing ASEXUALLY
         • Bacteria divides into two
         • A few animals for example greenfly reproduce asexually
         • Some plants grow stems called RUNNERS. They spread out and form clones at their tips.
         • other PLANTS make underground BULBS. These can grow into clones
     • When cells of an embryo SPLIT
       • IDENTICAL TWINS are clones
       • They are formed when an EMBRYO splits into TWO
   • Clones have Identical Genes
     • Clones have exactly the SAME GENES as each other.
     • any DIFFERENCES is due to the ENVIROMENT.
       • eg) If you ate more food than your clone, you would be bigger - even though you still had exactly the same genes.

4. stem Cells

   • Stem cells can become other types of cells
     • Most cells in your boyd are SPECIALISED to do a certain task.
       • for example red blood cells carry oxygen
     • Most cells in an organism become SPECIALISED when the organism in really young.
     • Some cells are UNSPECIALISED
       • UNSPECIALISED CELLS are called STEM CELLS
       • They can develop into different types of cells
   • There are TWO main types of stem cell
     • EMBRYONIC STEM CELLS
       • found in EMBRYOS
       • These can turn into any type of cell
     • ADULT STEM CELLS
       • found in ADULTS
       • Can turn into many types of cells but not all
   • Used to help people
     • STEM CELLS could be used by doctors to treat sick people
     • STEM CELLS could be turned into NEW CELLS that can REPLACE damaged cells.
       • For example- new heart cells for people with heart disease.