Science B1

Science B1

1. Genes, Chromosomes, DNA

   • -Nucleus of our cells, contains genetic material - typical human body cell contains 23 pairs for chromosome- A chromosome is made out of DNA molecule; An allele is different versions of the same genes. Genes code for proteins which give out characterstics. There are 2 types of protein:-structural proteins e.g collagen found in your bones and functional proteins e.g enzymes(help to break down food. CHARACTERISTICS- Some characteristics are controlled by the genes such as: blood groups and eye colour, some are controlled by the enviornment such as scars whereas they can also be a mixture of both characteristics, e.g Weight. PHENOTYPE- Displayed Characteristics. GENOTYPE- A gene that the organism contains. PHENOTYPE (TALL/SHORT) GENOTYPE(Hh,HH,hh)

2. SPERM AND EGG CELLS- Sperm and egg cells have 23 single chromosomes, compared to the human body cell, when the sperm fertilises the egg, the original number of chromosomes are restored (23 pairs=42 single) Brothers and sisters are look similar but are not identical because they have different alleles as every sperm and egg cells are different. HOMOZYGOUS- Two of the same alleles (BB or bb) HETEROZYGOUS- two different alleles (Bb)

3. Genetic Disorders are caused by FAULTY ALLELES. The allele that cause cystic fibrosis is a recessive allele 'f'.For a child to inherit the disorder both parents must be a carrier. NORMAL: FF, CARRIER:Ff, SUFFERER: ff. The other example of a genetic disorder caused by a dominant allele is HUNTINGTON'S DISEASE: NORMAL:hh and CARRIER/SUFFERER:Hh

   • GENETIC TESTING is used to test for genetic disorders in early embryos and fetus. 1. If a embryo has been produced using IVF. doctors can check the embryo for genetic disorders before implanting the embryo. 2. Doctors can also test fetuses by checking the fluid around the fetus for the disorders, this process is know as amniocentesis Amniotic fluid is around the fetus. Chorionic Villus Sampling is when a sample fof the placenta is taken and tested. EMBRYO is a ball of cells. FETUS is when it is recognisable to become a human
   • CLONES are genetically identical organisms, that are produced either but nature- asexually. BACTERIA, SOME PLANTS AND SOME ANIMALS can also produce clones. The only differences with clones depend on the environment and could cause extinction. Bacteria- it produces clones by just dividing into clones, Plants- produce runners but other plants like Garlic produce bulbs underground, Animals- Greenfly can produce asexually. Identical Twins are formed when a embryo splits into two, then the separate embryos begin to develop.

4. ISSUES AROUND TESTING: -NOT 100% ACCURATE. -IF THE RESULT IS POSITIVE, OTHER MEMBERS OF THE FAMILY MAY ALSO BE AFFECTED KNOWING THAT IS IS IN THEIR GENE. -IF PREGNANT FEMALES ARE POSITIVE IT COULD LEAD TO THE PREGNANCY BEING TERMINATED, BUT THE FETUS ALSO HAS A RIGHT TO LIFE.-INSURANCE COMPANIES MAY DISCRIMINATE THE PEOPLE WITH DISORDERS.