(bio 2) inheritance

• advantages of sexual reproduction is that is produces genetic variation it also allows selective breeding for higher yeilds ect.
• a genome is the entire genetic material of an organism
• scientists research the human genome to find how genes are linkes to disease (cancer) . to treat and help disorders (cystic fibrosis). and to track human migration patterns and ancestry .
• DNA is genetic material found in the nucleus
• chromosomes contain DNA , DNA contains genes
• DNA has a double helix structure of two polymer strands
• meiosis only happens in the reproductive organs eg. testes and ovaries
• a gene is a small section of DNA on a chromosome
• genes code for a specific sequence of amino acids which code for a specific protein
• sequence of bases ( agc tca cgs) determine the sequence of amino acids which determine the shape of the protein which determines the function eg. enzyme, hormone , structural protein
• a mutation is a change to a base which sometimes leads to a change in the structure of protein
• when a structural protein mutates the eg. collagen will lose its strength
• when a mutation takes place the active site changes and the substrate doesnt fit
• genotype tells us what alleles are present 'Ee' 'ee'
• homozygous is when the alleles are the same 'ee'
• heterozygous is when the alleles are different 'Ee'
• a phenotype is the characteristic caused by the allele
• dominant alleles will always show in the phenotype
• cysytic fibrosis is an inherited disorder of the cell membrane. caused by a homozygous recessive allele
• gene therapy is when scientist try correct faulty alleles. this is experimental
• issues of gene therapy

  1. expensive, money can be used elsewhere
  2. a large number of embryos are created and only a small amount is implanted so the rest are destroyed this is unethical
  3. people may pick embryos with desirable features this is unethical
• 22 pairs of chromosomes determine inherited charcateristics

  1 pair of chromosomes determine sex
• male chromosomes : xy
• female chromosomes: xx
• recessive alleles only become a characteristic if there is two recessive alleles, if there is one present the person is a carrier of the characteristic
• fertilisation involves the sperm cell and egg cell fusing(fertilisation) to create a fertilised egg which then divided by mitosis to create an embryo. this then differentiates into eg. nerve cells and muscle cells
• asexual reproduction requires one parent cell and offspring are genetically identical. sexual reproduction requires two parent cells and offsring have genetic variation.
• alleles are different versions of the same genes
• advantages of a asexual reproduction is it only needs one parent cell which saves more time and energy it also produces genetically identical cells rapidly. a disadvantage is that is conditions are unfavourable then they all die
• polydactyly is an inherited disorder for extra finger and toes. caused by a dominant allele
• 1. meiosis is a type of cell division that results in four gametes with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores
• some regions of a chromosome turn on and off and decide when a protein should be made. when a mutation takes place for eg. a protein is made when it should not, it could lead to uncontrolled mitosis leading to cancer
• embryo screening is when alleles are tested for inherited disorders . affected embryos are destroyed and healthy ones are implanted
• human have two copies of chromosomes from their mother and father which mean the have two copies of genes
• DNA is a polymer of nucleotides . nucleotides contains sugar phosphate backbones with nitrogenous bases such as A T C G (@cg)
• the steps to protein sythesis:

  1. transcription

  happens in the nucleus. base sequence of the gene is copied on

  a template (MRNA). the mrna moves out the nucleus through it

  pores.

  2. translation

  happens in the cytoplasm . mrna attaches to the ribosome . amino acids bought by carrier molecules ( trna) . ribosomes read the sequence of bases on the mrna molecule.

  
  

  3. after completion the protein fold to create a specific protein