meiosis

• what happens in meiosis

  Meiosis is a type of cell division that results in the production of four genetically different daughter cells from a single parent cell.
• why is meiosis necessary for sexual reproduction

  because if two diploid cells were to join in fertilisation, the zygote would have four sets of chromosomes instead of two. so meiosis is needed to produce haploid cells.
• meiosis produces haploid gametes (eggs or sperm) which contain half the number of chromosomes as body cells, so they can fuse to form diploid zygotes with two sets of chromosomes when fertilization occurs.
• what do genes code for? the sequence of amino acids in a protein
• proteins are polymers made by


  linking different amino acids together in a chain.
• what is the role of the genome in the manufacture of proteins?

  the dna of an organism is its genome. sections of the dna are called genes which code for different proteins.
• why do brothers and sisters look different?

  because they have a selection of chromosomes passed down from their parents
• state the name of human gametes

  sperm cells, egg cells
• the process that turns zygotes into a ball of cells

  mitosis
• how many chromosomes do: sperm cells, liver cells, zygotes have?

  sperm cells: 23 liver cells: 46 zygotes: 46
• how much of an organism's genome does a gamete contain?

  The zygote must contain genetic information from the mother and from the father, so the gametes must contain half of the chromosomes found in normal body cells.
• define the term gene.

  section of dna - controls a cells chemistry, particularly producing proteins.
• compare and contrast mitosis and meiosis.

  Mitosis produces two genetically identical “daughter” diploid cells from a single “parent” cell, for growth and repair, whereas meiosis produces four non identical haploid cells, that are genetically unique from the parent and contain only half as much DNA. Most cells in the body regularly go through mitosis
• diagram to show how a zygotes genome is created

  z

  A) .

  
• explain why chromosomes are x shaped at the start of meiosis.

  each chromosome replicates, the two copies remain attatched making the chromosome look like an x shape
• name the process the following cells are made: zygotes, embryos, sperm

  fertilisation, mitosis, meiosis
• 'triploid syndrome' is a rare human disease. what do you think the cells of someone with this disease look like?

  Extra chromosome set