Inheritance

• Gametes are made by a cell division called meiosis. Meiosis produces non-identical cells this means that every sperm and egg are different.
• Meiosis takes place in flowers the gametes are pollen and egg cells.
• Both animals and flowering plants carry out sexual reproduction.
• Sexual Reproduction:

  • sexual reproduction is the fusion of male and female gametes.
  • scientists call this fertilisation.
  • sperm cell joins the egg cell there is a mixing of genetic information.
  • every gamete is different this leads to variation in offspring.
• A-Sexual Reproduction:

  • In asexual reproduction there is only 1 parent involved, this means there are no gametes therefore no mixing of genetic information.
• In asexual reproduction the offspring are identical
• Asexual reproduction only involves mitosis.
• Cycle Of Meiosis:

  • cells with 2 pairs of chromosomes (diploid cell)
  • each chromosome replicates itself
  • chromosomes part company and move to opposite poles
  • cells divide for the 1st time
  • copies separate and 2nd cell division takes place
  • 4 non-identical gamete cells are produced each with half the number of chromosomes of the parent cell
• The genome is the genetic material in the nucleus of a cell it is made of a chemical called DNA, the DNA is structured by chromosomes.
• A gene is a small section of DNA on a chromosome
• each gene codes for a particular sequence of amino acids to make specific protein
• the genome of an organism is the genetic material of the organism
• uses of genome:

  • doctors can search for genes linked to different types of disorders
  • can help scientists to understand the cause of inherited disorders and how to treat them
  • scientists can investigate how humans may have changed over time.
• chromosomes contain DNA
• Structure of DNA:

  • 2 strands made by joining together lots of smaller molecules.
  • 2 strands wrap around each other to form a double helix
• a gene is a small section of a chromosome
• the human genome is the entire genetic material that makes a human
• benefits of genome:

  • help find genes linked to cancer or Alzheimer's disease.
  • to trace human migration patterns from the past.
• human gamete includes 23 single chromosomes
• meiosis only takes place in the reproductive organs.

  for males its the testes

  for females its the ovaries
• meiosis produces 4 gametes from one original cell.
• each of these 4 gametes are genetically different from each other, they contain different alleles.
• after fertilisation the cell has the normal number of chromosomes
• in meiosis the chromosomes half but for fertilisation they go back to the normal number.
• human sperm cell = 23 single chromosomes
• Human egg cell:

  • 23 single chromosomes
  • both of these gametes have 23 single chromosomes
  • after fertilisation, the fertilised egg have 23 chromosome pairs
• After fertilisation:

  • the new cell divides by mitosis producing a clump of identical cells this is called an embryo.
  • as the embryo develops the cells of differentiate forming different cell types.
  • in animals these include the nerve and muscle cells.
• Alleles are versions of a gene
• the genotype of a person tells us if alleles are present
• homozygous is a person who has 2 copies of the same allele
• a phenotype of a person tells us the characteristics caused by the persons alleles.
• heterozygous are people with 2 different alleles.
• a recessive allele will show if 2 copies are present this means if there are no dominant present.
• What is the disorder associated with defective cell membranes?

  Lushkeldrosis
• How is Cusic Erbrosis controlled genetically?

  By a single gene with alleles
• What type of inheritance pattern does cystic fibrosis follow?

  Recessive inheritance
• How many copies of the defective allele are needed to have cystic fibrosis?

  Two copies
• What is the genotype of a person who does not have cystic fibrosis but is a carrier?

  One defective allele and one normal allele
• What is polydactyly?

  Having extra fingers or toes
• What type of allele causes polydactyly?

  A dominant allele