Inheritance

• what is asexual reproduction?

  it involves one parent and produces genetically identical offspring.
• what is sexual reproduction?

  it involves the fusion of male and female gametes which leads to mix of genetic info.
• what are gametes?

  the sex cells e.g. sperm and egg.
• what is meiosis?

  • when copies of the genetic info are made.
  • the cell divides twice to form four gametes, each with each pair of chromosomes.
  • all gametes are genetically different from each other.
• what is a genome?

  the whole genetic material of an organism
• what is a gene?

  • a small section of DNA on a chromosome.
  • each gene codes for a particular sequence of amino acids.
• what are chromosomes?

  long molecules found in the nucleus made by DNA.
• what is meant by the term 'allele'?

  a version of a gene.
• what is a dominant allele?

  an always expressed allele.
• what is a recessive allele?

  an allele that is only expressed with two present copies.
• what is meant by the term 'homozygous'?

  when both of an organism's alleles for a trait are the same.
• what is meant by the term ' heterozygous'?

  an organism's alleles for a trait are different.
• what is a genotype?

  an organism's combination of alleles.
• what is a phenotype?

  the characteristics an organism has.
• what is polydactyly?

  a condition where someone has extra limbs and is caused by a dominant allele.
• what is cystic fibrosis?

  a cell membrane disorder which is caused by a recessive allele.
• how many pairs of chromosomes does a typical human body have?

  23.
• what are the male and female sex hormones?

  • women: XX
  • men: XY