genetic inheritance

• allele 


  an alternative version of a gene
• chromosome


  a long molecule of dna found in the nucleus. each chromosomes carries many genes
• gamete 


  a sex cell eg an egg cell or sperm cell in anima’s
• dominant allele


  the allele for the characteristic that’s shown by an organism if two different alleles are present for that characteristic
• recessive allele


  an allele whose characteristics only appears in an organism if there are two copies present
• homozygous 


  two alleles present are the same
• heterozygous 


  if the alleles are different for that trait (Hh)
• cystic fibrosis


  caused by a recessive allele. it results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas
• polydactyly


  caused by a dominant allele. a baby is born with extra fingers or toes
• embryo screening


  during IVF many genetic disorders can be detected by analysing the cells genes
• people for embryo screening

  • helps people not suffer
  • treating disorders costs the goverment a lot of money
• against embryo screening

  • implies people with genetic disorders are undesirable - causes prejudice
  • people may go to far with wanting desired features
  • screening is expensive
• how many chromosomes does the body contain?

  23 pairs
• 22 pairs control characteristics only, but one of the pairs carries the genes that determine sex.