Inherited Disorders

• genetic diagrams show possible gamete combinations
• punnet square

  
• allele

  two versions of the same gene
• genotype

  genetic makeup of organisms represented by letters
• phenotype

  physical characteristics of organisms represented by words
• homozygous

  genotype with either 2 dominant or 2 recessive alleles
• heterozygous

  genotype with 1 recessive & 1 dominant allele
• dominant

  a characteristic from 1 or both parents and is always expressed (capital letter)
• recessive

  a characteristic from both parents and expressed if there are 2 copies (lowercase letter)
• gender of a child will always be 50% female and 50% male

  A) XX

  B) XX

  C) XY

  D) XY

  E) female

  F) male

  
• annotations of punnet square

  A) heterozygous

  B) homozygous recessive

  C) homozygous dominant

  
• cystic fibrosis

  • caused by a single recessive allele
  • common inherited disease which results in body producing thick sticky mucus in air passages and pancreas
• cystic fibrosis punnet square

  A) no

  B) carrier

  C) yes

  D) carrier

  
• polydactyl

  • caused by a dominant allele
  • an inherited characterisitic which results in a person being born with an extra finger or toe
• polydactyly punnet square

  DD - is also present of polydactyly

  A) yes

  B) yes

  C) no

  D) no

  
• embryos can be screened for genetic disorders
• for embryonic screening

  • help to stop people suffering
  • costs government a lot of money
  • laws are put in place to stop it going too far
• against embryonic screening

  • implies people with genetic problems are undesirable
  • could increase prejudice
  • screening is expensive