Noadswood Science, 2012

 To understand how some diseases can be inherited Sunday, August 16, 2015

 Huntington’s disease is an inherited disorder that affects the nervous system – symptoms do not usually present themselves before ~40 years old  It is caused by a dominant allele – this means it can be passed on by just one parent if they have the disorder: -

 Cystic fibrosis is an inherited disorder that affects the cell membranes, causing the production of thick and sticky mucus  It is caused by a recessive allele meaning that it must be inherited from both parents

 Cystic fibrosis – two parent carriers (25% chance of child being normal; 50% chance of child being a carrier and 25% chance of the child having cystic fibrosis)

 Cystic fibrosis – one parent carrier (50% chance child will be normal and 50% chance the child will be a carrier)

 The amino acid valine is inserted instead of glutamic acid, which is shown by the bottom strand of DNA  The protein synthesised is altered and no longer functions normally resulting in sickle-shaped red blood cells (sickle cell anaemia)

 The amino acid valine is inserted instead of glutamic acid, which is shown by the bottom strand of DNA  The protein synthesised is altered and no longer functions normally resulting in sickle-shaped red blood cells (sickle cell anaemia)

 Polydactyly is caused by a dominant allele and causes extra fingers or toes  The disorder is caused by a dominant allele (D) and so can be inherited by one parent…