Single Gene Disorders

Turn to your partner… Odds first -tell them everything you know about DNA. Evens second - what can you add on

DNA Review DNA from all organisms is made up of the same pieces The order of A,C,T, and G’s spell out the exact instructions required to create a particular organism with its own unique traits.

Small sequence of DNA for making insulin protein Sequence 1 - Human insulin gene sequence DNA: C C A T A G C A C G T T A C A A C G T G A A G G T A A Sequence 2 – Cow insulin gene sequence DNA: C C G T A G C A T G T T A C A A C G C G A A G G C A C

Genes: Your special instructions Most of our DNA is “junk” DNA= no instructions The parts of our DNA that do have instructions are called Genes Genes vary in length Some contain thousands of base pairs Some contain millions of base pairs 20,000 human genes have been identified The instructions in your genes are directions for synthesizing (making) proteins. GENE

Proteins Proteins: -Perform most life's functions (enzymes in chemical reactions) -Make up the majority of cellular structures Proteins are made up of smaller subunits called ____________ (There are 20 amino acids) A chain of seven amino acids = 1 billion possible combinations amino acids Met Leu Ser Leu Thr Gly Ile

Human Chromosome Math How many chromosomes do humans have in every cell of their body (not including gametes)? 46

Human Chromosome Math _________________=chromosomes that have genes in them to make proteins to turn you into a boy or girl _________________= chromosomes with no genes for sex determination _______________ = is a picture of all 46 human chromosomes grouped together in homologous pairs from longest to shortest, with sex chromosomes last Sex Chromosomes Autosomes Karyotype

Autosomal? These types of gene disorders are only found in chromosome pairs 1-22!

What is a gene disorder? The instructions in 1 out of the 20,000 genes gets messed up

What is a gene disorder? Insertion, deletion or substitution of 1 or more bases changes amino acids and makes the protein incorrectly “Normal” DNA sequence Mutated DNA sequence DNA: TCACGATTT DNA: TCATGATTT mRNA: AGUGCUAAA mRNA: AGUACUAAA Ser Lys Ser Ala Lys Thr

Example: Cystic fibrosis (1 in 2000 Europeans) Gene on chromosome 7 Normal dominant allele (N) makes a protein to transport chloride ions across cells Mutated recessive allele (n) makes a protein that does not transport chloride ions across cell Result= mucus that clogs lungs and pancreas=shortened life expectance to early adulthood NN=normal Nn=normal nn=cystic fibrosis

Example: Tay-Sachs disease (1 in 600 Jews) Gene on chromosome 15 Normal dominant allele (N) makes a protein that is an enzyme which breaks stuff down in lysosome’s Mutated recessive allele (n) makes an enzyme that does not work Result= build up of waste causes nerve cells to die= brain damage and death in early childhood NN=normal Nn=normal nn=Tay-Sachs

Example: Sickle cell anemia (1 in 500 African Americans) Gene on chromosome 11 Normal dominant allele (N) makes a protein that carries oxygen in red blood cells Mutated recessive allele (n) makes a protein that causes the cell to change shape Result= Cylinder shaped red blood cells clog blood vessels= damaged organs due to lack of oxygen NN=normal Nn=Normal nn= sickle cell anemia

Example: Huntington’s Disease (1 in 10,000) Gene on chromosome 4 Normal recessive allele (n) makes a protein that helps move vesicles in nerve cells Mutated dominant allele (N) makes a damaged protein which causes defected nerves in brain Result=at middle age loss of body function and death NN=Huntington’s disease Nn=Huntington’s disease nn= normal