Genetic Changes Any mistake or change in the DNA sequence is called a mutation. Types of mutations are: point mutation frameshift mutation chromosomal mutation

A change in a single base in DNA. Point Mutation A change in a single base in DNA.

Frameshift Mutations A single base is added or deleted from DNA. Usually change the amino acid sequence results in a protein that may not function properly

Chromosomal Mutations Changes the number or structure of chromosomes Few are passed on to the next generation, because the zygote usually dies.

4 Types of Chromosomal Mutations Deletions: loss of all or part of a chromosome Insertions/Duplication: part of a chromatid breaks off and attaches to its sister chromatid causing a duplication of genes on the same chromosome Inversions: part of a chromosome breaks off and is reinserted backwards (inverted) Translocations: part of one chromosome breaks off and reattaches to a different chromosome

Nondisjunction The failure of homologous chromosomes to separate properly during meiosis Both chromosomes of a homologous pair move to the same pole of the cell. One cell will have an extra chromosome, and the other will be missing a chromosome. Organisms with extra chromosomes often survive; organisms lacking one or more chromosomes do not.

Causes of Mutations Any thing that causes a mutation is called a mutagen. Mutations are generally random events and provide variations that enables species to evolve. Many environmental agents also cause mutations. Exposure to X-rays, UV light, radioactive substances, or certain chemicals can cause changes to DNA.

Karyotypes A picture taken of stained chromosomes found in a cell during metaphase. Chromosomal disorders can be identified using a karyotype. The picture is enlarged so the geneticist can cut apart and arrange the chromosome pairs by length, banding pattern, and centromere placement. The geneticist can use the karyotype to see if there are too many chromosomes, too few chromosomes, or chromosomal abnormalities.

Normal Male Karyotype Trisomy 21, Male Karyotype

Genetic Disorders Hemophilia - Caused by a recessive gene on the X chromosome. One can bleed to death with small cuts. Downs Syndrome - Caused by non-disjunction of the 21st chromosome. 3 – 2lst chromosomes Sickle Cell Anemia - red blood cells, normally disc-shaped, become crescent shaped, and get stuck in blood vessels Cystic Fibrosis – Recessive disorder, deletion of only 3 bases on chromosome 7, Fluid in lungs, potential respiratory failure Tay-Sachs Disorder - autosomal recessive, Central nervous system degrades, ultimately causing death. Color Blindness - x-linked recessive, can’t distinguish between red and green

Down’s Syndrome or Trisomy 21

Pedigrees A diagram, similar to a family tree, used by geneticists to show genetic relationships within a family. Pedigrees can: Show if a trait is inherited. Show how a trait is passed from one generation to the next. Determine whether an allele for a trait is dominant or recessive.

Gel Electrophoresis DNA Fingerprinting