The New Genetics Part I

From one generation to another, genes are passed down from generation to generation. The phenotype of an organism provides the material from which evolution acts. Molecular studies of a species DNA and/or proteins can help determine its evolutionary past and establish its relationship with other organisms. A gene found in a given species is a modified version of a gene that existed millions of years ago.

i.e. Myoglobin- is a gene for a protein found in the muscles and it stores oxygen. It orginated from a bacterial cell that is an obligate anaerobe (meaning oxygen would kill it). The hemoglobin gene evolved from myoglobin. This happened by gene duplication and then gene modification. Hemoglobin has 4 polypeptide chains that are nearly identical to myoglobin. When two organisms have the same gene for the same function, scientists can compare the genes for differences and estimate how closely related they are.

Mutations in the DNA can cause changes in the protein being produced. Point mutations- One nucleotide is substituted for another in a gene. This may result in a different amino acid is switched. This may or may not have an effect. i.e. Sickle cell anemia- This is a gene inwhich one nucleotide has been switched. This substitutes one amino acid for another. This make hemoglobin less soluble and does not dissolve as well in the cytoplasm. i.e. The cat ate the fat rat. now substitute an r for the t The car ate the fat rat. The sentence has been changed but it is understandable

2.Frame Shift mutation Because the genetic code is read in codons (groups of 3 nucleotides) an addition or deletion can seriously affect a gene. i.e. The cat ate the fat rat. now delete the c The ata tet hef atr at This new sentence makes no sense. This is true of frame shift mutations.

i.e. The cat ate the fat rat. now delete the c The ata tet hef atr at This new sentence makes no sense. This is true of frame shift mutations. Mutagens are things that cause

Mutagens are things that cause mutations i. e Mutagens are things that cause mutations i.e. UV radiation, radioactivity, certain chemicals. Large scale mutations that cause chromosomal changes Chromosomes can have a major portion of their DNA changed.

1. Deletion-can result when a broken section of a chromosome is lost. 2. Duplication- a portion of the DNA is duplicated and inserted back into the chromosome 3. Inversion- a portion of the chromosome is cut out and is reinserted backwards.

4. Translocation- a portion of a chromosome is "translocated" to another chromosome. 5. Nondisjunction- an extra chromosome is included in gametes such as Down's syndrome. 6. Transposons-"jumping genes" are pieces of DNA on an organisms chromosome that is able to move itself from one position on a chromosome to another place. It is estimated that certain pieces of corn contains 50% transposons. They were first discovered by Barbara McClintock in corn.

7. Retroviruses are RNA viruses that have the ability of taking RNA and converting it to DNA. This DNA can insert itself into the host chromosome. Some chromosomal aberrations are lethal and result in miscarriages. Others can cause cancers or tumors.