Sources of Genetic Variation 1. Mutation - only source of new traits!!! 2. Recombination in Sexual Reproduction 3. Crossing Over during Meiosis 4. Independent Assortment during Meiosis 5. Gene Flow (immigration/emigration) 6. Epigenetic “Tags” / Factors
Mutation - is any unintended change in the genetic code. -is usually bad and sometimes passed on. -is only passed on if it occurs in the gametes (germ-line /sex cells) not somatic (body) cells. -changes something about Proteins (different one gets made, too much gets made, not enough gets made, protein doesn’t work). -is occasionally good and is then favored by Natural Selection and passed on to future generations.
*The reason that only Germ-Line Mutations are passed on to offspring is that the only genes an offspring has are the genes that it inherited from the sperm and egg. Somatic Cell Genes are not passed on!!!*
Mutations Unintended changes to the genetic code that result in – 1. the wrong protein. 2. too much protein. 3. not enough protein. 4. a more adaptive protein. -leads to Evolution!!!
Environmental Mutagens 1. Solar Radiation 2. Nuclear Radiation 3. Toxic Solvents like Benzene 4. Extremes of pH (too acidic or basic) 5. Hormones in Food 6. Epigenetic Factors
Meiosis is how we make gametes (sex cells, sperm and egg). is the process of two cell divisions starting with one Diploid Cell (2n) with both members of each Homologous Pair and ending with four Haploid Cells (1n) with only one member of each Homologous Pair.
Karyotype is a picture of someone’s Homologous Chromosome Pairs. There are 23 pairs in humans, containing Genes for nearly 21,000 different Proteins!
Antigens Surface Proteins that cells use as I.D. and receptors. Different Antigens result in different Blood Types. Our immune systems reject and attack “foreign” antigens. EX: An “A” person will make immune antibodies against “B” blood!!!
Epigenetics Epigenetic factors are “tags”, chemicals like Methyl groups that attach to our DNA and turn genes on and off. Epigenetic Factors accumulate as we age, resulting in more and more diseases like cancer.
Non-Disjunction Failure of Homologues to Segregate during Meiosis leading to too many or too few chromosomes. Leads to Chromosomal Mutations like- 1. Down’s Syndrome (Trisomy-21) 2. Turner’s Syndrome 3. Klinefelter’s Syndrome
Down’s Syndrome / Trisomy-21 -Resulting from non-disjunction and transposition. -Leads to mental and physical retardation.
Turner’s Syndrome -Resulting from non-disjunction -Condition of having only one X chromosome -Causes underdevelopment of sexual characteristics, neck webbing, infertility.
Klinefelter’s Syndrome -Resulting from non-disjunction -Condition of a male having more than one X chromosome -Causes underdevelopment of sexual characteristics, feminization, infertility.
Autosomal Recessive Diseases Usually caused by Point Mutations like Deletion and Insertion.
Sickle-Cell Anemia Where an Autosomal Recessive mutation creates a different form of the protein Hemoglobin, resulting in Erythrocytes (red blood cells) that have an elongated crescent shape. These “sickled” cells clump easily, causing pain and possible tissue death in the extremities
Cystic Fibrosis Where an Autosomal Recessive mutation creates a flawed receptor protein, resulting in a build-up of mucus in the lungs and pancreatic duct. This build-up causes poor digestive function and an early death (usually in one’s 30’s).
Phenyketonuria (PKU) Where an Autosomal Recessive mutation results in the lack of an enzyme to convert the amino acid Phenylalanine into Tyrosine. Phenylalanine is common in artificial sweeteners. The lack of Tyrosine prevents the proper development and function of the nervous system, leading to mental retardation.
Genetic Engineering - is the “cutting and pasting” of DNA to produce Proteins we want. -is done using Restriction Enzymes. -can produce Recombinant DNA which is a combo of genes from different organisms / viruses.