Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Principle of SegregationPrinciple of Independent AssortmentSlide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Genetics and the Mechanics of Natural Selection ANTH A-103, Human Origins and PrehistoryLarry J. Zimmerman, Ph.D., RPAIndiana University-Purdue University IndianapolisWhy study genetics?Your life and that of offspring may depend on it!But it’s hard!Yes, it does involve some memorization and thought…but how much is your life or that of your child worth?And…Of course there are questions of ethics…The essentialsGeneralized Cell StructureDNA is in the nucleus; protein synthesis occurs in the ribosomesThe body is composed of cells of two basic types: Somatic cells and gametes.Somatic cells are the cellular components of body tissue: muscle, skin, bone, nerve, heart and brain.Gametes are sex cells specifically involved in reproduction and not important structural parts of the body.The nucleus Contains two molecules or nucleic acids that contain the genetic information that controls the cell's function: DNA (deoxyribonucleic acid) RNA (ribonucleic acid).Outside the nucleus The ribosomes are involved with translating the instructions coded in the material of inheritance into proteins or chemical messengers that are used by the body's cells.Outside the nucleusMitochondria are involved with energy transfer within the cell, and are interesting because they contain their own set of hereditary material independent of that contained in the nucleus.Mitochondrial DNA can be traced through females and dated back into time.Chromosomes and DNAThe material of inheritance within the nucleus of a cell is arranged in long strands called chromosomes. On the molecular level the chromosomes are actually nothing more than two long strings of DNA wound together in a spiral-like structure called a double helix.The bases and genesEach of the two strands of DNA in a chromosome are composed of varying combinations of 4 simple molecules called bases. The four bases are adenine, cytosine, guanine, and thymine labeled A, C, G, and T. A single DNA strand is composed of a string of bases, each of which can be one of 4 types: A, C, G, or T. The order in which the bases occur on the DNA strand is not random. Genes are nothing more or less than unique, specific sequences of the 4 bases.Allele"Gene" is a layman's term. Scientists avoid the use of the word gene, because it is not very specific. Locus (plural = loci) and allele are used instead.LocusA locus is the section of a DNA strand that contains the instructions for one specific product (eye color, tongue rolling, blood serum protein albumin). A locus is simply a section of the chromosome that holds a sequence of bases and is like an address. The particular base sequence that resides at a given locus is called an allele. Only one allele can reside at a given locus in any one DNA strand.Gene Expression Alleles code for proteins which are either the desired product or are messengers or controlling substances that produce the desired result. A protein is simple a chain of amino acids. Just like a DNA strand is a chain of bases, a protein is a chain of amino acids. There are 4 different bases that can be chained together to form a DNA strandThere are about 20 different amino acids that can be chained together to form a protein.Chromosome Number Each cell of the body (except sperm and ova) has two of each chromosome or diploid. One chromosome came from the mother and one came from the father. So, the reproductive cells, the sperm and ova, must have only one chromosome or haploid. Haploid reproductive cells are called gametes.The processAnother way to diagram itHumans have 23 pairs of chromosomes, 46 altogether. For 22 of these chromosomes the two members of the pair are pretty much identical or autosomal chromosomes. 23rd pair of chromosomes is the sex chromosomes.The sex chromosomes come in two varieties, X and Y. Females have two X chromosomesMales have one X chromosome and one Y chromosome. Generally speaking, if you have a Y chromosome you are a male. Human Genetic StructureThe Human Karyotype46 chromosomes in 23 pairsPair 23 is the sex chromosome, in this case a maleChromosomes have two arms that are joined at the centromere.The short arm is called the p arm for the French word petit, which means small or short. The long arm is called the q arm because q comes after p in the alphabet.The ends of the chromosomes are called telomeres.Detail on Chromosome StructureAll the gametes produced by females carry only X chromosomes. But, half of the gametes produced by males carry the X chromosome and half carry the Y chromosome. Whether a given offspring is female or male depends on whether the father's sperm happens to have an X or a Y chromosome. Sex and the single chromosomeMost traits are autosomal traits, the loci carrying alleles for them are located on one of the autosomal chromosomes. A few traits are sex linked, carried on one of the sex chromosomes - usually the X. One sex-liked trait is hemophilia, caused by a recessive gene on the X chromosome. It occurs mostly in men because they only have one X chromosome. If they have the recessive gene, then they will have hemophilia. Autosomal and sex-linked chromosomesMendelian inheritance Gregor Mendel1822-1884Mendel’s Sweet Pea ExperimentsPunnet SquaresMedel’s Peas Punnet SquaresGenotype: the genetic structure of the populationPhenotype: the genetic structure of the individualHomozygous: both genes are the same (RR, YY)Heterozygous: the genes are different (Rr, Yy)Dominant: the characteristic shows (R, Y)Recessive: the characteristic normally is hidden (r, y)Dominant shows: RR, Rr, YY, YyRecessive shows: rr, yyKey Mendelian TermsDominant & RecessivePrinciple of Segregation•Genes occur in pairs because chromosomes occur in pairs. •During gamete production, the members of each gene pair separate so that each gamete contains one member of a pair. •During fertilization, the full number of chromosomes is restored and members of a gene or allele pairs are reunited.Principle of Independent Assortment•The distribution of one pair of alleles into gametes does not influence the distribution of another pair.