Homunculus How is “heredity passed on: Spermist vs Ovists Spermist conception of a human sperm Homunculus Leeuwenhoek’s black male and white female rabbit experiments: spermist “proof” Mendelian Genetics Gregor Mendel Mendel’s Three Principles • Dominance • Segregation (1822-1884) • Independent Assortment The foundation of “classical” science Dominance • Traits of both parents inherited, but one shows over the other • Traits are not blended Dominance Mechanism • Two alleles are carried for each trait • In true-breeding individuals, both alleles are the same. • Hybrids, on the other hand, have one of each kind of allele. • One trait is dominant, the other trait is recessive Segregation • Half the gametes (egg or sperm) will carry the traits of one parent and half the traits for the other parent 23n 23n Independent Assortment Two different parental characteristics will be inherited independently of one another during gamete formation. Example: eye, hair or skin color Human Genome Project U.S. govt. project coordinated by the Department of Energy and the National Institutes of Health, launched in 1986 by Charles DeLisi. Definition: GENOME – the whole hereditary information of an organism that is encoded in the DNA. Project Goal: to identify the approximate 100,000 genes in the human DNA. Modeled Organisms • Bacteria (E. coli, influenza, several others) • Yeast (Saccharomyces cerevisiae) • Plant (Arabidopsis thaliana) • Fruit fly (Drosophila melanogaster) • Mouse (Mus musculus) Craig Venter Celera Genomics Importance of genetics • Understanding hereditary diseases and to develop new treatments • Donor matches • Paternity • Forensics • Evolution • Migration Polynesian Origins mtDNA Bismarck Archipelago 3.5ka http://www.sciencedaily.com/releases/2011/02/110203124726.htm Polynesian Origins Genetic Testing Would you want to know? • Ethical concerns • Cost • Insurance companies Autosomes & Sex Chromosomes Difference between Meiosis and Mitosis Meiosis I Interphase Prophase I Metaphase I Anaphase I Telephase I Crossing Over of Nonsister Chromatids between Homologous Chromosomes Meiosis II Prophase II Metaphase II Anaphase II Telephase II X X-bearing sperm Y Y-bearing sperm X X Egg Egg XX Female XY Male Sex Determination • Maleness derived from Y chromosome • SRY gene produces MIS • Female reproductive structures degenerate Genes of the Sex Chromosome X chromosome • has over 1500 genes • Most genes on X don’t have corresponding alleles on the Y chromosome Y chromosome • Has only 231 protein encoding genes • Some genes are unique only to the Y Sex Chromosomal Disorders Turner Syndrome – XO only one sex chromosome • Short, thick neck and stature • Do not undergo puberty, or menstruate, • no breast development Kleinfelter Syndrome – XXY • • • • • Testis and prostate underdeveloped No facial hair Breast development Long arms and legs: big hands and feet Can be mentally retarded XXY XO An XY Individual with Androgen Insensitivity Syndrome • XY Chromosomes • Mutation in the SRY Gene causes testes to develop • Testes insensitive to testosterone Intersex or hyperandrogenic? Caster Semenya Genetic Testing Gel electrophoresis Polymerase Chain Reaction • PCR way of copying specific DNA fragments from small sample DNA material "molecular photocopying" • It’s fast, inexpensive and simple Genetic Testing $299, looks at specific diseases 23 and me Paternity Test $99 Genetic Definitions • Genes- genetic material on a chromosome that codes for a specific trait • Genotype- the genetic makeup of the organism • Phenotype- the expressed trait • Allel- an alternative form of a gene Dominance Mechanism • Two alleles are carried for each trait • In true-breeding individuals, both alleles are the same (homozygous). • Hybrids, on the other hand, have one of each kind of allele (heterozygous). • One trait is dominant, the other trait is recessive Genetic Information Genes are traits “Eye color” Ear lobe connectedness Genes produce proteins Enzymes are proteins Homologous Chromosomes gene: location allele: specific trait Allele Example Gene = “eye color” Alleles brown blue green lavender Allele Examples appearance B B eye color: homozygous Allele Examples appearance B b eye color: heterozygous, brown dominant over blue Genotype vs Phenotype genotype homozygous (dominant) B B heterozygous B b homozygous (recessive) b b phenotype appearance Punnett Square If male & female are heterozygous for eye color B b B B b B b B B B b b b female X B male b b brown: blue: 3/4 offspring 1/4 offspring PKU Each parent carries one gene for PKU. P p P X P p p Possible genotypes: 1PP P p P P P p P p p p 2Pp 1pp Possible phenotypes:no PKU PKU Compare this to what would have happened if one parent was homozygous for sickle cell. HbS HbA HbA X HbS HbS HbS HbA HbA HbA HbA HbS HbS HbA HbA HbS HbS all offspring are carriers of sickle cell trait Where Does Genetic Diversity Come From? Mutation Chromosomal Aberrations Genetic Recombination (e.g., from sexual reproduction) Sickle Cell Mutation NORMAL Hb CTG ACT CCT GAG GAG AAG TCT Leu Thr Pro Glu Glu Lys Ser SICKLE CELL CTG ACT CCT GAG GTG AAG TCT Leu Thr Pro Glu Val Lys Ser mutation Sickle Cell treatment using CRISPR red arrows show the sickled cells Autosomes and Sex Chromosomes Red-Green Color Blindness Sex-linked trait XC Y Normal male XC X XC Xc Normal female recessive gene Possible outcomes: Xc XC Y XC XC XC Y XC Xc Xc Y XCXC XCXc XCY Normal Normal Normal female Female male (carrier) XcY Color-blind male allele E e unconnected earlobe connected earlobe P gametes F1 gene EE x ee E unconnected e Ee connected F1 Ee x Ee gametes 1/2 E 1/2 e 1/2 E 1/2 e E Punnett Square F2 e E EE Ee e ee Ee 1 EE 2 Ee 1 ee Genotypes Phenotypes Experiment to determine dominant vs. recessive Genetic Sleuthing My eye color phenotype is brown. What is my genotype? Complexities • Multiple genes for one trait • Example: eye color • Blended traits (“incomplete dominance”) • Influence of the environment (UV, smoking, alcoholism) Complexities • Co-dominance-neither allele is recessive and the phenotypes of both alleles are expressed. • Blood types- AB (not O); sickle cell anemia heterochromia Disorders Down’s Syndrome (chrom 21) Alzheimer’s (chrom 1, 10, 14, 19, 21) Huntington’s (chrom 4) Tongue Roller R = Tongue Roller r = Unable to Roll Tongue Widow’s Peak W = Widows Peak w = Lack of Widow’s Peak Free Ear Lobe Attached Ear Lobe E = Free Ear Lobe e = Attached Ear Lobe Hitchhiker’s Thumb Hi = Straight Thumb hi = Hitchhiker’s Thumb Bent Little Finger Bf = Bent Little Finger bf = Straight Little Finger Mid-digital Hair M = Mid-Digital Hair m = Absence of Mid-Digital Hair Dimples D = Dimples d = Absence of Dimples Short Hallux Ha = Short Hallux ha = Long Hallux Short Index Finger Ss = Short Index Finger S1 = Long Index Finger *Sex-Influenced Trait Blaze B = blaze b = no blaze http://www.youtube.com/watc h?v=gCPuHzbb5hA
