Importance of genetics Understanding hereditary diseases and to

Importance of genetics • Understanding hereditary diseases and to develop new treatments • Donor matches • Paternity • Forensics • Evolution

Genes- genetic material on a chromosome that codes for a specific trait Genotype- the genetic makeup of the organism Phenotype- the expressed trait Allele- 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 eye color: homozygous

Allele Examples appearance eye color: heterozygous, brown dominant over blue

Genotype vs Phenotype genotype phenotype homozygous (dominant) heterozygous homozygous (recessive) appearance Phaner = visible

Punnett Square If male & female are heterozygous for eye color X male female 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: 1 PP P p P p p p 2 Pp 1 pp Possible phenotypes: no PKU

Compare this to what would have happened if one parent was homozygous for sickle cell. Hb. A Hb. S X Hb. S Hb. A Hb. S all offspring are carriers of sickle cell trait

Autosomes and Sex Chromosomes

Red-Green Color Blindness Sex-linked trait XC Y Normal male XC Xc Normal female recessive gene Possible outcomes: Xc XC Y XC XC XC Y XC Xc Xc Y X CX C X CX c X CY Normal female Female (carrier) Xc. Y Color-blind male

Dominance Most traits show complete dominance Blending unexpected

allele E e unconnected earlobe P gametes F 1 gene unconnected EE x ee E e Ee connected

F 1 Ee x Ee gametes 1/2 E 1/2 e Punnett Square F 2 E e E EE Ee ee 1 EE 2 Ee 1 ee

generation genotypes unconnected E: e P EE, ee 50% 1: 1 F 1 Ee 100% 1: 1 F 2 EE, 2 Ee, ee 75% 1: 1 phenotypes ratio of alleles in the population Basis of the Castle-Hardy-Weinberg Law

Genotypes Phenotypes Experiment to determine dominant vs. recessive

Genetic Sleuthing My eye color phenotype is brown. What is my genotype?

Pedigree phenotypes infer genotypes Alternative: look directly at the DNA

Complexities Multiple genes for one trait Example: eye color Blended traits (“incomplete dominance”) Influence of the environment

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 S 1 = Long Index Finger *Sex-Influenced Trait

Kiss me, you fool. Pttttthhhhhhhtttt! Presentation created by J. Kenyon