BIOL110s05-22 - BIOL 110: Principles of Biology Spring 2005...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: BIOL 110: Principles of Biology Spring 2005 Lecture 22, W 3/16/05 • ONLINE Quizzes (bi-weekly) from now on! (bi– Link TO QUIZZES: (Cañada College I.D. for login and password; (Cañ You can change it yourself with the REGISTER button) – Time-limited (so study well first!); Time– ~ 30 minutes to complete; once only. Posted this weekend!! • Study Guide for MT2 available. (Ch. 4-8) – Genetics Problems: #1-7 (look at 8 & 9 too) #1• Review Session, TODAY, 12:30pm-2pm in Lab. (bring Q’s) 12:30pm(bring Q’ – Extra office hours: W, 2-3:30pm and Thurs., 1-3pm. 21- REVIEW: • Ch. 8: Genetics: Observing Patterns of Inherited Traits. – Mendel’s Experiments & Laws: Mendel’ • Monohybrid Cross/ Segregation (alleles of the SAME gene separate); • Dihybrid cross/ Independent Assortment (alleles of DIFFERENT genes separate – see recombinant/non-parental phenotypes). recombinant/non- – Exceptions/Beyond Mendel – Incomplete dominance…. dominance… TODAY: • Ch. 8: Genetics: Observing Patterns of Inherited Traits. – Exceptions/Beyond Mendel – Incomplete Dominance, Codominance, Pleiotropy, Codominance, Pleiotropy, – Environment, Continuous Variation, Sex-Determination Sex- 1 A. Flower Color in Snapdragons: Flower Incomplete Dominance Red-flowered plant X White-flowered plant (homozygote) (homozygote) Pink-flowered F1 plants (heterozygotes) Flower Color in Snapdragons: Incomplete Dominance Pink-flowered plant X Pink-flowered plant (heterozygote) (heterozygote) White-, pink-, and red-flowered plants in a 1:2:1 ratio (3 Phenotypes!) 1:2:1 Can see the see heterozygotes!! 2 Flower Color in Snapdragons: Incomplete Dominance (Biochemical Explanation) (Biochemical 1. Red flowers - two alleles allow them to make a red pigment 2. White flowers - two mutant alleles; can’t make red pigment 3. Pink flowers - have one normal and one mutant allele; make a smaller amount of red pigment B. Genetics of ABO Blood Types: Three Alleles (Codominance) • Gene that controls ABO type codes for ABO enzyme that dictates structure of a glycolipid on blood cells • Two alleles (IA and IB) are codominant codominant when paired • Third allele (i) is recessive to others – = Multiple Alleles!! 3 ABO Blood Type: Allele Combinations • • • • Type A - IAIA or IAi Type B - IBIB or IBi Type AB - IAIB Type O - ii IB IB or Range of genotypes: IA IA or IA i Blood types: IA IB IB i ii A AB B O ABO Blood Type: Glycolipids on Red Cells • Type A - Glycolipid A on cell surface • Type B - Glycolipid B on cell surface • Type AB - Both glyocolipids A & B • Type O - Neither glyocolipid A nor B 4 ABO and Transfusions • Recipient’s immune system will attack blood cells that have an unfamiliar glycolipid on surface – (attack “non-self” molecules) • Type O is universal donor, because it has universal neither type A nor type B glycolipid • Type AB is universal recipient, because universal neither A nor B are considered “non-self”. C. Pleiotropy • Alleles at a single locus may have effects on two or more traits – One gene, but affects multiple characteristics! • effects of the mutant allele at the beta-globin locus that gives rise to sickle-cell anemia; sickle • Cystic Fibrosis • Manx Cat • Siamese cat….. 5 III. Environmental Effects on Phenotype: eg., Temperature • Genotype and environment interact to produce phenotype • Himalayan rabbits are Homozygous for an allele that allele specifies a heat-sensitive heat version of an enzyme in melanin-producing pathway – Melanin is produced only in cooler areas of body • Also: plants & altitude, pH, nutrients (flamingos),….. IV. Continuous Variation • A more or less continuous range of continuous small differences in a given trait among individuals • The greater the number of genes and greater environmental factors that affect a trait, the more continuous the more variation in versions of that trait 6 Plotting Variation Number of individuals with some value of the trait Range of values for the trait V. Homologous Chromosomes & Sex Determination • Homologous autosomes are identical in length, size, shape, and gene order (position) – Homology required for proper pairing and Meiosis/Gametogenesis Meiosis/Gametogenesis • Sex chromosomes are nonidentical but still homologous – (along portions of X & Y) • Homologous chromosomes interact, then segregate from one another during meiosis 7 Sex Determination • Gene on X chromosome makes the “Anti-Testes Factor” Factor – Ovaries = Female Ovaries female (XX) male (XY) eggs X X x x X X Y XX XY X XX XY sperm Y X • Another gene on Y chromosome inhibits ATF – SRY gene – Testes = Male!!! Testes The Y Chromosome • Fewer than two dozen genes identified • One is the master gene for male sex determination – SRY gene (sex-determining region of Y) (sex- • SRY present (XY, XXY, XYY), testes form • SRY absent (XX, XO, XXX), ovaries form 8 The X Chromosome • Carries more than 2,300 genes • Most genes deal with nonsexual traits • Genes on X chromosome can be expressed in both males and females – Many recessive “X-linked” recessive alleles show up in males (no second X to mask!!) Examples of X-Linked Traits • Color blindness – Inability to distinguish among some or all colors • Hemophilia – Blood-clotting disorder Blood– 1/7,000 males has allele for hemophilia A – Was common in European royal families • Cats: Calico coat color – Orange or Black alleles? – Heterozygous females: 1 XXchromosome inactivated in early embryo; – random patches of color produced 9 X-Linked Recessive Inheritance • Males show disorder more than females • Son cannot inherit disorder from his father • Mothers give disorder to ½ of sons Midterm 2 REVIEW: 1. 2. 3. 4. Energy & Enzymes Photosynthesis Respiration & Fermentation – both use glycolysis Reproduction – Cell Cycle, Interphase 1. Nuclear Divisions – Mitosis (constancy; 2n 2n); 2n); Meiosis (diversity; 2n n) n) 2. Gametogenesis & Fertilization 5. Genetics: Mendel & Beyond 1. Monohybrid & Dihybrid crosses – segregation; independent assortment 2. Incomplete Dominance and Codominance 3. Pleiotropy, Environment, Continuous Variation Pleiotropy, 4. Sex Determination 10 Genetic Disorder • Inherited conditions that cause mild to severe medical problems • Why don’t they disappear? – Mutation introduces new rare alleles – In heterozygotes, harmful allele is masked, so it can still be passed on to offspring • Sometimes, Heterozygote has rare Advantage! – Eg: Sickle Cell Hemoglobin Eg: Pedigree Symbols male female marriage/mating offspring in order of birth, from left to right Individual showing trait being studied sex not specified I, II, III, IV... generation 11 Pedigree for Polydactyly I female male II 5,5 6,6 III * 5,5 6,6 6 7 6,6 5,5 5,5 6,6 5,5 6,6 5,5 6,6 12 6,6 5,5 5,6 6,7 IV 5,5 6,6 V *Gene not expressed in this carrier. 6,6 6,6 Autosomal Recessive Inheritance Patterns • If parents are both heterozygous, child will have a 25% chance of being affected 12 ...
View Full Document

This document was uploaded on 03/18/2010.

Ask a homework question - tutors are online