Lecture 12 - BILD1 The Cell Prof Lisa M Boulanger Problem Set 4 KEY posted Midterm 2 THIS THURSDAY In this room Does not include todays material

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1 02/20/07 BILD1 - Lecture 12 1 BILD1 The Cell Prof. Lisa M. Boulanger 02/20/07 BILD1 - Lecture 12 2 Problem Set 4 KEY posted Midterm 2 THIS THURSDAY In this room Does not include today’s material! Exam will be ready for pickup TUESDAY Problem Set 5 will be posted in one week 02/20/07 BILD1 - Lecture 12 3 Genes = the unit of heredity = sections of DNA Asexual reproduction by mitosis-like process Sexual reproduction by alternation of meiosis and fertilization Timing of both can vary Humans n (haploid, gametes) = 23 2n (diploid, somatic cells) = 46 Karyotypes, FISH Homologous chromosomes, autosomes Highlights from previous lecture: 02/20/07 BILD1 - Lecture 12 4 Highlights from previous lecture: Meiosis I reduces number of chromosomes (reduction division); 2n Æ n Homologous chromosomes (tetrads) align on metaphase plate Synapsis allows crossing over (recombination) S skipped between meiosis I and II Meiosis II Resembles mitosis except starting material differs Produces 4 nonidentical haploid daughter cells Sources of variation: Independent assortment Recombination Random fertilization 02/20/07 BILD1 - Lecture 12 5 THIS LECTURE: MENDELIAN GENETICS! 02/20/07 BILD1 - Lecture 12 6 • What genetic principles account for the transmission of traits from parents to offspring?
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2 02/20/07 BILD1 - Lecture 12 7 • One possible explanation of heredity is a “blending ” hypothesis – The idea that genetic material contributed by two parents mixes in a manner analogous to the way blue and yellow paints blend to make green • An alternative to the blending model is the “particulate ” hypothesis of inheritance: the gene idea – Parents pass on discrete heritable units, genes 02/20/07 BILD1 - Lecture 12 8 Mendel’s Experimental, Quantitative Approach • Mendel discovered the basic principles of heredity – By breeding garden peas in carefully planned experiments • Mendel chose to work with peas – Because they are available in many varieties • Only looked at traits that were binary (purple or white flower, wrinkly or smooth seed) • Only started with “true-breeding” plants – Because he could strictly control which plants mated with which 02/20/07 BILD1 - Lecture 12 9 –Character : a heritable feature, such as flower color –Trait : a variant of a character, such as purple or white flowers Some genetic vocabulary 02/20/07 BILD1 - Lecture 12 10 • In a typical breeding experiment – Mendel mated two contrasting, true-breeding varieties, a process called hybridization • The true-breeding parents – Are called the P generation • The hybrid offspring of the P generation – Are called the F 1 generation • When F 1 individuals self-pollinate – The F 2 generation is produced 02/20/07 BILD1 - Lecture 12 11 • When Mendel crossed contrasting, true- breeding white and purple flowered pea plants – All of the offspring were purple • When Mendel crossed the F 1 plants – A ratio of about three to one, purple to white flowers, in the F 2
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This note was uploaded on 03/26/2010 for the course BENG 110 taught by Professor Schmid-schoenbein during the Spring '08 term at UCSD.

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Lecture 12 - BILD1 The Cell Prof Lisa M Boulanger Problem Set 4 KEY posted Midterm 2 THIS THURSDAY In this room Does not include todays material

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