Lecture 12 BILD1 S10

Lecture 12 BILD1 S10 - Announcements Midterm #2 regrade...

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1 Announcements Midterm #2 regrade requests due by Mon. May 17th. Turn in today in class, or to NSB 6109 in bin outside Dr. Kiger’s office. Unclaimed exams can be picked-up outside NSB 4119. Problem Set #4 & 5 posted. Next class is Movie Night! Double Helix (Life Story) The movie will be tested…plus you will enjoy it! No class meetings Monday, May 31st. See website for rescheduled Sections and OHs Lecture 12 DNA Heredity & Replication Morgan 1857 1933 Mendel The Chromosomal basis of Mendel’s Laws Yel ow-round seeds ( YYRR ) Green-wrinkled seeds ( yyr ) Meiosis Fertilization Gametes Al F1 plants produce yel ow-round seeds ( YyRr ) P Generation Meiosis Two equal y probable ar angements of chromosomes at metaphase I LAW OF SEGREGATION Anaphase I Metaphase I Fertilization among the F1 plants 9 : 3 : 3 : 1 1 4 1 4 1 4 1 4 YR yr yr yR Gametes Y R R Y y r r y R Y y r R y Y r R y Y r R Y r y r R Y y R Y r y R Y Y R R Y r y r y R y r Y r Y r Y r Y R y R y R y r Y F2 Generation Starting with two true-breeding pea plants, we fol ow two genes through the F1 and F2 generations. The two genes specify seed color (al ele Y for yel ow and al ele y for green) and seed shape (al ele R for round and al ele r for wrinkled). These two genes are on dif erent chromosomes. (Peas have seven chromosome pairs, but only two pairs are il ustrated here.) al eles segregate at anaphase I, yielding two types of daughter cel s for this locus. Each gamete gets one long chromosome with either the R or r al ele. 2 Fertilization recombines the R and r al eles at random. 3 ar angement at metaphase I. Compare the ar angement of the R and r al eles in the cel s on the left and right 1 Each gamete gets a long and a short chromosome in one of four al ele combinations. 2 Fertilization results in the 9:3:3:1 phenotypic ratio in the F2 generation. 3 Law of Segregation = separation of alleles at anaphase I Law of Independent Assortment = combinations of alleles for different genes depend on arrangement at metaphase I If you really understand this figure, you know all the main points! Figure 15.2
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2 In 1953, James Watson and Francis Crick shook the world with an elegant double-helical model for the structure of deoxyribonucleic acid, or DNA Figure 16.1 DNA - the center of life Hereditary information – is encoded in DNA and reproduced in all cells of an organism The DNA program – directs the development of many different types of traits DNA is the Genetic Material The Search for the Genetic Material The role of DNA in heredity – was first worked out by studying bacteria and the viruses that infect them 1. DNA can transform bacteria (Griffith and Avery) 2. Viral DNA can program cells (Hershey and Chase) 3. DNA composition can explain variation (“Chargaff’s Rule”) Frederick Griffith (1928) Mixed heat-killed pathogenic bacterial strain (S) with living non-pathogenic strain (R)… …found living R cells became pathogenic (like S cells)!
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Lecture 12 BILD1 S10 - Announcements Midterm #2 regrade...

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