CH 4 PART 1

CH 4 PART 1 - Basic Principles: How Traits Are Transmitted...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
1 CHAPTER CHAPTER Basic Principles: How Traits Are Transmitted Basic Principles: How Traits Are Transmitted Chapter 4: The Chromosome Theory of Inheritance .1 Chromosomes: The Carriers of Genes .2 Mitosis: Cell Division That Preserves Chromosome Number .3 Meiosis: Cell Divisions That Halve Chromosome Number GENE3200 - Chapter 4 - Bedell - 6/17/11
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Evidence that genes reside in the nucleus Evidence that genes reside in the nucleus 1667: Anton Van Leeuwenhoek Microscopy revealed that semen contain spermatozoa ("sperm animals") Hypothesized that sperm may enter egg to achieve fertilization Mid-to-late 1800s: Cytology – the study of cell structure and function using microscopy Direct observations of fertilization through union of nuclei of eggs and sperm (frog and sea urchin) Conclusion: something in the nucleus must contain the hereditary material 2 GENE3200 - Chapter 4 - Bedell - 6/17/11
Background image of page 2
Evidence that genes reside in chromosomes Evidence that genes reside in chromosomes 1880s – improved microscopy and staining techniques Long, threadlike bodies (chromosomes) visualized in the nucleus Movement of these bodies followed through cell division Mitosis - nuclear division that generates two daughter cells containing the same number and type of chromosomes as parent cell Meiosis - Nuclear division that generates gametes (egg and sperm) containing half the number of chromosomes found in other cells 3 GENE3200 - Chapter 4 - Bedell - 6/17/11
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The chromosome theory of inheritance The chromosome theory of inheritance Walter Sutton – 1902, chromosomes carry Mendel's units of heredity 1.Two copies of each kind of chromosome 2.Chromosome complement is unchanged during transmission to progeny 3.Homologous chromosomes separate to different gametes 4.Maternal and paternal chromosomes move to opposite poles 5.Fertilization of eggs by random encounter with sperm 6.In all cells derived from fertilized egg, half of chromosomes are maternal and half are paternal GENE3200 - Chapter 4 - Bedell - 6/17/11 4
Background image of page 4
Sutton hypothesized that one chromosome pair Sutton hypothesized that one chromosome pair determines sex in grasshoppers determines sex in grasshoppers GENE3200 - Chapter 4 - Bedell - 6/17/11 5 Careful observations of chromosomes in testes and ovaries before and after meiosis, and after fertilization Sutton identified 24 chromosomes, of which 22 were in 11 matched pairs and the other two chromosomes (X and Y) were unmatched Fig. 4.5 Before meiosis , both sexes have the 11 matched pairs and the X and Y After meiosis , testis cells have 11 chromosomes plus either X or Y (~ 50:50) and eggs have 11 chromosomes and an X (no Y!)
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Concluding remarks in Sutton Concluding remarks in Sutton ’s 1902 paper ’s 1902 paper I may finally call attention to the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reducing division as indicated above may constitute the physical basis of the Mendelian law of heredity Sutton, W. S. (1902) On the morphology of the chromosome group in Brachystola magna. Biol Bull. 4:24-39 If you’re interested, there is a short review of Sutton and his work at www.genetics.org/content/160/1/1.full 6 GENE3200 - Chapter 4 - Bedell - 6/17/11
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/22/2011 for the course GENE 3200 taught by Professor Condie during the Summer '08 term at UGA.

Page1 / 30

CH 4 PART 1 - Basic Principles: How Traits Are Transmitted...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online