View
225
Download
1
Tags:
Embed Size (px)
Citation preview
Reading
• Chapters 12, P 1068 - 1074, & 13
Quiz Material
• Questions on P 240, 1080, & 276-278
• Chapter 12, 50, & 13 Quizzes on Text Website (www.mhhe.com/raven7)
Outline
• Meiosis (cntd.)
• Gametogenesis
• Genetics
Mendelian Patterns of Inheritance
Non-Mendelian Patterns of Inheritance
Mitosis Vs. Meiosis
MITOSIS MEIOSIS
# Divisions
# Daughter Cells
Final Ploidy
Cell Type
Genetic Variation?
Metaphase Alignment
Anaphase Separation
Mitosis Vs. MeiosisMITOSIS MEIOSIS
# Divisions 1 2
# Daughter Cells 2 4
Final Ploidy 2N N
Cell Type Somatic Gametes
Genetic Variation?
No Yes
Metaphase Alignment Chromosomes
I - Homologues
II - Chromosomes
Anaphase Separation Sister chromatids
I - Homologues
II - Sister chromatids
Evolutionary Consequences of Sex
• Random Fertilization
In addition to independent assortment and crossing over, random fertilization generates diversity because 2 gametes (each of which is different from the parent) fuse.
• Importance for Evolution
The diversity generated by sexual reproduction results in individuals that may be fitter than others (not always!) in a particular environment and will therefore be selected by that environment.
http://webanatomy.net/histology/reproductive/seminiferous_tubule.jpg
Structure of Seminiferous Tubules
Initial Ideas About Heredity
• Pre-Mendel
Read about classical assumptions (P 242) & the work of Koelreuter & Knight.
• Mendel (1822-1884)
What was different about Mendel’s work?
Mendel’s Experiments• Characteristics of the Study SubjectThe garden pea was a good choice because:
1. Can cross or self-fertilize.
2. Produces large numbers of offspring.
3. Easy to grow.
4. Has a number of varieties with different traits.
5. Short generation times.
6. Produces hybrid varieties.
Mendel’s Experiments• Experimental DesignMendel worked with 7 easily distinguishable traits as follows:
1. Ensured the parental (P) generation was true-breeding.
Eg. White flowered plants White flowered progeny
2. Crossed varieties with alternate traits.
Eg.
Mendel’s Experimental Design (Cntd.)
3. Self-fertilized the hybrid generation (F1)
Mendel’s Results
• F1 Generation
No intermediate progeny - all resembled one of the parents. This was referred to as the dominant trait.
Eg. P: Purple X White
F1: Purple
Mendel’s Conclusions
1. Blending (hybridization) was not occurring.
2. For each alternative trait, one alternative was not expressed in the F1, but reappeared in the F2.
3. Pairs of alternate traits segregated among progeny of a particular cross.
4. These alternate traits were expressed in the F2 generation as 3 dominant : 1 recessive.
Principles of GeneticsMendel’s ideas in modern terms:
• Genes
Information about traits is transmitted from parent to offspring in the form of genes.
• Homologous Chromosomes
A diploid individual receives 2 alleles (forms of a gene) for each trait, one on each of 2 homologous chromosomes.
Homozygous
Heterozygous