1. Chromosomes and Cell Reproduction
Chapter 6 & 7

2. I. Chromosomes
Chromosome- made of 2 exact copies of DNA coiled around proteins
(*this is after replication but before cell division)
Chromatid- each copy of the DNA on a chromosome
Centromere- place where the chromatids attach to make a chromosome
Genes- Segments of DNA on a chromosome that code for a specific protein/trait

4. *Draw a chromosome and label chromatids, centromere and gene

5. II. Chromosome Number
Each human somatic cell (body cell) has 2 copies of 23 different chromosomes for a total of 46 chromosomes
We inherit 1 of each chromosome from mom and 1 from dad
Homologous Chromosomes- similar in size, shape and genetic content

7. D. Diploid cells- contain 2 sets of chromosomes, all somatic cells are diploid
(ex. Somatic cells in humans have a total of 46 chromosomes)
E. Haploid Cells- contain only 1 set of chromosomes, only gametes can be haploid
(ex. Gametes in humans have 23 chromosomes)

8. III. Karyotypes
A picture of the chromosomes of an organism arranged by size
Used to examine an individuals chromosomes:
Karyotypes can determine only 2 things about the organism:
Sex of individual
Any abnormalities in the chromosomes (number or shape

9. C. Humans have 1 pair of sex chromosomes and 22 pairs of autosomal chromosomes (non sex chromosomes)
D. Sex Chromosomes-
XX= Female XY= Male
(the sex chromosomes are the last pair of chromosomes shown in a karyotype)

10. Trisomy – when there is three of a certain chromosome instead of the normal 2

11. IV. Cell Cycle G1 Phase- period of cell growth
S Phase- when DNA replication occurs
G2 Phase- cell growth and preparation for mitosis
Mitosis- division of the nucleus
Cytokinesis- division of the cytoplasm

12. Cell Cycle Animations http://www.cellsalive.com/cell_cycle.htm

13. V. Mitosis The division of the nucleus in somatic cells
Chromosomes have replicated prior to the start of mitosis
Produces 2 identical daughter cells
4 phases

14. Prophase-
chromatin coils into chromosomes
Nuclear envelope dissolves
Spindle fibers form

15. 2. Metaphase (middle)
Chromosomes line up in the middle of the cell
Centrioles move to opposite poles
Spindle fibers attach to chromosomes

16. 3. Anaphase (apart)
Spindle fibers shorten and pull chromatids toward opposite poles

17. 4. Telophase (opposite of prophase)
Nuclear envelope forms around chromatids
Chromatids uncoil
Cleavage is formed
Spindle fibers dissolve

18. Cytoplasm is divided in half
E. Cytokinesis
Occurs after Mitosis
Cytoplasm is divided in half
Cell membrane encloses each cell
**New cells are now in interphase and the cell cycle starts over.

21. Mitosis Animation http://iknow.net/cell_div_education.html

22. VI. Meiosis Two divisions of the nucleus
Results in the formation of 4 gametes (egg, sperm)
Halves the number of chromosomes (in humans from 46 to 23)

23. Stages of Meiosis I
1.*Prophase I- crossing over occurs, (portions of one chromosome are broken and exchanged with portions of the other homologue)**results in genetic variability
2. Metaphase I- homologous chromosome pair up together at the equator
3. Anaphase I- centromeres do not divide
4. Telophase I and Cytokinesis

24. Meiosis II 1. Prophase II 2. Metaphase II 3. Anaphase II
4. Telophase II & Cytokinesis
Interphase
P 1
M 1
A 1
T1 & C
P 2
M 2
A 2
T 2
Cytokinesis

26. Females- called oogenesis, forms 1 ovum and 3 polar bodies
Males- called spermatogenesis, forms 4 sperm cells

27. http://www. biologyexams4u

28. Meiosis Animations
Meiosis Animation
Meiosis Square Dance Video