1. DNA in the Cell Inside the nucleus are chromosomes, which house DNA
Chromosome made from proteins + histones. Coils DNA so it can fit into a cell
Each chromosome consists of identical halves called chromatids
Center of the chromosome is called the centromere

2. Number & Types of Chromosomes
Sex chromosomes determine the sex of an organism
XX = female
XY = Male
All other chromosomes are called autosomes
Homologous Chromosomes
Each organism gets two copies of each autosome; 1 from mom and 1 from dad (46 total chromosomes; 23 pairs in humans)
Each 2 paired chromosomes are called homologous chromosomes
Homologous chromosomes carry genes for the same traits

3. Homologous Chromosomes

4. How Many Chromosomes?

11. CARP- 104 ELEPHANT-56 KANGAROO-12 PINEAPPLE-50 SHRIMP-92 ADDER’S TONGUE FERN-1200

12. Diploid & Haploid Cells
Diploid Cells  Cells with 2 copies of each chromosome
Haploid Cells  Cells with 1 copy of each chromosome
Most cells in the body are diploid
Sex cells (sperm & egg) are haploid

13. Diploid & Haploid Cells

14. Why Do Cells Divide?
Get too big (take in more nutrients than they can metabolize)
Death/ Need replacement
Surface to volume ratio; too much volume, not enough surface
When do cells divide?
Depends on the type of cell (days, weeks, months, some never divide)
Cell Cycle  Cells will grow, replicate, and die

15. Cell Division in Prokaryotes
Prokaryote  unicellular bacteria with no nucleus
Binary Fission  DNA is replicated, cell doubles in size and splits

16. Stages of Cell Cycle in Eukaryotes
Interphase  Growth Phase
G1  Cell growth
S  Synthesis/ Replication of DNA
G2 -> Final growth
Mitosis  DNA, which has
been replicated (remember last unit?)
needs to be distributed equally
to each new cell

17. Stages of Mitosis Prophase
Chromatin condenses (chromosomes) & nucleus disappears
Spindle fibers (microtubules) form & move chromosomes
Metaphase
Spindles align chromosomes in the middle of the cell
Anaphase
Centromeres divide and sister chromatids split
Chromatids move toward opposite poles
Telophase
Chromosomes arrive at opposite ends of cell
Nucleus reappears
Spindle disappears
Cell splits (cytokinesis)

18. Stages of Mitosis

19. Cytokinesis
Animal Cell  cleavage furrow pinches one cell into 2 cells
Plant Cell  cell plate makes new cell wall; cell splits

20. Mitosis Animation

21. Additional Mitosis Vocabulary
G0 Phase  Cell is neither growing or dividing
Centrioles Create Ropes that pull chromosomes around the cell (make
spindle fibers)

22. Difference Between Plant Cell & Animal Cell Mitosis
Plant cells are surrounded by a tough outer case called a cell wall
Animal cells are surrounded by a soft outer case called a cell membrane
The first 3 stages of mitosis in plant and animal cells are the same
Telophase
Animal Cell  Formation of a cleavage furrow
Plant Cell  Formation of cell plate

23. Meiosis Vocabulary
Diploid Cells  cells with 2 of each type of chromosome (1 from mom and 1 from dad)
n= number of pairs of chromosomes
Diploid Cells = 2n
Zygote = fertilized egg
Gametes= haploid sex cells
Fertilization= union of egg and sperm
Sexual Reproduction  Parents generate specialized sex cells

24. Meiosis Getting from diploid to haploid cells: Meiosis
Where does it occur in humans?
Males Testes
Females  Ovaries

25. Meiosis Overview Meiosis I Diploid cells splits into 2 haploid cells
Meiosis II
2 haploid daughter cells undergo mitosis
Forms 4 haploid sex cells
Same as mitosis

26. Meiosis I
Prophase I
Homologous chromosomes pair together (called synapsis)
Each homologous pair of chromosomes is called a tetrad
Some chromatids break off and attach to adjacent homologous chromatids (crossing over)
Crossing Over creates new genetic combinations
Metaphase I
Homologous chromosomes line up in the middle of the cell
Anaphase I
Homologous CHROMOSOMES move to opposite poles of the cell
Random separation of homologous chromosomes is called Independent Assortment
Telophase I
Chromosomes reach opposite poles of the cell
Cytokinesis begins

27. Meiosis I

28. Meiosis II
2 haploid cells go through the process of mitosis & cell division
End result of meiosis II is 4 haploid cells
Gamete Formation
In males meiosis creates 4 sperm cells (called spermatids)
In females the cytoplasm is unevenly divided so that only 1 big cell is formed, along with 3 other polar bodies

29. Meiosis II

30. Meiosis Animation
Meiosis Animation