1. Chapter 6 Chromosomes and Cell Reproduction

2. Cell division (cell reproduction)
Section 6-1
Cell division (cell reproduction)
Occurs in humans and LT at diff times in their life
Formation of gametes (egg/sperm) involves special types of cell ÷ (this will be covered in chapter 7)
When cells ÷, DNA is 1st copied and then ÷

3. Prokaryotic (Bacteria) Cell Reproduction: Binary fission:
Section 6-1
Prokaryotic (Bacteria) Cell Reproduction:
Binary fission:
Form of asexual reproduction in bacteria cells that produces identical offspring
Binary fission occurs in 2 stages: 1st, DNA is copied, then cell ÷, eventually the ÷ prokaryote is pinched into 2 independent cells

4. Eukaryotic Cell Reproduction:
Section 6-1
Eukaryotic Cell Reproduction:
Gene: piece of DNA that codes for a protein or RNA
As eukaryotic cell prepares to ÷, DNA and proteins associated w/ DNA coil into chromosomes
Chromatids: 2 exact copies of DNA that make up each chromo
Centromere: where 2 chromatids of chromo are attached

5. Homologous chromosomes: chromo similar in size, shape, genetic content
Section 6-1
Homologous chromosomes: chromo similar in size, shape, genetic content
Each homologue in a pair of homologous chromosomes comes from 1 of the 2 parents
46 chromosomes in human somatic (body) cells are actually two sets of 23 chromosomes (23 from mom, 23 from dad)
Diploid: cell w/ 46 chromo (23 from mom, 23 from dad)
Haploid: cell w/ only 23 chromo, such as gametes
Zygote: fusion of 2 haploid gametes (fertilization) to form 1 diploid fertilized egg cell (mom’s 23 w/ dad’s 23 = 46)

6. Section 6-1
Autosomes: chromo not directly involved in determining sex (gender) of an individual; pairs #1-22
Sex chromosomes: 1 pair of chromo in humans, contain genes that determine sex of individual; pair #23 referred to X and Y; XX = female, XY = male

7. Humans missing 1 of 46 chromosomes usually don’t survive
Section 6-1
Change in Chromo #:
Humans missing 1 of 46 chromosomes usually don’t survive
Trisomy: more than 2 copies of a chromosome, will not develop properly; 3 copies of #21= Down’s Syndrome
Karyotype: photo of chromo in a dividing cell showing chromo arranged by size

8. Change in Chromo Structure:
Section 6-1
Change in Chromo Structure:
∆ in organism’s chromo structure are mutations
Breakage of chromo can lead to 4 types of mutations:
1. deletion mutation: piece missing
2. duplication mutation: piece added
3. inversion mutation: piece turned upside down
4. translocation mutation: piece from chromo is put on a different chromo

9. Repeating sequence of cellular growth/÷ during life of organism
Section 6-2
Cell Cycle:
Repeating sequence of cellular growth/÷ during life of organism
Interphase:
1st 3 phases of cell cycle, 90% of cell’s time is in this phase

10. 2. Synthesis (S) phase: DNA is copied
Section 6-2
5 Phases of Cell Cycle:
1. 1st growth (G1) phase: cell grows rapidly and carries out routine functions
2. Synthesis (S) phase: DNA is copied
3. 2nd growth (G2) phase: preparations made for nucleus to ÷
4. Mitosis: nucleus of cell ÷ into 2 nuclei
5. Cytokinesis: cytoplasm ÷

11. 1. Cell growth (G1) checkpoint makes decision of whether cell will ÷
Section 6-2
Control of Cell Cycle:
Checkpoints at which feedback signals from cell can trigger or delay next phase of cell cycle
1. Cell growth (G1) checkpoint makes decision of whether cell will ÷
2. DNA synthesis (G2) checkpoint DNA replication is checked by DNA repair enzymes
3. Mitosis checkpoint triggers exit from mitosis

12. When Control Is Lost: Cancer!
Section 6-2
When Control Is Lost: Cancer!
If a gene that controls cell growth/÷ is mutated, then regulation of cell growth/÷ can be disrupted = cancer and uncontrolled cell growth results!
Bladder cancer

13. Mitosis - Division of the Nucleus in 4 phases:
Section 6-3
Mitosis - Division of the Nucleus in 4 phases:
1. Prophase: Nuclear envelope dissolves; spindle forms
2. Metaphase: Chromo move to center and line up along the equator
3. Anaphase: Centromeres ÷; chromo move to opposite ends of cell
4. Telophase: Nuclear envelope forms around chromo at each pole; Mitosis is complete

14. Cytokinesis – Division of the Cytoplasm:
Section 6-3
Cytokinesis – Division of the Cytoplasm:
As mitosis ends, cytokinesis begins
Cytoplasm of cell ÷ in 1/2, cell membrane grows to enclose each new cell, forming 2 separate genetically identical cells from 1 cell