Download CH 14 notes - Lincoln Park High School

CH 10: Cell Division (p.240)
10-2: Cell Division (p.244)
 In unicellular organisms, cell division via mitosis is a form of asexual reproduction
 In multicellular organisms cell division is a source of new cells for (a) growth & (b) repair
 Triggered by growth factors: chemical signals released by ther cells
 Chromosomes
o Chromatin condenses into visible chromosomes during cell division
o Prokaryotes usually have 1 simple, circular chromosome of DNA
o Eukaryotes have multiple complex, rod-shaped chromosomes
 Consist of DNA wrapped around proteins called histones (fig 12-10)
 Chromosomes replicate before cell division into 2 identical sister chromatids attached at
centromere (fig 10-3)

Cell Cycle – series of events a cell goes thru as it grows & divides (fig 10-4)
o 4 phases:
a. G1 – period of normal growth
b. S – DNA replication (synthesis)
c. G2 – growth & prep for division
d. M – mitosis & cytokinesis
I. Interphase (G1, S, G2 phases) – period of cell growth btwn divisions
II. Mitosis – division of nucleus (P-M-A-T) (fig 10-5)
o Prophase
 chromosomes become visible
 Centrioles move to opposite ends of the cell & form the spindle which lines up and
separates chromosomes
 Nucleolus disappears & nuclear envelope breaks down
o Metaphase –chromosomes line up in middle of cell
o Anaphase – sister chromatids are separated & pulled to opposite poles
 chromatids become separate chromosomes
o Telophase – chromosomes uncoil
 Nuclear envelope & nucleolus reappear in each daughter cell
III. Cytokinesis – division of cytoplasm
o Cell membrane pinches to separate animal cells
o Cell plate (cell wall) forms in plant cells
o Results in 2 identical daughter cells
10-3: Regulating the Cell Cycle (p.250)
 Density-dependent inhibition: cells stop dividing when crowded (fig 10-7)
 Cancer: disorder in which cells do not respond to normal cell cycle regulation
o caused by exposure to carcinogens
o cells divide uncontrollably & form tumors
 Benign tumors are harmless (“benign is nice”)
 Malignant tumors are harmful & spread to other tissues in a process called metastasis
o Some types of cancer:
 Carcinoma/melanoma: skin or tissues lining organs
 Sarcoma: connective tissues (bone, cartilage, fat, muscle, blood, etc.)
 Leukemia: white blood cells, blood-forming tissue (bone marrow)
 Lymphoma: lymph nodes, spleen, or bone marrow
Prophase
Metaphase
Anaphase
Telophase
Date:
11-4: Meiosis (p.275)
 Chromosome Number
o Homologous chromosomes: pair of chromosomes that have genes for the same traits
 1 of each pair comes from each parent
 Gene: a section of DNA that codes for a specific trait
o Somatic cells are diploid (2N): they contain 2 sets of chromosomes in homologous pairs
 Diploid number for humans is 46 (2N = 46)
o Gamete: sex cell (sperm or egg)
 Haploid (N): contains only 1 set of chromosomes
 Haploid number for humans is 23 (N = 23)



Meiosis: form of cell division that forms 4 gametes for sexual reproduction (fig 11-15)
o Meiosis I
 Homologous chromosomes pair up to form tetrads during prophase I
 Crossing-over occurs when homologous chromosomes exchange portions of their chromatids (fig
11-16)
- Recombination increases genetic diversity in offspring
 Homologous chromosomes line up in pairs & separate to form 2 haploid (N) cells
 Sister chromatids do NOT separate
o Meiosis II
 Sister chromatids separate
 Results in 4 haploid (N) daughter cells (NOT identical!)
Independent Assortment: chromosomes line up randomly & separate independently from one another
o Increases genetic diversity in offspring
Fertilization occurs when a haploid sperm & egg join to form a diploid zygote (N + N = 2N)
CH 14: The Human Genome (p.340)
Date:
14-1: Karyotypes and Chromosomal Disorders (p. 341)
 Genome: all of a cell’s DNA
 Karyotype: picture of chromosomes arranged in order
o Karyotypes of human somatic cells contain 2 sets of 23 chromosomes (23 pairs)
 Sex chromosomes - determine sex/gender
o XX = female ; XY = male
 All other chromosomes are autosomes (22 pairs)
 Gametes have 22 autosomes & 1 sex chromosome
o All egg cells have 1 X; sperm have either X or Y (50/50) (fig 14-2)
14-2: Human Chromosomes (p.349)
 Nondisjunction occurs when homologous chromosomes do NOT separate during meiosis (fig 14-15)
o Leads to chromosomal disorders
 Trisomy: having an extra chromosome (3 homologous chromosomes instead of 2)
 Monosomy: missing a chromosome
- Ex: Down syndrome (trisomy 21)  3 copies of chromosome 21
- Ex: Turner’s syndrome – females w/ only one X (45,X)  sterile
* Y determines sex of individual
--> XXX (Triplo-X / trisomy X) – fertile, normal intel); XYY – antisocial, fertile