Chapter 6  Chromosomes & Cell Reproduction
I. Chromosomes  DNA & histones (organizing proteins)
A. Formation of New Cells by Cell Division
• 2 Trillion cells/day or 25 million/sec
• PURPOSE  growth & development, repair & sex cells/gametes*
• Cell Genetic Info  DNA to make proteins  enzymes (cell machinery)  metabolism
• Each new cell needs a complete set of DNA or genetic info
1. Prokaryotic Cell Reproduction  (bacteria) binary fission  1 circular chromosme
2. Eukaryotic Cell Reproduction  (rest of organisms) Mitosis & Cytokinesis
• gene  segment of DNA that codes for a protein/enzyme or RNA molecule
• Chromosome  long segment of DNA with 1000s of genes (2%) & 98% non-coding
DNA
• chromatids  “condensed” chromosomes for dividing & moving (DNA has been
duplicated)
• centromere  area that holds identical chromatids together until cell division
• Fg. 2 p. 119  organization of chromosomes
B. How Chromosomes Number & Structure Affect Development
• Humans  46 chromosomes (23 prs)
• Each chromosome contains 1000s of genes (20,000 -25,000 genes total)
1. Sets of Chromosomes
• Homologous chromosomes  chromosomes similar in size, location & genetic content
• Diploid  full set of chromosomes (½ from mother/female & ½ from dad/male)
• Haploid  half set of chromosomes for SEXUAL REPRODUCTION
• Zygote  fertilized egg with 2 haploid sets or 1 diploid set
2. Sex Chromosomes
• Sex Chromosomes  23rd pair of chromosomes that contain gender determination
• Autosomes  1st through 22nd pairs of chromosomes
3. Change in Chromosome Number
• Down Syndrome  47 chromosomes/cell (extra 21st chromosome)(Triosomy 21)
• Klinefelter’s Syndrome  47 chromosomes/cell (extra sex chromosome) (XXY)
• Turner’s Syndrome  45 chromosomes/cell (missing sex chromosome) (XO)
• Patua’s Syndrome  47 chromosomes/cell (extra 13th Chromosome)
• Edward’s Syndrome  47 chromosomes/cell (extra 18th chromosome)
• Triosomy X  47 chromosomes/cell (Extra X chromosome)
• 47 XYY  (extra sex chromosome)
4. Change in Chromosome Structure
a. Deletion  Example: Cri-du-chat  Partial Deletion of Chromosome 5
b. Duplication  Example: Fragile X  Extra portion of the X chromosome
c. Inversion  may or may not cause any harm, but may lead to a chromosome
mutation in offspring
d. Translocation  TWO chromosomes switch parts (may or may not be a
problem, but may lead to a chromosome disorder)
II. The Cell Cycle
A. The Life of a Eukaryotic Cell
• Cell division is eukaryotic cells is more complex than prokaryotic (bacteria) cells
• nucleus and other organelles must be divide into TWO functioning cells
1. The Cell Cycle  repeating sequence of events of cell division
a. Interpahse  generally 90% of cell’s life
i. G1 (First Growth) phase  cell growth and functioning
ii. S (Synthesis) phase  duplication of DNA
iii. G2 (Second Growth) phase  preparation for cell division
b. Mitosis  division of the nucleus and the chromosomes (identical number &
type)
c. Cytokinesis  division of the cell’s cytoplasm into 2 cells after mitosis
B. Control of a Eukaryotic Cell
• ensures normal and appropriate growth
• complex systems are in place to control cell growth
1. Three Checkpoints
a. G1 (Cell Growth) Checkpoint  allows cell to move on to S phase for mitosis
b. G2 (DNA Synthesis) Checkpoint  “repair” enzymes will check DNA before
mitosis
c. Mitosis Checkpoint  triggers the completion of mitosis and the beginning of
cytokinesis
2. When Control Is Lost: Cancer
• cancer  uncontrolled cell growth & division; no response to checkpoints; error in
cell systems allow cells to divide uncontrollably and disrupt metabolism
III. Mitosis & Cytokinesis
• 2 million RBCs produced every second in bone marrow
• Spindles direct movement of chromosomes to opposite sides of the cell
• Centrioles (animal cells only) are the destination of the moving chromosomes in cell division
A. Chromatid Separation in Mitosis
1. Forming the Spindle
• pathway for chromosome movement that begin to be formed in G2 phase of cell cycle
2. Separation of Chromosome by attaching Spindle Fibers
• centromeres split to allow chromatids (now chromosomes to move to opposite sides
during cell division
B. Mitosis & Cytokinesis
1. Mitosis  4 stages (track nucleus membrane, chromosomes, centrioles & spindle)
a. Prophase  nucleus breaks down & disappears, chromosomes are condensing,
centrioles divide into 2 & move to opposite sides of cell, spindle begin to form
b. Metaphase  nucleus is completely broken down, chromosomes are fully
condensed and lined-up at center of cell, centrioles are opposite sides of cell,
spindles stretch from centrioles to centromeres of chromosomes
c. Anaphase  nucleus is still gone, centromere of chromosomes split and
chromosomes begin to move to opposite sides of cell, centrioles are directing
movement, spindle is the chromosomes pathway
d. Telophase  2 nuclei begins to form, chromosomes are opposite sides of the cell
and begin to “un-condense”, centrioles are finished directing movement of
chromomes and spindle begins to break down and disappear
2. Cytokinesis  other cell organelles have duplicated and are divided into the 2 new cells
formed by cleavage furrow (animal cells only) or cell plate (plant & fungi cells with cell
walls)
Chapter 43 – Reproduction & Development
I. Male Reproduction System
A. Testes
1. Production of Sperm
2. Maturation of & Storage of Sperm
3. Structure of Speam
4. Semen
5. Delivery of Sperm
II. Female Reproduction System
A. Ovaries
1. Production of Eggs
2. Structures of the Female
3. Reproductive System
B. Ovum
1. Phases of the Ovarian Cycle
2. Preparation for Pregnancy
3. Menstruation
III. Development
A. Fertilization
1. Cleavage & Implantation
2. Pregnancy
a. First Trimester
b. Second & Third Trimester
IV. Sexually Transmitted Diseases
A. STDs
1. Bacterial STDs
a. Gonorrhea
b. Syphilis
c. Chlamydia
d. PID
2. Viral STDs
a. AIDS/HIV
b. Genital Herpes (HSV)
Chapter 7 – Meiosis & Sexual Reproduction
I. Meiosis
A. Formation of Haploid Cells
1. Prophase I
2. Metaphase I
3. Anaphase I
4. Telophase I
5. Cytokinesis I
6. Prophase II
7. Metaphase II
8. Anaphase II
9. Telophase II
10. Cytokinesis II
B. Meiosis & Independent Assortment
1. Independent Asortment
2. Crossing-over & Random Fertilization
3. Importance of Genetic Variation
C. Meiosis & Gamete Formation
1. Meiosis in Males
2. Meiosis in Females
II. Sexual Reproduction
A. Sexual & Asexual Reporduction
1. Types of Asexual Reporduction
2. Genetic Diversity
3. Evolution of Sexual Reporduction
B. Sexual Life Cycles in Eukaryotes
1. Haploid Life Cycle
2. Diploid Life Cycle
3. Alteration of Generations