Download Cell Division Notes

CH 8: Cell Division (p.126)
Objectives:
 Compare sexual and asexual reproduction.
 Compare the relationship between a parent and its offspring resulting from asexual versus
sexual reproduction.
 Explain why cell division is essential for eukaryotic and prokaryotic life.
 Compare the structure of prokaryotic and eukaryotic chromosomes.
 Describe the stages and significance of the cell cycle.
 List the phases of mitosis, and describe the events characteristic of each phase. Recognize
the phases of mitosis from diagrams and micrographs.
 Compare cytokinesis in animals and plants.
 Explain the factors that control the cell cycle.
 Explain how cancerous cells are different from healthy cells. Distinguish between benign
and malignant tumors, and explain the strategies behind some common cancer treatments.
 Describe the functions of mitosis.
MYP Unit: Central Dogma (DNA)
Key Concept: Systems
Systems are sets of interacting or interdependent components. Systems provide structure and order in human, natural,
and built environments. Systems can be static or dynamic, simple or complex.
Related Concepts: Transformation & Models
Global Concept: Scientific & Technical Innovation
Statement of Inquiry: The foundation of living systems can be understood through modeling the related forms and
transformations.
Date:
Cell Division (p.128)
 In unicellular organisms, cell division is asexual reproduction in response to environmental cues
 In multicellular “
” a source of new cells for (a) growth & (b) repair
o Triggered by growth factors: chemical signals released by cells
 Chromosomes
o Chromatin condenses into visible chromosomes during cell division
o Prokaryotes usually have 1 simple, circular chr. of DNA & proteins
o Eukaryotes have multiple complex, rod-shaped chr.
 consist of DNA wrapped around proteins called histones
 chr. replicate before cell division into 2 identical sister chromatids attached at
centromere
Date:
Cell Cycle (p.131) –sequence of events from 1 division to the next
 4 phases:
a. G1 – growth (includes ↑’ing # of proteins & organelles)
b. S – DNA replication (synthesis)
c. G2 – more growth & prep for division
d. M – mitosis & cytokinesis
I. Interphase (G1, S, & G2) – period of high metabolic activity btwn divisions
II. Mitosis – division of nucleus (PMAT)
o Prophase –longest phase
 chr. appear
 centrosomes move apart & form the spindle which guides chr. separation
 nucleolus disappears & nuclear envelope breaks down
o Metaphase – spindle fibers line up chr. in middle of cell
o Anaphase – spindle fibers pull apart sister chromatids
 chromatids become separate chr.
o Telophase – chr. uncoil
 nuclear env. & nucleolus reappear in each daughter cell
III. Cytokinesis – division of cytoplasm/cell
o cleavage furrow forms in animal cells
o cell plate (cell wall) forms in plant cells
o daughter cells are identical
Prophase
Metaphase
Anaphase
Telophase
Date:
Regulation (p.135)
 Density-dependent inhibition: cells stop dividing at high population density
 Cancer: disorder in which cells do not respond to normal cell cycle regulation (p.137)
o caused by exposure to carcinogens that cause gene mutations
o cells divide uncontrollably & form tumors
 Benign tumors are harmless
 Malignant tumors are cancerous & spread to distant tissues (metastasis)
o Categories:
 Carcinoma/melanoma: skin or tissues lining organs
 Sarcoma: supporting tissues (bone, muscle)
 Leukemia/Lymphoma: white blood cells, spleen, bone marrow, lymph nodes
Objectives:
 Explain how chromosomes are paired. Distinguish between autosomes and sex
chromosomes.
 Distinguish between (a) somatic cells and gametes and (b) diploid cells and haploid cells.
 List the phases of meiosis I and meiosis II, and describe the events characteristic of each
phase. Recognize the phases of meiosis from diagrams or micrographs.
 Describe key differences between mitosis and meiosis. Explain how the result of meiosis
differs from the result of mitosis.
 Explain how crossing over, independent assortment, and random fertilization contribute to
genetic variation in sexually reproducing organisms.
 Explain how and why karyotyping is performed.
 Define nondisjunction, explain how it can occur, and describe what can result.
Date:
Chromosome Number (p.138)
 Homologous chr: pair of chromosomes that have genes for the same traits
o 1 of each pair comes from each parent
o Gene: a section of DNA that codes for a specific trait
o Sex chr. - determine sex/gender
- XX = female ; XY = male
o All other chr. are autosomes (22 pairs)
 Somatic cells are diploid (2N): they contain 2 sets of chr. in homologous pairs
o Diploid number for humans is 46 (2N = 46)
 Gamete: sex cell (sperm or egg)
o Haploid (N): contains only 1 set of chr.
o For humans, N = 23 (22 autosomes + 1 sex chromosome)
o All egg cells have 1 X; sperm have either X or Y (50/50)
Date:
Meiosis: form of cell division that forms 4 gametes (occurs in ovaries & testes) (p.139)
 Meiosis I
o Homologs pair up to form tetrads during prophase I
o crossing-over occurs when homologs exchange portions of their chromatids
- Recombination ↑’s genetic diversity in offspring
o Homologs line up in pairs & separate to form 2 haploid (N) cells
o Sister chromatids do NOT separate
 Meiosis II
o Sister chromatids separate
o Results in 4 haploid (N) daughter cells (NOT identical!)
 Independent Assortment: homologs line up randomly, and all chr. separate independently from one
another  ↑’s genetic diversity
 Fertilization: haploid sperm & egg unite to form a diploid zygote (N + N = 2N)
Date:
Karyotyping (p.146)
 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)
 Nondisjunction occurs when homologs or sister chromatids do NOT separate during meiosis
o Leads to chromosomal disorders:
 Cri-du-chat: deletion in chr. 5
 Trisomy: having an extra chr.
- Down syndrome (trisomy 21)  3 copies of chr. 21
- Klinefelter’s syndrome – males w/ extra X  sterile
 Monosomy: missing a chr.
- 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