Chapter 8-The Cellular Basis of Reproduction and Inheritance8.3- Prokaryotes reproduce by binary fission

Objectives: 1) Describe the events of binary fissionI. Cell Division in Prokaryotes

A. Binary fission1. Cell division in prokaryotic cells resulting in 2 cells2. The Steps

a. Chromosome make a copy of itself

1. A single, circular strand of DNA

b. Cell grows to approx. twice the cells original size

c. Cell wall forms between the 2 chromosomes

d. Cell divides into 2 identical cells

8.4-The large, complex chromosome of eukaryotes duplicate with each cell divisionObjectives: 1) Define chromatin

2) Describe the structure of a chromosome3) Distinguish the difference between sister chromatids

and chromosomes I. DNA StructureA. The form in which info in the cell is containedB. The cells alphabetC. Comprised of nucleic acids D. A double helixE. Each strand contains thousands of

genes1. Each gene contains a specific code

which is responsible for a different trait

II. ChromatinA. The state in which DNA is normally found in nondividing cells

1. DNA is too long to fit into the cella. Each chromosome contains approx. 5 cm of DNA when

uncoiledB. DNA coiled around proteins called histones C. When cell division is initiated, this chromatin coils &

condenses into microscopic chromosomes.

III. A chromosomeA. Strands of DNA wrapped around proteins (chromatin) and

tightly condensedB. In most cells, chromosomes are only visible during cell

divisionC. Most other times, they are uncoiled

8.5-The cell cycle multiplies cellsObjectives: 1) Define the cell cycleI. Cell Cycle

A. Repeating set of events that make up the life of a cell1. The sequence of division and growth of a cell’s life cycle

a. Interphase1. Subdivided into G1, S, G2

b. Mitotic phase (M phase)1. Subdivided into mitosis and cytokinesis

8.6-Cell division is a continuum of dynamic changesObjectives: 1) Describe each phase of interphase

2) Describe each phase of mitotic phase3) Summarize the phases of interphase &

mitosisI. InterphaseA. The growth phaseCells spend most of their lifetime in this

phase

II. Mitotic Phase (M phase)A. Nuclear division occurs

1. The process by which 2 daughter cells are formeda. Each containing a complete set of chromosomes

B. G1 phase1. Offspring cells grow to mature size

C. S phase 1. Cell’s DNA is copiedD. G2 phase

1. Cell prepares for cell division

B. Phases of mitosis1. Prophase/Prometaphase: the 1st phase

a. Chromatin coils into visible chromosomes

1. Remember in S phase the DNA was copied2. Sister chromatids stay connected by the centromere

b. Nuclear membrane disappearsc. Centrioles & Spindle fibers form

1. Spindle fibers are a network of protein fibersd. Spindle fibers attach to centromeres

2. Metaphase: the 2nd phase1. The chromosomes line up in center of cell

3. Anaphase: the 3rd phase1. Sister chromatids separate

a. Spindle fibers pull each chromosome to opposite sides of cell

d. Telophase: the 4th phase1. Each side of cell now has a complete set of chromosomes2. Chromosomes begin to unwind3. Spindle fibers break down4. Nuclear envelope forms around each set of chromosomes5. A new plasma membrane begins to form between the two

nuclei

C. Cytokinesis1. Actual cell division2. Cytoplasm is pinched in half

a. Cleavage furrow1. Area of the cell membrane that pinches in

b. Forms 2 new cells3. Each cell contains identical DNA4. Cell enters growth phase

Cleavage Furrow

8.7- Cytokinesis differs for plant and animal cellsObjectives: 1) Describe the difference between plant and animal cell cytokinesesI. Animal cells

A. Cleavage furrow develops between 2 new cells

II. Plant cellsA. Cell plate forms between 2 new cells

8.10-Growing out of control, cancer cells produce malignant tumors

II. What happens when the cell cycle is not controlled?A. A tumor develops

1. A mass off cells that results from

uncontrolled growth2. Benign tumor

a. A tumor that remains in the region in

which it was originally formedb. Usually harmless

B. Cancer develops1. A tumor that does not remain in the region in which it was

originally formeda. Malignant tumor

2. Uncontrolled cell division

3. Most prevalent types of cancer in U.S.a. Lungb. Prostatec. Colond. Breast

8.12-Chromosomes are matched in homologous pairsI. Human cells & chromosomes

A. Somatic cells1. Body cells2. Composed of 46 chromosomes

a. Remember: Chromosomes are composed of 2 sister chromatidsb. Each chromosome has a twin chromosome that is identical in

length and centromere position1. 23 pairs of chromosomes

a. Homologous chromosomes (or homologs)2. The exception

a. Sex chromosomes1. Female XX, Male XY

8.13-Gametes have a single set of chromosomesI. Somatic cells

A. 46 chromosomes or 23 pairsB. Diploid

1. Cells with 2 homologous sets of chromosomes2. Represented as 2n

a. Humans: Diploid number is 46 - 2n=461. In order to be human you must have 46 chromosomes

II. Sex cells (gametes)A. Reproduction

1. In order to reproduce sexually the chromosome number in sex cells must be reduced to half

a. A single set of chromosomesb. Haploid cell

1. Humans: Haploid number is 23 – n=232. Dad gives 23 chromosomes/mom gives 23 chromosomes = 46

chromosomesa. Dad’s gamete (sperm/haploid) fertilizes mom’s gamete

(egg/haploid) creating a diploid zygoteB. How do we get from a diploid cell to a haploid cell?1. Meiosis

8.14-Meiosis reduces the chromosome number from diploid to haploidObjectives: 1) Describe each phase of meiosis

2) Summarize the phases of meiosis3) Be able to describe the purpose and

importance of meiosisI. Stages of meiosis

A. Defined1. Process of nuclear division that reduces the number of

chromosomes in new cells to half the # of diploid chromosomes2. Cells go through interphase

B. Meiosis I1. 4 phases

a. Prophase I1. Chromatin coils into chromosomes2. Spindle fibers appear3. Nuclear membrane disappears

4. Homologous chromosomes pair upa. Called synapsisb. Does not happen in mitosisc. Each pair is called a tetrad

d. Chromatids line up so corresponding genes line up next to each other

e. Crossing-over1. Portions of broken chromatids attach to adjacent chromatids on homologous chromosomes

2. Results in genetic recombinationa. Producing a new mixture of genetic material

b. Metaphase I1. Tetrads randomly line up along equator of cell2. Spindle fibers attach to centromeres

3. Spindle fibers from opposite poles attach to different centromeres w/in tetrad

c. Anaphase I1. Each homologous chromosome moves to opposite ends

of cell

d. Telophase I1. Spindle fibers disappear

C. Cytokinesis I

C. Meiosis II1. Same as Mitosis w/ the exception of no nuclear envelope break

down

8.15- Mitosis and meiosis have important similarities and differencesObjectives: 1) Be able to describe the difference between mitosis and meiosis