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I. Cell Growth and DivisionA. Cell Cycle:

1. Sequence of events that occurs in a cell from mitosis to mitosis.

2. 5 parts:a) G1 phase – cell growth occurs (make

new proteins + organelles).b) S phase – DNA is copied in

preparation for mitosis.c) G2 phase – Organelles needed for

nuclear division are made.d) Mitosis – nuclear division.e) Cytokinesis – cytoplasm divides.

3. Interphase – G1 + S + G2 phases.

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4. Figure 10-4 page 245

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B. Mitosis1. Chromosome structure:

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2. Done to produce more cells (growth and replacement).

3. Occurs in somatic cells (body cells) not sex cells (gametes)

4. 4 steps: a)Prophase:

1)Nuclear membrane + nucleolus disappear.

2)Chromosomes condense + become visible.

3)Centrioles form + move to poles.4)Spindle fibers first appear.

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b)Metaphase:1)Spindle fibers attach to

centromere (center of chromosome).2)Chromosomes line up at the

equator.c)Anaphase:

1)Sister chromatids spilt.2)Chromosomes (now w/ only 1

chromatid) move to opposite poles.d)Telophase:

1)Nuclear membrane + nucleolus reappear.

2)Chromosomes spread out + become invisible.

3)Spindle fibers disappear.

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5. Figure 10-5 page 246-47

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C. Cytokinesis – division of the cytoplasm.1. After mitosis, one cell with two

nuclei.2. Animals – cytoplasm pinches in

(cleavage furrow)3. Plants – cell plate forms in the center

and works towards the cell wall.a)Figure 10-6 page 248

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D. Uncontrolled cell growth1. Cancer – uncontrolled cell growth

(tumor).2. Causes:

a)Smoking/chewing tobaccob)Radiation exposure (X-rays, tanning

beds, etc.)c)Virusesd)Other (chemicals, defective genes,

etc.)

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II. Production of Sex CellsA. Meiosis

1. Nuclear division that reduces the number of chromosomes by half.

2. Production of gametes (sex cells: sperm + eggs)

3. Homologous chromosomes – pairs of the same chromosomesa) Humans – 46 chromosomes (23 pairs)b) Diploid – both homologs are present

(2N)c) Haploid – only 1 chromosome of each

homolog pair is present. (1N)

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4. 2 parts:a)Meiosis Ib)Meiosis II

B. Meiosis I1. Prophase I: 2N

a)Chromosomes become visible.b)Nuclear membrane + nucleolus

disappear.c)Spindle fibers appear.d)Synapsis (pairing of homologs)

occurs.1)Forms a tetrad (4 chromatids = 2

chromosomes).e)DNA may be exchanged between tetrad

(crossing over) = genetic variety

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2. Metaphase I: 2Na)Tetrads move to equator by the

spindle fibers.3. Anaphase I: 2N -> 1N

a)Tetrad splits, however each chromosome still has two chromatids.

4. Telophase I: 1Na)Cytoplasm divides.b)Nuclear membrane + nucleolus

reappear.c)Spindle fibers disappear.d)Now have two cells.

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C. Meiosis II (1N)1. Prophase II:

a)New spindle fibers form.b)Nuclear membrane + nucleolus

disappear.2. Metaphase II:

a)Chromosomes move to equator by spindle fibers.

3. Anaphase II:a)Sister chromatids are split with each

chromatid moving to opposite poles.4. Telophase II:

a)Same as Telophase I.b)Have 4 cells now.

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Figure 11-15 page 276 – 77 Meiosis I

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• Meiosis II

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Summary:15Start End

Mitosis: 1 cell, 2N 2 cells, 2NMeiosis: 1 cell, 2N 4 cells, 1N

D. Human gamete Production1. Males = 4 (1N) sperm cells from

Meiosis.a)Starts at puberty

2. Females = 1 egg (1N) + 3 polar bodies (garbage).a)Starts in the womb but not completed

until ovulation.

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Figure 11-7, page 278

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III. Deoxyribonucleic acid, DNA – double helix molecule that carries hereditary information for genes.

A. Structure:1. Composed of 3 parts:

a) Deoxyribose (sugar)b) Phosphate groupc) Nitrogen base

2. Double helix shapea) Discovered by James Watson and

Francis Crick.b) Twisted ladder shape.

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c)Figure 12-7 page 294

3. Four Nitrogen Basesa)Adenine (A) Purineb)Guanine (G) “c)Thymine (T) Pyrimidined)Cytosine (C) “

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4. Bonding patterns:a) G ≡ C (3 bonds)b) A = T (2 bonds)

B. Replication – process of copying a DNA molecule.

1. Needed for mitosis (S phase)

IV. Ribonucleic acid, RNA – single strand nucleic acid used for protein synthesis.

A. Different from DNA:1. Single stranded2. Ribose not Deoxyribose3. Uracil instead of Thymine (A = U)

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B. Types:1. Messenger RNA (mRNA) – carries message

from DNA to make proteins.2. Transfer RNA (tRNA) – brings amino

acids to ribosome to make proteins.3. Ribosomal RNA (rRNA) – makes up the

ribosomes.4. Figure 12-12 page 300

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C. Transcription – process of making RNA from DNA.1. DNA all types of RNA2. Ex:

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V. Protein synthesis – formation of proteins using genetic code from DNA and carried out by RNA.

A. Translation – process of forming proteins from mRNA.

1. mRNA leaves nucleus (nuclear pores) and goes to ribosomes.

2. mRNA is grouped into 3 consecutive bases called codons.a) Each codon corresponds with a

certain amino acid.

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b)Figure 12-17 page 303

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3. DNA – transcription – mRNA – translation – proteins

4. tRNA has a compliment (opposite) base sequence to the codon called anticodon.a)The amino acid that corresponds with

the codon is attached to the tRNA.

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5. Figure 12-18 page 304

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VI. Mutations – spontaneous changes in a gene or chromosome.

A. Many types1. Single Base switch:

a) Ex:Normal MutationDNA: ATG CGA GTG CGARNA: UAC GCU CAC GCUAA : Tyrosine Histidine - Arginine

- Arginine

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2. Single Base Deletion:a)Ex:

Normal MutationDNA: ATG CGA T AGC GATRNA: UAC GCU A UCG CUAAA : Tyrosine Serine - Leucine

- Arginine

3. Environmental factors may cause, but not always.

4. Not passed to offspring unless occurs in gametes (sex cells)