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1 art of Exercise 4 of Human Anatomy & hysiology Laboratory Manual, 8th Edition, by Elaine Marieb lease wait 20 seconds before starting slide show. Mouse click to advance. Arrow keys etc.also work. Hit ESCAE Key to exit. Dr.Susan Maskel BIO 105 Western Connecticut State University A& I BIO 211 Naugatuck Valley Community College A& I Some graphics and all definitions courtesy of Benjamin Cummings Background Information CHROMOSOMES DNA (deoxyribonucleic acid) stores genetic information rotein controls processes DNA 2 strands double helix each strand contains: sugars (deoxyribose) phosphates (O 4 ) nitrogenous bases adenine thymine guanine cytosine - O - = O O phosphate Structure of Components of DNA O -

2 DNA S S B B B B S S S B B S S B B S S B B S Key: S = sugar = phosphate B = base sugarphosphate backbone nitrogenous bases form rungs of ladder Bases in DNA Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Specificity of base pairing A - T C - G Types of Chromosomes DNA (1 double stranded (ds) DNA + protein) duplicated (2 ds DNAs + protein)

3 Duplicated Chromosomes centromere DNA Humans have 46 in their somatic (i.e., not sperm or egg) cells. Diploid number = 2 N = 46 Humans have 23 in their sex cells (sperm & egg). Haploid number = 1 N = 23 sister chromatids THE CELL CYCLE At any given time, a cell is either: not dividing dividing When Cells are Not Dividing: Interphase G1 Normal cell metabolism Synthesis of proteins not used for mitosis Chromosomes Centrioles replicate S Normal cell metabolism DNA synthesis (DNA replication): duplicated G2 Normal cell metabolism Synthesis of proteins used for mitosis Chromosomes duplicated DNA Replication DNA unzips New nucleotides (sugar-phosphatebase combinations) add according to specificity of base pairing

4 NOTE: forming sister chromatid of duplicated chromosome old strand new strand The 2 forming sister chromatids have an identical base sequence to each other. Semiconservative Replication: each sister chromatid has 1 new & 1 old strand ds DNA of chromosome sister chromatids of duplicated chromosome When Cells Are Dividing: Nuclear Division Mitosis occurs in somatic cells maintains the # of Meiosis occurs in sex cells halves the # of Cytokinesis division of cytoplasm occurs during mitosis & meiosis G1 S duplicate G2 duplicated M start with duplicated ; end with

5 Before mitosis begins, the cell is in INTERHASE. INTERHASE cell is not dividing includes G1, S & G2 nuclear membrane visible nucleoli visible chromatin in nucleus NOT ART OF MITOSIS Interphase NOTE: Interphase Nuclear membrane present Chromatin not visible -nuclear membrane intact nucleolus visible chromatin not visible Interphase Nuclear division in somatic cells takes place via MITOSIS.

6 prophase metaphase anaphase telophase ROHASE (1 - several hours) nuclear membrane disappears nucleoli disappear chromatin centrioles move to opposite poles of cell spindle & asters form Centrioles Spindle & Asters at end of G1, centrioles replicated (to form 2 pairs) made of microtubules aster probably anchors apparatus to cell membrane spindle helps organize during mitosis rophase rophase NOTE: nuclear membrane disappears nucleolus disappears chromatin spindle & asters form In this hypothetical cell, 2 N = 4. In humans, 2 N = 46. Nuclear membrane still present but is disappearing

7 rophase METAHASE (5-15 minutes) line up on center of spindle are attached to spindle fibers in area of centromere Metaphase Metaphase NOTE: lined up in single file in center of spindle aster Chromosomes lined up on center of spindle aster In this hypothetical cell, 2 N = 4. In humans, 2 N = 46. Metaphase ANAHASE (2-10 minutes) spindle fibers pulled toward opposite poles of cell centromeres splits sister chromatids pulled toward opposite poles of cell as microtubules of spindle shorten

8 Anaphase Anaphase aster NOTE: sister chromatids being pulled toward opposite poles of cell chromatids separated & being pulled toward opposite poles of cell aster In this hypothetical cell, 2 N = 4. In humans, 2 N = 46. Anaphase TELOHASE (10-30 minutes) cleavage furrow formed cell invaginates at cleavage furrow until 2 daughter cells formed (= cytokinesis) opposite of prophase nuclear membrane reappears nucleoli reappear uncoil to chromatin spindle & asters disappear Telophase NOTE: cleavage furrow forms; 2 daughter cells will form; the opposite of prophase will occur In this hypothetical cell, 2 N = 4. In humans, 2 N = 46. Telophase cleavage furrow unwinding unwinding

9 INTERHASE ROHASE METAHASE Telophase spindle ANAHASE TELOHASE TELOHASE art of Exercise 4 of Human Anatomy & hysiology Laboratory Manual, 8th Edition, by Elaine Marieb Dr.Susan Maskel BIO 105 Western Connecticut State University A& I BIO 211 Naugatuck Valley Community College A& I Name the phase of mitosis indicated. Some graphics and all definitions courtesy of Benjamin Cummings Name the phase of mitosis indicated. Answer: metaphase

10 Name the phase of mitosis seen. Answer Anaphase ANSWER: prophase Name the phases of mitosis indicated ANSWERS 2 Name the phases of mitosis indicated. 1 = metaphase 2 = telophase 3 = anaphase 4 = prophase

11 1 = anaphase 2 = metaphase ANSWERS 3 = anaphase Now it s YOUR turn to identify stages of mitosis with a microscope!