MITOSIS PRESENTATION DR. SUSAN MASKEL (WCSU)

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1 MITOI REENTATION 1 2 MITOI ackground Information CHROMOOME proteins deoxyribonucleic acid interspersed with stores genetic info controls processes Dr. usan Maskel Western CT tate University 2 strands double helix sugars (deoxyribose) phosphate groups nitrogenous bases: adenine, thymine, guanine, cytosine O - - O - = O O phosphate tructure of Components of Key: = sugar = phosphate = base sugarphosphate backbone nitrogenous bases form rungs of ladder age 1

2 MITOI REENTATION Nitrogenous ases in Adenine (A) Thymine (T) Cytosine (C) Guanine (G) pecificity of base pairing A - T C - G 10 Types of Chromosomes unduplicated (1 double stranded (ds) + protein) duplicated (2 ds s + protein) Duplicated Chromosomes centromere Humans have chromosomes in their somatic cells (i.e., not sperm, not egg) Humans have 2 chromosomes in their sex cells (i.e., egg or sperm) diploid number = 2N = haploid number = 1N = 2 sister chromatids age 2

3 MITOI REENTATION The Cell Cycle At any given time, a cell is either: 1 When NOT dividing: INTERHAE G1 phase (growth phase 1) normal cell metabolism synthesis of proteins not used in mitosis chromosomes are unduplicated phase (synthesis phase) normal cell metabolism synthesis ( replication or duplication) chromosomes go from unduplicated to duplicated 1 not dividing dividing G2 phase (growth 2 phase) normal cell metabolism synthesis of proteins needed for mitosis chromosomes are duplicated Replication unzips New nucleotides (sugarphosphate-base combinations) add according to specificity of base pairing 2 sister chromatids form; are identical each sister chromatid has 1 new & 1 old strand semiconservative replication sister chromatid sister chromatid old strand 1 new strand When cells ARE dividing: MITOI division of the nucleus of somatic cells; 1 division maintains the chromosome number 1 mother cell with chromosomes gives rise to 2 daughter cells, each with chromosomes MEIOI division of the nucleus of sex cells; 2 divisions halves the chromosome number 1 mother cell with chromosomes gives rise to daughter cells, each with 2 chromosomes CYTOKINEI division of cytoplasm occurs during mitosis & meiosis 1 CELL CYCLE INTERHAE G1: unduplicated chromosomes : chromosomes duplicate G2: duplicated chromosomes MITOI (M phase) start with duplicated chromosomes; end with unduplicated chromosomes phases: rophase Metaphase Anaphase Telophase (cytokinesis occurs mainly during telophase) 1 INTERHAE before mitosis begins; NOT part of mitosis cell is not dividing includes G1,, G2 phases nuclear membrane visible nucleoli visible chromatin in nucleus - nuclear membrane intact - nucleolus visible - chromatin not visible as individual structures 1 age

4 MITOI REENTATION Interphase nuclear membrane present chromatin not visible 1 MITOI nuclear division of somatic cells phases: rophase Metaphase Anaphase Telophase cytokinesis division of cytoplasm occurs mainly during telophase 20 ROHAE lasts 1 several hours nuclear membrane disappears nucleoli disappear chromatin winds upon itself to form chromosomes; chromosomes are duplicated centrioles made of microtubules; (replicated to form 2 pairs at end of G1); move to opposite poles of cell spindle and asters form 21 aster probably anchors apparatus to cell membrane pindle & Asters spindle 22 helps organize chromosomes during mitosis 21 rophase 2 rophase 2 nuclear membrane disappears nucleolus disappears chromatin chromosomes spindle & asters form In this hypothetical cell, 2 N =. In humans, 2 N =. age

5 MITOI REENTATION METAHAE 1 minutes chromosomes line up in single file along center of spindle 2 Metaphase 2 chromosomes are attached to spindle fibers in area of centromere chromosomes lined up in single file in center of spindle In this hypothetical cell, 2 N =. In humans, 2 N =. ANAHAE 2 10 minutes spindle fibers pulled toward opposite poles of cell centromere splits sister chromatids pulled toward opposite poles of cell 2 Anaphase 2 sister chromatids being pulled toward opposite poles of cell In this hypothetical cell, 2 N =. In humans, 2 N =. TELOHAE 10 0 minutes 2 Telophase 0 cleavage furrow forms & deepens until cell divides into 2 daughter cells (cytokinesis) opposite of prophase occurs: nuclear membrane & nucleoli reappear chromosomes uncoil into chromatin spindle & asters disappear cleavage furrow forms; 2 daughter cells will form; the opposite of prophase will occur In this hypothetical cell, 2 N =. In humans, 2 N =. age

6 MITOI REENTATION TET YOUR KNOWLEDGE: Name the phase of mitosis seen on the following slides prophase 2 anaphase metaphase telophase anaphase age

7 MITOI REENTATION prophase 2 telophase anaphase anaphase metaphase prophase metaphase metaphase metaphase metaphase late anaphase/ early telophase 2 telophase anaphase prophase 10 metaphase anaphase 11 anaphase anaphase 12 anaphase prophase 1 metaphase metaphase 1 prophase Now it s YOUR turn to identify stages of mitosis with a microscope! age