2INTERPHASE is part of the cell cycle that occurs between divisions. -During this phase the cell is producing materials necessary for cell division.-3 PhasesG1- growth and developmentS - (Synthesis) chromosomes replicate (copy)G2- synthesis of organelles for cell divisionEX. centrioles.
3What is Happening with the DNA? 1. DNA is generally found in the CHROMATIN form which is thin and fibrous during interphase.2. Chromatin condenses to form sister chromatids which are identical structures of replicated chromosomes joined at the centromere.centromere - point where sister chromatids are joined together. This point varies depending on the chromosome.
4SISTER CHROMATIDChromosome 1 is an exact copy of Chromosome 2Chromosome 1Chromosome 2
5MITOSIS-Process during which the cell nucleus divides into 2 identical nuclei -4 StagesI - ProphaseII - MetaphaseIII - Anaphase IV - Telophase
61. ProphaseChromosomes in the nucleus condense to form sister chromatids. Centrioles move to opposite sides of the cell.B. Spindle Fibers (small tubules made up of proteins) start to form from each centriole.Nuclear Membrane breaks into fragments. Spindle Fibers attach to the centromeres.D. Nuclear Membrane disappears. Spindle fibers begin to move the sister chromatids towards the center of the cell.
72. MetaphaseSpindle fibers pull sister chromatids to line up in the center of the cell. This imaginary line is called the metaphase plate. If this does not happen correctly, genetic material will not be evenly distributed.
83. Anaphase Centromeres break up. B. Spindle fibers pull 1 set of chromatids (1 sister- 1 set of chromosomes) towards 1 pole and 1 set towards the other pole.
94. Telophase – Reverse of Prophase Nuclear Membranes begin to form.B. Spindle fibers disassemble.C. Chromosomes uncoil to form chromatin.D. 2 complete nuclear membranes are finished.
10Name each stage as you see it occur? Mitosis Animation
11Cytokenesis -cell division (cytoplasm divides) In animal cells- cell membrane pinches off.In plant cells – pieces of membrane form at the metaphase plate & grow together to forma new cell membrane. A cell wall forms between the membranes.Mitosis occurs in ALL of our cells. ALL of our cells have copies of ALL of our DNA. Each cell produced by mitosis is diploid.
12CytokinesisCleavage furrow in animal cellCell plate in plant cell
13It’s all about the number of Chromosomes. Diploid – Contains 2 complete sets of chromosomes (2n). In humans 1 set from mom, 1set from dad so a total of 46 chromosome Ex. Chromosomes containing genes for blond AND black hair color.(Don’t forget chromosomes double right before cell division so you are looking at 92 chromosomes at the start of mitosis and meiosis for humans)Mitosis produces new somatic (body cells) and Asexual reproduction.
15Name the Stages of Mitosis: Early prophaseEarly AnaphaseMetaphaseInterphaseEarly Telophase,Begin cytokinesisLate ProphaseLate telophase,Advanced cytokinesisMid-ProphaseLate Anaphase
16Identify the Stages ? ? ? ? ? ? ? Early, Middle, & Late Prophase MetaphaseAnaphaseLate Prophase???Telophase & CytokinesisLate AnaphaseTelophase
17Meiosis occurs to produce gametes in SEXUAL reproduction. Gametes – sex cells, haploid reproductive cells. In humans the sperm and the egg.Haploid – Contains only 1 set of chromosomes (1n).In humans only gametes contain a total of 23 chromosomes. Ex. Chromosomes containing genes are for either blond OR black.
18Meiosis –cell reproduction by division which reduces the number of chromosomes in half- In humans 46 (pg )1 cell divides to form 4 cells with half the number of chromosomes. (Don’t forget chromosomes double right before cell division so you are looking at 92 chromosomes at the start of meiosis for humans)
19Why do I want ½ number of chromosomes in sex cells? from momfrom dadchildtoomuch!meiosis reducesgenetic contentThe right number!
21How Homologous chromosomes Lining Up in Metaphase 1 is 1 Key to Variation. Gene XHair colorSister Chromatids(same genes,same alleles)Homologoussame genes,different alleles(choice Of genes blond hair/blackHair)Homologs separate in meiosis I and therefore different alleles separate.
22Crossing-Over1. Homologous chromosomes in a tetrad cross over each other2. Pieces of chromosomes or genes are exchanged3.Produces Genetic recombination in the offspring