Keeping Cells Identical The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules.

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1 CELLULAR DIVISION

2 Cell Theory Pro/Euk review Cells are the basic unit of life. All living things have cell(s). All cells are formed from existing cells. Keeping Cells Identical The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules.

3 DNA Replication üdna must be copied or replicated before cell division üeach new cell will then have an identical copy of the DNA Original DNA strand Two new, identical DNA strands 3

4 In NON- Baby Making Cells Two identical daughter cells Parent Cell 4

5 How is DNA stored & what are its different shapes it can take? DNA is a uniquely flexible molecule. Using proteins and complex chemical structures it can CONDENSE into each of the following forms FROM SMALLESTTO LARGEST Nucleic Acid DNA Chromatin Chromatid Chromosome 5

6 Nucleic Acids Monomer: Nucleotides One of our 4 macromolecules, responsible for storage of genetic information. These pictures are of DNA only; however, nucleic acids can come in the form of RNA or ATP. The monomer, nucleotide, has three parts: 1. Five-Carbon Sugar 2. Phosphate 3. Nitrogenous Base

7 DNA Twisted ladder or Double Helix Shape. DNA for eukaryotes stores so much information that the ladder MUST twist and scrunch together to make it take up as little space as possible. Four Nitrogenous Bases Adenine Thymine Cytosine Guanine

8 Chromatin When cells are not in the process of cellular division the DNA exists as chromatin inside the nucleus. DNA is tightly coiled around proteins called histones

9 Sister Chromatids Chromosomes Every 200 nucleotide pairs, the DNA wraps twice around a group of 8 histone proteins. Coiling and supercoiling also help condense and package the chromatin inside the nucleus. Duplicated chromosomes are called chromatids & are held together by the centromere

10 Human Chromosomes Karyotype Humans have 22 pairs of chromosomes that are called autosomes or chromosomes that are NOT sex-determining chromosomes. Total, humans have 23 pairs of chromosomes or 46 individual chromosomes. The 23 rd pair determines gender.

11 Gender Determination Lies with the 23 rd chromosome pair.

12 CELLULAR DIVISION FOR REAL NOW

13 Why do cells need to divide? 1. Solves the problem of increasing size by reducing cell volume 2. Reproduction! Two Types of Cell Reproduction 1. Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells Mitosis & binary fission are examples of asexual reproduction 2. Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells Meiosis is an example

14 Asexual vs. Sexual Reproduction Asexual Repro. Prokaryotes such as bacteria divide into 2 identical cells by the process of binary fission Single chromosome makes a copy of itself Cell wall forms between the chromosomes dividing the cell CLONES Parent cell Chromosome doubles Cell splits 2 identical daughter cells Sexual Repro. Most often, eukaryotes go by sexual reproduction because of the advantage it gives in terms of evolution. Possible means for cool mutations or unique capabilities for survival.

15 THE CELL CYCLE

16 The Cell Cycle Overview/ 5 Main Parts In order to divide, the cell must go through a series of events. Starting with a new cell, there are 5 main parts of the Cell Cycle: 1. G1 phase 2. S phase 3. G2 phase 4. Mitosis 5. Cytokinesis All of these together are called INTERPHASE Sometimes called the M phase

17 The Cell Cycle Interphase / G1 Interphase is the longest phase of the cell cycle. All of cell growth, development and DNA replication happen in this phase (or phases, G1, S, and G2) G1 Phase: baby to pre-puberty 1st growth stage. Cells mature by making more cytoplasm & organelles

18 The Cell Cycle Interphase / S phase Interphase is the longest phase of the cell cycle. All of cell growth, development and DNA replication happen in this phase (or phases, G1, S, and G2) S Phase: puberty DNA is replicated

19 The Cell Cycle Interphase / S phase Interphase is the longest phase of the cell cycle. All of cell growth, development and DNA replication happen in this phase (or phases, G1, S, and G2) G2 Phase: post-puberty to ready for kids 2nd Growth Stage Occurs after DNA has been copied All cell structures needed for division are made (e.g. centrioles) Both organelles & proteins are synthesized