Somatic Cellular Reproduction 1 The Cell Cycle and

Somatic Cellular Reproduction: 1 The Cell Cycle and Mitosis

Cell Division in Prokaryotes • Reproduction is done by binary fission (making a clone)

Cells that make up the “body” of an organism 2

Why Should Cells Divide? ? ? In Unicellular Organisms: • Reproduction In Multicellular Organisms: • Maintain a favorable surface area to volume ratio • Maintain correct number of chromosomes 3

4 Structures that contain the genetic material

Chromosomes are composed of chromatin, a tangled mass of DNA and proteins The Full Number of Chromosomes Found in all Somatic Cells is the Diploid Number (2 N) The Diploid Number includes 2 of each chromosome (a pair) 5

Chromosome and Centromere

Chromosome Number • Humans have a total of 46 chromosomes in each cell (diploid) • Gametes (sperm & eggs) have 23 chromosomes each (haploid)

Homologous Chromosomes - Chromosomes that are similar in size, shape and genetic content - Each of the 23 pairs of chromosomes consist of two homologous chromosomes

Haploid vs. Diploid

Autosomes • Chromosomes that are not directly involved in determining the sex (gender of an individual) • Chromosomes 1 -22 are considered autosomes

Sex Chromosomes The 23 rd Pair! - This pair of chromosomes are responsible for determining sex

Analysis of Chromosome • In order to insure the correct amount of chromosomes are present scientists study a karyotype.

Normal Karyotype

Down Syndrome Karyotype

The cycle of growth and division in all cells Consists of Interphase and Mitosis • Mitosis (M phase) is a period of cell division • Interphase is a period of DNA replication and growth in preparation for cell division 7

8 The Cell Cycle Protein Synthesis Cell Division Growth DNA copies itself interphase mitosis

Each Chromosome contains two identical parts called “sister chromatids” attached at a centromere 6

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8 Growth and DNA synthesis and Replication (G 1, S, G 2) Longest period of Cell Cycle Chromatin in nucleus appears as mass of threadlike structures

11 • Chromatin Condensed Into Visible Chromosomes • Nucleolus Disappears and Nuclear Envelope Fragments • Centrioles move to opposite sides of the cell

12 • Chromosomes lined up on equatorial plate • Spindle fibers attach at centromeres

13 • Centromeres divide • Sister chromatids pulled towards the poles

14 • Spindles disappear and nuclear envelope returns • Nucleolus returns • Chromosomes unwind into chromatin

Animal Cell 15 Plant Cell

Identify the Stages of Mitosis 1 2 4 16 3 5