Chromosomes and Cell Reproduction Section 1 Section 2 Section 3 Chromosomes Cell Cycle Mitosis

3 Types of Cell Division Prokaryotic Cells (bacteria) undergo reproduction by dividing (asexual reprod.) Eukaryotic Cells undergo growth, repair, development by mitosis Meiosis is the formation of gametes, which are the organisms’ reproductive cells (eggs/sperm) *** Each cell ends up with a complete set (copy) of DNA

Prokaryotic Cell Reproduction No NUCLEUS DNA is circular ad attached to the inner cell membrane. Binary fission-form of asexual reproduction that produces identical offspring

Eukaryotic Cell Reproduction Most information encoded in DNA is organized into genes Genes are segments of DNA that code for a protein or RNA molecule Chromosomes are coiled structures of DNA DNA is copied (2 chromatids) and each new cell gets one chromatid.

DNA, Chromosomes, Genes

Chromosome Number Each human somatic cell contains 23 pairs of chromosomes (total of 46) Each chromosome contains thousands of genes that determine how a person develops Homologous chromosomes are chromosomes that are similar in shape, size, and genetic content One set of chromosomes from each (mom/dad)

Somatic Cells vs. Gametes Body cells (somatic) are diploid, which means they contain 2 sets of chromosomes Gametes (sperm/egg) are haploid - 1 set. N = 23 2N = 46 Fertilization - fusion of 2 haploid gametes Zygote - fertilized egg cell

Fertilization/Meiosis

Sex Chromosomes Autosomes - (1-22) chromosomes that are not involved with determining gender Sex Chromosomes- 1 chromosome out of 23 determines gender XX or XY 23rd Chromosome

Change in Chromosome # Down’s Syndrome - Trisomy 21 (3 copies of the 21st chromo.) Karyotype - a photo of chromosomes that sorts them by size Non-disjunction if one of more chromosomes fail to separate properly

Mutation - A Mistake Mutation- change in chromosome structure Deletion mutation - piece breaks off Duplication mutation - 2 copies of genes Inversion mutation - reverse order of genes Translocation mutation - piece of chromosome attaches to a non-homologous chromosome

The Cell Cycle Cell cycle is a repeating sequence of cellular growth and division Interphase- 1st three phases of the cycle (cell spends 90% of time here) 1st (G1) = first growth phase 2nd (S) = synthesis phase (DNA copied) 3rd (G2) = second growth phase 4th (mitosis) = process of cell division 5th (cytokinesis) = cytoplasm divides in half

Cell Cycle Continued Proteins control cell cycle (tell when to divide) Cancer - uncontrolled growth of cells or disorder of cell division Either produce growth- promoting molecules or inactivate control proteins.

Mitosis and Cytokinesis During mitosis the nucleus divides, each containing a complete set of chromosomes Chromatids on each chromosome are physically moved to opposite sides of the dividing cell with the help of the spindle. Spindles are cell structures made up of centrioles and microtubule fibers that are involved in moving chomo. In cell division

Stages of Mitosis 1= Prophase - chromosomes coil up 2= Metaphase - chromosomes move to center of cell and line up on equator 3=Anaphase - centromeres divide and chromatids move toward opposite poles 4=Telophase - nuclear envelope forms around chromosomes at each pole Cytokinesis - cytoplasm divides in half

Mitosis

Mitosis Animation