Suzanne D'Anna1 Cell Division

Suzanne D'Anna2 Cell Division n process by which cells reproduce themselves n Includes: - nuclear division - cytoplasmic division n Two types: - somatic cell division - reproductive cell division

Suzanne D'Anna3 Transcription n process by which genetic information encoded in DNA is copied onto a strand of RNA n when strands divide, one strand (the sense strand) acts as the template for mRNA synthesis n the other strand is called the antisense strand

Suzanne D'Anna4 What is DNA? n composed of building blocks called nucleotides n double strand of nucleotides n ladder-like molecule n coiled into a spiral n double helix

Suzanne D'Anna5

6 DNA Replication n DNA helix uncoils n gradually separates into two nucleotide chains n template for next strand n each nucleotide joins in a complementary sequence

Suzanne D'Anna7 Nucleotide Structure n Composed of: - nitrogenous base - pentose monosaccharide - phosphate groups

Suzanne D'Anna8 Nucleotide Structure (cont.) n nitrogenous base - purines (adenine and guanine) - pyrimidines (cytosine, thymine, and uracil

Suzanne D'Anna9 DNA n DNA bases: - adenine (A) - guanine (G) - cytosine (C) - thymine (T) n adenine (A) bonds with thymine(T) n guanine (G) bonds with cytosine (C)

Suzanne D'Anna10 RNA n RNA bases: - adenine (A) - guanine (G) - cytosine (C) - uracil (U)

Suzanne D'Anna11 Messenger RNA n carries genetic information from DNA to cytosol where it serves as template for protein synthesis

Suzanne D'Anna12 Translation n process by which nucleotide sequence on a strand of mRNA is used as a template for protein synthesis n generates a corresponding amino acid sequence in a polypeptide chain n three consecutive nucleotides are called a codon, which specifies one amino acid

Suzanne D'Anna13 Somatic Cell Division n results in an increase in number of cells in body (growth, repair) n Cell life cycle has two major periods: - interphase (resting stage) - mitotic phase (cell division reproduction occurs)

Suzanne D'Anna14 Interphase n series of activities before reproduction n between divisions n each chromosome makes copy of self n two identical chromosomes n chromatids are united by centromere n metabolic activities continue n longest phase of the cell cycle n very active

Suzanne D'Anna15 Cell Division n Process includes: - mitosis nuclear division formation of two daughter nuclei - cytokinesis division of cytoplasm begins once mitosis is nearly complete

Suzanne D'Anna16 Stages of Mitosis n prophase n metaphase n anaphase n telophase

Suzanne D'Anna17 Prophase (pro = before) n chromosomes become visible as chromatids n nucleolus disappears n mitotic spindle appears

Suzanne D'Anna18 Prophase (cont.) n chromatin threads coil and shorten into chromosomes - double stranded (chromatids) n each chromatid is held together by small median body called a centromere n centrosome and its centrioles each move to opposite sides of cell

Suzanne D'Anna19 Prophase (cont.) n mitotic spindle between centrioles (responsible for attachment and movement of chromosomes) n end of stage - nuclear membrane and nucleoli have broken down and disappeared n chromosomes are randomly attached to centromeres by spindle fibers

Suzanne D'Anna20 Prophase Prophase 1 Prophase 2

Suzanne D'Anna21 Metaphase (meta = after) n short n chromosome pairs line up on the metaphase plate (exact midpoint or center of the mitotic spindle) n straight line of chromosomes

Suzanne D'Anna22 Metaphase

Suzanne D'Anna23 Anaphase (ana=upward) n centromeres divide and separate n identical chromosomes move to opposite poles with centromeres

Suzanne D'Anna24 Anaphase

Suzanne D'Anna25 Telophase (telo = far or end) n begins as soon as chromosomal movement stops n chromosomes at poles uncoil n resume chromatin form (threadlike) n nuclear membrane forms around each chromatin mass n nucleoli reappear n mitotic spindle disappears

Suzanne D'Anna26 Telophase

Suzanne D'Anna27 Cytokinesis (kinesis = motion) n division of cytoplasm and organelles n occurs in late anaphase n furrow develops and progresses inward dividing cell into two separate portions of cytoplasm

Suzanne D'Anna28 Conclusion n two daughter cells genetically identical to the original mother cell n each cell diploid in number

Suzanne D'Anna29 Meiosis n cell division n restricted to sex cell (gametes) production n involves two successive nuclear divisions n results in daughter cells with haploid (1/2) number of chromosomes

Suzanne D'Anna30 Haploid n one half the normal number of chromosomes (23 in humans) Diploid n number of chromosomes characteristically found in somatic cells of an organism (46 in humans)