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Explore the intricate process of cell division including DNA replication, transcription, nucleotide structure, and the stages of mitosis. Understand how genetic information is transferred through RNA to synthesize proteins. Learn about the significance of somatic and reproductive cell division in growth and reproduction.
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Cell Division • process by which cells reproduce themselves • Includes: - nuclear division -cytoplasmic division • Two types: - somatic cell division - reproductive cell division
Transcription • process by which genetic information encoded in DNA is copied onto a strand of RNA • when strands divide, one strand (the sense strand) acts as the template for mRNA synthesis • the other strand is called the antisense strand
What is DNA? • composed of building blocks called nucleotides • double strand of nucleotides • ladder-like molecule • coiled into a spiral • double helix
DNA Replication • DNA helix uncoils • gradually separates into two nucleotide chains • template for next strand • each nucleotide joins in a complementary sequence
Nucleotide Structure • Composed of: - nitrogenous base - pentose monosaccharide - phosphate groups
Nucleotide Structure (cont.) • nitrogenous base - purines (adenine and guanine) - pyrimidines (cytosine, thymine, and uracil
DNA • DNA bases: - adenine (A) - guanine (G) - cytosine (C) - thymine (T) • adenine (A) bonds with thymine(T) • guanine (G) bonds with cytosine (C)
RNA • RNA bases: - adenine (A) - guanine (G) - cytosine (C) - uracil (U)
Messenger RNA • carries genetic information from DNA to cytosol where it serves as template for protein synthesis
Translation • process by which nucleotide sequence on a strand of mRNA is used as a template for protein synthesis • generates a corresponding amino acid sequence in a polypeptide chain • three consecutive nucleotides are called a codon, which specifies one amino acid
Somatic Cell Division • results in an increase in number of cells in body (growth, repair) • Cell life cycle has two major periods: - interphase (resting stage) - mitotic phase (cell division reproduction occurs)
Interphase • series of activities before reproduction • between divisions • each chromosome makes copy of self • two identical chromosomes • chromatids are united by centromere • metabolic activities continue • longest phase of the cell cycle • very active
Cell Division • Process includes: - mitosis nuclear division formation of two daughter nuclei - cytokinesis division of cytoplasm begins once mitosis is nearly complete
Stages of Mitosis • prophase • metaphase • anaphase • telophase
Prophase (pro = before) • chromosomes become visible as chromatids • nucleolus disappears • mitotic spindle appears
Prophase (cont.) • chromatin threads coil and shorten into chromosomes - double stranded (chromatids) • each chromatid is held together by small median body called a centromere • centrosome and its centrioles each move to opposite sides of cell
Prophase (cont.) • mitotic spindle between centrioles (responsible for attachment and movement of chromosomes) • end of stage - nuclear membrane and nucleoli have broken down and disappeared • chromosomes are randomly attached to centromeres by spindle fibers
Prophase Prophase 2 Prophase 1
Metaphase (meta = after) • short • chromosome pairs line up on the metaphase plate (exact midpoint or center of the mitotic spindle) • straight line of chromosomes
Anaphase (ana=upward) • centromeres divide and separate • identical chromosomes move to opposite poles with centromeres
Telophase (telo = far or end) • begins as soon as chromosomal movement stops • chromosomes at poles uncoil • resume chromatin form (threadlike) • nuclear membrane forms around each chromatin mass • nucleoli reappear • mitotic spindle disappears
Cytokinesis(kinesis = motion) • division of cytoplasm and organelles • occurs in late anaphase • furrow develops and progresses inward dividing cell into two separate portions of cytoplasm
Conclusion • two daughter cells genetically identical to the original mother cell • each cell diploid in number
Meiosis • cell division • restricted to sex cell (gametes) production • involves two successive nuclear divisions • results in daughter cells with haploid (1/2) number of chromosomes
Haploid • one half the normal number of chromosomes (23 in humans) Diploid • number of chromosomes characteristically found in somatic cells of an organism (46 in humans)