Chapter 6 Chromosomes and Cell Division

Chapter 6 Chromosomes and Cell Division - Chapter 6...

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Chapter 6 Chromosomes and Cell Division 6.1 Immortal cells can spell trouble: cell division in sickness and in health - Telomere… - Becomes shorter after each cell division and loses its funtion - Located at each tip of every chromosome - Supports about 50 cell divisions - Cancer, cells cannot stop dividing 6.2 Some chromosomes are circular, others are linear - One way organisms’ DNA differ depends on how it is organized - Bacteria/Prokaryotes, genetic information is carried in a single, circular chromosome, a stand of DNA that is attached at one site to the cell membrane - Eukaryotes, have much more DNA, and organize into free floating linear chromosomes - Most important part of a eukaryotic chromosome is the DNA molecule, that carries information about how to carry out the processes needed to support the life of the organism 6.3 Prokaryotes divide by binary fission - Bacteria and other prokaryotes use binary fission when it is time to reproduce - Begins with replication - Double-stranded molecule unwinds and splits like a zipper - Free-floating nucleotide bases attach to the bases of the separated DNA molecules - Original cell, called the parent cell, pinches into 2 new cells called, daughter cells - Considered as asexual reproduction 6.4 There is a time for everything in the cell cycle - Eukaryotic cells spend time occupied with activities relating solely to growth and then suspend activities as they segue into a period devoted exclusively to reproducing themselves - Known as the cell cycle - Cells of a multicellular eukaryotic organisms dived into 2 types 1. Somatic Cells: Form the body of the organism 2. Reproductive Cells: Sex cells or gamete - Describes the series of phases that leads to somatic cell division - 2 main phases in the cell cycle 1. Interphase: Cell grows and prepares to divide
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2. Mitotic Phase/M Phase: 1 st nucleus and genetic material within the cell divides, and then the rest of the cellular contents divides - Interphase 1. Gap 1: Cell grows and performs all cellular functions. 2. DNA synthesis: Cell prepares for cell division. Chromosomes create an exact duplicate. 3. Gap 2: Cell continues to grow and prepare for cellular division. Genetic material has now been duplicated and is much longer than Gap 1. - Mitotic Phase - Begins with mitosis - Mitosis: A process in which the nucleus of the parent cell duplicates - Cytokinesis follows mitosis - Cells duplicate and separate into 2 daughter cells 6.5 Cell division is preceded by replication - Complementarity: The characteristic that in the double-stranded DNA molecule, the base on one strand always has the same pairing partner - The process of DNA duplication is called replication - DNA replication occurs in 2 steps 1. Unwinding: DNA molecules unwind and separates into 2 strands 2. Rebuilding: Single strands becomes a double strand - Errors in replication can lead to mutations 6.6 Most cells are not immortal: mitosis generates replacements - Mitosis has one purpose: To enable existing cells to generate new, identical cells
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Chapter 6 Chromosomes and Cell Division - Chapter 6...

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