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Cell Reproduction Introduction Cell reproduction is different for prokaryotes than eukaryotes. Why? What do you know about the two different types of cells? Chromosome Terminology • Chromatin: tangled mass of threadlike DNA in nondividing cell • Chromosomes: condensed rod-shaped DNA molecules formed during division • Sister chromatids: 2 exact copies of genetic information that make up each chromosome • Centomere: location where sister chromatids are attached together • Genes: segment of DNA that CODES FOR A PROTIEN • Each duplicated chromosome consists of two sister chromatids which contain identical copies of the chromosome’s DNA. • As they condense, the region where the strands connect shrinks to a narrow area, is the centromere. • Later, the sister chromatids are pulled apart and repackaged into two new nuclei at opposite ends of Fig. 12.3 the parent cell. Prokaryotic Cell Reproduction Binary fission • Asexual reproduction • Offspring are identical • 2 stages: 1) DNA is copied 2) Cell divides a) New cell membrane formed between 2 copies of DNA b) Squeezes together and eventually pinches off to 2 cells Eukaryotic Cell Reproduction •Two types of Cell Reproduction For Eukaryotes –Cell Division/Reproduction involving Mitosis –Cell Division/Reproduction involving Meiosis • Mitotic Reproduction: Asexual; produces 2 identical daughter cells from original mother cell. • Meiotic Reproduction: Produces 4 non-identical “gametes” from one mother cell; reduces the number of chromosomes in the cell by ½; leads to sexual reproduction Chromosome Number Terminology • Diploid number (2N) : characteristic chromosome number in common somatic eukaryotic cells chromosomes exist in pairs due to presence of two complete sets of chromosomes one maternal set one paternal set Chromosome Number Terminology • Haploid number (N): half the diploid number; only one set of mixed maternal and paternal chromosomes; found only in gametes (Technically, all prokaryotes are haploid) Cell Type Terminology • Somatic Cells: All non-sex cells; normal body cells (skin, muscle, liver, root, leaf, stem, etc.) –Theoretically always Diploid • Gametes (germ cells): Sex cells –sperm, egg (ovum), sexual spores –Theoretically always Haploid Let’s Practice! Get out your packets and turn to page 19.