Cell reproduction

“Introduction Biology PART : Cell reproduction Kittisak Buddhachat, Ph.D

Outline of Cell Reproduction1. Cell division2. Mitosis3. Meiosis

1 Cell division Key roles of cell division • The ability of organism to produce more of their own kind. • “Every cell from a cell” is concept of Rudolf Virchow as the continuity of life. • Prokaryotic cell division and unicellular eukaryote (e.g. Amoeba) is actually reproducing, giving a new organism. • But for multicellular eukaryote  growth, development and tissue renewal

1 Cell division Functions of cell division • An amoeba, a single-celled eukaryote, is dividing into new cell. Each new cell will be an individual organism (LM). • This micrograph shows a sand dollar embryo shortly after the fertilized egg divided, forming two cells (LM). • These dividing bone marrow cells will give rise to new blood cells (LM).

1 Cell division • The continuity of life is transmission of genetic information from generation to next generation. • The genetic information in one cell is genome • In human, genome length is about 2 m, 250,000 times greater than cell’s diameter. • DNA molecules are packed into structure called chromosomeProkaryote Eukaryote

1 Cell division Most cell division  genetically identical daughter cells. • Binary fission is a common process for propagation in bacteria and yeast • Mitosis in animal cells • The exception is meiosis, producing sperm and egg. The simple process: • DNA duplication • Cytokinesis is a process for splitting cell, forming two cells

1 Cell division Chromosome duplication and distribution during cell division Not yet duplication Centromere is a region of the chromosomal DNA where theOnce duplicated, a chromatid is attached mostchromosome consist of closely to its sister chromatid.two sister chromatids Karyotype = all chromosomes in a individualSeparating sister Frog: 2n = 22chromatid to twodaughter cells

2 MitosisIncreasing the number of cell resulting in growth, development andtissue repair or renewal.Phases of the cell cycle. Cell grows by producing proteins and Consist of two phase cytoplasmic organelles such as • Mitotic (M) phase = mitosis and mitochondria and endoplasmic cytokinesis reticulum • Interphase = cell growth and copying DNA in preparation for cell divisionInterphase – about 90% of the cycle.• Can be subdivided the following: • G1 phase “first gap” preparation for S phase • S phase “synthesis” duplication of DNA • G2 phase “second gap” preparation for Mitosis

2 Mitosis Mitotic phase in animal cells Can be broken down into five stages: • Prophase • Prometaphase • Metaphase • Anaphase • telophase Cytokinesis is overlapping with telophase, completes the mitotic phase

2 Mitosis

2 Mitosis

2 Mitosis Mitotic phase in plant cells

2 Mitosis CytokinesisIn animal cells, cytokinesis occurs by a process In plants cells, they have no cleavage furrowknown as cleavage using a contractile ring of due to cell walls. During telomere, vesiclesactin microfilaments derived from the Golgi apparatus move along microtubules to the middle of the cell, producing cell plate.

3 Meiosis Meiosis reduces the number of chromosome sets from diploid (2n) to haploid (n) to produce gamete cell for sexual reproduction. Diploid cell = cell with two chromosome sets. For somatic cell in human, the diploid number = 46 (2n=46) Haploid cell = cell with a single chromosome set which is observed in gametes (sperm or egg). For human gamete, the haploid is 23 (n = 23) Describing chromosome Fertilized egg = sperm + eggHomologous chromosome have same length,centromere and staining position Human life cycle

3 Meiosis Meiosis, like mitosis, is preceded by the duplication of chromosomes and followed by two consecutive cell divisions called meiosis I and meiosis II.

3 Meiosis The stage of Meiosis

3 MeiosisThe stage of Meiosis I: Separating homologouschromosomeSynapsis of homologouschromosomeCrossing over =recombination betweenhomologous chromosomeChiasmata = a region whereoccurs crossing over.

Meiosis 3The stage of Meiosis II: Separating sister chromatid

3 MeiosisOrigin of Genetic variation among offspring: that’s why individual isdifferent even in sister or brother. 1. Independent Assortment of Chromosomes

3 MeiosisOrigin of Genetic variation among offspring 2. Crossing over

3 MeiosisA comparison of mitosis and meiosis

3 MeiosisA comparison of mitosis and meiosis

Book References For more informationCore books Gerald Karp. Cell Biology, seventh editionCampbell et al., Biology: Aglobal approach, tenthedition,Download media at https://pubhtml5.com/homepage/wfgm/