Lecture 6 Mitosis.pptx

Lecture 6: Mitosis BIO1101 Biology Department College of Science IMSIU © 2021 Pearson Education Ltd. CONCEPT 12.1: Most cell division results in genetically identical daughter cells • The ability of organisms to produce more of their own kind is the one characteristic that distinguishes living th...

Lecture 6: Mitosis BIO1101 Biology Department College of Science IMSIU © 2021 Pearson Education Ltd. CONCEPT 12.1: Most cell division results in genetically identical daughter cells • The ability of organisms to produce more of their own kind is the one characteristic that distinguishes living things from nonliving matter • The continuity of life is based on the reproduction of cells, or cell division © 2021 Pearson Education Ltd. Figure 12.1b © 2021 Pearson Education Ltd. Key Roles of Cell Division • Cell division plays several important roles in life • Single-celled organisms give rise to new organisms through cell division • Multicellular eukaryotes undergo embryonic development through cell division • Cell division continues to function in renewal and repair in fully grown multicellular eukaryotes © 2021 Pearson Education Ltd. • A crucial function of most cell division is the distribution of identical genetic material to the two daughter cells • Cell division is remarkably accurate in passing DNA from one generation to the next © 2021 Pearson Education Ltd. Cellular Organization of the Genetic Material • All the DNA in a cell constitutes the cell’s genome • A genome can consist of a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells) • DNA molecules in a cell are packaged into chromosomes • The DNA molecule of a chromosome carries several hundred to a few thousand genes © 2021 Pearson Education Ltd. Figure 12.3 © 2021 Pearson Education Ltd. • Eukaryotic chromosomes consist of chromatin, a complex of DNA and protein that condenses during cell division • Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus • Somatic cells (nonreproductive cells) have two sets of chromosomes • Gametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells © 2021 Pearson Education Ltd. Distribution of Chromosomes During Eukaryotic Cell Division • In preparation for cell division, DNA is replicated and the chromosomes condense • Each duplicated chromosome has two sister chromatids (joined copies of the original chromosome), attached along their lengths by cohesins • The centromere is the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached © 2021 Pearson Education Ltd. • During cell division, the two sister chromatids of each duplicated chromosome separate and move into two nuclei • Once separate, the chromatids are called chromosomes © 2021 Pearson Education Ltd. Figure 12.5 © 2021 Pearson Education Ltd. • Eukaryotic cell division consists of – mitosis, the division of the genetic material in the nucleus – cytokinesis, the division of the cytoplasm • Gametes are produced by a variation of cell division called meiosis • Meiosis yields nonidentical daughter cells that have half as many chromosomes as the parent cell © 2021 Pearson Education Ltd. Phases of the Cell Cycle • The cell cycle consists of – mitotic (M) phase (mitosis and cytokinesis) – interphase (cell growth and copying of chromosomes in preparation for cell division) © 2021 Pearson Education Ltd. • Interphase (about 90% of the cell cycle) can be divided into three phases: – G1 phase (“first gap”) – S phase (“synthesis”) – G2 phase (“second gap”) • The cell grows during all three phases, but chromosomes are duplicated only during the S phase © 2021 Pearson Education Ltd. • Mitosis is conventionally broken down into five stages: – – – – – prophase prometaphase metaphase anaphase telophase © 2021 Pearson Education Ltd. Figure 12.7a © 2021 Pearson Education Ltd. Figure 12.7b © 2021 Pearson Education Ltd.