Cell Reproduction. Objectives

Transcription

1 Cell Reproduction Lecture 10 Objectives At the end of this series of lectures you should be able to: Define terms. Describe the functions of cellular reproduction. Compare the parent offspring relationship in asexual and sexual reproduction. Describe chromosomes and their structure. Explain how chromosomes are paired. Distinguish between autosomes and sex chromosomes. Distinguish between somatic cells and gametes and between diploid cells and haploid cells. 1

2 Objectives Describe the stages of the cell cycle. List the phases of mitosis and describe the events characteristic of each phase. Recognize the phases of mitosis from diagrams and micrographs. Explain how cancerous cells are different from healthy cells. Cellular Reproduction Functions Reproduction of single celled organisms (asexual reproduction) Growth of multicellular organisms Damage repair Sperm and egg production (sexual reproduction) 2

3 Reproduction Asexual reproduction Produces offspring that are identical to the original cell or organism and Involves inheritance of all genes from one parent. Sexual reproduction Produces offspring that are similar to the parents, but show variations in traits. Inheritance of unique sets of genes from two parents. OpenStax, CC BY 3.0, 3

4 Chromosomes Chromatin DNA Proteins (histones) Prior to division DNA condenses becomes visible (coils) Duplicates Sister chromatids Structure Arms Centromere 4

5 Chromosomes Homologous chromosomes Same lengths Same centromere position Same genes loci/locus Alleles Same banding patterns Chromosomes Somatic cells Sex cells or gametes Sperm and eggs 5

6 Chromosomes A human somatic cell has 46 chromosomes or 23 pairs of chromosomes 22 pairs of homologous chromosomes (1 from each parent) 1 pair of sex chromosomes (X and Y chromosomes) Diploid Chromosomes A human gamete has 23 chromosomes 22 autosomes not paired 1 sex chromosome Haploid 6

7 Sexual Life cycles In sexual reproduction, gametes (haploid) are formed through meiosis. Gametes, an egg and a sperm, are united to form a zygote (diploid). The zygote undergoes mitosis to grow. Some of the cells that develop become specialized to undergo meiosis and produce more gametes. Cell Cycle Interphase duplication of cell contents G 1 S G 2 Mitotic phase: division Mitosis division of the nucleus Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis division of cytoplasm 7

8 Biology by OpenStax College is licensed under a Creative Commons Attribution 3.0 Kelvinsong, Public Domain, 8

9 Interphase G 1 Growth Cell resulting at end of cytokinesis is small S DNA is replicated Synthesis G 2 Growth Organelles double Interphase William Vann, 9

10 Mitosis Prophase Mitotic spindle begins to form Centrosomes Spindle fibers Centrioles (Asters) DNA condenses (coils) and become visible Chromosomes are unorganized Nucelolus disappears Prophase Interphase William Vann, 10

11 Roy van Heesbeen, Public Domain, Mitosis Prometaphase Spindle fibers reach the centromeres of the chromosomes. Chromosomes move the center of the cell. Nuclear envelope disappears. 11

12 Prometaphase Prophase William Vann, Roy van Heesbeen, Public Domain, 12

13 Mitosis Metaphase Chromosomes are lined up in the middle of the cell. Metaphase Prometaphase William Vann, 13

14 Afunguy, Public Domain, Mitosis Anaphase The microtubules attached to the chromosomes shortens. The centromeres of sister chromatids separate. Chromosomes move to opposite poles of the cell. 14

15 Anaphase Metaphase William Vann, Roy van Heesbeen, Public Domain, 15

16 Mitosis Telophase Chromosomes reach the poles. Chromatin uncoils and chromosomes disappear. Nuclear envelope reforms. Spindle disappears. Telophase Anaphase William Vann, 16

17 Roy van Heesbeen, Public Domain, Cytokinesis The cytoplasm divides Animal cells Cleavage furrow develops a contacting ring of microtubules Plant cells Cell plate forms vessicles carry cell wall materials 17

18 Telophase Cytokinesis William Vann, Biology by OpenStax College is licensed under a Creative Commons Attribution

19 Kelvinsong, Public Domain, Biology by OpenStax College is licensed under a Creative Commons Attribution

20 Cell Reproduction Controlled by Nutrient availability Growth factors proteins Density dependence Anchorage dependence Cancer Cells that divide in an uncontrolled manner. Divide rapidly Spread Not inhibited Tumors Benign Malignant Treatment Localized surgery or radiation Metastasized chemotherapy 20