Chapter 2 Chromosome Transmission During Cell Division and Sexual Reproduction PDF

Because learning changes everything. ® Chapter 2 Chromosome Transmission During Cell Division and Sexual Reproduction © 2021 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the...

Because learning changes everything. ® Chapter 2 Chromosome Transmission During Cell Division and Sexual Reproduction © 2021 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.  Topics Features of chromosomes Karyotypes Cell division in prokaryotes and eukaryotes Mitosis Meiosis Mechanisms of sex determination © McGraw Hill 2  General Features of Chromosomes Chromosomes - structures within living cells that contain the genetic material (genes) Composed of DNA - the genetic material Proteins - provide an organized structure In eukaryotes the DNA-protein complex is called chromatin May also contain non-coding RNAs (eukaryotes) © McGraw Hill 3  Two Types of Cells Two types of cells: Prokaryotes Eukaryotes Bacteria and Archaea Protists, fungi, plants, and animals © McGraw Hill 4  Features of a Prokaryotic Cell (a) Prokaryotic cell This example is typical of bacteria such as Escherichia coli, which has an outer membrane and flagellum. © McGraw Hill 5  Features of a Eukaryotic Cell (b) Eukaryotic cell © McGraw Hill 6  Two Types of Animal Cells Animal cells are of two types Somatic cells Body cells, other than gametes Blood cells, for example Germ cells Gametes Sperm and egg cells https://www.genome.gov/genetics-glossary/Somatic-Cells © McGraw Hill 7  Cytogenetics Microscopic examination of chromosomes Allows the detection of individuals with abnormal chromosome number or structure Provides a way to distinguish between two closely-related species https://research.tamu.edu/2014/10/14/new-microscope-is-used-to-isolate-chromosomes-of-key-forest-specie https://research.tamu.edu/2014/10/14/new-microscope-is-used-to-isolate-chromosomes-of-key-forest-species/ © McGraw Hill 8  A Karyotype of a Diploid Human Cell Cytogenetics For a diploid human cell, two complete sets of chromosomes from a single cell constitute a karyotype of that cell. (a) Preparing cells for a karyotype © McGraw Hill 9  Most Eukaryotic Species Are Diploid Diploid species have two sets of chromosomes For example Humans 46 total chromosomes (23 per set) Dogs 78 total chromosomes (39 per set) Fruit fly 8 total chromosomes (4 per set) © McGraw Hill 10  Eukaryotic Chromosomes are Inherited in Sets Members of a pair of chromosomes are called homologs (homologous pair) Nearly identical in size Same banding pattern and centromere location Same genes, but not necessarily the same alleles DNA sequences on homologous chromosomes are also very similar → usually less than 1% difference between homologs These slight differences in DNA sequence provide the allelic differences in genes Example: Eye color gene Herc2→ Blue vs brown allele © McGraw Hill 11  Eukaryotic Chromosomes are Inherited in Sets The sex chromosomes (X and Y) are not homologous Differ in size and genetic composition Have short regions of homology The physical location of a gene on a chromosome is called its locus. https://socratic.org/questions/are-the-sex-chromosomes-for-humans-x-and-y-expressed-in-all-somatic-cells-or-jus © McGraw Hill 12  Homologous Chromosomes Have the Same Loci Genotype: AA: Homozygous for the dominant allele Bb: Heterozygous cc: Homozygous for the recessive allele © McGraw Hill 13  Cell Division 1. One purpose = asexual reproduction (produce new individuals) Bacteria Amoeba Yeast 2. A second purpose = achieving multicellularity Plants, animals and certain fungi and protists are derived from a single cell that has undergone repeated cell divisions Example: Humans start as single fertilized egg → adult with several trillion cells © McGraw Hill 14  Binary Fission FtsZ protein recruits other proteins to create a new cell wall Prior to division, the bacterial cell replicates its chromosome Then the cell divides into two daughter cells by a process termed binary fission Binary fission does not involve genetic contributions from two different gametes © McGraw Hill 15  The Eukaryotic Cell Cycle Cell division in eukaryotes DNA requires a replication and sorting Replication process that is more complicated than simple binary fission Access the text alternative for slide images. © McGraw Hill 16  Chromosomes Following DNA Replication 1 The two copies of a replicated chromosome are termed sister chromatids (dyad). Joined by centromere (a) Homologous chromosomes and sister chromatids © McGraw Hill (top left & bottom inset) ©Leonard Lessin/Science Source; (right): ©Biophoto Associates/Science Source 17  Chromosomes Following DNA Replication 2 (b) Schematic drawing of sister chromatids © McGraw Hill 18  Chromatids and Chromosomes During Mitosis At the end of S phase, a cell has twice as many chromatids as in the G1 phase A human cell has 46 chromosomes in G1 phase 46 pairs of sister chromatids after S phase The term chromosome is relative In G1 and late in the M phase = one chromatid In G2 and early in the M phase = a pair of sister chromatids joined at the centromere © McGraw Hill 19  Mitosis Primary purpose = distribute the replicated chromosomes to the two daughter cells Five Phases Prophase Prometaphase Original mother cell is diploid (2n) Metaphase Two daughter cells will be diploid (2n) Anaphase Telophase © McGraw Hill 20  Structure of the Mitotic Spindle Access the text alternative for slide images. © McGraw Hill 21  Entire Process of Mitosis © McGraw Hill 22  Cytokinesis In most cases, mitosis is quickly followed by cytokinesis In animals Formation of a cleavage furrow In plants Formation of a cell plate © McGraw Hill 23  Cytokinesis (a) Cleavage of an animal cell © McGraw Hill ©Don W. Fawcett/Science Source 24  Cytokinesis (b) Formation of a cell plate in a plant cell © McGraw Hill © Ed Reschke 25  Meiosis Sexual reproduction is a common way for eukaryotic organisms to produce offspring Parents (diploid) make gametes with half the amount of genetic material (haploid) These gametes fuse with each other during fertilization to create a new diploid individual © McGraw Hill 26  Meiosis Produces Haploid Gametes Gametes - haploid Contain a single set of chromosomes Gametes are 1n, while diploid cells are 2n A diploid human cell contains 46 chromosomes A human gamete contains only 23 chromosomes During meiosis, haploid cells are produced from diploid cells In humans, a gamete must receive one chromosome from each of the 23 pairs © McGraw Hill 27  Meiosis Like mitosis, meiosis begins after a cell has progressed through interphase of the cell cycle Unlike mitosis, meiosis involves two successive divisions to reduce the chromosome content These are termed Meiosis 1 and Meiosis 2 Each meiotic division is subdivided into Prophase Prometaphase Metaphase Anaphase Telophase © McGraw Hill 28  Meiosis 2 Meiosis 1 is followed by cytokinesis and then meiosis 2 The sorting events that occur during meiosis 2 are similar to those that occur during mitosis However the starting point is different For a diploid organism with six chromosomes Mitosis begins with 12 chromatids joined as six pairs of sister chromatids (= 6 chromosomes) Meiosis 2 begins with 6 chromatids joined as three pairs of sister chromatids (= 3 chromosomes) © McGraw Hill 29  Entire Process of Meiosis © McGraw Hill 30  Mitosis versus Meiosis Mitosis produces two diploid daughter cells Genetically identical Meiosis produces four haploid daughter cells Not genetically identical © McGraw Hill 31  Sexual Reproduction Sexual reproduction – common in eukaryotes Parents (diploid) make gametes through the process of gametogenesis with half the amount of genetic material (haploid) These gametes fuse with each other during fertilization to begin the life of a new diploid organism © McGraw Hill 32  Types of Gametes Some simple eukaryotic species are isogamous They produce gametes that are morphologically similar Example: Many species of fungi and algae © McGraw Hill 33  Types of Gametes Most eukaryotic species are heterogamous These produce gametes that are morphologically different Sperm cells (male gametes) Relatively small and mobile Egg cell or ovum (female gametes) Usually large and nonmotile Stores a large amount of nutrients (animal species) © McGraw Hill 34  Spermatogenesis (a) Spermatogenesis © McGraw Hill 35  Oogenesis Unlike spermatogenesis, the divisions in oogenesis are asymmetric The divisions produce polar bodies that contain very little cytoplasm (b) Oogenesis © McGraw Hill 36  The Chromosome Theory of Inheritance and Sex Chromosomes Describes how the transmission of chromosomes account for Mendelian patterns of inheritance Established how chromosomes carry and transmit genetic determinants of traits © McGraw Hill 37  Basis for the Chromosome Theory of Inheritance The chromosome theory of inheritance unfolded as a result of three lines of scientific inquiry Analysis of the transmission of traits from parent to offspring Mendel’s plant hybridization studies Inquiry into the material basis of heredity Microscopic examination of the processes of mitosis, meiosis, and fertilization © McGraw Hill 38  Sex Determination In many animal species, chromosomes play a role in sex determination Factors other than chromosomes can also determine sex Sex in some reptiles and fish is controlled by temperature In alligators, environmental temperatures determine sex © McGraw Hill 39  Human Sex Determination Humans have 46 chromosomes 44 autosomes 2 sex chromosomes Males contain one X and one Y chromosome They are termed heterogametic Females have two X chromosomes They are termed homogametic The Y chromosome determines maleness © McGraw Hill 40  Human Sex Determination (a) X-Y system in mammals © McGraw Hill 41  X-0 Sex Determination in Some Insects In some insects, Males are X0 and females are XX In other insects (fruit fly, for example) Males are XY and females are XX The Y chromosome does not determines maleness Rather, it is the ratio between the X chromosomes and the number of sets of autosomes (X/A) If X/A = 0.5, the fly becomes a male If X/A = 1.0, the fly becomes a female © McGraw Hill 42  X-0 Sex Determination in Some Insects (a) X-Y system in mammals © McGraw Hill 43  Z–W Sex Determination in Birds and Some Fish The sex chromosomes are designated Z and W to distinguish them from the X and Y chromosomes of mammals Males contain two Z chromosomes They are homogametic Females have one Z and one W chromosome They are heterogametic (c) The Z-W system in birds © McGraw Hill 44  Haplodiploid Sex Determination in Bees Males are known as the drones They are haploid Produced from unfertilized haploid eggs Females include the worker bees and queen bees They are diploid Produced from fertilized eggs © McGraw Hill 45  Haplodiploid Sex Determination in Bees 2 (d) The haplodiploid system in bees © McGraw Hill 46  Ch 2 Study Guide Differentiate prokaryotic and eukaryotic cells Define chromosome Structure Number in humans Describe the focus of cytogenetics, and describe the procedure for making a karyotype Describe the process of binary fission in bacteria Summarize the phases of the eukaryotic cell cycle Differentiate mitosis and meiosis Process (phases) Function (when it occurs and why) End product Differentiate sexual and asexual reproduction Differentiate somatic cells and germ cells Describe the process of gamete formation Isogamous vs heterogamous species Describe different mechanisms for sex determination in various species © McGraw Hill 47