DOCSLIB.ORG

6 Chapter 12

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
6 Chapter 12 Chapter 12: Inheritance Chapter 12 Who is the Father of Modern Genetics? Patterns of Inheritance Answer : Johann Gregor Mendel Definitions: Character - a heritable feature Trait - each variant for a character Chapter 12: Inheritance Definitions: 1) Self-fertilization : • Same flower provides • True/pure breeding pollen and eggs • True-breeding (homozygous) consistently gives rise to offspring with same trait x 2) Cross-fertilization : when selfed (or bred with • Different flowers provide same type). pollen and eggs (by hand) • Hybrid cross Carpel cross between parents true- (eggs) breeding for different trait(s) Stamen (pollen) Black lab with a golden lab. 1 Controlled genetic crosses Chapter 12: Inheritance Inheritance of Single Traits: P (parental) • Mendel raised true-breeders Generation for different forms of a trait and then cross-fertilized the forms: F1 (filial 1) Generation Progeny (offspring) • Mendel then allowed F 1 to self-fertilize: Intercross or self F1 offspring F2 (filial 2) Generation Chapter 12: Inheritance Chapter 12: Inheritance Modern Genetic Concepts: Modern Genetic Concepts: Locus : Specific location of a gene on Locus: Specific location of a gene on a chromosome a chromosome Locus Locus Alleles : Alternate forms of a nucleotide Locus Locus Alleles: Alternate forms of a nucleotide sequence for a single gene sequence for a single gene Heterozygous (“different pair”) Heterozygous (“different pair”) • Homologous chromosomes have • Homologous chromosomes have different alleles for a gene different alleles for a gene Homozygous (“same pair”) • Homologous chromosomes have same allele for a gene Chapter 12: Inheritance Mendel’s Hypothesis : Mendel’s model: 1) Traits are determined by pairs of discrete physical units 1. Hereditary units (genes) come in different forms • Physical units = genes (alleles) • One allele of each gene / homologous chromosome Gene = hair color 2) Alleles of a gene segregate from one another during meiosis Alleles = blonde hair, red hair, black hair, brown hair. • Law of Segregation 2. Two hereditary units for each trait (per individual) • Which allele enters which gamete occurs by chance One from each parent 3) Differing alleles can mask one another if occupying same cell • Dominant Allele : Allele expressed (observed) purple • Recessive Allele : Allele mask (not observed) One may be 4) True-breeding individuals have two of the same alleles dominant to purple the other. • Hybrids have two different alleles for the gene white 2 Chapter 12: Inheritance Inheritance of Single Traits: B. The law of segregation • Dominant trait - The trait exhibited by the F1 generation • Recessive trait - the trait NOT seen in the F1 generation P x Phenotype : • Outward expression of a trait (appearance, behavior) Genotype : F1 • Actual combination of alleles carried by an individual Chapter 12: Inheritance Chapter 12: Inheritance Inheritance of Single Traits: Punnett Square Method: (“Genetic Bookkeeping”) Individual 1 = Pp Individual 2 = Pp Phenotype : 3 purple : 1 white Genotype : 1 PP : 2 Pp : 1 pp Keep in Mind : Predicted proportions will fluctuate in real life Chapter 12: Inheritance Chapter 12: Inheritance Inheritance of Multiple Traits: Mendel’s hypothesis can be used to predict cross outcomes: • Mendel raised true-breeders Test Cross : for different forms of two traits and then cross-fertilized the Crossing a dominate phenotype individual with a homozygous forms: recessive individual to determine what the genotype of the dominate individual YYSS x yyss PP P p YySs p Pp Pp p Pp pp PP or Pp • Mendel then allowed F 1 to self-fertilize: p Pp Pp p Pp pp YySs x YySs pp 100% Purple 50% Purple / 50% White 3 Chapter 12: Inheritance Chapter 12: Inheritance Inheritance of Multiple Traits: • Resulting ratio of self-fertilization: 9 Yellow, smooth seeds Law of Independent Assortment : 3 Yellow, wrinkled seeds Y y • The alleles for one trait may be distributed to the gametes 3 Green, smooth seeds independently of the alleles for other traits 1 Green, wrinkled seeds Y YY Yy • Occurs via random assortment of chromosomes 3/4 yellow 9 : 3 : 3 : 1 during Meiosis I 1/4 green • Traits located on separate chromosomes y Yy yy Yy = Seed Color Ss = Seed Texture S s 9/16 Yellow, smooth seeds S SS Ss 3/16 Yellow, wrinkled seeds 3/4 smooth 3/16 Green, smooth seeds 1/4 wrinkled 1/16 Green, wrinkled seeds s Ss ss 9 : 3 : 3 : 1 Chapter 12: Inheritance Law of independent assortment Punnett Square (Multiple Traits): YySs x YySs Sperm Each pair of alleles segregates independently YS Ys yS ys of other allele pairs. YS as long as they are unlinked Ys Egg yS i.e., not on the same chromosome ys Independent Chapter 12: Inheritance Assortment Punnett Square (Multiple Traits): of Alleles: YySs x YySs Sperm YS Ys yS ys YS YYSS Ys Egg yS ys (Figure 12.7) 4 Punnett Square Chapter 12: Inheritance for Two Traits: Genes on the Same Chromosome Tend to be Inherited Together • Linked Genes = Genes on same chromosome 9 Yellow, smooth seeds 3 Yellow, wrinkled seeds 3 Green, smooth seeds 1 Green, wrinkled seeds 9 : 3 : 3 : 1 (Figure 12.6) Chapter 12: Inheritance Chapter 12: Inheritance Linked genes may be separated Sex Chromosomes: by crossing over events: • Determine sex of individual: • Crossing Over = Exchange • Humans = X and Y chromosomes of segments of homologous • Female = XX : Male = XY chromosomes • Birds/Reptiles = W and Z chromosomes • Occurs during metaphase • Female = WZ : Male = ZZ of meiosis I • Only one pair per species: • Humans = 23 chromosome pairs (1 pair sex) • Dogs = 39 chromosome pairs (1 pair sex) • Autosomes = All other chromosome pairs other than sex chromosomes (usually same size) Genetic Recombination Chapter 12: Inheritance Cross: Sex-linked Genes: • Genes present on one sex chromosome but not the other female Bb x male B • Human Y chromosome ∼ 80 genes B b ∼ X X • Human X chromosome 1500 genes X • Color vision genes B • Blood clotting factors X XB XB XB Xb • Females = Normal dominant/recessive relationships A difference in phenotypic ratios exist for alleles on X chromosomes XB Y Xb Y between male and female Y • Males = Fully express alleles on X chromosome progeny always indicates sex linkage . i.e., more males have the disorder than females. 5 Example of Sex-linked Chapter 12: Inheritance Trait: Variations on the Mendelian Theme: • Assumptions so far: 1) One allele is completely dominant over another allele Fact : Alleles can display Incomplete Dominance : • Heterozygous phenotype is intermediate between homozygous phenotypes Flower Color in Snapdragons (Figure 12.10) (Figure 12.11) Chapter 12: Inheritance Chapter 12: Inheritance Variations on the Mendelian Theme: Variations on the Mendelian Theme: • Assumptions so far: • Assumptions so far: 3) Each trait is completely controlled by a single gene 2) There are only two possible AA or AO BB or BO alleles for each gene Fact : Many traits are influenced by several genes Fact : Genes can have multiple • Polygenic Inheritance : alleles: • Interaction of 2 or more genes contribute to a AB O single phenotype • Most genes have > 10 alleles • Alleles arise from mutation • Skin Color = 3 or 4 genes Codominance : • Eye Color = 2 genes Remember : An individual will • Both phenotypes expressed have only a maximum of two equally in heterozygotes unique alleles for a gene(diploid) Chapter 12: Inheritance Example of Polygenic Inheritance: Additional Variations on the Mendelian Theme: • Pleiotrophy : Single genes may have multiple phenotypic effects • SRY gene: Codes for protein that activates other proteins in male cascade Fertilization Sex Determining Region of the Y Hormones Gonad Formation Sexual Differentiation of phenotype (similar idea to Figure 12.12) 6 Pleiotropy Chapter 12: Inheritance Additional Variations on the Mendelian Theme: • Marfan’s syndrome • The Environment influences Gene Expression: Pleiotropic trait that causes • Temperature in Himalayan Rabbits Tall, lanky bodies • Enzyme deactivated at high temperature Detached retinas Collapsed lungs Humans: Aortic dissections • Skin color (exposure) • Height (nutrition) Nearsightedness (myopia) • Intelligence (?) Chapter 12: Inheritance Pedigrees: Recessive Trait Human Genetic Disorders: How are Human Genetic Disorders Investigated? Answer : Pedigrees • Diagrams which show the genetic relationship among related individuals • Can reveal whether trait is dominant, recessive, or sex-linked Dominant Trait (Figure 12.14) Chapter 12: Inheritance Chapter 12: Inheritance Inheritance of Human Disorders (Single Gene): Inheritance of Human Disorders (Single Gene): 1) Recessive Alleles: 2) Dominant Alleles : • Disease if individual inherits two recessive alleles • Potential Effects: • Carrier = Heterozygous individual (not affected) • Produce abnormal protein • Carry out toxic reactions Albinism (no pigmentation; pink eyes) • Produce “overactive” proteins • Huntington Disease (deterioration of brain) • Abnormal protein production 3) Sex-linked : • Genes associated with sex chromosomes • Frequently in males… often skip generations • Color blindness (defective color receptors) • Hemophilia (defective clotting proteins) Sickle-cell Anemia (defective hemoglobin) 7 Royal Families of Europe: Chapter 12: Inheritance Errors in Chromosome Number can Affect Humans: • Nondisjunction : Homologous pairs don’t separate during meiosis (affects gamete chromosome counts) 1) Sex Chromosomes : • XO (Female ) = Turner Syndrome (Infertile; lack 2°sexual char.) • XXX (Female) = Trisomy X (Fertile; usually tall; potential ↓ IQ) • XXY (Male) = Klinefelter Syndrome (Infertile; often unnoticed) • XYY (Male) = Fertile; Excess testosterone (violent?) ; ↓ IQ) Chapter 12: Inheritance Errors in Chromosome Number can Affect Humans: • Nondisjunction: Homologous pairs don’t separate during meiosis (affects gamete chromosome counts) 2) Autosomal Chromosomes : • Down Syndrome (Trisomy 21) • Physical characteristics • Mental retardation • Heart malformations • Frequency increase with age at pregnancy 8.
Load more

Recommended publications
  • Homologous Chromosome Pairing in Wheat
    Journal of Cell Science 112, 1761-1769 (1999) 1761 Printed in Great Britain © The Company of Biologists Limited 1999 JCS3883 Homologous chromosome pairing in wheat Enrique Martínez-Pérez, Peter Shaw, Steve Reader, Luis Aragón-Alcaide*, Terry Miller and Graham Moore‡ John Innes Centre, Colney, Norwich NR4 7UH, UK *Present address: NIH, Bethesda, Maryland 20892, USA ‡Author for correspondence (e-mail: [email protected]) Accepted 24 March; published on WWW 11 May 1999 SUMMARY Bread wheat is a hexaploid (AABBDD, 2n=6x=42) (bouquet) is formed in the meiocytes only by the onset of containing three related ancestral genomes, each having 7 leptotene. The sub-telomeric regions of the homologues chromosomes, giving 42 chromosomes in diploid cells. associate as the telomere cluster forms. The homologous During meiosis true homologues are correctly associated in associations at the telomeres and centromeres are wild-type wheat, but a degree of association of related maintained through meiotic prophase, although, during chromosomes (homoeologues) occurs in a mutant (ph1b). leptotene, the two homologues and also the sister We show that the centromeres are associated in non- chromatids within each homologue are separate along the homologous pairs in all floral tissues studied, both in wild- rest of their length. As meiosis progresses, first the sister type wheat and the ph1b mutant. The non-homologous chromatids and then the homologues associate intimately. centromere associations then become homologous In wild-type wheat, first the centromere grouping, then the premeiotically in wild-type wheat in both meiocytes and the bouquet disperse by the end of zygotene. tapetal cells, but not in the mutant.
    [Show full text]
  • Meiosis II) That Produces Four Haploid Cells
    Zoology – Cell Division and Inheritance I. A Code for All Life A. Before Genetics - __________________________________________ 1. If a very tall man married a short woman, you would expect their children to be intermediate, with average height. 2. The history of blending inheritance, as an idea, remains in some animal scientific names. For example… a. Giraffe = Giraffa camelopardalis (described as having characteristics like both a camel and a leopard) b. Mountain Zebra = Equus Hippotigris zebra (having characteristics of a hippo and a tiger) B. History of Central Tenets of Genetics 1. Genetics accounts for resemblance and fidelity of reproduction. But, it also accounts for variation. 2. Genetics is a major unifying concept of biology. 3. _______________________________________________ described particulate inheritance. 4. ____________________&_____________________described nature of the coded instructions (the structure of DNA). C. Some vocabulary 1. _______________________ – a unit of heredity. A discreet part of the DNA of a chromosome that encodes for one trait, or protein, or enzyme, etc. 2. _______________________ – (deoxyribonucleic acid) a molecule that carries the genetic instructions for what the cell will do, how it will do it, and when it will do it. 3. _______________________ – a linear sequence of genes, composed of DNA and protein. a. Think of the chromosome as a bus that the genes are riding in. Where the bus goes, the genes must go. 4. _______________________- The location of any one gene on a chromosome. 5. _______________________ - Alternative forms of a gene; one or both may have an effect and either may be passed on to progeny. 6. _______________________pairs of chromosomes – Chromosomes that have the same banding pattern, same centromere position, and that encode for the same traits.
    [Show full text]
  • Chromosomal Theory and Genetic Linkage
    362 Chapter 13 | Modern Understandings of Inheritance 13.1 | Chromosomal Theory and Genetic Linkage By the end of this section, you will be able to do the following: • Discuss Sutton’s Chromosomal Theory of Inheritance • Describe genetic linkage • Explain the process of homologous recombination, or crossing over • Describe chromosome creation • Calculate the distances between three genes on a chromosome using a three-point test cross Long before scientists visualized chromosomes under a microscope, the father of modern genetics, Gregor Mendel, began studying heredity in 1843. With improved microscopic techniques during the late 1800s, cell biologists could stain and visualize subcellular structures with dyes and observe their actions during cell division and meiosis. With each mitotic division, chromosomes replicated, condensed from an amorphous (no constant shape) nuclear mass into distinct X-shaped bodies (pairs of identical sister chromatids), and migrated to separate cellular poles. Chromosomal Theory of Inheritance The speculation that chromosomes might be the key to understanding heredity led several scientists to examine Mendel’s publications and reevaluate his model in terms of chromosome behavior during mitosis and meiosis. In 1902, Theodor Boveri observed that proper sea urchin embryonic development does not occur unless chromosomes are present. That same year, Walter Sutton observed chromosome separation into daughter cells during meiosis (Figure 13.2). Together, these observations led to the Chromosomal Theory of Inheritance, which identified chromosomes as the genetic material responsible for Mendelian inheritance. Figure 13.2 (a) Walter Sutton and (b) Theodor Boveri developed the Chromosomal Theory of Inheritance, which states that chromosomes carry the unit of heredity (genes).
    [Show full text]
  • Content Online Course Engineering Life
    Content Online Course Engineering Life Where do you draw the line? 1 Content Lesson 1 – Fundamentals of the CRISPR-Cas System and its Applications ................................................... 4 1.1 Introduction - Video ............................................................................................................................... 5 1.2 Pre-Questionnaire Erasmus MC............................................................................................................ 7 1.3 Video Summary - Introduction to Genetics ...................................................................................... 9 1.4 The Genotype Influences the Phenotype ......................................................................................... 10 1.5 Heredity – How Genetic Information is Passed on ........................................................................ 15 1.6 Mutations and Genetic Modifications – Changing the Genetic Code ....................................... 22 1.7 Quiz: Test Your Knowledge on Genetics and Biology! (Multiple-Choice) ................................ 28 1.7 Quiz: Test Your Knowledge on Genetics and Biology! (Open Questions) ................................ 30 1.7 Quiz: Open Questions ........................................................................................................................... 31 1.8 Video Summary: Genome editing with CRISPR-Cas ...................................................................... 32 1.9 Quiz: CRISPR-Cas ..................................................................................................................................
    [Show full text]
  • Chromosomal Basis of Inherited Disorders
    366 Chapter 13 | Modern Understandings of Inheritance were very far apart on the same or on different chromosomes. In 1931, Barbara McClintock and Harriet Creighton demonstrated the crossover of homologous chromosomes in corn plants. Weeks later, Curt Stern demonstrated microscopically homologous recombination in Drosophila. Stern observed several X-linked phenotypes that were associated with a structurally unusual and dissimilar X chromosome pair in which one X was missing a small terminal segment, and the other X was fused to a piece of the Y chromosome. By crossing flies, observing their offspring, and then visualizing the offspring’s chromosomes, Stern demonstrated that every time the offspring allele combination deviated from either of the parental combinations, there was a corresponding exchange of an X chromosome segment. Using mutant flies with structurally distinct X chromosomes was the key to observing the products of recombination because DNA sequencing and other molecular tools were not yet available. We now know that homologous chromosomes regularly exchange segments in meiosis by reciprocally breaking and rejoining their DNA at precise locations. Review Sturtevant’s process to create a genetic map on the basis of recombination frequencies here (http://openstaxcollege.org/l/gene_crossover) . Mendel’s Mapped Traits Homologous recombination is a common genetic process, yet Mendel never observed it. Had he investigated both linked and unlinked genes, it would have been much more difficult for him to create a unified model of his data on the basis of probabilistic calculations. Researchers who have since mapped the seven traits that Mendel investigated onto a pea plant genome's seven chromosomes have confirmed that all the genes he examined are either on separate chromosomes or are sufficiently far apart as to be statistically unlinked.
    [Show full text]
  • Chapter 5 Cancer: DNA Synthesis, Mitosis, and Meiosis
    Chapter 5 Cancer: DNA Synthesis, Mitosis, and Meiosis Copyright © 2007 PearsonCopyright Prentice © Hall, 2007 Inc. Pearson Prentice Hall, Inc.1 5.6 Meiosis • Another form of cell division, meiosis, occurs within gonads, or sex organs – The point of meiosis is to cut the number of chromosomes in half • Male gonads are testes and female gonads are ovaries – Meiosis (my-oh-sis) happens in my ovaries – Mitosis (my-toe-sis) happens in my toes • Meiosis produces sex cells = gametes: – Male gametes: sperm cells – Female gametes: egg cells Copyright © 2007 Pearson Prentice Hall, Inc. 2 Meiosis • Gametes have half the chromosomes (23) that somatic or regular body cells do (46) • Meiosis reduces the number of chromosomes by one-half (23) • Fertilization or joining of the male (23) and female (23) gamete will result in 46 chromosomes Copyright © 2007 Pearson Prentice Hall, Inc. 3 Meiosis • Which 23 of the 46 chromosomes end up in each gamete? – One of each kind or pair • Chromosomes come in homologous pairs • Each somatic body cell has two of every chromosome – 1 through 22 pairs of autosomal chromosomes • Two copies of chromosome #1, two copies of chromosome #2, etc – And XX (female) or XY (male) sex chromosomes • Each gamete has one chromosome from each homologous pair – One copy of chromosome #1, one copy of chromosome #2, etc – And an X or a Y but not both Copyright © 2007 Pearson Prentice Hall, Inc. 4 Copyright © 2007 Pearson Prentice Hall, Inc. 5 Meiosis • There are 22 pairs of autosomes – non-sex chromosomes • Each pair of chromosomes carry the same genes – That’s why they are called homologous pairs – Homo = same • There is one pair of sex chromosomes: – Males have one X and one Y chromosome – Females have two X chromosomes Copyright © 2007 Pearson Prentice Hall, Inc.
    [Show full text]
  • Chromosome.Pdf
    Chromosomes What Exactly is a chromosome? Chromosomes are the rod-shaped, filamentous bodies present in the nucleus, which become visible during cell division. They are the carriers of the gene or unit of heredity. Chromosome are not visible in active nucleus due to their high water content, but are clearly seen during cell division. Chromosomes were first described by Strausberger in 1875. The term “Chromosome”, however was first used by Waldeyer in 1888. They were given the name chromosome (Chromo = colour; Soma = body) due to their marked affinity for basic dyes. Their number can be counted easily only during mitotic metaphase. Chromosomes are composed of thin chromatin threads called Chromatin fibers. These fibers undergo folding, coiling and supercoiling during prophase so that the chromosomes become progressively thicker and smaller. Therefore, chromosomes become readily observable under light microscope. At the end of cell division, on the other hand, the fibers uncoil and extend as fine chromatin threads, which are not visible at light microscope Number of chromosomes Normally, all the individuals of a species have the same number of chromosomes. Closely related species usually have similar chromosome numbers. Presence of a whole sets of chromosomes is called euploidy. It includes haploids, diploids, triploids, tetraploids etc. Gametes normally contain only one set of chromosome – this number is called Haploid Somatic cells usually contain two sets of chromosome - 2n : Diploid 3n – triploid 4n – tetraploid The condition in which the chromosomes sets are present in a multiples of “n” is Polyploidy When a change in the chromosome number does not involve entire sets of chromosomes, but only a few of the chromosomes - is Aneuploidy.
    [Show full text]
  • X/Y Translocations Resulting from Recombination Between Homologous Sequences on Xp and Yq PAULINE H
    Proc. Natl. Acad. Sci. USA Vol. 88, pp. 8944-8948, October 1991 Genetics X/Y translocations resulting from recombination between homologous sequences on Xp and Yq PAULINE H. YEN*t, SIAO-PING TSAI*t, SHARON L. WENGERf, MARK W. STEELEt, THULUVANCHERI K. MOHANDASt, AND LARRY J. SHAPIRO*t§ *Howard Hughes Medical Institute, and Departments of tPediatrics and §Biological Chemistry, University of California, Los Angeles, School of Medicine, Harbor-University of California, Los Angeles, Medical Center, Torrance, CA 90509; and tDivision of Medical Genetics, Children's Hospital of Pittsburgh, PA 15213 Communicated by Elizabeth F. Neufeld, July 17, 1991 ABSTRACT Several regions of sequence homology be- tric inversion of the Y chromosome during primate evolution tween the human X and Y chromosomes have been identified. (11). These segments are thought to represent areas of these chro- X/Y translocations occur rarely in the human population mosomes that have engaged in ineiotic recombination in rela- and some 50 cases have been reported (16-21). The majority tively recent evolutionary times. Normally, the X and Y of these-translocations have breakpoints at Xp22 and Yq11 chromosomes pair during mdosis and exchange DNA only when analyzed cytogenetically. The reciprocal products of within the pseudoautosomal region at the distal short arms of the translocations have never been recovered. Some ofthese both chromosomes. However, it has been suggested that aber- translocations are sporadic events, whereas others are inher- rant recombination involving other segments ofhigh homology ited. All females with Xp22;Yqll translocations have been could be responsible for the production of X/Y translocations. phenotypically normal except for short stature.
    [Show full text]
  • Basic Molecular Genetics for Epidemiologists F Calafell, N Malats
    398 GLOSSARY Basic molecular genetics for epidemiologists F Calafell, N Malats ............................................................................................................................. J Epidemiol Community Health 2003;57:398–400 This is the first of a series of three glossaries on CHROMOSOME molecular genetics. This article focuses on basic Linear or (in bacteria and organelles) circular DNA molecule that constitutes the basic physical molecular terms. block of heredity. Chromosomes in diploid organ- .......................................................................... isms such as humans come in pairs; each member of a pair is inherited from one of the parents. general increase in the number of epide- Humans carry 23 pairs of chromosomes (22 pairs miological research articles that apply basic of autosomes and two sex chromosomes); chromo- science methods in their studies, resulting somes are distinguished by their length (from 48 A to 257 million base pairs) and by their banding in what is known as both molecular and genetic epidemiology, is evident. Actually, genetics has pattern when stained with appropriate methods. come into the epidemiological scene with plenty Homologous chromosome of new sophisticated concepts and methodologi- cal issues. Each of the chromosomes in a pair with respect to This fact led the editors of the journal to offer the other. Homologous chromosomes carry the you a glossary of terms commonly used in papers same set of genes, and recombine with each other applying genetic methods to health problems to during meiosis. facilitate your “walking” around the journal Sex chromosome issues and enjoying the articles while learning. Sex determining chromosome. In humans, as in Obviously, the topics are so extensive and inno- all other mammals, embryos carrying XX sex vative that a single short glossary would not be chromosomes develop as females, whereas XY sufficient to provide you with the minimum embryos develop as males.
    [Show full text]
  • 00326673.Pdf
    Unda_standing Inheritance ~ hat like begets like–that what is now called a species begets offspring ;! of the same species—must have been evident to the earliest humans. ;! Recognition of the inheritance of variations within a species must also j; have come early, since domestication of animals undoubtedly involved II !-i elimination of individuals with undesirable characteristics (a penchant for human flesh, for example). The first animals to be domesticated may well have been members of the dog family, which were used as food, and domestication of canines may have started even before the advent of Homo” sapiens. The remains of an old hominid relative of ours, Hmno erectus (also known as Java or Peking man), have been found associated with those of a dog-like animal in 500,000-year-old fossils. The earliest canine remains associated with our own species are a mere 12,000 years old. The domestication of food plants probably began between 8000 and 9000 years ago, although some authorities contend that the domestication of cereals preceded that of most animals. Humans must also have very early related treating between “male” and “female” animals, including humans, with the subsequent issuance of offspring. Sexual repro- duction in plants was probably recognized much later—many plants, after all, are discreet] y bisexual—but at least 4000 years ago, as evidenced by the Babylonians’ selective breeding, through controlled pollination, of the date palm (Ph~jeni.~ du(fylif- eru),which occurs as separate male and female trees. (The dates borne by a female tree result from fertilization of its eggs by spern-containing pollen from male trees.) The oldest recorded thoughts about heredity appear in the religious writings of the ancient Hindus and Jews, which reveal recognition of the heritability of disease, health, and mental and physical characteristics.
    [Show full text]
  • Principles of 3D Nucleus Organization and Epigenetic Regulation in Diploid
    bioRxiv preprint doi: https://doi.org/10.1101/783662; this version posted September 26, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-ND 4.0 International license. Principles of 3D Nucleus Organization and Epigenetic Regulation in Diploid Genome Revealed by Multi-omic Data from Hybrid Mouse Running Title: 3D Nucleus Organization of Diploid Genome Zhijun Han1,2, Cui Kairong3, Katarzyna Placek3, Ni Hong1, Chengqi Lin2, Wei Chen1, Keji Zhao3*, Wenfei Jin1* 1Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China; 2Institute of Life Sciences, Southeast University, Nanjing 210096, China; 3Systems Biology Center, National Heart, Lung and Blood Institute, NIH, Bethesda, MD 20892, USA. *Corresponding authors: [email protected] and [email protected] Keywords: Hybrid mouse; 3D nucleus; chromatin architecture; Hi-C; epigenetic regulations 1 bioRxiv preprint doi: https://doi.org/10.1101/783662; this version posted September 26, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-ND 4.0 International license. Abstract Most mammalian genomes are diploid and previous studies have extensively investigated the average epigenetic profiles of homologous chromosomes. Here we use hybrid mice to distinguish the epigenetic status and three-dimensional organization of homologous chromosomes. We generated Hi-C, ChIP-seq and RNA-seq datasets from CD4 T cells of B6, Cast and hybrid mice, respectively, and systematically analyzed the 3D nucleus organization and epigenetic regulation.
    [Show full text]
  • Homologous Chromosomes Make Contact at the Sites of Double-Strand Breaks in Genes in Somatic G0/G1-Phase Human Cells
    Homologous chromosomes make contact at the sites of double-strand breaks in genes in somatic G0/G1-phase human cells Manoj Gandhia,1, Viktoria N. Evdokimovaa,1, Karen T.Cuencob,c, Marina N. Nikiforovaa, Lindsey M. Kellya, James R. Stringerd, Christopher J. Bakkenistd,e, and Yuri E. Nikiforova,2 aDepartment of Pathology and Laboratory Medicine, University of Pittsburgh, Pittsburgh, PA 15213; bDepartment of Oral Biology, School of Dental Medicine and cDepartment of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219; dDepartment of Molecular Genetics, University of Cincinnati, Cincinnati, OH 45267; and eDepartments of Radiation Oncology and Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213 Edited by James E. Cleaver, University of California, San Francisco, CA, and approved May 1, 2012 (received for review April 5, 2012) Double-strand DNA breaks (DSBs) are continuously induced in cells Results by endogenously generated free radicals and exogenous geno- Homologous Chromosomes Form Arm-Specific Contact Spontaneously toxic agents such as ionizing radiation. DSBs activate the kinase and After Exposure to Ionizing Radiation. We used four-color 3D- activity in sensor proteins such as ATM and DNA-PK, initiating FISH and confocal microscopy (11, 12) to analyze the pattern a complex DNA damage response that coordinates various DNA and frequency of interaction between homologous chromosomes repair pathways to restore genomic integrity. In this study, we in untreated and irradiated primary cultured human epithelial report the unexpected finding that homologous chromosomes thyroid cells and fibroblasts. Cells were highly enriched in G0/G1 contact each other at the sites of DSBs induced by either radiation by plating at high density in the absence of serum and other or the endonuclease I-PpoI in human somatic cells.
    [Show full text]