Class Note for ECOL 320 at UA
Popular in Course
Popular in Department
This 22 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Arizona taught by a professor in Fall. Since its upload, it has received 16 views.
Reviews for Class Note for ECOL 320 at UA
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 02/06/15
F 1393 J quot F I Section 16 Variation in Chromosome Nunber and Structure a m I n r H 13 quot391 r 4 a M It 39 quot 1 5 i 1 3 g 3939 V 1 139 1 139 ad 39 3 3 39 quot n quotv 3 I I I 5 39 S r H 3 F E ITJ I F A r J 1 LI E 1 uri 1I j39TL 1T39m i M J f 1113MIIFREITELE T 39v u n 3 i f n V C a L Jewer red I a M i f 5 quot LE AR a N quot739quot p A LIE 39 i L n u M 3 V T 8 quot 10 1 ll I 2 a 2 39 yr a i g i a g a V of 3 a T 1 It 139 IL39 Iquot 13 quot11 393 t i z 39E F 39 H l j ZIJ 1 22 H 139 The karyotype can change due to rare events Changes are inherited Consequently The karyotype can vary somewhat within a species The karyotype evolves Different species and less often different individuals within a species have different numbers of chromosomes and different arrangements of genes on the chromosomes Chimp Human Indian Muntjac 2N 67 Chinese Muntjac 2N 46 JCRBQ1 DOlndian Munq39ac 030394 P5 Qhanding l I v II llll lll Mam VARIATIONS IN CHROMOSOME NUMBER Variations in chromosome number include euploidy varying numbers of complete chromosome sets and aneuploidy partial chromosome sets Euploids have varying numbers of complete chromosome sets varieties include diploid haploid auto and allopolyploid polytene Aneuploids have partial chromosome sets Ploidy of organism number of chromosome sets Euploid multiples of complete sets haploid N A B C diploid 2N A A B B C C polyploid gt 2N triploid 3N A AA B B B C C C tetraploid 4N AAAABBBBCCCC Aneuploids diploid i partial set monosomic 2N 1 A A B B C monosomic C trisomic 2N 1A A A B B C C trisomic A Aneuoploidy important because genetic tool 0 results in genetic defects 94 511 a is h a m 3 La quot5quot 134 r39 39 V a gt Polyploidy important because 0 plant evolutionpolyploidization gt new species especially in grasses lant breeding polyploidization gt new useful variety Bread wheat Triticum aestivum is allotetraploid with diploid chromosome sets from 3 different parent species each of which had 2N 14 so total in wheat is 42 39 I 23 n o Variations in chromosome number are usually caused by errors in mitosis meiosis or fertilization Errors in mitosis meiosis or fertilization cause polyploidy Eg a 2 sperm 1 egg gt 3N b Failure of anaphase separation in mitosis in germ line gt 4N gametocyte gt 2N gametes Can be induced with agents that block spindle formation or dissolve spindle Aneuploids result from nondisjunction 39iEiEi H iEE fax llquot IIIi H i I in I nondis Linctmn 4 x as 0 u an a alga i39i39ii39iiEi Ei x3 x Ralf39139 El 3 E El 5 its L 3 Kg 39 539 n quot 9 if 3 t g r at 2 If 65 w a 5 E 39939 2 539 s 5 4 A 5 6 5 E Total E D Q 4 8 3 First I39I39IEIOtIc F diusion 3 MI 93 50 2 Second meiotic division tri 5mm 2 3 4 mcinnsumi39c A 0 lt 25 25 29 3034 3539 gt40 Maternal Age Thanx for 1 adding mam us E 3 3 n ymmzranmm creative pimkrock 3 Changes in chromosome number often cause abnormalities in gene expression and hence the phenotype and in meiosis Gene dosage effects aneuploidy results in unbalanced genomes and abnormal development hence aneuploidy is usually lethal or detrimental Embryo with one extra or one too few chromosome has unbalanced genome gt abnormal development Genome evolved to work with two functional copies of each gene If have too few or too many of some genes those make too much or too little gene product and may upset metabolic pathways eg if some enzymes are too abundant may make too much product Aneuploidy in humans is common medical problem Occurs in ca 35 of all embryos Aneuploidy for large chromosome in humans usually causes unbalance for one or many important genes usually lethal gt stillbirth Accounts for ca 20 of all stillbirths Aneuploidy for small chromosomes maybe viable Eg Down39s syndrome 2 trisomy 21 Or part of 21 attached to another chromosome Causes of trisomy 21 z 75 female M1 or Mll nondisjunction 25 male M1 or Mll quot Female eggs arrested in prophase of M1 at birth Eggs age gt increasing frequency of nondisjunction with increasing maternal age especially gt 45 years Meiosis in aneuploids and autopolyploids may be abnormal because of problems with synapsis resulting in sterility Don39t have time to cover in course can omit corresponding sections of reading VARIATIONS IN CHROMOSOME STRUCTURE Also called chromosomal mutations OK when they rst occur chromosomal abnormalities or aberrations not strictly applicable because sometimes 2 2 different structures are present in population in high frequency can39t say that either one is aberrant or abnormal Changes in chromosome structure occur in both prokaryotes and eukaryotes We will focus on eukaryotes 1 Transposable elements TEs AKA quotjumping genes Tranposition TE moves to new location rare event frequency is on order of mutation rate or somewhat higher but not so frequent that they interfere with mapping duplicative transposition puts a copy of the TE in the new position leaving the old one behind nonduplicative transposition moves the TE 1 2 3 4 5 6 7891 duplicative transpositiongt 1 2 3 4 5 6 2219 nonduplicative transpositiongt 1 3 4 5 6 Z8921Q Duplicative transposable elements can spread in genome even if they are of no selective advantage to the organism and even if they are mildly detrimental Sometimes called selfish DNA Tzansposable elements Wexe flzst dlscovezed by Baxbaxa McClmtock flzst woman elected to Natlonal Academy of Sclencem maize Nobel Fuze Mechamsms Some have tzansposase gene egt tzansposase plotem whlch cuts TE out and Inselts In tazget sequence Retzotxansposons tzansczlbed to make RNA Copy then levexse txanscxlptase makes DNA Copy of the RNA and DNA 15 lntegzated Into tazget sequence The act Oftxansposltlon ltselfmay cause zeazzangements ofadjacent sequences TE msezted In gene 01 In Contxollmg sequences can make gene lnactlve Just llke a mutatlon Iftzansposon exclses cleanly gene actlvlty can be testotecl The Coples of a tzansposable element ate sltes of homology at whlch Clossmgr ove can occuzwlthln a Chzomosome and between homologous oz nonhomologous Chzomosomes 77gt changes In Chzomosome stzuctuze Clossmgr ove pxobably In mtexphase 2 Repeats repeated sequences Repeats are segments of DNA that are present two or more times in the genome of an organism 1 Many short repeats arise in the course of evolution due to mutations just by chance 2 Short simple sequence tandem repeats arise by replication slippage ATTTCG replicationgt ATTTTCG ATGATGATG 69 ATGATGATG Some human hereditary defects are due to increases in number of tandem repeats eg Myotonic muscular dystrophy Some regions of chromosomes are rich in short tandem repeats notably centromeres These are the bane of DNA sequencers this is why a large part of the human genome still hasn t been sequenced 3 Longer repeated sequences arise by duplicative transposition Polytene Chromosomes Some insects including Drosophila During differentiation of some tissues salivary glands Malpighian tubules etc cells go through repeated S phases eg 10 Without mitosis gt polyploid or polytene nuclei Polytene chromosomes all copies held tightly together and in alignment 3 3 m I U I Stain see bands Where DNA is more concentrated PHYSICAL LANDMARKS 3 Duplication process of duplicating a segment usually a whole gene or genes also used to denote the repeated copies 1 2 3 4 5 6 duplicationgt 1 2 3 4 5 4 5 6 Might be called dup45 1 Duplications can arise by duplicatiVe transposition 2 Duplications can occur Via processed pseudogenes leader mRNA 001939 3 reverse tr anscriptase EDNA I integration K E DEF IVE CIRF IVSDPF processed pseudngene 3 Duplication can occur Via unequal crossingeover between existing repeats usually in sister chromatids produced by replication of a chromosome Classic case Bar eye mutation is actually a duplication of several bands Sturtevant amp Bridges Unequal Crossingeover between sister chromatids or homologous X chromosomes in females 9 doubleBar and wild type DoubleBar in v 1 1L I6Aquot 1isnquot vsnquot391rss mi Redrgreen colorblindness can result from this process as described in textbook Ribosomal RNA genes in eukaryotes are present in long tandem arrays which Vary in number Duplica ons are important in the evolution ot new genes Duphcahon a 2 Copies of a gene tn a genome Diplolds have two genomes so diploid Initially heterozygous for duplication and has 3 Copies Sexual reproduchon can produce 1ndw1duals thn 4 Copies We Wm Just track the tate of two Copies duphcauon mumuon mactwates A 4 AA 4 A WA mu uons se e ted accu Mate A A 4 a quotjunkquot DNA A a neummomzanon suommomzmmn nonmmumzmmn Most often pseudogene dwerges further so eventually not recogmzable as related to gene Conmbutes to quotJunkquot DNA unique or repeated sequencesmtn no detectable funchon Eventually de1eted Duplicate can also acquire mutations that turn it into a gene with simnilar function eg binding protein duplicates one copy gt hemoglobin blood other copy gt myoglobin eg human globins example of clustered multigene family alpha beta gamma delta epsilon zeta ps1 ewm ooltmg chromosome 16 chromosome 11 major adult major adult fetal infant minor adult embryonic embryonic pseudogene 0L family C2 11 pal 12 11 Bfamily cpr 3 Gy Ay cpbl 5 a When we discuss molecular evolution will see how we can trace the evolution of all of these genes in detail from a single ancestral gene That gene duplicated to give myoglobin and globin genes the latter duplicated to form 0L and 3 globin genes and each of those duplicated further 4 Deletion loss of a segment of DNA and the result of that loss 1 Deletions arise by unequal crossing over together with duplication 2 Deletions arise by intrachromosomal crossing over between direct repeats deletion deficiency e i 7 gt 1 2 3 4 5 6 deletion gt 1 2 3 6 Might be called def45 D 61 eti on of 8p23 1 Origins of deletions Died age 3 lntrachromosomal crossing over between direct repeats acentric r1 g 105 123 123 5 Inversions arise by intrachromosomal crossingover between inverted repeats Inversions arise by intrachromosomal crossing over between inverted repeats I 1233b3321 39 LES rth I 123CDE13 123 a Inversions act as cross over quotsuppressorsquot in inversion heterozygotes because cross overs within the inverted region gt unbalanced genomes with duplications and deletions hence inviable gametes and or progeny 6 Reciprocal translocations arise by crossingover between homologous regions on nonhomologous chromosomes Reciprocal translocations arise by crossingover between homologous regions on nonhomologous chromosomes 1 2 3 4 r 5 6 7 8 r 9 10 recipr0cal translocation gt 1 2 3 4 r 9 10 7 8 r 5 6 7 Robertsonian fusions change N l Ii Eiutler39tslzlnian 3 Z39 quot 3 fusion Small arms are lost Extreme example of change in chromosome number is seen in deer Reeve39s muntjac 2N 46 same order of magnitude as most other deer species Indian muntjac 2N 6 Note that most rearrangements may take place by crossing over between repeats or other homologous DNA segments segments With similar sequence Duplicative transposition is a major source of such duplicated regions If a transposable element invades a genome it can spread and facilitate rearrangements Thus it can increase variation in chromosome structure and eventually lead to evolution of neW gene arrangements and neW phenotypes Transpsable elements can contribute to or even give rise to promoters and other regulatory sequences Transposable elements can spread from one organism to another eg P element was transferred from Drosophila willislom39 or a close relative to Drosophila melanogasler probably by a parasitic mite that sucks cytoplasm from y eggs The evolutionary origins of transposable elements are unknown last I heard Rearrangements can affect meiosis and mitosis What happens When rearranged chromosomes synapse in meiosis l Textbook discusses in detail Main point synapsis and recombination is always between homologous chromosome regions Centromeres segregate normally but chromosome segments may not Will have examples in practice problems Visible in polytene chromosomes in heterozygotes for rearrangements Position effect 2 phenotype of a gene or region of a chromosome depends on its neighbors One obvious rationale move gene to different position may put under control of different set of upstream controlling sequences Delelions and other slructural changes are imporlanl tools for mapping genes on chromosomes tying linkage maps to physical maps Relating recombination maps and physical maps of landmarks Can use deletions and other structural changes to map genes Can use deletions and other structural changes to tie linkage map to physical map of chromosome 1 Map deletion on physical map See What landmarks are missing Drusuumla maize J I J 34 2 Map deletions on genetic map determine which recessive mutations are quotuncoveredquot by deletions An alternative way of looking at this is to see what mutations complement a deletion If a mutation and a deletion don39t complement each other they involve the same gene Note this is a slightly different way of using the term complement Testcross a deletion heterozygote aBEFE 1lialjcljefg EiCEIEFE abcdefg x xi uEIEDEFE iEEFE abcdefg abodefg Wit mutant d a 3 Tie the physical map to the genetic map by using overlapping deletions 1 3 4 5 a lt Dene number c eh tene SHE39Sma IJr I I I Eli DrilEIEIEIITIE If Ill I I39ll f I i tintage IE I I map a e e e e lt ieei missing missing eeneiusien fer Jf 4 eenes genes gene as 1 S e net in 5 34 13 net in 3 4 3 455 ede net in E 4 23 ee e is in 2 5 12 as e in 139 Eu 56 ee net in T T 1 nene net in 1 B T nene net in 7 From these data can39t tell whether d is 5 6 or both But we know it can39t be both if d is a point mutation Order and sometimes the position of genes can be determined using overlapping deletions even without a physical map Physical and Genetic Maps Agree in Gene Order Not Distances Reason recombination frequencies aren t uniform along chromosome 11 5 1 1 quotf 111 21v 11511111111211 1 311 1 M111 Inltlklsmclnlig 1mm 11141111 Add n It 7 7 I1 r1 5 6 a a 3 m 1 1 I m n nv no 41 mm m 5st 4 W113 m a 1 mm 1 y 1 I I a w m J m M II Jw 1 a 5n m w m n 1 MK I 1 I 1 1 1 I 1 I 1 4 1011111 1215111111111112111111115 1111 1111111111 I 1 1 quot 5 11111 1 111 1111 111111LID11111111n11cl D 1111111 11M 13 1314 1415 1516 1617 1718 18 9 1920 20 F10 inn gt1 Centmmere Other Methods of Relating Physical and Genetic Maps FISH Finding genes in complete genome sequences
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'