Human Genome Content II BE301 Slides PDF

11/18/20 Overview Content of the Human Genome I & II BE301 Overview of Human G...

11/18/20 Overview Content of the Human Genome I & II BE301 Overview of Human Genome Content. Eukaryotic Genetics and Expression Coding DNA. Prof. Anne Parle-McDermott - Gene Clusters - RNA genes Topic 4: Human Genome Content II Non-coding DNA. - Repetitive DNA: classes, transposons. - Non-repetitive DNA 1 2 How Are Genes and Other Sequences Non Coding DNA Distributed? § Repeated sequences (present in more than one copy) account for more Repetitive DNA than 50% of the human genome. Copyright © 2021 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com -Tandemly repeated noncoding DNA § The great bulk of repeated sequences consist of copies of nonfunctional -Interspersed repetitive noncoding transposons. § There are many duplications of large chromosome regions. Non-repetitive [single copy] DNA We will focus on repetitive DNA… 3 4 Non Coding DNA-Repetitive Non Coding DNA: 1.Tandemly Repeated 2 Classes Highly repeated noncoding human DNA often occurs in blocks of tandem repeats of a sequence: - Simple 1-10 nucleotides - Moderately complex 10s -100s nucleotides. 3 Major Subclasses based on block size: - Satellite DNA - Minisatellite DNA - Microsatellite DNA Figure 7.22 Genomes 3 (© Garland Science 2007) 5 6 1  11/18/20 Tandem Repeated DNA Classes Satellite DNA Satellite DNA makes up most of the heterochromatin regions of the genome (transcriptionally silent). Found in the vicinity of the centromeres. Alpha Satellite: form that makes up the bulk of the centromeric heterochromatin. Tandem repeats of 171bp in size. Thought to be important for centromere function but exact role is unclear. Table 9.14 Human Molecular Genetics 3 pg. 267 7 8 Satellite DNA Minisatellites & Microsatellites Minisatellites: Repeat unit range 9-64bp. Dispersed over a large portion of the genome but mainly at subtelomeric regions. Rarely transcribed. Hypervariable minisatellites were used in DNA fingerprinting. Telomeric minisatellites are responsible for telomere function. Microsatellites (also called Simple Sequence Repeats): The locations of different classes of satellite DNA are Tandem repeats of 2million copies in genome 3. LTR (long terminal repeats) elements (~8%) Transposon: 4. DNA transposons - (~3% of genome) *TE= mobile DNA sequences which can move to different regions of the genome. Table 9.15 Human Molecular Genetics 3 pg. 269 11 12 2  11/18/20 Transposons: autonomous & nonautonomous Structure of Alu and LINE-1 elements SINE SINE: originated from copies of tRNA or SRP(7SL) RNA. Alu repeat is the most abundant in the genome. Figure shows an Alu dimer with a 32 base insertion in the 2 nd repeat. Monomers also occur. LINE : LINE-1 has 2 ORFs. ORF1: RNA-binding protein. ORF2: a protein with RT and endonuclease activity. An internal promoter lies in 5’UTR. ORFs facilitate copying and excision for re-integration elsewhere in the genome. Figure 9.17 Human Molecular Genetics 3 pg. 269 Strachan & Read 2 or 3 (Figure 9.18) 13 14 Revision Topic 3 & 4 Alu Family –most abundant member of Overview of genome content- Pie charts. SINES Coding DNA Definitions of a gene family, pseudogenes, gene > 1.1 million copies around the genome clusters. Occur approx once every 3Kb; GC-rich Examples of each. ~280 bps in length & seem to have originated from a How did gene families arise? 130pb tandem duplication Knowledge of rRNA transcription in Eukaryotes. In addition to contributing to noncoding DNA, Alus are also found in intronic sequences Non-Coding DNA How its categorised: Repetitive and Non-repetitive. Primate specific Description of repetitive DNA classes and examples of each class. 15 16 3