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chapter 7

chapter 7 - www.sumanasinc.com Chapter 7 Genomes and...

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www.sumanasinc.com Chapter 7- Genomes and Chromosomes * Read this chapter * Genetics Molecule of heredity Deoxyribonucleic acid (DNA) Gene Information in DNA that codes for a single polypeptide Sequence of nucleotides corresponds to sequence of amino acids RNA serves as an intermediate The three key processes of macromolecular synthesis are: (1) DNA replication – making a copy of DNA (2) Transcription – synthesis of RNA from a DNA template (3) Translation – synthesis of proteins using messenger RNA as a template. Central dogma of molecular biology Basic processes are the same in prokaryotes & eukaryotes, but the organization of genetic information is more complex in eukaryotes. Two major differences: 1. Eukaryotes contain non-coding regions called introns - introns are later spliced out and exons are translated 1
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2. Single prokaryotic mRNA often contains more than one coding region - can have one mRNA that is translated into one or more proteins; this mRNA is an operon; which is and mRNA that can code for more than one gene; it is polycistronic RNA; This occurs in prokaryotes ONLY DNA is a double-stranded helix (twisted ladder) The two strands in the double helix are antiparallel (run in opposite directions) The 2 DNA polynucleotide strands have base sequences that are complementary: Adenine always pairs with Guanine (A=T) Guanine always pairs with Cytosine (G=C) Hydrogen bonds hold the two strands together DNA is made of deoxyribonucleotides linked by phosphodietser bonds Deoxyribonucleotide = sugar (deoxyribose)+ nitrogenous base+ phosphate When not joined to anything, the 5’ end has 3 phosphates Nitrogen Bases : Purines (adenine and guanine) and Pyrimidines (cytosine and thymine) 2 5’ end = phosphate 3’ end = hydroxyl
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- Know which carbon attaches to what in a hydrogen bond (Watson-Crick base pairing) Size of DNA Expressed as number of thousands of nucleotides bases or base pairs per molecule 1000 bases = 1 kb (kilobase) or 1kbp (kilobase pairs) Escherichia coli 4640 kbp
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