MICRO CH7

MICRO CH7 - Chapter 7- Genomes and Chromosomes Genetics...

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Chapter 7- Genomes and Chromosomes Genetics Molecule of heredity Deoxyribonucleic acid (DNA) Gene Sequence of nucleotides in DNA that codes for a protein Nucleotide sequence 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 (small section) (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. Major differences: Eukaryotes - chromosomes are linear 1
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- Introns- DNA sequences within genes that are not part of coding sequence for protein - contain huge amount of noncoding DNA between genes - In humans over 90% of the total DNA is noncoding (enhancer sequences, promoters, gene remnants, pieces of viral genomes) Prokaryotes - Chromosomes are usually circular - Have little noncoding DNA (less than 15%) - Operons are common - Cluster of genes controlled by 1 regulatory sequence - Genes are transcribed together into 1 mRNA strand then translated into separate proteins 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 pairs with thymine by 2 hydrogen bonds Guanine pairs with cytosine by 3 hydrogen bonds DNA is made of deoxyribonucleotides linked by phosphodiester bonds. Deoxyribonucleotide = sugar deoxyribose + nitrogenous base + phosphate 2
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Nitrogen Bases: purines (adenine and guanine) and Pyrimidine’s (cytosine and thymine) 1-nitrogenous base 3- hydroxyl 5- triphosphate Size of DNA Expressed as number of thousands of nucleotide bases or base pairs per molecule 1000 bases = 1 kb (kilobase) or 1kbp (kilobase pairs) Mycoplasma has smallest cellular genome known at 580 kbp Escherichia coli 4640 kbp –typical for most bacteria Humans over 3.2 million kbp Nucleoid of E. coli- circle of dsDNA 150x the size of the cell Can be packaged into the cell because it is supercoiled Topoisomerases assist in supercoiling DNA gyrase- type II topoisomerase introduces supercoiling by breaking and resealing the DNA Quinolone antibiotics such as ciprofloxacin target bacterial type II topoisomeras In addition to the chromosome, several other genetic elements exist in cells. Plasmids
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This note was uploaded on 02/23/2012 for the course BIOL 2051 taught by Professor Brininstool during the Fall '07 term at LSU.

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MICRO CH7 - Chapter 7- Genomes and Chromosomes Genetics...

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