Chapter 7 - The Blue Print of Life, from DNA to Protein

Dorothy B
Flashcards by Dorothy B, updated more than 1 year ago
Dorothy B
Created by Dorothy B almost 4 years ago
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1220 Microbiology Flashcards on Chapter 7 - The Blue Print of Life, from DNA to Protein, created by Dorothy B on 03/09/2016.
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GENETICS - The science of heredity
MOLECULAR BIOLOGY - The science dealing with DNA and protein synthesis
GENOME - The total DNA contained in the cell - this consists of the chromosomes and any plasmids
GENES - Located in the chromosomes - Sections of DNA that code for a functional product
Deoxyribonucleic acid (DNA) - Macromolecules made of nucleotides - Each DNA has: 1. nitrogenous base (ATGC) 2. sugar (deoxyribose - numbered 1-5) 3. phosphate - it also forms a double helix 1. 2 strands are held together by hydro bonds 2. the base pairing rule: A-T, G-C 3. strands of DNA are complementary = sequence of one strand determines the sequence of the other 4. nucleotides are linked together by covalent phosphodiester bonds 5. 5' carbon of one nucleotide is joined to 3' carbon of the next nucleotide, w/ a phosphate between them. 6. we usually consider DNA in the 5' to 3' direction 7. 2 strands of DNA run antiparallel
REPLICATION - DNA is copied before cell division
GENE EXPRESSION - DNA is used to make proteins
RECOMBINATION - DNA can flow between 2 different bacterial
DNA REPLICATION!!! - One parental double stranded DNA molecule is used to make 2 identical double stranded DNA molecules - Because the strands are complementary: -> one strand can serve as a template for synthesis of the other strand -> DNA polymerase reads the order of nucleotides in the template strand to make a complementary new strand - WOW! 1. A small segment of the DNA unwinds and the strands are separated -> forms the replication fork -> each separated strand serves as template for synthesis of a complementary strand -> a short RNA primer is produced by the enzyme : PRIMASE -> PRIMASE serves as starting site for nucleotides to form new strand of DNA
DNA REPLICATION, cont'd!!!!! 2. Synthesis of the leading strand -> DNA can only synthesize DNA in one direction - 5'->3' -> template must be read in the 3'-5' (antiparallel) -> follows the replication fork -> synthesis of the leading strand is continuous in the 5'->3' direction. 3. Synthesis of the lagging strand -> DNA polymerase can only make DNA in 5'->3' direction - but the second strand must be made in the opposite direction -> DNA polymerase synthesizes small fragments of DNA: Okazaki fragments - made in the 5'->3' direction, afterwards the RNA primers are removed and the fragments are joined together by the enzyme DNA ligase
GENE EXPRESSION 2 parts: Transcription - info stored in DNA is copied into RNA Translation - info in RNA is decoded to make protein
TRANSCRIPTION - Synthesis of RNA from a DNA template - sequence is complementary to a gene EXCEPT: it contains Uracil instead of Thymine - There are 3 types of RNA: -> mRNA: Carries info for making specific protein -> rRNA: forms part of the ribosome -> tRNA: transports specific amino acids for protein synthesis
STEPS IN TRANSCRIPTION!!!!! 1. Initiation -> RNA polymerase binds to the gene at specific site called the promoter oooo - separates (melts the 2 strands) - only one DNA strand is copied (the template) - the template is made in the 3' to 5' direction so that RNA can be made in the 5'->3' direction
STEPS IN TRANSCRIPTION, cont'd!!! 2. Elongation -RNA polymerase moves along the template synthesizing new RNA -Allows the DNA the rewind behind it 3. Termination -When RNA comes across the terminator (end of the gene) it falls off the template and releases the newly synthesized RNA
THE GENETIC CODE - info in mRNA must be translated to make proteins - organized into sets of 3 nucleotides - codons - each codon specifies an amino acid to be added during protein synthesis EX. GGC specifies the amino acid glycine -sequence of codons in an mRNA determines sequence of amino acids in the protein -3 codons that specify no amino acid: UAA, UAG, UGA - 'stop codons' - signal the end of protein synthesis
TRANSLATION: Initiation 1. Initiation - a ribosome assembled on the mRNA - a tRNA carrying the amino acid formyl-methionine enters the P-site -a tRNA carrying a second amino acid enters the ribosome -specified by the codon in the A site - the ribosome then joins the amino acids together by a peptide bond
TRANSLATION, cont'd: Elongation 2. Elongation - the ribosome moves a distance of one codon down the mRNA -> the next codon is now in place in the A site -the correct tRNA enters the A site, bringing with it the next amino acid to be added - the amino acid is joined to the chain - forms a polypeptide - elongation continues until a 'stop codon' is reached
TRANSLATION, cont'd: Termination 3. Termination -when a stop codon enters the A site, the ribosome disassembles and releases the polypeptide -the polypeptide is folded into the correct shape and becomes a protein -the ribosome can initiate translation of another mRNA
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