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DNA (Flow of genetic information (Translation (codon recognition the…
DNA
Flow of genetic information
transcription
initiation occurs after RNA polymerase binds to promoter the DNA strands unwind polymerase initiates RNA synthesis at the start point on template stand
elongation the polymerase flows downstream unwinding DNA and elongating RNA transcript 5' to 3' in the wake of transcription the DNA strands reform double helix
happens near the DNA to make RNA
transcription at a eukaryotic promoter
transcription factors recognize the TATA box that binds to DNA before RNA polymerase II can bind to correct position/orientation
more transcription factors bind to DNA along with RNA polymerase II unwinds DNA double helix, and RNA synthesis begins a the start point of template stand
Translation
codon recognition the anticodon of a aminocyl tRNA base pairs with complementary mRNA codon in A site. Hydrolysis of GTP increase accuracy/efficiency. Aminoacyl tRNA's with appropriate anticodon will bind and allow cycle progress
peptide bond formation an rRNA molecule of larger ribsomal subuint catalyzes the formation of peptide bond between amino acid in the Asite and carboxyl end of growing polypeptide in P site. This step removes polypeptide from tRNA in the P site and attached to the amino acid on the tRNA in the A site
arrival of large ribosomal subuint completes initiation complex. Initiation factors (proteins) are required to bring translation components together
translocation the ribsome translocates the tRNA in A site to P site. the empty tRNA in the P site moves to E site where it is released, the mRNA moves along with bound tRNAs bringing the next codon to be translated in A site
ribsomal subuint bind to mRNA. (in bacteria cell, mRNA binding site on this subuint recognize a specific nucleotide on the mRNA upstream of the codon)
Genes specify proteins by transformation/translation
transcription produces messenger RNA
Translation is the synthesis of polypeptide using information in the mRNA
transcription is the synthesis of RNA using information in DNA
ribsomes are the sites of translation
mutations
silent mutations have no observable effects on phenotype
missense mutations change one amino acid to another
point mutations change a single nucleotide pair of a gene
nonsense mutation cause translation to be terminated prematurely; lead to non functional proteins
split genes and the RNA splicing
RNA splicing where large portions of the RNA molecules are removed and the remaining portions are reconnected
average length of transcription unit along a human DNA is about 27,000 nucleotide pairs
tRNA
a cell keeps its cytoplasm stocked with 20 amino acids either by synthesizing then from other compounds or by taking them from surrounding solution
ribsome is a structure made of proteins and RNAs add each amino acid brought to it by tRNA to the growing end of polypeptide chain
transfer RNA is for transferring amino acids from cytoplasmic pool of amino acids to growing polypeptide
RNA processing words to know
exon: rejoins genes that are apart of the final mRNA, regions that are expressed
ribozyme: biological catalyst that is an RNA molecule
introns: sections of primary transcript not in mRNA because they are intervening; don't code functional proteins & must be removed
spliceosomes: enzymes complexes that act on pre-mRNA, joining exons together after removal of introns
Life's operating instructions
What role does proteins play in DNA replication?
because both strands of DNA are complementary each strand acts as a template for building a new strand
semi-conservative model of replication predicts that when a double helix replicate each daughter molecule will have one old strand
relationship between structure and function is in the double helix
origins of replication where the two DNA strands are separated, opening up a replication bubble
proteins work together in DNA replication
DNA polymerase: links nucleotide subunits to form new DNA strand from DNA template
single-strand bonding protein: bind to single strand of DNA and prevent helix from reforming
DNA primase: synthesize short RNA primers on the lagging strand; begins replication of leading strand
topoisomerase: break DNA strand, preventing excessive coiling and rejoining them in a more relaxed configuration
DNA ligase: link okazaki fragments by joining the 3' end of new DNA fragment to 5' end of the adjoining DNA
helicase: disrupts hydrogen bonds opening double helix
Telomeres
special nucleotide sequence at their ends called telomeres
do not prevent shorting of DNA but do postpone erosion of genes
connected to aging
What is DNA?
bacteriophages are used in molecular genetics research
a virus is DNA enclosed in a protective coat
transformation is a change in genotype and phenotype due to assimilation of foreign DNA
nitrogenous base in nucleic acids consists of
guanine
thymine
cytosine
adenine
purines: guanine and adenine
pyrimidines: cytosine and thymine
AT, GC
DNA is a polymer of nucleotides
DNA consists of a nitrogenous base, a deoxyribose sugar and a phosphate group
DNA composition varies from one species to the next
DNA is genetic material
Deoxyribonucleic acid
hydrogen bonds give DNA their 3D shape
Chromosome
unfolded chromatin resemble beads on a string with each bead being a nucleosome which is the basic unit of DNA packaging
in eukaryotic cells DNA is precisely combined with proteins in a complex called chromatin
loosely packed chromatin is called euchromatin
proteins called histones are responsible for the first level of packing chromatin
consist of DNA molecule packed with proteins