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DNA (OTHER Terms of chapter 17 (Gene expression-the proccess by which DNA…
DNA
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Chapter 17
Transcription
The synthesis of RNA using information in the DNA. The 2 nucleic acids are written in different forms of the same language and the info is simply transcribed or re written.
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RNA polymerase- an enzyme that pries apart the 2 strands of DNA and joins together RNA nucleotides complementary to the DNA template strand thus elongating the RNA polynucleotide.
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Unlike DNA polymerase, RNA polymerase can start a chain from scratch
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Terminator- in bacteria the sequence that signals the end of transcription (termination mechanism is diff in eukaryotes)
Direction of transcription is considered "downstream" and other direction is "upstream".... these terms also used to describe positions of nucleotides in the DNA and RNA
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Start point-in transcription the nucleotide position on the promoter where RNA polymerase begins synthesis of RNA
Transcription factors-a collections of proteinsmediate the binding of RNA polymerase and the initiation of transcription
TATA box-a DNA sequence in eukaryotic promoters crucial to forming the transcription initiation complex
Translation
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During this stage there is a change in language ; the cell must translate the nucleotide sequence of an mRNA molecule into the amino acid sequence of a polypeptide.
As a molecule of mRNA is moved through a ribosome, codons are translated into amino acids one by one. The translators or interpreters are tRNA molecules each type with a specific anticodon at one end and a corresponding amino acid at the other end.
:arrow_up: A tRNA adds its amino acid cargo to a growing polypetide chain when the anticodon hydrogen bonds to the complimentary codon on the mRNA
transfer RNA (tRNA)- An RNA molecule that functions as a translator between nucleic acid and protein languages by picking up a specific amino and carrying it to the ribosome where the tRNA recognizes the appropriate codon in the mRNA
Anticodon-a nucleotide triplet at one end of an RNA molecule that base pairs with a particular complementary codon on an mRNA molecule
Aminoacyl-tRNA synthetases- an enzyme that joins each amino acid to the appropriate tRNA. There are 20.
ribosomal RNA's (rRNAS)-RNA molecules that, together with proteinsakes up ribosomes; the most abundant type of RNA
RNA proccesing
RNA processing-Enzymes in nucleus modify pre-mRNA in specific ways before the genetic message is dispatched to the cytoplasm. During this both ends of the primary transcript are altered.
(Alteration of mRNA ends.) 5' cap-a modified form of a guanine nucleotide added onto the 5' end after transcription of the first 20-40 nucleotides.
RNA splicing-large portions of the RNA molecules removed and remaining portions are re-connected (like editing a movie)
Introns-a non-coding intervening sequence within a primary transcript that is removed from the transcript during RNA processing also refers to the region of DNA from which the sequence was transcribed
Exons- sequence within a primary transcript that remains in the RNA after RNA processing that also refers to the region of DNA from which this sequence was transcribed
Spliceosome-a large complex made up of proteins and RNA molecules that plices RNA by interacting with the ends of an RNA intron releasing the intron and joining the two adjacent exons
Ribozymes- an RNA molecule that functions as an enzyme such as an intron that catalyzes it's own removal during RNA splicing
:arrow_up: the modified ends may promote the export of mRNA from the nucleus and they help protect RNA from degradation.When the mRNA reaches the cytoplasm the modified ends in conjunction with certain cytoplasmic proteins facilitate ribosome attachment.
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During RNA processing the introns are cut out and the exons spliced together . in many genes the exons are shorter than the introns
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Has 3 binding sites
P site- this site holds the tRNA carrying the growing polypeptide chain. (P stands for peptidyl tRNA)
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A site-This site holds the tRNA carrying the next amino acid to be added to the polypeptide chain (A stands for aminoacyl-tRNA)
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