lecture 12- DNA, transcription, translation Flashcards
dna
deoxyribonucleic acid
griffith experiment
s strain- kills mouse
r strain- mouse lives
s strain with heat- mouse lives
s strain with heat, and r strain- kills mouse
avery and colleagues transformation experiment
found that DNA, not RNA was responsible for the transformation
Hershey and Chase
labeled bacteriophage with radioactivity
building block of DNA
deoxyribose (pentose sugar) with 3’ -OH
phosphate (on 5’ carbon)
nitrogenous base ( adenine, guanine, cytosine, thymine)
purine
adenine, guanine
pyriminide
cytosine, thymine
nucleotide
the smallest heritable unit
DNA structure
Double helix (spiral), nucleotide held together by phosphodiester bonds- phosphate groups form bridge between OH- and 2 adjacent sugar residues, helices connected by hydrogen bonds, hydrogen bonds between bases
DNA replication
the 2 strands of the parental double helix unwind and each strand serves as template for synthesis of complement, using rules of base pairing also known
1.) helicase opens the helix while topoisomerase prevents overwinding
- this type of replication is also known as semiconservative replication
synthesizing the lagging strand
1.) primase synthesizes the short RNA oligonucleotides (primers) copied from DNA
2.) DNA polymerase III elongates the RNA primers with new DNA
3.) DNA polymerase I removes RNA at 5’ end of neighboring fragment and fills gap
4.) DNA ligase connects adjacent fragments
DNA unit of measurement
base pair (bp)
kilobase (kb)
megabase (Mb)
mutation
replacement, insertion, deletion of nucleotide results in altered sequence
introns
found in eukaryotes not prokaryotes
RNA
ribonucleic acid- single stranded, has ribose and phosphate group
adenine, uracil, guanine, cytosine
informational RNA
intermediate in the synthesis of a functional product of a gene. in the majority of genes, this is the messenger RNA (mRNA)
functional RNA
transfer RNA (tRNA) brings amino acids to mRNA during translation
intron
noncoding region of gene, excised by processing from primary transcript
exon
coding region of gene (sequences that are included in mature transcription)
promoter
regulatory region where typically RNA polymerase binds
UTR
untranslated regions at both 5’ and 3’ ends that are part of a transcript
RNA polymerase
catalyzes transcription ( RNA synthesizes from DNA)
RNA polymerase I
located in the nucleolus, transcribes the 3 major rRNAs
RNA polymerase II
located in the nucleoplasm, transcribes mRNAs and some snRNAs
RNA polymerase III
located in the nucleoplasm, transcribes tRNAs, 5S rRNA, and the remaining snRNAs
initiation
- at 5’ end of gene
- binding of RNA polymerase to promoter
- unwinding of DNA
elongation
addition of nucleotides to 3’ end
termination
- at 3’ end of gene
transcription step by step
- RNA is transcribed 5’ to 3’
- the template DNA strand is read to 3’ to 5’
- the non-template DNA strand has the same polarity as the RNA 5’-3’
5’ end: capping
addition of 7-methylguanosine
3’ end: poly(A) tail
- addition of up to 200 adenine nucleotides
- downstream of AAUAAA polyadenylation signal
eukaryotic RNA processing
intron removal by spliceosome which are small nuclear ribonucleoprotein particles (snRNPs) associated with pre-mRNAs
amino acids (aa)
- twenty naturally occurring amino acids belong to 4 major protein groups:
- basic
- acidic
- neutral polar
- neutral non-polar
the genetic code
- it is almost universal
- it is a triplet code
- each 3- nucleotide codon in mRNA specifies an a.a. in the polypeptide
- it is comma free
- it is nonoverlapping
protein synthesis
- protein synthesis is mostly similar in prokaryotes and eukaryotes.
3 stages:
initiation
elongation
termination
initiation of translation requires
- a mRNA
- ribosome complex
- specific initiator tRNA
- initiation factors
the polypeptide
- a linear arrangement of amino acids linked with peptide binds (primary structure)
- a peptide chain has polarity
primary structure
- amino acid chain
secondary structure
hydrogen bonds between amino acids at different locations in polypeptide chain (alpha helix and beta pleated sheet)
tertiary structure
heme, beta polypeptide
quaternary structure
actual ball looking thing at this point (you know)
protein function
- function determined by the amino acid sequence
- two broad types of protein (structural proteins, active proteins including enzymes)
