Chapter 7 Flashcards
DNA
Deoxyribonucleic Acid
Deoxyribose sugar
Bases - Adenine, Thymine, Guanine, Cytosine
Biosynthesis
processes that synthesize and assemble macromolecule subunits, use ATP energy.
DNA Structure
Double Helix
Sugar-phosphate chains on outside
Complementary base pairing (A-T, G-C) with hydrogen bonds
Two strands run antiparallel
Antiparallel strands
One strand of DNA runs one way the other side runs the opposite direction. 5 prime and 3 prime ends
RNA structure
Ribonucleic acid ribose sugar Bases A,G,C,U Single strand Three types: mRNA, tRNA, rRNA
DNA replication
DNA is copied in binary fission to give two exact copies of chromosome to the dividing cell
What does semiconservative mean in terms of DNA replication
- Only one strand is “conserved” from original
- One strand is the template and the other is the copy
New DNA strand is only made from …
5’ to 3’
Nucleotides are only added to which end of the DNA strand
3’
Starting Replication envolves what two areas
Origin of replication
Replication fork
Origin of replication
Specific DNA sequence that is recognized by enzymes as the starting point
-Unwinding of DNA (unzipping) starts here
Replication fork
where unwinding occurs
Two different DNA stands
Leading strand and Lagging strand
Leading strand
the new DNA strand that is made continuously toward the replication fork 5’ to 3’
Lagging Strand
the new DNA strand that is made in pieces AWAY from the replication fork
Leading Strand
process
- Helicase unzips DNA
- Gyrase relaxes twisting of unwinding strands
- Primase adds RNA primer at origin of replication
- DNA polymerase adds nucleotides to 3’ end of new DNA through complementary base pairing
- goes in direction of unwinding parent DNA
Lagging Strand
process
- Primase starts near the replication fork
- DNA polymerase adds neucleotides in 5’ to 3’ direction AWAY from unwinding and replication fork
- DNA polymerase detaches and goes back to replication fork and a new primer to make a new Okazaki fragment
- RNA Primers are removed by DNA polymerase
- Fragments are joined by DNA ligase
Lagging strand is formed in pieces called…
Okazaki fragments
Prokaryote DNA replication vs Eukaryote
Prokaryote will only have one point of origin, where eukaryotes can have several replication bubbles to speed up the process
Protein Synthesis Overview
Transcription - DNA to mRNA
Translation - mRNA to protein using tRNA and ribosomes
Transcription Steps
protein synthesis
Initiation
Elongation
Termination
Initiation
Transcription-Protein
- Sigma factor on RNA polymerase recognizes promoter on DNA
- RNA polymerase binds to promoter
- RNA polymerase unwinds DNA
Elongation
transcription - protein
RNA nucleotides matched to DNA nucleotides
A to U, T to A, G to C, C to G
Termination
transcription - protein
Terminator on DNA tells RNA polymerase to detach
Translation
protein synthesis
mRNA to protein using tRNA and ribosomes
Codon
three mRNA nucleotides “translate to one amino acid”