Chapter 7 Flashcards
4 Nucelotides
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G
Genome
complete set of genetic information Chromosome plus technically plasmids All cells: DNA Viruses may have RNA Functional unit is gene Encodes gene product, usually a protein Study of nucleotide sequence is genomics
2 Tasks cell must do to multiply
1.Dna Replication
2. Gene Expression (transcription and translation)
DNA-RNA-Protein
DNA doublestranded helix is jioned by
5’PO4 and 3’OH, forms sugar phosphate backbone.
Single strand will have 5’ and 3’ end. Strands are complementary and antiparallel
How are strands held together?
Hydrogen bonds between nucleobases
How many hydrogen bonds in base pair AT and CG
AT-2
CG-3
Melting/Denaturing
separating of strands
RNA characteristics
Uracil instead of thymine, shorter strand and synthesized from DNA template strand
3 types of required gene expression for RNA
Messenger RNA mrna
Ribosomal rRna
Transfer RNA trna
Dna characteristics
creates two replication forks. replicatoin is semiconservative, dna contains 2 original, new synthesized stran,
replication begins in origin of replication
Steps in Dna Replicatoin
- Untwisting the DNA strand and forming a replication fork
Enzyme: helicase (unwinds the strands), single-strand binding proteins to help stabilize the strand - Untangling the DNA strands
Enzyme: topoisomerase (breaking and rejoining the strands) - Adding nucleotides to the leading strand
Enzyme: DNA polymerase III (adding nucleotides from the RNA primer), primase (to produce primers at 5’ end) - Adding nucleotides to the lagging strand
Enzyme: primase (produces primers at each Okazaki fragment), DNA polymerase I and III - Rejoining the strands
Enzyme: DNA ligase (rejoins the Okazaki fragment
Replisomes
“assembly line” complex of enzymes and other proteins that synthesize dna
Dna Gyrase
breaks strands of dna, releiving tensions
Dna Ligase
joins two dna fragments by covalent bonds
DNA Polymerase
enzymes that synthesize dna, use one strand of dna as a template to make another complementary strand. New nucleotides are added only at the 3’end, occurs 5’to3’ direction
Helicases
Unwind dna strand ahead of replication fork
Okazaki fragments
fragments produced during discontinous synthesis of lagging strand
Origin of replication
region where dna molecules are being replicated
Primase
enzymes that synthesize fragments of RNA to serve as primers for dna synthesis
Primer
framgents of nucleic acid to which dna polermase can add nucleotides
Leading strands
synthesized continously
Lagging Strands
synthesize discontinously, production of Okazaki fragments, different dna polyermase replace primers
Transcription
Rna polyermase synthesizes single strand rna, uses dna template and synthesizes 5’3’ direction
can initiate without primer
Binds to promoter-found upstream of genes and stops at Terminator-transcription ends
Promoter
nucleotide sequence eto which rna polymerase binds to initiate transcriptions
3 steps in Transcription
- Initiation, RNA polyermase binds to the promoter and mets a shoot stretch of dna,
- Elongation, Sigma factor dissociates from RNA polymerase, leaving the core enzyme to complete transcription.
- Termination: RNA polymerase finds terminator, falls off the template and releases new Rna
TRNA job
delivery correct amino acid, acts as a key that interprets the genetic code,
Translation in prokayries
Begings before transcription is complete
