DNA 2 Flashcards
Specialized nucleotide sequences at ends of eukaryotic chromosomes
telomeres
What is the end replication problem
Lagging strand template (3’ end) cannot be replicated in linear chromosomes
shortens it
shelterin
Covered by proteins forming protective chromosome cap on telomere
What does Telomerase
Recognizes telomere sequence and elongates it in 5’ → 3’ direction
Replicative cell senescence
Phenomenon observed in cell cultures in which cell proliferation slows down and finally irreversibly stops
Telomerase activity decreases as you age causing
Replicative cell senescence
7 proteins involved in DNA replication
DNA polymerase III DNA polymerase I Primase Helicase DNA ligase Topoisomerases (i.e., DNA gyrase) Telomerase
DNA polymerase III does what
Adds nt
is a complex of 10 proteins
DNA polymerase I does what
Removes RNA primer; adds nt
Primase does what
Adds RNA primer
Helicase
Unwinds DNA
DNA ligase
Joins DNA fragments
functions on both lagging strand (most active)
and leading strand (1 spot in ori)
Topoisomerases (i.e., DNA gyrase)
Adds & removes supercoils
Telomerase
Adds telomeres in eukaryotes
Single-strand binding proteins
Stabilize ssDNA
Origin binding protein (DnaA)
Opens origin of replication
initiates DNA replication
3 types of telomerases
DNA gyrase, topoisomerase I, topoisomerase IV
What is the general process involved in DNA replication?
Semiconservative replication
Use “old” strand as template for “new” strand
Resulting DNA contains ½ “old” and ½ “new” DNA
what enzymes/proteins are involved in DNA replication?
DNA polymerase (I, III), including DNA primase,
DNA helicase,
DNA ligase,
topoisomerase.
What is the general process of transcription?
Synthesis of mRNA from DNA template from
- DNA template (single strand)
- RNA polymerase
- Ribonucleoside triphosphates (A,G,C,U)
What are some differences between prokaryotic and eukaryotic transcription?
Prokaryotic-RNAs are released/processed in cytoplasm
1 RNA polymerase
transcription/translation occurs simultaneously
Eukaryotic-RNAs are released/processed in the nucleus
3 RNA polymerase
transcription in nucleus then translation occurs separately in cytoplasm
prokaryotic transcription?
RNAs are released/processed in cytoplasm
1 RNA polymerase
transcription/translation occurs simultaneously
eukaryotic transcription?
RNAs are released/processed in the nucleus
3 RNA polymerase
transcription in nucleus then translation occurs separately in cytoplasm
What are sigma factors?
- released after RNA polymerase binds promoter
- subunits of all bacterial RNA polymerases
- direct transcription initiation
What are transcription factors,
- Eukarya and Archaea
- Not part of RNA polymerase
- Bind to promoter
- proteins that transcribe DNA to RNA
What are promoters?
- sequence of DNA needed to turn a gene on or off
- initiates transcription
- Recognized by a factor (Bacteria) or transcription factors (Archaea and Eukarya)
