Topics 5-6 Flashcards
What is a single nucleotide composed of?
The sugar deoxyribose, attached to a phosphate and nitrogenous base
Helicase
unwinds double helix for DNA replication
single strand binding proteins
stabilize unwound template strands in DNA replication
DNA Polymerase
Elongates new DNA at replication fork during DNA replication by adding nucleotides to the growing chain in the 5 to 3 direction
Okazaki fragements/DNA ligase
The lagging strand is synthesized in separate pieces by okazaki fragments, which are then sealed together by DNA ligase
Nucleotide excision repair
incorrectly placed nucleotides are removed by nucleases and filled in with correct ones
Telomeres
Short repetitive nucleotide sequences that do not contain genes. These cap the linear ends of eukaryotic chromosomes to avoid losing genes during mitosis because DNA Polymerase can only add to the 3 end of molecule, it cant complete the 5 end
Bacterial vs Eukaryotic chromosomes
Bacterial: 1, double stranded; circular DNA molecule, small amount of protein
Eukaryotic: Linear DNA molecules, large amounts of protein
transcription location and purpose
Synthesize RNA using DNA as a template, takes place in nucleus
mRNA
Messenger RNA, it carries the message of DNA to the protein making ribosomes
RNA processing
process that make pre-mRNA into mRNA
translation purpose and location
produces polypeptide chain using the mRNA transcript, occurs at ribosomes
Template strand
The one strand of DNA transcribed during transcription, producing mRNA or the complementary strand
Codons
mRNA base triplets, written in the 5 to 3 direction
Promoter/terminator
DNA sequence where RNA polymerase attaches is the promoter, whereas the DNA sequence that signals the end of transcription is called the terminator
3 stages of transcription
- Initiation: In eukaryotes, the transcription initiation complex forms, in bacteria, RNA polymerase binds to the promoter
- Elongation: RNA polymerase moves along DNA, adding nucleotides to the 3 end of the chain. Double helix reforms bands with the RNA molecule hanging off
- Termination
Modifications after transcription
Occurs in Eurkaryotes
5 cap and poly-A tail: facilitate export of mRNA from the nucleus, protect it from degradation and facilitates attachment of mRNA to the ribosome
RNA splicing: Large portions of newly synthesized RNA(introns) are removed/spliced, leaving exons behind.
Ribozymes
RNA that serves a catalytic role
Types of RNA that are important in translation
mRNA: messenger RNA, produced during transcription, carries genetic message of DNA to the ribosome
tRNA: transfer RNA, transfers amino acids from pool of amino acids in cytoplasm to a ribosome. Each type of tRNA is specific to an amino acid. It uses anticodons to pair specifically to a complementary codon on mRNA
rRNA: ribosomal RNA, complexes with proteins to form 2 subunits that form ribosomes. Have P, A, and E sites that bind with tRNA
Codons and anticodons
codons: an mRNA triplet nucleotides. 64 combos possible
anticodons: nucleotide triplet used to pair with a codon by tRNA
P, A and E sites
P: holds tRNA carrying the growing polypeptide chain
A: holds tRNA that carried the amino acid that will be added to the chain next
E: Exit site for tRNA