2.7 DNA Replication, Transcription and Translation Flashcards
What does the replication of DNA depend on?
Complementary base pairing
What does helicase do to DNA?
Helicase unwinds the double helix and separates the two strands
How does helicase unwind the double helix?
By breaking hydrogen bonds
What does DNA polymerase do?
Links nucleotides together to form a new strand, using the pre-existing strand as a template
What is an Okazaki fragment?
DNA fragments that are formed on the lagging template strand during DNA replication
What keeps an unwound DNA strand apart?
Single-strand binding proteins
What are RNA primers?
Short segments of RNA (10 nucleotides long) formed by primase
What is the purpose of RNA primers?
Must bind to DNA segments to begin replication
What does primase do?
Primase forms the short segments of RNA needed by RNA primer
In which directions do DNA strands grow?
5’ to 3’
What does the 3’ end of DNA contain?
Hydroxyl
What does the 5’ end of DNA contain?
Phosphate
What binds to unzipped DNA?
Free nucleotides (Nucleoside triphosphates)
What catalyzes the nucleotide binding process?
DNA Polymerase
Where does DNA polymerase elongate?
The 3’ end
What is DNA polymerase?
The catalyse of free nucleotides binding to DNA
What are the two strands during DNA nucleotide-binding?
The leading strand and the lagging strand
What is Polymerase Chain Reaction?
Produces large quantities of DNA
What are the three steps of Polymerase Chain Reaction?
Occurs in a thermal cycler through:
Denaturation, annealing, and elongation
What does mRNA do?
Takes a message from DNA in nucleus to ribosomes in cytoplasm
What does rRNA do?
rRNA and proteins make up ribosomes where proteins are synthesized
What does tRNA do?
tRNA transfers a particular amino acid to a ribosome
What is transcription?
Transcription is the synthesis of mRNA copied from the DNA base sequences by RNA polymerase
Where does transcription take place?
In the nucleus
What are the steps of transcription? (1-3)
- RNA polymerase attaches to a promoter on DNA
- Transcription factor is needed for polymerase to bind to DNA
- Complementary RNA nucleotides pair with DNA nucleotides of the strand
What are the steps of transcription? (4-5)
- RNA polymerase covalently bonds RNA nucleotides
5. Terminator sequence causes RNA polymerase to stop transcribing DNA, and to release mRNA
What do spliceosomes do?
Remove introns from DNA
What is an exon?
The part of DNA that will be expressed
What is a codon?
Three sequential bases on mRNA that correspond to one amino acid
What is genetic code made of?
mRNA triplets(codons)
How many codons are there?
64
How many amino acids are there?
20
How many start codons are there? Stop codons?
One start, three stop
What is translation?
The synthesis of polypeptides on ribosomes
Where does translation take place?
Takes place in cytoplasm
What is a polypeptide?
A chain of amino acids
What does translation depend on?
The complementary base pairing between codons on mRNA and anticodons on tRNA
What is translated during translation?
Nucleic acids are translated to proteins
What are the steps of translation?
- Chain Initiation
- Chain Elongation
- Chain Termination
What is Chain initiation?
- A small ribosomal subunit attaches to mRNA start codon
2. First tRNA pairs with this codon and large ribosome subunit attaches to smaller ribosome subunit
What is required to bring together necessary components during translation?
Initiation proteins
What is Chain Elongation?
- New tRNA arrives at A site
2. Amino acid at P site is attached by a peptide bond to the newly arrived amino acid
What catalyzes Chain Elongation?
Larger ribosome’s ribozyme
What is translocation?
When tRNA moves from site A to P in translation
What is Chain Termination?
- Occurs at stop codon that does not code for amino acid
2. Release factor protein binds to stop codon
What are polyribosomes?
Clusters of several ribosomes synthesizing the same protein
In what way is DNA replicated?
Semi-conservative
What does conservative replication look like?
One old DNA, and one new DNA
What does dispersive DNA look like?
Chunks of new and old DNA for each new strand