Storing and Using Genetic Information Flashcards
DNA replication is said to be
- Semi conservative
- Bi directional
What does semi-conservative mean?
- Each half of DNA molecule is old, the other is new
What does bi directional mean?
Strands are created in opposite directions
What enzyme unzips the double helix?
DNA Helicase
What enzyme adds new nucleotides?
DNA Polymerase
In which direction is the new strand formed? C’what to C’what?
C’5 to C’3
What happens with the other strand?
- It first attaches a primer
- Then a polymerase enzyme adds nucleotides
What is the role of DNA ligase in the formation of the lagging strand?
- Joins fragmented segments together
What are the discontinued fragments called before the action of DNA ligase?
Okazaki fragments
What is a sequence of 3 bases called?
Codon
What is the term given to the fact that a codon can refer to more than 1 amino acid?
Degenerate
What is the start codon?
Methionine
How does the sequence of codons stop?
A stop codon is in the sequence
What happens after the sequence is transcribed?
Alternative splicing of exons to leave only introns
What is attached to the mRNA to stop it from being broken down by enzymes?
- A cap is attached to the 5’ end
- A tail is attached to the 3’ end
Where does translation occur in the cell?
Endoplasmic reticulum
What is the first step in translation?
- Attachment of a small ribosomal subunit to the mRNA
What happens in step 2
- Specific tRNA molecule carrying methionine binds to the corresponding codon on the mRNA
What happens in step 3
The large unit of the ribosome joins the smaller one and the tRNA, the tRNA occupies the P section of the binding sites
What happens in step 4
- Another tRNA comes along carrying the next amino acid
- It binds to the A site
What happens as the ribosome moves along the code?
The tRNA in the P site leaves and the one in the A site takes its place
What happens when the process reaches a stop codon?
The process stops and the polypeptide is released
