DNA replication Flashcards
What is stage one of DNA replication called?
Transcription
What happens first during transcription?
The enzyme DNA Helicase attaches to the DNA molecule
What does DNA helicase do?
It causes the hydrogen bonds between the complementary bases to break which causes the two polypeptide strands to separate from each other (unzip)
What happens 2nd during transcription?
Free nucleotides line up with their complementary bases on the DNA strands, which are only held in place by hydrogen bonds between the complementary bases. Theses are called activated nucleotides.
What happens 3rd during transcription?
A second enzyme called DNA polymerase now attaches, this moves down the group and catalyses the formation of a phosphodiester bond between the activated nucleotides. (bonds in the backbone)
How are the phosphodiester bonds formed during transcription?
Via a condensation reaction
During transcription before splicing occurs what is formed?
A pre-mRNA strand
What is splicing?
Where introns which are non-coding sections of DNA, are removed.
What is the type of mRNA formed at the end of transcription?
Mature mRNA - only formed of exons
What is the 2nd stage of DNA replication called?
Translation
What happens 1st during translation?
The exon leaves the nucleus through nuclear pores via diffusion
What happens 2nd during translation?
The exon attaches to a ribosome which reads mRNA codon.
What happens 3rd during translation?
tRNA with complementary anticodon binds to mRNA. tRNA carries a specific amino acid.
What happens 4th during translation?
Next codon is read; tRNA with complementary anticodon is brought into position.
What happens 5th during translation?
Condensation reaction occurs between adjacent amino acids, forming a peptide bond.
