Unit 1.3
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Gene expression involves what of DNA?
Transcription and translation
What are the bases of RNA?
Adenine, uracil, cytosine and guanine
How many strands does RNA have?
1
What type of sugar is included in RNA?
Ribose sugar
What is mRNA?
Messenger RNA carries a copy of the DNA code from the nucleus to the ribosome. Each triplet of bases on the mRNA is called a codon. Each codon codes for a particular amino acid
What is tRNA?
Transfer RNA folds due to complementary base pairing. Each tRNA molecule carries its specific amino acid to the ribosome.
What is the rRNA?
Ribosomal RNA proteins and forms ribosome
What are the steps of transcription?
Step 1: Transcription occurs in the nucleus. RNA polymerase move along the DNA, unwinding the double helix and breaking hydrogen bonds Step 2: Free RNA nucleotides pair up with their complementary DNA bases: Adenine pair with Uracil and Guanine pairs with Cytosine Step 3: RNA polymerase synthesise a primary transcript Step 4: Introns are removed from the primary transcript and exons are joined to form the mature transcript this process is called RNA splicing
When does translation start?
Translation starts when the ribosome reads an mRNA start codon
The first codon of the mRNA forms weak hydrogen bonds with?
The complementary anticodon of a tRNA molecule
Each tRNA molecule has a specific what?
Amino acid
What forms between the amino acids during translation?
Peptide bond
What does the first tRNA end up doing?
Disconnects from its amino acid and leaves the ribosome
What does used tRNA end up doing?
Exits the ribosome and collects another specific amino acid
After the process of translation has occurred many times, what is created?
Polypeptide chain (chain of amino acids)
What is the last codon of an mRNA?
Stop codon which signals the end of translation