Chapter 13 and 14
6. How is messenger RNA (mRNA) processed before leaving the eukaryotic nucleus?
10.10
Explain how DNA replicates semiconservatively. What role does DNA polymerase play? What role does helicase play?
DNA replicates semi conservatively because each daughter DNA double helix contains an old strand from the parental DNA double helix and a new strand. DNA polymerase is an enzyme complex that carries out complementary base pairing and joining during DNA replication. Helicase unwinds the parent DNA
Compare the function of mRNA, transfer RNA (tRNA) and ribosomal RNA (rRNA) during protein synthesis.
MESSENGER RNA (mRNA) carries the genetic information copied from DNA in the form of a series of three-base code "words," each of which specifies a particular amino acid. TRANSFER RNA (tRNA) is the key to deciphering the coder words in mRNA. Each type of amino acid has its own type of tRNA, which binds it and carries it to the growing end of a polypeptide chain if the next code word on mRNA calls for it. The correct tRNA with its attached amino acid is selected at each step because each specific tRNA molecule contains a three-base sequence that can base-pair with its complementary code word in the mRNA. RIBOSOMAL RNA (rRNA) associates with a set of proteins to form ribosomes. These complex structures, which physically move along an mRNA molecule, catalyze the assembly of amino acids into protein chains. They also bind tRNAs and various accessory molecules necessary for protein synthesis. Ribosomes are composed of a large and small subunit, each of which contains its own rRNA molecule or molecules.
What specific steps occur during transcription of RNA off a DNA template?
Modifications to mRNA transcripts. The 5' end is capped with a start signal, the 3' end is capped with an end signal and a poly A tail. Noncoding introns are cut out. Coding exons are spliced together to make a finished product.
What are the specific events of translation?
Translation is the process by which mRNA is decoded and translated to produce a polypeptide sequence, otherwise known as a protein. This method of synthesizing proteins is directed by the mRNA and accomplished with the help of a ribosome, a large complex of ribosomal RNAs (rRNAs) and proteins. In translation, a cell decodes the mRNA's genetic message and assembles the brand-new polypeptide chain. Transfer RNA, or tRNA, translates the sequence of codons on the mRNA strand. The main function of tRNA is to transfer a free amino acid from the cytoplasm to a ribosome, where it is attached to the growing polypeptide chain. tRNAs continue to add amino acids to the growing end of the polypeptide chain until they reach a stop codon on the mRNA. The ribosome then releases the completed protein into the cell.
