Key Concepts:

Terms in this set (65)

-The flow of information from gene to protein is based on a triplet code: the genetic instructions for a polypeptide chain are written in the DNA as a series of non overlapping, three nucleotide words. the series of words in a gene is transcribed into a complementary series of non overlapping, three-nucleotide words in mRNA, which is then translated into a chain of amino acids
-During transcription, the gene determines the sequence of nucleotide bases along the length of the RNA molecule that is being synthesized. For each gene, only one of the two DNA strands is transcribed. This strand is called the template strand because it provides the pattern, or template, for the sequence of nucleotides in an RNA transcript
-For any given gene, the same strand is used as a template every time the gene is transcribed. For other genes on the same DNA molecule, however, the opposite strand may be the one that always function as the template
-An mRNA molecule is complementary rather than identical to its DNA template because RNA nucleotides are assembled on the template according to base pairing rules
-Like a new strand of DNA, the RNA molecule is synthesized in an antiparallel direction to the template strand of DNA
-The mRNA nucleotide triplets are called codons, and they are customarily written in the 5' to 3' direction
-These codons are complementary to the template strand and thus identical in sequence to the mRNA except that they have T instead of U
-During translation, the sequence of codons along an mRNA molecule is decoded, or translated, into a sequence of amino acid making up a polypeptide chain. The codons are read by the translation machinery in the 5' --- 3' direction along the mRNA. Each codon specifies which one of the 20 amino acids will be incorporated at the corresponding position along a polypeptide
-Because codon are nucleotide triplets, the number of nucleotides making up a genetic message must be three times the number of amino acids in the protein product