DNA Replication

DNA Replication: A process that occurs during cellular division where two identical molecules of DNA are created from a single molecule of DNA.

Semiconservative– each newly made DNA molecule is made up of one old strand and one new strand

Central Dogma of DNA Replication: Starts with DNA…transcribed into mRNA…translated into proteins by tRNA

Compare and Contrast RNA and DNA: The sugar in RNA is ribose instead of deoxyribose. RNA is generally single-stranded. RNA contains uracil in place of thymine.

Three types of RNA:

• mRNA →“messenger” made from DNA in nucleus…travels out of nucleus and finds a ribosome.

• tRNA → “transfer” brings amino acids to the ribosomes; found in cytoplasm

• rRNA →“ribosomal” part of the ribosome; this is where proteins are made

How is mRNA edited?

• Introns are cut out before leaving the nucleus

• Exons are left, and this shortened piece of mRNA leaves the nucleus to get translated into proteins

Summarize the three steps of Translation:

STEP 1: Initiation Translation begins when an mRNA molecule attaches to a ribosome. As each codon (group of 3 nucleotides) of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome by tRNA.

STEP 2: Elongation In the ribosome, amino acids are transferred to the growing polypeptide chain by the action of the tRNA (elongation)

STEP 3: Termination When the “STOP” codon is reached, the mRNA uncouples from the ribosome.