DNA, RNA, and Protein Synthesis Molecular Genetics DNA, RNA, and Protein Synthesis

DNA DNA – deoxyribonucleic acid DNA carries our genetic information. Recall where is DNA found? In the Nucleus What type of macromolecule is DNA an example of? Nucleic Acid Nucleotides are the subunits of nucleic acids Two types of nucleic acids - DNA - RNA

History A scientist named Franklin was the first to do an X-Ray model of DNA. Watson and Crick determined that DNA has a helical structure. They were able to determine this with the help of Franklin’s X-Ray Model.

DNA DNA is double stranded and helical. It is composed of three things: 1) A 5-carbon sugar called deoxyribose 2) a nitrogenous base 3) a phosphate group. There are four different types of nitrogenous bases - Adenine (A) - Thymine (T) Cytosine (C) - Guanine (G)

Chargaff’s Rule Pyrimidines – Cytosine and Thymine Chargaff’s Rule – states that the amount of G should equal the amount of C and the amount of A should equal the amount of T. A will bond to T , G will bond with C! A-T , G-C Pyrimidines – Cytosine and Thymine Purines – Adenine and Guanine Purines will always bond to pyrmidines.

DNA is like a ladder where the sides are made up of phosphate and sugar. The rungs of the ladder are made up of bases. Phosphate is bonded to Sugar. They make up the “backbone” of DNA. Bonded to the Sugar is the Base. The bases are held together by a hydrogen bond!

Structure RNA DNA

How to make a protein There are three steps involved in making a protein. 1st – The DNA must be replicated 2nd – The DNA must be transcribed. This means the DNA must be made into RNA 3rd- The RNA must be translated. This means the RNA must be made into proteins.

Central Dogma DNA → RNA → Protein (Transcription) (Translation)

DNA Replication To make a protein, first DNA replication will occur. It occurs during the S phase of the cell cycle.

DNA Replication First the double stranded DNA will unzip or unwound -DNA helicase is the enzyme responsible for the unzipping.

Now with a single strand of DNA , DNA polymerase, another enzyme will add the complementary nucleotides to the new DNA strand. After replication, the new DNA strand will be complementary to the old DNA strand.

Transcription After DNA has been replicated, the DNA must be transcribed. Transcription is DNA being converted into RNA. DNA codes for many messages, but DNA can not leave the nucleus. It must be made into RNA to leave the nucleus.

RNA RNA – Ribonucleic Acid Single stranded Contains a ribsose sugar, a nitrogenous base, and a phosphate group. G-C and A-U There is no Thymine in RNA, Thymine is replaced with Uracil!!!!!

Types of RNA mRNA, used to carry the information from the nucleus to the ribosome. * Used in transcription (M-Messenger) tRNA, used to carry or transfer amino acids to the ribosome * Used in translation (T-Transfer) rRNA, used to form the structures of ribosomes (R- Ribosomal)

Transcription Occurs in the nucleus of the cell RNA polymerase, an enzyme, will unzip the DNA The new RNA strand will be complementary to the unzip part of the DNA. It will follow the base pairing rule! Recall different for RNA!

Transcription The product from transcription is mRNA The mRNA will release and go to the cytoplasm where ribosomes are located

Translation Translation is converting RNA into protein. What are the subunits of proteins? Amino Acids There are 20 amino acids. Proteins are made on ribosomes; therefore, Translation will occur on a ribsome. Recall – Where can ribsomes be found in a cell?

Codon There are 64 codons Only 61 codons actually code for an amino acid There is 1 start codon – it also codes for the amino acid methionine There are 3 stop codons What is the start codon? AUG What are the stop codons? UGA, UAA, UAG

Codon Three base code – can be in DNA or mRNA

Translation Occurring on the ribosomes where mRNA made in transcription will travel outside to nucleus to a ribosome. - During translation, the tRNA will come and attach to the codon regions on the mRNA. -tRNA has a sequence of bases, called the anticodon. tRNA is also carrying the amino acid.

The anticodon will be complementary to the codon region of mRNA. Recall again what is the function of tRNA…… tRNA will carry the amino acids to the ribosome to begin translation. So, on one end of the tRNA is the anticodon and the other end has the amino acid attached.

Once the tRNA anticodon has attached to the mRNA codon, the appropriate amino acid will be released. Now, the next codon will be read and the tRNA will release appropriate amino acid. That amino acid will link with the previous amino acids. Recall- What type of bond holds amino acids together. These chains of amino acids will build a polypeptide chain which will create a specific protein.