Deoxyribonucleic Acid Structure of DNA Deoxyribonucleic Acid

DNA DNA in in the shape of a double helix DNA is made up of nucleotides A nucleotide is: A Sugar A Phosphate And one of four bases

Deoxyribose Sugar The carbon atoms are numbered 1', 2', 3', 4', and 5' The hydroxyl groups on the 5'- and 3'- carbons link to the phosphate groups to form the DNA backbone. The DNA backbone is a polymer with an alternating sugar-phosphate sequence

G C The Bases A is for Adenine G is for Guanine C is for Cytosine T is for Thymine A T G C

Purine VS Pyrimidine Adenine and Guanine Larger Cytosine and Thymine Smaller

How Many Scientists Does it Take to Discover a Molecule?

Erwin Chargaff (Born 1905) Russian Moved to the U.S. Discovered that there was always an equal number of A’s to T’s and C’s to G’s. There could be different amounts of these two groupings.

Rosalind Franklin (1920 – 1958) British Worked under Maurice Wilkins Used X-ray diffraction to get images of DNA Her work was passed along to Watson and Crick by Wilkins. She did not get recognized for her work possibly because she was a woman in science when it was not fully acceptable

Watson and Crick Crick (Born 1916) British Watson (Born 1928) American Used images and papers produced by Franklin Discovered double helix shape They got the Nobel Prize in 1953 along with Wilkins

DNA Replication DNA replicates when the cells divide and when the sex cells are formed Groups of proteins guide the process, but DNA polymerase is the major functioning enzyme.

Three major events to begin DNA replication The two nucleotide chains must separate forming a replication fork. The chains are separated by enzymes called helicases DNA polymerase binds to the separated chains of DNA and assembles complimentary nucleotides to the old strand The new strand of DNA hydrogen bonds with the old strand and winds back to form a helix

Checking the System Incoming nucleotides bind to the DNA polymerase and the polymerase checks to see if the incoming nucleotide pairs correctly with the DNA template. Error rate is about 1 error in 10000 base pairs (108)

Direction of Replication Replication takes place in both directions. DNA polymerase begins replication simultaneously at many points along the separated nucleotide.

The Other Nucleic Acid Remember that: DNA is located in the nucleus and under no circumstances can leave the nucleus. Proteins are manufactured in the cytoplasm at the ribsomes. DNA is the instructions for making those proteins.

RNA: Ribonucleic Acid Sugar: Ribose Phosphate group Nitrogen bases Single Stranded Made of nucleotides Sugar: Ribose Phosphate group Nitrogen bases The nitrogen bases in RNA have one difference. Thymine is replace by uracil So A pairs to U; G pairs to C

Three Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA) Carries the code from DNA to the ribosome Transfer RNA (tRNA) Picks up individual amino acids in the cytoplasm and carries them to the ribosome to be delivered Ribosomal RNA (rRNA) Helps bind mRNA and tRNA together during protein synthesis

RNA Transcription DNA transcribes a copy of mRNA in the nucleus of the cell. The mRNA takes the DNA code out of the nucleus and to the ribosomes.

Steps of Transcription RNA polymerase makes RNA copies of specific segments of DNA. This begins at a promotor site on DNA Only the DNA template is used for transcription

Steps of Transcription RNA polymerase adds complimentary RNA nucleotides to form a new RNA molecule. Complimentary base pairing determines the nucleotide sequence

Steps of Transcription Transcription ends at the DNA terminator. Both DNA and RNA are released by the RNA polymerase. All three types of RNA molecules are transcribed by this process.

Protein Synthesis – Structure and Composition Proteins are polymers made of amino acids bonded by peptide bonds Proteins are made up of specific sequences of amino acids There are 20 kinds of amino acids

Protein assembly Codon AUG means “Start” or can code for the amino acid methinone MRNA codon is paired with tRNA anticodon Amino acids are bonded with peptide bonds and the polypeptide chain grows into a protein At the stop codon (UAA, UAG, UGA) translation ends and the protein is finished The protein folds up Several ribosomes can translate the same mRNA transcript at the same time

A mutation is any change in the DNA sequence Genetic Changes A mutation is any change in the DNA sequence

Mutations Mutations are caused by spontaneous mistakes during replication They are influenced by mutagens. Radiation Chemicals High temperatures Mutations in body cells can cause individuals to become ill, Cancer

Types of Gene Mutations Frame Shift – addition of deletion of a base, altering the whole sequence More harmful because it effects more base sequences Point - Change in a single base

Types of Chromosomal Mutations Deletion Duplication Inversion Insertion Translocation