Replication Transcription Translation DNA 1 Double Stranded Helix

Replication Transcription Translation

DNA 1. Double Stranded Helix 2. Hydrogen Bonds between Nitrogenous Base Pairs 3. Adenine-Thymine and Guanine-Cytosine

Adenine shares 2 hydrogen bonds with Thymine Guanine shares 3 hydrogen bonds with Cytosine

Gene • A gene is a segment of DNA • A gene is a sequence of nucleotides that codes for a functional product (usually a protein) • 1 gene = 1000’s of base pairs • 41000 possibilities of combinations

A Gene is a Segment of DNA When a gene is expressed, DNA is transcribed to produce RNA and RNA is then translated to produce proteins.

Replication • The duplication of DNA which occurs during the S phase of Interphase. • 1 Strand 2 Complementary Strands • Where? In the nucleus

Hydrogen bond (H-bonds) thymine adenine cytosine guanine phosphate deoxyribose sugar Sugar / phosphate “strand” Nitrogenous base “rung” DNA nucleotide Deoxyribose sugar phosphate RNA nucleotide ribose sugar Nitrogenous base (guanine) phosphate Nitrogenous base (uracil)

Step 1: Hydrogen bonds between complementary bases break DNA “unzips” DNA strands pull apart from each other

Step 2: DNA nucleotides in the cell match up with each side of the “unzipped” DNA each “unzipped’ strands forms a template for a new strand

Step 3: Each “old’ strand forms a template for a “new” strand two identical DNA molecules form “new” strand, identical sequence to the original “old” (original) strand

RNA Review • Like DNA, RNA is a chain of nucleotides. • RNA contains the base Uracil, instead of Thymine. • RNA is small enough to exit through nuclear pores, unlike DNA. • RNA can be found in the nucleus, in the cytoplasm, or in the ribosomes (r. RNA).

Transcription • The process by which a gene found in DNA is copied into a complementary strand of RNA. • 1 Strand DNA 2 Strands RNA • Where? In the nucleus

DNA RNA

Label the Following

Step 1: Hydrogen bonds between complimentary bases break DNA “unzips” as the strands pull apart from each other

Step 2: RNA nucleotides in the cell match up with only one side of the “unzipped” DNA each “unzipped’ strands forms a template for a m. RNA strand RNA nucleotide

m. RNA strand Step 3: m. RNA strand breaks off from the DNA strand One side of DNA strand

Step 4: m. RNA strand leaves the nucleus for the ribosome

Step 5: Once the m. RNA leaves, the DNA “zips” back together

• Transcription is different from DNA replication – during the process of transcription, only a segment of DNA, or gene, is transferred into an RNA message (whereas replication copies the whole chromosome). • m. RNA then takes the gene’s coded message to the ribosome for protein synthesis. • Transcription not only produces m. RNA – t. RNA and r. RNA are also made through the process of transcription.

Translation • The process that converts, or translates, an m. RNA message into the amino acid sequence of a protein. • 1 Strand RNA Amino Acid Chain Protein • Where? Cytoplasm or Rough E. R. – at the ribosomes

Definitions Codon • Three-base segment of m. RNA that code for amino acids. Anticodon • Three-base segment of t. RNA that is complementary to an m. RNA codon. • Pairing results in deposition of amino acid. Amino Acid • Monomer of protein

The problem: How does a particular sequence of nucleotides specify a particular sequence of amino acids? By means of transfer RNA (t. RNA) molecules, each specific for one amino acid and for a particular triplet of nucleotides in m. RNA called a codon. The family of t. RNA molecules enables the codons in a m. RNA molecule to be translated into the sequence of amino acids in the protein.

Step 1 – The m. RNA codon attracts and pairs up with a complementary t. RNA anticodon Step 2 – The ribosome helps forms a peptide bond between the two amino acids carried by the t. RNA molecules Step 3 – The ribosome pulls the m. RNA strand to expose the next codon, and the steps repeat until the protein is complete

RNA and Protein Synthesis • RNA is a singlestranded nucleic acid • RNA acts as a messenger between DNA and ribosomes • The process of translation takes amino acids and forms proteins

Why Is It Necessary? • DNA in the Nucleus • Ribosomes in the Cytoplasm • Need a Messenger

Protein Synthesis • Proteins are coded directly from the m. RNA with 3 bases (one codon) for each amino acid. What’s up with that?

Mutation • A change in the nitrogenous base sequence of DNA; that change causes a change in the product coded for by the mutated gene.

Mutations What happens when you get insertions or deletions of bases in the DNA sequence? Usually you end up with a mess. THE BIG FAT CAT ATE THE RAT AND GOT ILL Deletion of one base THE IGF ATC ATA TET HER ATA NDG OTI LL And its all pops and buzzes.

Sickle-Cell Anemia

Definitions • Carcinogens Substances and preparations which, if they are inhaled or ingested or if they penetrate the skin; may induce cancer or increase its incidence and can affect any cells or tissues • Mutagens may induce hereditary genetic defects or increase their incidence and effect the germ cells (gonads) • Teratogens may induce non-hereditary congenital malformations or increase their incidence and effect the growing fetus

Mutagens • • Tobacco products Nitrous Acid Mold Toxins X-rays Gamma Rays UV Radiation Some Artificial Sweeteners