DNA, RNA AND PROTEIN SYNTHESIS

DNA (DEOXYRIBONUCLEIC ACID) Nucleic acid that composes chromosomes and carries genetic information.

CHROMOSOME ORGANIZATION 1. A chromosome is an enormous strand of super coiled DNA. 2. Sections of DNA on the chromosome that code for proteins are called genes. 3. Noncoding sections of DNA are called “junk DNA” (regulatory or unknown function)

BUILDING BLOCKS OF DNA Composed of nucleotides Nucleotides contain three parts: 1. 5-Carbon Sugar (deoxyribose) 2. Phosphate Group 3. Nitrogen Base (four types, adenine, guanine, thymine and cytosine)

Adenine and Guanine are purines (composed of two rings of nitrogen atoms)

Thymine and Cytosine are pyrimidines (composed of one ring of nitrogen atoms)

STRUCTURE OF DNA Consists of two strands of nucleotides that form a twisted ladder (double helix) Sugar and phosphate alternate along the sides of the ladder (linked by strong covalent bonds) Pairs of nitrogen bases form the rungs of the ladder (linked by weak hydrogen bonds).

Specific base pairing arrangement A-T : 2 hydrogen bonds C-G : 3 hydrogen bonds Nitrogen bases attach to the sugar portion of the side (NOT the phosphate) Strands run in opposite directions

FUNCTION OF DNA DNA codes for proteins (structural proteins, enzymes, and hormones) information for building proteins is carried in the sequence of nitrogen bases proteins determine physical and metabolic traits and regulate growth and development.

DNA REPLICATION Process in which DNA is copied

PURPOSE OF DNA REPLICATION Gives daughter cells produced by cell division a complete set of genetic information identical to the parent cell.

WHERE DNA REPLICATION OCCURS Nucleus

WHEN DURING THE CELL CYCLE DOES REPLICATION OCCUR? Interphase

HOW REPLICATION OCCURS 1. Helicase enzymes unzip the parent strand by separating the nitrogen base pairs. (The Unzipper) 2. DNA polymerase pairs free DNA nucleotides with the exposed bases on both strands following the base pair rules. (The Builder) –each strand from the parent molecule serve as a template 3.Primase (The Initializer) Makes the primer to polymerase knows where to go. Piece of RNA 4.Ligase (The Gluer) Helps glue DNA fragments together 5.Hydrogen bonds reform spontaneously sealing the two strands of each DNA molecule together Amoeba Sisters Video at minute 2:00-3:22. Take notes on the 4 DNA Replication Characters and JobVideo

RESULTS OF REPLICATION Two molecules of DNA that are identical Each is half old (strand from parent) and half new (strand synthesized by DNA polymerase)

RNA (RIBONUCLEIC ACID) Nucleic acid involved in the synthesis of proteins

RNA STRUCTURE Composed of nucleotides, but differs from DNA in three ways. 1.Single strand of nucleotides instead of double stranded 2.Has uracil instead of thymine 3.Contains ribose instead of deoxyribose

RNA FUNCTION Three forms of RNA involved in protein synthesis 1. mRNA (messenger): copies instructions in DNA and carries these to the ribosome. 2. tRNA (transfer): carries amino acids to the ribosome. 3. rRNA (ribosomal): composes the ribosome.

PROTEIN SYNTHESIS Cells build proteins following instructions coded in genes (DNA). Consists of two parts, transcription and translation

TRANSCRIPTION DNA is copied into a complementary strand of mRNA. WHY? DNA cannot leave the nucleus. Proteins are made in the cytoplasm. mRNA serves as a “messenger” and carries the protein building instructions to the ribosomes in the cytoplasm.

LOCATION OF TRANSCRIPTION Nucleus

RESULT OF TRANSCRIPTION mRNA strand with instructions for building a protein leaves the nucleus and goes to the cytoplasm.

TRANSCRIPTION EXAMPLE Transcribe the following DNA Sequence in mRNA TAC CGG ATC CTA GGA TCA AUG GCC UAG GAU CCU AGU DNA RNA

PROTEINS Structural and functional components of organisms. Composed of amino acids (20) Order of nucleotides in DNA determines order of amino acids in a protein One gene codes for one protein

GENETIC CODE The “language” that translates the sequence of nitrogen bases in DNA (mRNA) into the amino acids of a protein. Codon = three nucleotides on DNA or mRNA One codon specifies one amino acid The genetic code is universal to all organisms

TRANSLATION Instructions in mRNA are used to build a protein

LOCATION OF TRANSLATION ribosome (in the cytoplasm)

PROCESS OF TRANSLATION RNA is transcribed in the nucleus. As a single strand, it is able to leave through the pores of the nucleus and move to the cytoplasm. mRNA (messenger RNA) carries the code for the assembly of proteins to the ribosomes which are located throughout the cytoplasm. The mRNA is held in place on the ribosomes. tRNA (transfer RNA) picks up amino acids which are spread throughout the cytoplasm and brings them to the mRNA on the ribosomes. There the assembly of proteins is completed.

RESULT OF TRANSLATION A Protein! Codon VideoVideo