RNA Protein Synthesis I DNA to Genes A

RNA & Protein Synthesis

I. DNA to Genes • A. We now know how the double helix is replicated but we still don’t know how it is then transformed into genes. • B. Remember genes are coded DNA instructions that control the production of proteins within the cell. • C. A little sequence from DNA is copied and transferred into RNA, which then carry the sequence to make proteins

II. What is RNA: Structure of RNA • A. RNA consists of a long single stranded chain of nucleotides. • B. The 3 parts of a RNA nucleotide: – 1. 5 carbon sugar ribose – 2. Phosphate group – 3. Nitrogenous bases : Adenine, Guanine, Cytosine & Uracil • C. RNA can be a disposable copy of a tiny segment of DNA that carries a sequence for a single gene

III. Types of RNA • A. There are 3 main types of RNA: – 1. messenger RNA – carry the copy of DNA to the rest of the cell (m. RNA) – 2. ribosomal RNA – make up ribosomes which make proteins (r. RNA) – 3. transfer RNA – carry an amino acid to the ribosome (t. RNA) • B. The 3 types of RNA play a key role in protein synthesis

IV. Transcription • A. Transcription is the process in which RNA molecules are produced by copying a specific part of the DNA sequence. • B. During transcription RNA polymerase binds to DNA and separates the DNA at a promoter site using 1 DNA strand as a template. – 1. promoter – a section of DNA with a specific base sequence that indicates to RNA polymerase to bind and begin transcription

V. RNA Editing • A. RNA molecule require a little bit of editing getting copied directly from DNA. • B. DNA in eukaryotic cells have sections of nucleotides called introns that are not involved in coding for proteins • C. The sequences that code for proteins on DNA are known as exons. (expressing sections) • D. Prior to leaving the nucleus the introns are cut out and the exons are spliced back together

VI. Genetic Code • A. Proteins are made by joining the 20 different amino acids into long chains called polypeptides – 1. the sequence of the amino acids determines the protein • B. The genetic code from the DNA transcribed into m. RNA is read 3 letters at a time making each amino acid a different 3 letter “word” • C. The 3 letter word along the m. RNA is called the codon the t. RNA that carries the amino acid to match the codon is called the anticodon.

• 1. There are over 64 possibilities of codons but only 20 amino acids so many codons may read for the same amino acid. • 2. There is also a very specific codon (AUG) that is known as a start/stop codon that starts/ends protein synthesis – Ex. DNA Sequence: AGC GTG m. RNA Sequence codon: UCG CAC Amino Acid that will match: Serine Histidine

Anticodons

VII. Translation • A. In order for proteins to be made from the m. RNA the ribosome has to carry out its main job – 1. Decoding the m. RNA message into a polypeptide chain is known as translation • B. As the m. RNA is moves through the ribosome t. RNA brings the correct amino acid to the ribosome assembles the amino acids into a chain it releases the t. RNA again • Once the ribosome reaches a stop codon the polypeptide chain as well as the m. RNA are released as well

IIX. Mutations • A. Mutations are changes in the genetic material. • B. 2 types of mutations: – 1. Gene mutations – changes in a few nucleotides can cause either point mutations or frameshift mutations • Ex. TAC GCA -> AUG CGU -> Met Arg • TAC GTA -> AUG CAU -> Met His – 2. Chromosomal mutations – changes in the structure of the chromosome caused by deletion, duplication, inversion, translocation

IX. Comparing Roles of DNA & RNA A. DNA • • • 1. Double stranded 2. Deoxyribose 3. Thymine 4. Never leaves nucleus 5. “Master plan” B. RNA • • • 1. Single stranded 2. Ribose 3. Uracil 4. Enter & leave nucleus 5. “Blueprint”

X. Why Proteins are Important • A. Remember proteins are created from your DNA sequence which are your genes. – 1. the sequence will identify the protein being made, that protein can regulate chemical reactions & catalyze others. • Ex. Enzymes can produce color pigment in a flower or are proteins that regulate growth