3.3.3 Protein Synthesis

Drill

• What are three similarities and three differences between RNA and DNA?

• What is DNA replication?

Which is which?

• DNA RNA

DNA vs. RNA

DNA RNA

Deoxyribonucleic acid Ribonucleic acid

Double-stranded; double helix Single-stranded

Nucleotide bases: A T G C Nucleotide bases: A U G C

Only in nucleus of eukaryotes (in cytoplasm of prokaryotes)

In cytoplasm

Stores genetic information Translated into amino acids which are then assembled into proteins

Organic molecules

Nucleic acids

Nucleotides are building blocks

Made up of sugar, phosphate, and nitrogen bases

DNA Replication

• DNA makes a copy of itself• Original strand of DNA is “unzipped”

by enzymes• Following the base pair rules for DNA

(A T, T A, G C, and C G), each exposed strand is used as a template for a new complementary strand

• Occurs in the nucleus

Objectives

• Define gene.• Differentiate between the three

types of RNA.• Explain how the sequence of

nitrogen bases in DNA direct protein formation.

• State that proteins determine traits.

Key Questions

• What is a gene?• What are the roles of each molecule in

protein formation?• Sequence of nitrogen bases in DNA• Three types of RNA• Enzymes• Amino acids• Ribosomes

• What macromolecule determines traits?

Vocabulary

• Codon• Gene• mRNA• tRNA• rRNA• Replication• Transcription• Translation

Definition of Gene

• A gene is a segment of DNA that codes for a protein or RNA

• Albinism occurs when an organism produces little to no melanin (pigment) in the eyes, skin, and/or hair• There are at least 6 different genes

involved in pigmentation (chromosome 9, 10, 11, 13, and 15)

Albino Reptiles and Amphibians

Albino Mammals

Parkinson’s Disease- chromosome 4

How are DNA sequences used to make proteins?

• DNA's instructions are used to make proteins in a two-step process. First, enzymes read the information in a DNA molecule and transcribe it into an intermediary molecule called messenger ribonucleic acid, or mRNA.

• Next, the information contained in the mRNA molecule is translated into the "language" of amino acids, which are the building blocks of proteins. This language tells the cell's protein-making machinery the precise order in which to link the amino acids to produce a specific protein. This is a major task because there are 20 types of amino acids, which can be placed in many different orders to form a wide variety of proteins.

Types of RNA

• Messenger RNA (mRNA)- RNA molecules that carry copies of instruction for making amino acids from DNA to the rest of the cell

• Ribosomal RNA (rRNA)- make up ribosomes

• Transfer RNA (tRNA)- transfers each amino acid to the ribosome as it is specified by coded messages in mRNA

How Proteins are Made Animation

• http://www.genome.gov/Pages/Education/DNADay/HowProteinsAreMade.html

Transcription

• RNA molecules are produced by copying part of the nucleotide sequence of DNA (ATGC…) to a complementary sequence in RNA

• During transcription, RNA polymerase (an enzyme) binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA.

Base Pair Rules for Transcription

• A U• T A• G C• C G

• THERE IS NO THYMINE (T) IN RNA

Location of RNA

• RNA is formed in the nucleus• It leaves the nucleus and goes into

the cytoplasm

Transcribe this strand of DNA

G T C A A T T T C G G C A T A

C A G U U A A A G C C G U A U

Codons

• Codons are groups of three consecutive RNA nucleotides that specify an amino acid• Ex: U G C

Codon Chart

Translation

• In translation, the cell uses information from mRNA to produce proteins.

• The codons from transcribed RNA are decoded and used to make amino acids. These amino acids are then used to make proteins.

Translate this strand of RNA

C A G U U A A A G C C G U A UGlutamine Leucine Lysine Proline Tyrosine

Why are the nucleotides of RNA separated into these sections?

Ribosomes Make Proteins

• The ribosomes assemble these amino acids into proteins.

• Most genes contain nothing more than instructions for assembling proteins. Proteins are the keys to almost anything that living cells do.

Other Activities

• Protein Synthesis Power Point with Notes• Billy Madison Activity• Bird Abuse Crime Lab Activity• DNA and Messenger RNA BCR• Crossword Puzzle• Deciphering Duck DNA• DNA to Amino Acid Notes• Protein Synthesis Quiz

Homework

• Protein Synthesis Review Questions

Closure

• List and explain the steps of protein synthesis.

HSA Practice

• Hemoglobin is an important protein in red blood cells. The DNA code for hemoglobin contains the following segment:

TGC-GGA-CTC-CTC Which of these is the messenger RNA code for

this segment of DNA?• A     ACG-CCT-GAA-GAA    • B     TCC-GGT-CTC-CTC    • C     ACG-CCU-GAG-GAG    • D     UGC-GGA-CUC-CUC

• This diagram shows the key steps for making proteins. In which step is messenger RNA being constructed?• A I• B II• C III• D IV

This diagram shows the key steps for making proteins. Which step involves transfer RNA?

A IB IIC IIID IV

• How many nucleotides are needed to code for one amino acid?• 1• 3• 4• 6

• Which RNA sequence is produced using the DNA sequence AGC-TAC-ACT?• A     UCG-AUG-UGA    • B     UCG-UAC-ACU    • C     TCG-ATG-TGA    • D     AGC-UAC-ACU