Transcription and Translation Protein Synthesis Transcription and Translation

The Central Dogma of Biology The “Central Dogma of Biology” - genes hold the instructions for making proteins. DNA is used to make RNA which is used to make proteins. Involves the processes called Transcription and Translation

RNA (Ribonucleic Acid) Nucleotides

Comparing RNA to DNA DNA is double- stranded DNA nucleotides use Deoxyribose Sugar DNA bases Adenine Thymine Cytosine Guanine RNA is single- stranded RNA nucleotides use Ribose Sugar RNA bases Adenine Uracil Cytosine Guanine

Types of RNA Used in Protein Synthesis mRNA – carries the message from the DNA to the ribosome, where proteins are made tRNA – carries amino acids to the ribosomes to be used in building proteins. rRNA – composes part of the ribosome (the other part of the ribosome is made of protein). rRNA tRNA mRNA

Transcription Similar to replication Occurs in the nucleus of the cell The enzyme RNA polymerase is used to add RNA nucleotides to a growing polymer of RNA. C bonds to G A bonds to U (not T) Link to animation Occurs in the nucleus of the cell DNA is split apart and only one strand is transcribed. DNA is used as a template for RNA

DNA  RNA  Protein mRNA carries the genetic code from the DNA to the ribosome for translation

Translation Codon – three consecutive bases on mRNA that code for one amino acid Anticodon – three consecutive bases on tRNA that are complementary to a codon on the mRNA

Translation mRNA molecule attaches to the ribosome. tRNA molecules bring specified amino acids to the ribosome. The anticodon on the tRNA is complementary to a codon on the mRNA One at a time, the ribosome then attaches each amino acid to the growing chain. Animation

The Genetic Code How do we “read” the genetic code? The codon wheel shows which codons code for which amino acids. There are 64 possible different codons, but only 20 different amino acids, so some amino acids have more than one codon. There are also 3 different “stop” codons, which signal the end of translation.

The Genetic Code The Codons on mRNA determine the sequence of amino acids. Amino acids make proteins. Proteins determine traits!

The Genetic Code What amino acid sequence would be produced from this DNA sequence? T A G A C G T C G G A C A T A G C G A U C U G C A G C C U G U A U C G C Iso Cys Ser Leu Tyr Arg mRNA: Amino Acids

How do Proteins Determine Traits? The HBB gene is found on the 11th chromosome in humans at the location shown here The HBB gene holds the instructions for making part of a protein called hemoglobin, an important part of red blood cells.

How do Proteins Determine Traits? Mutations in the HBB gene can cause an altered form of hemoglobin, leading to a disease called sickle cell anemia.

How Do Proteins Determine Traits? The CFTR gene is located on human chromosome number 7. The CFTR gene holds the information for making an active transport protein called the CFTR protein. The CFTR protein pumps chlorine ions outside of lung cells

How Do Proteins Determine Traits? When the CFTR protein is functioning normally, it causes the mucus lining to lungs to be wet and thin. This helps the person cough up the mucus and anything harmful the mucus has trapped. When the CFTR protein is not functioning normally, the mucus outside of the lungs is dry and sticky, which causes it to stay trapped in the lungs, often making a person very sick.