Protein Synthesis

Objectives

• Recognize that components that make up the genetic code are common to all organisms (TEKS 6B)

• Explain the purpose and process of transcription and

translation using models of DNA and RNA (TEKS 6C)

Remember… • Genes on a DNA molecule code for specific proteins. • Proteins are a bunch of amino acids put together to

form a polypeptide chain, which folds together to make a protein.

• Proteins are what makes YOU. From the cells in your body, to tissues, to organs; proteins are the building blocks of life. DNA is the blueprint that makes that happen.

• How exactly does DNA “code” for a protein?

The Universal Genetic Code

• The sequence of a gene is just a bunch of A, T, C, and G’s. The order of those nucleotides tell the cell what amino acid to make.

• Every three nucleotides makes up a codon.

-Codons produce specific amino acids -An amino acid may have more than one codon

-There are 20 amino acids, but 64 possible codons

-Some codons tell the ribosome to stop translating

• Proteins are made by joining these amino acids together into long polypeptides chains.

The Universal Genetic Code

The Universal Genetic Code • All living things from bacteria to humans have DNA which code for

these 20 amino acids. • The closer two species are in relation to one another, the

more of their genetic code will be shared or similar. • In fact, humans and primates share about 95% of their

genome (genetic code) • The order of the specific amino acids and thus the specific

proteins produced are what makes us unique from one another and from other species.

Central Dogma

Transcription Translation

The Universal Genetic Code

Let’s practice… DNA sequence: 5’ ATGGGAATT 3’ mRNA sequence? UACCCUUAA What are the codons? UAC CCU UAA What amino acids would be produced? Tyrosine Proline Stop

Objectives

• Recognize that components that make up the genetic code are common to all organisms (TEKS 6B)

• Explain the purpose and process of transcription and

translation using models of DNA and RNA (TEKS 6C)

RNA

Remember, RNA is made up of nucleotides like DNA. RNA is different from DNA though: -Has a ribose sugar instead of deoxyribose sugar -Has Uracil (U) instead of Thyamine (T) for one of its nitrogen bases -Is typically single stranded whereas DNA is a double stranded helix

RNA There are 3 different types of RNA which are involved in the transcription and translation process: • mRNA or messenger RNA. This RNA is the copied down RNA version of a specific gene.

mRNA is made in the nucleus and due to its small size, can fit through the nuclear pores of the nuclear membrane. It then enters the cytoplasm and carries its message to ribosomes to be translated.

• rRNA or ribosomal RNA. This RNA helps to form ribosomes. These complex structures physically move along an mRNA molecule, and catalyze the assembly of amino acids into protein chains. They also bind tRNAs and various accessory molecules necessary for protein synthesis.

• tRNA or transfer RNA. There is a specific tRNA for every codon on the mRNA strand. tRNA holds the specific amino acid for that codon. tRNA binds to its complementary mRNA strand and moves through the ribosome eventually leaving behind its amino acid. As different tRNAs bind and then leave behind their amino acid, a polypeptide chain is formed which then folds to create a specific protein.

Transcription and Translation EduSmart Video Video posted on carnahanbiology.weebly.com that is a good review video Pages 364-371