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1 Review How does a cell interpret the genetic code Explain What are codons and anticodons 2 Review What happens during translation Compare and Contrast.

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Presentation on theme: "1 Review How does a cell interpret the genetic code Explain What are codons and anticodons 2 Review What happens during translation Compare and Contrast."— Presentation transcript:

1 1 Review How does a cell interpret the genetic code Explain What are codons and anticodons 2 Review What happens during translation Compare and Contrast How is protein synthesis different from DNA replication 3 Review Why is the genetic code considered universal Infer In what way does controlling the proteins in an organism control it’s characteristics 4 Choose one component of translation. Write a question about that component and use it to form a hypothesis that could be tested in an experiment

2 CH 13 RNA AND PROTEIN SYNTHESIS 13.2 Ribosomes and Protein Synthesis

3  Proteins are made from long chains of amino acids or polypeptides  20 different amino acids  Order of amino acids make proteins different.

4 Codon  Each three-letter “word” in mRNA  Consists of three consecutive bases that specify a single amino acid.

5 How to Read Codons  Four different bases in RNA, so 64 possible three- base codons (4×4×4 = 64)  To read a codon, start at the middle of the circle and move outward.

6

7  Starts with AUG  Has three stop codons.

8 Translation  Decoding of an mRNA message into a protein  From RNA to protein  Different languages.

9 Translation Steps  mRNA is transcribed in the nucleus and then enters the cytoplasm for translation.

10  Ribosome attaches to an mRNA molecule  Ribosome reads each codon of mRNA  Directs tRNA to bring the specified amino acid  Ribosome then attaches each amino acid to the growing chain.

11  tRNA has three unpaired bases or anticodon which is complementary to one mRNA codon  Codon AUG  Anticodon UAC.

12  Next codon is UUC  tRNA molecule with an AAG anticodon brings the amino acid to ribosome.

13  Ribosome helps form a peptide bond between 1 st and 2 nd amino acid  Bond between tRNA molecule and amino acid is broken  tRNA shifts to 3 rd site.

14  Ribosome moves over one codon  New tRNA enters ribosome  Process repeats itself.

15  Translation continues until a stop codon  Ribosome release polypeptide and mRNA.

16 Molecular Basis of Heredity  Most genes contain instructions for assembling proteins.

17 Proteins Can  Be enzymes  Produce pigment or odor  Regulate growth  Trigger development  Operate cell parts.

18 Gene Expression  What DNA actually ends up doing  How the genes gets expressed or shown.

19  Genetic code is nearly universal in all living organisms.

20 1. A certain gene has the following base sequence GACAAGTCCACAATC 2. Write this sequence down 3. From left to right, write the sequence of mRNA molecule transcribed from this gene 4. Using the figure on pg. 311, read the mRNA from left to right and write down the amino acid sequence 5. Repeat step 3 reading the codons from right to left.

21 Analyze and Conclude 1. Apply Concepts Why did steps 3 and 4 produce different polypeptides 2. Infer Do cells usually decode nucleotides in one direction only or in either direction


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