RNA & Protein Synthesis

Essential Question:How do our cells determine who we are?

Why are proteins important to living things?

• Control rate of chemical reactions as _e__________• Building materials for skin, bone, and _m_________• Help fight infections as _a__________________• Help control what goes in and out of cell through cell

_m____________________

nzymesuscles

ntibodies

embranes

1. What is a gene?

• Small section of DNA that holds code for making a particular protein, or for particular trait.

2. What is RNA? How is it different from DNA?

• Ribonucleic acid.• DNA has two strands, RNA only has one.• RNA has U (uracil) instead of T (thymine). The

other bases are the same (A, G, C).

3. What happens to DNA in the process of transcription?• DNA in nucleus is “unzipped.” A copy of one

strand is made in the form of messenger RNA (mRNA)

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

mRNA

DNA

4. Proteins are made by joining ___________________ into long chains called polypeptides.

amino acids

Protein molecule

5. Each polypeptide contains a combination of how many different amino acids? __________20

6. “Words” in the genetic code of DNA and RNA are made up of how many bases? __________3

7. How are codons translated into different amino acids?

• Codon made up of 3 nucleotide bases, e.g. AAG, CUA, etc.

• Each set of 3 bases translates into different amino acid, e.g. AAG = lysine,

• CUA = _________leucine

8. What do “start” and “stop” codons do?

• Start = beginning of polypeptide

• Stop = end of polypeptide.• If protein = paragraph,

polypeptide = sentence, amino acids = words.

Quick Lab: How does a cell interpret DNA?

1. A certain gene has the following sequence of nucleotides:

GACAAGTCCACAATC Write this sequence on your sheet of paper.

2. From left to right, write the sequence of the mRNA molecule transcribed from this gene:

CUGUUC AGGUGUUAG

Quick Lab: How does a cell interpret DNA?

3. Look at Figure 12-17. Reading the mRNA codons from left to right, write the amino acid sequence of the polypeptide translated from the mRNA.

CUGUUCAGGUGUUAG• CUG = ______________• UUC = ______________• AGG = ______________• UGU = ______________• UAG = ______________

LeucinePhenyl-alanine

ArginineCysteineStop

Quick Lab: How does a cell interpret DNA?

4. Repeat step 3, reading the codons from right to left.

CUGUUCAGGUGUUAG• GAU = ______________• UGU = ______________• GGA = ______________• CUU = ______________• GUC = ______________

Aspartic acidCysteineGlycineLeucineValine

Analyze and Conclude

1. Why did steps 3 and 4 produce different polypeptides?

Reading bases from left to right produces different codons from reading right to left.

Analyze and Conclude

2. Do cells usually decode nucleotides in one direction only or in either direction?

Usually one direction only

9. What happens to messenger RNA (mRNA) in the process of translation?• mRNA is translated into chains of amino acids that

form proteins.

9. What happens to messenger RNA (mRNA) in the process of translation?• mRNA is translated into chains of amino acids that

form proteins.

10. Explain the role of the following in protein synthesis: a. gene

Contains code for making a protein

10. Explain the role of the following in protein synthesis: b. mRNA

Copy of gene that can be taken out of nucleus into cytoplasm.

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

mRNA

DNA

10. Explain the role of the following in protein synthesis: c. tRNA

Transfers amino acids over to mRNA, where they can be joined together to form protein.

10. Explain the role of the following in protein synthesis: d. codon

3-letters/bases on mRNA that holds code for 1 amino acid

10. Explain the role of the following in protein synthesis: e. anticodon

3 letters/bases on tRNA that match with codon on mRNA

anticodon

codon

10. Explain the role of the following in protein synthesis: f. ribosome

Helps join amino acids together to form protein/polypeptide

ribosome

10. Explain the role of the following in protein synthesis: g. amino acid

Molecules that join together to form protein

Protein molecule

Video: Protein Synthesis

http://www.youtube.com/watch?v=D3fOXt4MrOM

Pop Quiz: Copy the codons below and identify the corresponding amino acids. p. 303

1. GCU = __________2. CAA = __________3. UGG = __________4. AUG = __________5. CAU = __________

alanineglutaminetryptophanmethioninehistidine

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