TRANSCRIPTION & TRANSLATION: From DNA to Protein

Chapter 11, Section 2 pgs. 288-295

Genes & Proteins• What is the function of a gene?• codes for traits, inherited from parents• Genes code for specific proteins• Proteins make up muscles, hair, tissues,

enzymes, & pigments• Protein Synthesis = reading the DNA,

forming RNA, using RNA to make the protein (DNA RNA Protein)

Replication DNADNA

Transcription DNA RNA

Translation RNA Amino Acids

Describe what you see in the diagram.

RNA pg. 288

• RNA is a nucleic acid (like DNA)

• Differs in structure from DNA:

DNA RNA

Number of Strands 2 1

Nucleotide Sugar Deoxyribose Ribose

Nitrogenous Base Pairs

Thymine(T), Adenine(A), Guanine (G), Cytosine (C)

Uracil (U), Adenine(A),

Guanine (G),

Cytosine (C)

Types of RNA – mRNA, rRNA, tRNA

• 1. Messenger RNA (mRNA) – Single strand – Transfers info from

the gene (made of DNA inside the nucleus) to make a protein

– mRNA carries genetic “message” from DNA to the ribosomes in the cytosol

• 2. Ribosomal RNA (rRNA)– Part of the structure of ribosomes– Ribosome = protein and rRNA

• 3. Transfer RNA• Transfers amino acids to the ribosome to make

protein

Transcription – DNA mRNA(occurs in nucleus) Figure 11.7 pg. 290

• Transcription = enzymes make RNA by copying a portion of DNA in the nucleus

• If a DNA sequence is AATCCGGA, what is the complimentary RNA sequence? (Remember RNA doesn’t have Thymine, it has Uracil instead)

• UUAGGCCU• The mRNA that gets sequenced is sent out

of the nucleus to help make protein

Genetic Code• A certain sequence of Nitrogenous Bases codes

for a specific Amino Acid needed to make a Protein

• Codon (on mRNA) = the nitrogenous bases of 3 adjacent nucleotides in mRNA that code for– Start Signal (starts the protein making process)

– Stop Signal (stops the protein making process)

– Amino Acid

• An amino acid can be coded for by more than one codon

• 20 amino acids combine in different combinations to make various proteins

Table 11.1 pg. 292, What do you see?

Translation – mRNA protein(occurs in cytoplasm) pg. 293

• Translation = using the mRNA to make protein, reading the codons

• Translation takes place at the ribosomes which attach to the mRNA

• tRNA (Fig. 11.8) is the carrier that comes in bringing the amino acid coded for by the mRNA codons

• tRNA has an anticodon that pairs up with the mRNA codon

• If an mRNA codon is UUG, what is the matching tRNA anticodon?

• AAC• As the amino acids are brought in peptide bonds

form between them to link them in a chain

Http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__how_translation_works.html