Chapter Ten: Molecular Biology of the Gene

Questions:

1. What is DNA composed of?
2. What occurs during transcription?
3. What is elongation?

Answers:

1. DNA is composed of two nucleotide chains joined together by hydrogen bonding between bases, twisted into a helical shape.  The sugar phosphate backbone is on the outside.
2. The two DNA strands separate.  One strand is used as a pattern to produce an RNA chain, using specific base pairing.  RNA polymerase catalyzes the reaction.
3. Elongation is the addition of  amino acids to a polypeptide chain.  Each cycle has three steps: codon recognition, peptide bond formation, and translocation.

Important Facts:

1. DNA replication follows a semi-conservative model. The two DNA strands separate and then each strand is used as a pattern to produce a complimentary strand, using specific base pairing. Each new DNA helix has one old strand with one new strand.  
2. A gene is a sequence of DNA that directs the synthesis of a specific protein.  DNA is transcribed into RNA and then RNA is translated into a protein.  The actions of proteins determine the phenotype of an organism.
3. The one gene–one enzyme hypothesis was based on studies of inherited metabolic diseases.  The one gene-one protein hypothesis expands the relationship to proteins other than enzymes. 
4.  Initiation brings together the components  needed to begin RNA synthesis.  It occurs in 2 steps.  mRNA binds to a small ribosomal subunit, and the first tRNA binds to mRNA at the start codon.  A large ribosomal subunit joins the small subunit, allowing the ribosome to function.
5. Emerging viruses cause human diseases through mutation, contact between species, and spread from isolated populations.  

Key Terms:

Bacteriophage- viruses that infect bacterial cells.

Viruses- invaders that sabotage our cells.

DNA polymerase- adds nucleotides to a growing chain.

DNA ligase- joins small fragments into a continuous chain.

Messenger RNA- contains codons for protein sequences.

Introns- interrupting sequences. 

Exons- the coding regions. 

RNA Splicing- removal of introns and joining of exons to produce a continuous coding sequence.

Transfer RNA- match an amino acid to its corresponding mRNA codon.

Anticodon- allows the tRNA to bind to a specific mRNA codon, complementary in sequence.

 

Diagram:

Relevant Video: 

http://www.youtube.com/watch?v=-mtLXpgjHL0