Biology 12

Chapter 8 Protein Synthesis • MHR 281

CHAPTER 8 REVIEW

Summary of Expectations

Briefly explain each of the following points.

• The four different nucleotides found in DNA
  make up the genetic “words” that code for all
  20 different amino acids. (8.1)


• The two-step process of gene expression has
  both costs and benefits for cells. (8.1, 8.4)


• The genetic code is redundant but not
  ambiguous. (8.1)


• Many transcripts can be simultaneously
  produced from a single gene. (8.2)


• Several types of processing are required before
  a pre-mRNA transcript can meet the needs of a
  eukaryotic cell. (8.2, 8.4)


• Four different types of RNA are involved in
  the main steps of protein synthesis. (8.2, 8.3)


• In prokaryotes, translation can begin before
  transcription is done. (8.2)


• The process of translation involves enzymes
  both inside and outside the ribosomes. (8.3)


• An active ribosome complex has at least four
  RNA binding sites. (8.3)


• An E. colicell will only produce lactose-
  metabolizing enzymes if lactose is present in
  the cell’s environment. (8.4)


• Crick’s “central dogma” does not fully capture
  the process of gene expression. (8.1, 8.4)

Language of Biology

Write a sentence including each of the following

words or terms. Use any six terms in a concept map

to show your understanding of how they are related.

• codon • anticodon


• triplet hypothesis • amino acid attachment


• transcription site


• translation • amino-acyl tRNA


• reading frame (aa-tRNA)


• initiation • activating enzyme


• elongation • ribosome


• messenger RNA (mRNA) • ribosomal RNA (rRNA)


• termination • translocation


• processing • release factor


• sense strand • polyribosome


• anti-sense strand • operon


• promoter sequence • operator


• RNA polymerase • repressor


• precursor mRNA • negative gene
  (pre-mRNA) regulation


• 5 ′cap • inducer


• poly-A tail • activator


• spliceosome • positive gene


• small nuclear RNA regulation
  (snRNA) • co-repressor


• transfer RNA (tRNA) • transcription factors

1.A given organism has many different tissues,
yet its cells all carry the same genetic
information. Explain how this is possible.

2.Identify the significance of the discovery that
the specific arrangement of amino acids is
directly related to the structure of specific
proteins.

3.Describe how Crick tested the triplet hypothesis.

4.What is the codon concept?

5.What was the term Crick coined to describe
the process by which he believed genes were
expressed? Why did he choose this term?

6.How is it possible for information on DNA that
is confined to the nucleus of a eukaryotic cell
to be expressed as protein products outside the
nucleus?

7.How did Nirenberg and Matthaei begin
working out the genetic code?

8.Identify the amino acids coded for by the
following codons: AGC, GUU, UAU, AUG.

9.Name three characteristics of the genetic code

and explain why they are important.

10.One species of bacteria manufactures 37

different tRNA molecules. Explain how these

bacteria can still match anticodons to all of

the 64 different potential mRNA codons.

11.RNA transcription in eukaryotes consists of

four steps. Identify and describe each.

12.Define the term “sense strand.” What is its

counterpart called, and why?

13.Explain how activating enzymes work.

14.What causes RNA polymerase to cease

transcription?

15.Draw a diagram that illustrates the main steps

in the elongation cycle of translation. What

enzymes play a role in maintaining this cycle?

16.Identify two different mechanisms that help

a single gene produce very high levels of a

polypeptide product in a short time.

UNDERSTANDING CONCEPTS