6.5.1 Transcription and Translation: An Overview

Question 1

note

Answer 1

• The central dogma of molecular genetics as formulated by Francis Crick is that information flows from DNA to RNA to protein. The process is no longer considered dogma and has been substantiated by
  ample experimental evidence.
• DNA contains all of the information needed for protein synthesis and can be likened to the “master copy” of the information. For eukaryotic cells, the DNA is protected in the nucleus. During transcription, mRNA is like a scribe “transcribing” or making a new version of the master text. The scribe version is then translated into protein.
• The illustration at left shows the replication of the DNA of the prokaryotic chromosome. During transcription, a
  molecule of mRNA is synthesized along a template strand of DNA. Prokaryotic cells lack nuclei and so mRNA produced by transcription is immediately translated into a chain of amino acids.
• The eukaryotic cell has compartmentalized organelles.
  Transcription takes place in the nucleus and translation
  occurs in the cytoplasm. During transcription,
  messenger RNA is synthesized along a template DNA
  strand. The mRNA moves from the nucleus to the cytoplasm via nuclear pores. Translation occurs in the ribosomes. Transfer RNA molecules bring specific amino acids to a growing polypeptide strand. The sequence is dictated by the sequence of bases along the mRNA strand.

Question 2

The term’s transcriptionand translationdescribe the molecular processes by which information flows from DNA to RNA to protein.

Answer 2

· Transcription is the enzymatic process by which genetic information contained in one strand of DNA is used to direct the synthesis of a complementary sequence of bases of messenger RNA (mRNA).
· Translation is the synthesis of a polypeptide using the genetic information in the mRNA

Question 3

A ____________ is three bases on an mRNA strand that designate a particular amino acid.

Answer 3

• codon

Question 4

Which one of the following statements is false?

Answer 4

• In eukaryotes, translation occurs in the nucleus

Question 5

The process of synthesizing a strand of messenger RNA from a DNA template is known as:

Answer 5

• Transcription

Question 6

Which of the following is not a difference between RNA and DNA in eukaryotes?

Answer 6

• RNA is never found in the nucleus. DNA is always found in the nucleus

Question 7

A codon is a linear combination of three bases in a mRNA sequence. The codons are associated with specific tRNA’s (which, in turn, are associated with specific amino acids). There are 4 bases in mRNA, how many possible codons are there?

Answer 7

• 64

Question 8

The process of decoding messenger RNA to produce a protein is called:

Answer 8

• Translation