The gene for the hemoglobin b subunit is 1,420 bp long and contains two introns

Question

The gene for the hemoglobin b subunit is 1,420 bp long and contains two introns that are 131 bp and 851 bp long. How long is the b-subunit polypeptide?

146 amino acids long

327 amino acids long

438 amino acids long

473 amino acids long

2,140 amino acids long

Which statement is correct:
A. DNA replication is initiated at promoter sequences in the DNA
B. RNA polymerase requires primers to initiate RNA synthesis
C. Okazaki fragments are the short fragments of DNA that are produced on the leading strand at the DNA replication fork.

D. Transcription is terminated at stop codons in the mRNA

E. The 5' to 3' direction of DNA synthesis implies that deoxyribonucleotides are added to the 3' OH group on the

growing strand.

Explanation / Answer

1. Answer A: 146 amino acids long

The beta subunit of hemoglobin is 146 amino acids long and has a total molecular weight as 15,867 Dalton.

2. E. The 5' to 3' direction of DNA synthesis implies that deoxyribonucleotides are added to the 3' OH group on the growing strand.

- DNA replication starts at origin of replication and not at the promoter site.

- RNA polymerase does not require primers.

- DNA polymerase requires primers since it cannot start afresh synthesis.

- Okazaki fragments are present in the lagging strand and not leading.

- Translation is terminated by stop codons. Transcription is terminated by rho factor or without rho factor.

Option E is the only correctly stated statement.

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