Question

Given that the chromosomes of mammalian cells may be 20 times as large as that of an Escherichia coli chromosome, how can replication of mammalian chromosomes be carried out in just a few minutes?

a) The presence of histones speeds up the rate of eukaryotic chromosomal DNA replication
b) Different RNA polymerases carry out replication simultaneously on eukaryotic chromosomal DNA
c) The higher temperature of mammalian cells allows for an exponentially higher replication rate
d) Hundreds of replication forks work simultaneously on each piece of eukaryotic chromosomal DNA
e) Eukaryotic DNA polymerases are extraordinarily fast compared with prokaryotic polymerases

Answer 1

Mammalian cells replicate their DNA quickly by using multiple origins of replication, allowing many replication forks to work at once(OPTION D).

Step-by-step explanation:

The replication of mammalian chromosomes can be carried out quickly despite their large size because eukaryotic cells utilize multiple origins of replication simultaneously. While replication in prokaryotes like Escherichia coli is initiated at a single origin, eukaryotic chromosomes can have up to 100,000 origins of replication. This allows for hundreds of replication forks to work simultaneously, speeding up the process considerably despite eukaryotic polymerases having a slower nucleotide addition rate compared to their prokaryotic counterparts.

Answer (d) "Hundreds of replication forks work simultaneously on each piece of eukaryotic chromosomal DNA" is correct and explains how eukaryotic cells can replicate their DNA quickly despite having larger chromosomes compared to prokaryotes.