GENETICS AND EVOLUTION
MOLECULAR BASIS OF INHERITANCE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The evolution of telomerase enzyme
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DNA polymerase that cannot replicate the leading strand template to its 5’ end
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Gaps left at the 5’ end of the lagging strand because of the need for a 3’ onto which nucleotides can attach
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Gaps left at the 3’ end of the lagging strand because of the need for a primer
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Detailed explanation-1: -Unlike bacterial chromosomes, the chromosomes of eukaryotes are linear (rod-shaped), meaning that they have ends. These ends pose a problem for DNA replication. The DNA at the very end of the chromosome cannot be fully copied in each round of replication, resulting in a slow, gradual shortening of the chromosome.
Detailed explanation-2: -Telomerase adds complementary RNA bases to the 3′ end of the DNA strand. Once the 3′ end of the lagging strand template is sufficiently elongated, DNA polymerase adds the complementary nucleotides to the ends of the chromosomes; thus, the ends of the chromosomes are replicated.
Detailed explanation-3: -Abstract. Telomeres are chromosome-capping structures that protect ends of the linear genome from DNA damage sensors. However, these structures present obstacles during DNA replication. Incomplete telomere replication accelerates telomere shortening and limits replicative lifespan.
Detailed explanation-4: -At each cell division, the telomeres shorten because of the incomplete replication of the linear DNA molecules by the conventional DNA polymerases. This is called the end replication problem [6]. This is specifically due to the resection and fill-in reaction during the synthesis of the telomere leading-strand [7, 8].