Question

Original DNA sequence (coding strand), starting at the beginning of the gener Normal: 5-ATGATCTCCTAATACAA... Mutation: 5'-TTGATCTCCTAATACAA... 30. Can a single nucleotide be a conserved sequence? Explain your answer. (4 points) 31. Explain why self-splicing introns support the RNA world first Hypothesis (life evolved via RNA). (3 Points) 32. How can the speed of DNA replication increase, while the rate of replication remains constant7 For example, if each chromosome in the human genome initiates DNA replication, at a rate of 50 bases per second, it would take two years to replicate the genome. Yet, it takes - 24 hours for cells to completely divide. How does the cell overcome this problem? (3 Points) 33. Druw the polypeptide R-V-Y (10 Points) (Be cognizant of space)

Answer 1

30.Many individual nucleotides located outside of well-defined conserved regions exhibit sequence conservation across multiple species. Such conservation may be due to mere chance or, for a certain fraction of these nucleotides, may reflect their importance for fitness and hence function.SCONE provides conservation scores for individual nucleotide positions, and can be applied to predict continuous sequence regions with an elevated level of conservation.Conserved sequences may be identified by homology search, using tools such as BLAST, HMMER and Infernal.^[16] Homology search tools may take an individual nucleic acid or protein sequence as input, or use statistical models generated from multiple sequence alignments of known related sequences.

31.spliceosomal introns indeed descend from group II introns and the latter are indeed self-splicing because they inherited their catalytic core from the RNA world.It provides evidence for ‘the idea that modern ribonucleoprotein enzymes evolved from a primordial “RNA world”.’The group I self-splicing intron can interact specifically with a guanosine cofactor.

32.The conundrum of DNA replication is that in humans the replication enzymes can copy at a rate of 50 base pairs per second. That may seem like a fast rate but there are 3.1 billion base pairs in the human genome. At that rate, if the machinery started at one end of the DNA and replicated all the way down to the other end, it would take ~ 2 years to copy one DNA molecule. Replication occurs much faster than that. DNA replication starts at many places along the molecule. These separate “origins of replication” form “replication bubbles”. Once a bubble forms, replication moves in both directions. These expanding bubbles of replication will eventually meet and the whole genome will be copied in a matter of hours rather than years.