Using a computer algorithm that searches for sequence similarities in other organisms, you discover that hexose kinase is a highly conserved gene that is expressed by many species, both prokaryotic and eukaryotic. The most closely related prokaryotic homolog of hexose kinase has a protein sequence in which 90% of the amino acids are identical to those of the human version of the gene. To learn more about their similarity at the DNA level, you obtain segments of the genomic DNA coding for the hexose kinase gene in both humans and this prokaryotic species. After combining both DNA samples, you heat them to denature the DNA strands and then allow them to cool and reanneal. Finally, you examine the DNA hybrids you obtain under the electron microscope. Practice Question 3 A) Your analysis reveals that there are three different DNA hybrids in this sample, these can be seen below. You reason that one must belong to the prokaryotic species, one to the humans and the third arose when one strand from each species base paired. Identify the origin of the DNA in each one of the observed structures by circling the correct answers below

A common feature of many eukaryotic mRNAs is the presence of a rather long 3′ UTR, which often contains consensus sequences. Creatine kinase B (CK-B) is an important enzyme in cellular metabolism. Certain cells—termed U937D cells—have lots of CK-B mRNA, but no CK-B enzyme is present. In these cells, the 5′ end of the CK-B mRNA is bound to ribosomes, but the mRNA is apparently not translated. Something inhibits the translation of the CK-B mRNA in these cells. Researchers introduced numerous short segments of RNA containing only 3′ UTR sequences into U937D cells. As a result, the U937D cells began to synthesize the CK-B enzyme, but the total amount of CK-B mRNA did not increase. The introduction of short segments of other RNA sequences did not stimulate the synthesis of CK-B; only the 3′ UTR sequences turned on the translation of the enzyme. On the basis of these results, propose a mechanism for the inhibition of CK-B translation in the U937D cells. Explain how the introduction of short…

A double-stranded fragment of viral DNA, one of whose strands is shown below, encodes two peptides, called vir-1 and vir-2. Adding this double-stranded DNA fragment to an in vitro transcription and translation system yields peptides of 10 residues (vir-1) and 5 residues (vir-2). Solve, (b) Determine the amino acid sequence of each peptide.

Human Chromosome 22 (48 × 106 nucleotide pairs in length) has about 700 protein-coding genes, which average 19,000 nucleotide pairs in length and contain an average of 5.4 exons, each of which averages 266 nucleotide pairs. What fraction of the average protein-coding gene is converted into mRNA? What fraction of the chromosome do these genes occupy?