Why can’t the lagging strand be synthesized in the same direction of the replication fork

Figure 14.14 You isolate a cell strain in which the joining of Okazaki fragments is impaired and suspect that a mutation has occurred in an enzyme found at the replication fork. Which enzyme is most likely to be mutated?

If the genetic code used 4 bases at a time, how many amino acids could be encoded?

How does DNA replication occur in a precise manner to ensure that identical genetic information is put into the new chromatid? See Figures 8.12 and 8.13. FIGURE 8.12 In DNA replication, the two polynucleotide strands uncoil, and each is a template for synthesizing a new strand. A replicated DNA molecule contains one new strand and one old strand. This mechanism is called semiconservative replication. FIGURE 8.13 A close-up look at the process of DNA replication. (a) As the strands uncoil, bases are added to the newly synthesized strand by complementary base pairing with bases in the template strand. The new bases are linked together by DNA polymerase. (b) DNA synthesis can proceed only in the 5 3 direction; newly synthesized DNA on one template strand is made in short segments and linked together by the enzyme DNA ligase.

Replication involves a period of time during which DNA is particularly susceptible to the introduction of mutations. If nucleotides can be incorporated into DNA at a rate of 20 nucleotides/second and the human genome contains 3 billion nucleotides, how long will replication take? How is this time reduced so that replication can take place in a few hours?

What percentage of the DNA in the genome actually corresponds to genes? How much is actually protein-coding exons? What makes up the rest?

Transcribe and translate the following DNA sequence (nontemplate strand): 5’-ATGGCCGGTTATTAAGCA-3’

Explain the events taking place at the replication fork. If the gene for helicase is mutated, what part of replication will be affected?

Define replication, transcription, and translation. In what part of the cell does each process occur?

Given the following tRNA anticodon sequence, derive the mRNA and the DNA template strand. Also, write out the amino acid sequence of the protein encoded by this message. tRNA: UAC UCU CGA GGC mRNA: protein: How many hydrogen bonds would be present in the DNA segment?