17. When errors in nucleotide sequencing occur,

a. DNA polymerases replaces the incorrect nucleotide with the correct nucleotide
b. enzymes dissolve the incorrect nucleotide so DNA polymerase can add the correct one
c. purines replace pyrimidines in the DNA molecule
d. DNA polymerase proofreads for errors while another enzyme corrects it
A?

18. Which of the following is NOT a step in transcription?
a. RNA polymerase unwinds the double helix of the transfer RNA
b. RNA polymerase attaches to a gene's promoter region on a strand of DNA
c. RNA polymerase adds complementary RNA nucleotides to the growing strand of RNA
d. RNA polymerase unwinds and separates the DNA strands
D?

19. During translation, the amino acid detaches from the transfer RNA molecule and attaches to the end of a growing protein chain when
a. the ribosomal RNA anticodon binds to the messenger RNA codon
b. the transfer RNA anticodon binds to the messenger RNA codon
c. a "stop" codon is encountered
d. the protein chain sends a signal through the nerve cells to the brain
Not sure...

21. Which of the following procedures is NOT a usual step in a genetic engineering experiment?
a. inducing a mutation in a source of chromosome
b. cleaving DNA with a restriction enzyme
c. recombining pieces of DNA from different species
d. cloning and screening target cells
I'm not sure between A and C, but I think it's C...

Thanks
-MC

17. The correct answer is D. DNA polymerase proofreads for errors while another enzyme corrects it. When errors occur in nucleotide sequencing, DNA polymerase, which is the enzyme responsible for synthesizing new DNA strands, performs proofreading. It checks for any mistakes made during nucleotide incorporation and corrects them. Another enzyme, called exonuclease, is responsible for removing the incorrect nucleotide and allowing DNA polymerase to replace it with the correct nucleotide.

18. The correct answer is A. RNA polymerase unwinds the double helix of the transfer RNA. Transcription is the process through which RNA molecules are synthesized from a DNA template. The steps in transcription include RNA polymerase binding to the promoter region of a gene on the DNA strand, unwinding and separating the DNA strands, and RNA polymerase adding complementary RNA nucleotides to form the growing RNA strand. RNA polymerase does not directly interact with transfer RNA (tRNA) molecules during transcription.

19. The correct answer is B. The transfer RNA (tRNA) anticodon binds to the messenger RNA (mRNA) codon. Translation is the process in which the information encoded in mRNA molecules is used to assemble proteins. During translation, ribosomes read the codons on the mRNA molecule, and tRNA molecules with complementary anticodons bring the corresponding amino acid to the ribosome. The amino acid then detaches from the tRNA molecule and attaches to the growing protein chain. This attachment occurs when the tRNA anticodon matches the mRNA codon at the ribosome.

21. The correct answer is A. Inducing a mutation in a source of chromosome is not a usual step in a genetic engineering experiment. Genetic engineering involves manipulating the genetic material of an organism to achieve desired traits or outcomes. Common steps in a genetic engineering experiment include cleaving DNA with restriction enzymes to create DNA fragments, recombining pieces of DNA from different species (recombinant DNA technology), and cloning and screening target cells to identify organisms with the desired genetic modifications. Inducing a mutation in a chromosome source is not typically part of genetic engineering experiments.