BIO 141 EXAM 3 2025/2026 BANK CURRENTLY
TESTING 2 VERSIONS COMPLETE ACTUAL
QUESTIONS WITH DETAILED VERIFIED ANSWERS
EXPERT VERIFIED /ALREADY GRADED A+.
1. the central dogma of molecular biology
...ANSWER... The flow of genetic information from DNA to RNA to protein.
2. Name the pyrimidine bases found in DNA.
...ANSWER... Cytosine and Thymine.
3. What type of bond connects the sugar-phosphate backbones of the DNA double helix
...ANSWER... Phosphodiester bonds.
4. During DNA replication, which enzyme synthesizes the RNA primer
...ANSWER... Primase.
5. the function of DNA ligase
...ANSWER... Joins the Okazaki fragments on the lagging strand.
6. Define the term 'semiconservative replication'.
...ANSWER... Each new DNA molecule consists of one old (parental) strand and one new
(daughter) strand.
7. a point mutation
...ANSWER... A change in a single nucleotide pair in a DNA sequence.
8. the start codon for protein synthesis, and which amino acid does it code for
...ANSWER... AUG; Methionine.
9. What are the three stop codons
...ANSWER... UAA, UAG, UGA.
10. the role of tRNA in translation
...ANSWER... To bring the correct amino acid to the ribosome based on the mRNA codon.
11. the primary transcript in eukaryotic gene expression
...ANSWER... The initial RNA transcript before processing (pre-mRNA).
12. What are introns and exons
...ANSWER... Introns are non-coding intervening sequences; exons are coding sequences that
are expressed.
13. the function of the spliceosome
,...ANSWER... To remove introns and join exons from a pre-mRNA molecule.
14. the purpose of the 5' cap and poly-A tail added to eukaryotic mRNA
...ANSWER... To protect the mRNA from degradation and facilitate its export from the nucleus
and ribosome binding.
15. Define a 'frameshift mutation'.
...ANSWER... An insertion or deletion of nucleotides that is not a multiple of three, altering the
reading frame.
16. the name of the complex where transcription occurs in prokaryotes
...ANSWER... The transcription bubble.
17. a promoter
...ANSWER... A specific DNA sequence where RNA polymerase binds to initiate transcription.
18. the role of RNA polymerase
...ANSWER... To catalyze the synthesis of RNA from a DNA template.
19. In a bacterial operon, the function of the operator
...ANSWER... It is the DNA sequence where a repressor protein binds to block transcription.
20. Name the parts of a nucleotide.
...ANSWER... A nitrogenous base, a pentose sugar, and one or more phosphate groups.
21. What does it mean for the two strands of DNA to be 'antiparallel'
...ANSWER... One strand runs 5' to 3', while the other runs 3' to 5'.
22. Which enzyme relieves the strain caused by the unwinding of the DNA double helix during
replication
...ANSWER... Topoisomerase (e.g., DNA gyrase).
23. the function of single-strand binding proteins
...ANSWER... To bind to and stabilize single-stranded DNA after the double helix is unwound.
24. the key difference between the leading and lagging strands during DNA replication
...ANSWER... The leading strand is synthesized continuously toward the replication fork, while
the lagging strand is synthesized discontinuously away from the fork in Okazaki fragments.
25. a telomere and its function
...ANSWER... The repetitive nucleotide sequence at the ends of eukaryotic chromosomes; it
protects genes from being eroded during repeated rounds of replication.
26. What enzyme maintains telomere length
...ANSWER... Telomerase.
, 27. the primary level of packing for eukaryotic DNA
...ANSWER... The nucleosome, where DNA is wrapped around histone proteins.
28. a codon
...ANSWER... A three-nucleotide sequence on mRNA that codes for a specific amino acid.
29. the 'wobble' hypothesis
...ANSWER... The third base in a codon can form non-standard base pairs, allowing a single
tRNA to recognize multiple codons.
30. What are the P, A, and E sites of a ribosome
...ANSWER... P site holds the tRNA carrying the growing polypeptide chain; A site holds the
tRNA carrying the next amino acid; E site is the exit site for discharged tRNAs.
31. a signal peptide and its role
...ANSWER... A sequence at the leading end of a polypeptide that targets the protein to the
endoplasmic reticulum.
32. a silent mutation
...ANSWER... A nucleotide change that codes for the same amino acid, resulting in no change to
the protein.
33. a missense mutation
...ANSWER... A nucleotide change that results in one amino acid being substituted for another.
34. a nonsense mutation
...ANSWER... A nucleotide change that changes an amino acid codon into a stop codon, leading
to a truncated protein.
35. What are mutagens
...ANSWER... Physical or chemical agents that can cause mutations in DNA.
36. the function of the TATA box in eukaryotic promoters
...ANSWER... It is a key DNA sequence for the initiation of transcription, where transcription
factors bind.
37. What are transcription factors
...ANSWER... Proteins that assist RNA polymerase in binding to the promoter and initiating
transcription in eukaryotes.
38. alternative RNA splicing
...ANSWER... When different combinations of exons from the same primary transcript are
joined, allowing one gene to code for multiple proteins.
39. the lac operon and in what type of organism is it found
...ANSWER... A cluster of genes involved in lactose metabolism; found in E. coli (prokaryotes).
TESTING 2 VERSIONS COMPLETE ACTUAL
QUESTIONS WITH DETAILED VERIFIED ANSWERS
EXPERT VERIFIED /ALREADY GRADED A+.
1. the central dogma of molecular biology
...ANSWER... The flow of genetic information from DNA to RNA to protein.
2. Name the pyrimidine bases found in DNA.
...ANSWER... Cytosine and Thymine.
3. What type of bond connects the sugar-phosphate backbones of the DNA double helix
...ANSWER... Phosphodiester bonds.
4. During DNA replication, which enzyme synthesizes the RNA primer
...ANSWER... Primase.
5. the function of DNA ligase
...ANSWER... Joins the Okazaki fragments on the lagging strand.
6. Define the term 'semiconservative replication'.
...ANSWER... Each new DNA molecule consists of one old (parental) strand and one new
(daughter) strand.
7. a point mutation
...ANSWER... A change in a single nucleotide pair in a DNA sequence.
8. the start codon for protein synthesis, and which amino acid does it code for
...ANSWER... AUG; Methionine.
9. What are the three stop codons
...ANSWER... UAA, UAG, UGA.
10. the role of tRNA in translation
...ANSWER... To bring the correct amino acid to the ribosome based on the mRNA codon.
11. the primary transcript in eukaryotic gene expression
...ANSWER... The initial RNA transcript before processing (pre-mRNA).
12. What are introns and exons
...ANSWER... Introns are non-coding intervening sequences; exons are coding sequences that
are expressed.
13. the function of the spliceosome
,...ANSWER... To remove introns and join exons from a pre-mRNA molecule.
14. the purpose of the 5' cap and poly-A tail added to eukaryotic mRNA
...ANSWER... To protect the mRNA from degradation and facilitate its export from the nucleus
and ribosome binding.
15. Define a 'frameshift mutation'.
...ANSWER... An insertion or deletion of nucleotides that is not a multiple of three, altering the
reading frame.
16. the name of the complex where transcription occurs in prokaryotes
...ANSWER... The transcription bubble.
17. a promoter
...ANSWER... A specific DNA sequence where RNA polymerase binds to initiate transcription.
18. the role of RNA polymerase
...ANSWER... To catalyze the synthesis of RNA from a DNA template.
19. In a bacterial operon, the function of the operator
...ANSWER... It is the DNA sequence where a repressor protein binds to block transcription.
20. Name the parts of a nucleotide.
...ANSWER... A nitrogenous base, a pentose sugar, and one or more phosphate groups.
21. What does it mean for the two strands of DNA to be 'antiparallel'
...ANSWER... One strand runs 5' to 3', while the other runs 3' to 5'.
22. Which enzyme relieves the strain caused by the unwinding of the DNA double helix during
replication
...ANSWER... Topoisomerase (e.g., DNA gyrase).
23. the function of single-strand binding proteins
...ANSWER... To bind to and stabilize single-stranded DNA after the double helix is unwound.
24. the key difference between the leading and lagging strands during DNA replication
...ANSWER... The leading strand is synthesized continuously toward the replication fork, while
the lagging strand is synthesized discontinuously away from the fork in Okazaki fragments.
25. a telomere and its function
...ANSWER... The repetitive nucleotide sequence at the ends of eukaryotic chromosomes; it
protects genes from being eroded during repeated rounds of replication.
26. What enzyme maintains telomere length
...ANSWER... Telomerase.
, 27. the primary level of packing for eukaryotic DNA
...ANSWER... The nucleosome, where DNA is wrapped around histone proteins.
28. a codon
...ANSWER... A three-nucleotide sequence on mRNA that codes for a specific amino acid.
29. the 'wobble' hypothesis
...ANSWER... The third base in a codon can form non-standard base pairs, allowing a single
tRNA to recognize multiple codons.
30. What are the P, A, and E sites of a ribosome
...ANSWER... P site holds the tRNA carrying the growing polypeptide chain; A site holds the
tRNA carrying the next amino acid; E site is the exit site for discharged tRNAs.
31. a signal peptide and its role
...ANSWER... A sequence at the leading end of a polypeptide that targets the protein to the
endoplasmic reticulum.
32. a silent mutation
...ANSWER... A nucleotide change that codes for the same amino acid, resulting in no change to
the protein.
33. a missense mutation
...ANSWER... A nucleotide change that results in one amino acid being substituted for another.
34. a nonsense mutation
...ANSWER... A nucleotide change that changes an amino acid codon into a stop codon, leading
to a truncated protein.
35. What are mutagens
...ANSWER... Physical or chemical agents that can cause mutations in DNA.
36. the function of the TATA box in eukaryotic promoters
...ANSWER... It is a key DNA sequence for the initiation of transcription, where transcription
factors bind.
37. What are transcription factors
...ANSWER... Proteins that assist RNA polymerase in binding to the promoter and initiating
transcription in eukaryotes.
38. alternative RNA splicing
...ANSWER... When different combinations of exons from the same primary transcript are
joined, allowing one gene to code for multiple proteins.
39. the lac operon and in what type of organism is it found
...ANSWER... A cluster of genes involved in lactose metabolism; found in E. coli (prokaryotes).
