MCAT Biology Complete Exam
2026/2027 Updated Verified
Questions and Solutions A+
Pass Guaranteed
1. Central Dogma
- ANS - DNA → RNA → Protein
2. Purines
- which bases?
- how many rings?
- ANS -
3. Pyrimidines
- which bases?
- how many rings?
- ANS - Remember: "Pyrimidine" has a "y" in it; so does
"cytosine" and "thymine."
4. Phosphodiester Bond
- ANS - Joins one nucleotide to the next; between the 3rd C of one
ribose and the 5th C of the other to create the sugar-phosphate
backbone
,5. Directionality of DNA (convention)
- ANS - 5' → 3'
6. (but strands are antiparallel, so other strand is opposite)
7. 3' of DNA attached to ...
- ANS - OH
8. 5' of DNA attached to ...
- ANS - Phosphate group
9. DNA composition
- ANS - 1. Phosphate group
10. 2. 5-Carbon sugar
11. 3. Nitrogenous base (A, T, G, C)
12. Which nitrogenous bases form 2 hydrogen bonds?
- ANS - A, T
13. Which nitrogenous bases form 3 hydrogen bonds?
- ANS - G, C
14. Replisome
- ANS - Proteins that govern the replication process
15. Origin of replication
- ANS - Where replication begins. Prokaryotes have 1; eukaryotes
have many on each chromosome
,16. DNA synthesis: direction of synthesis
- ANS - 5' → 3'
17. (the DNA is read 3' → 5')
18. Steps of replication (5)
- ANS - 1. Helicase unzips double helix
19. 2. RNA polymerase builds a primer
20. 3. DNA polymerase adds leading/lagging strands
21. 4. Primers removed
22. 5. Okazaki fragments joined
23. RNA vs. DNA: differences
- ANS - RNA:
- C2 is oxygenated (has OH)
- Single stranded
- Uses uracil instead of thymine
- Can move through nuclear pores out of nucleus
24. DNA
- C2 is deoxygenaged (has H)
- Double stranded (double helix)
- Uses thymine
- Stuck in the nucleus
25. Transcription
- ANS - Process of making RNA (rRNA, mRNA, tRNA)
, 26. Promoter
- ANS - Required for transcription. Sequence of DNA nucleotides
that signals beginning point for transcription.
27. Primer
- ANS - Required for DNA replication
28. Consensus sequence
- ANS - Most common promoter sequences; closer the DNA
nucleotides are to the consensus sequence, the more tightly the
RNA polymerase can bind, which leads to more frequent
transcription (and vice versa)
29. RNA polymerase
- ANS - Synthesizes RNA in transcription
30. Transcription: Steps
- ANS - 1. Initiation - transcription factors, transcription initiation
complex (including RNA pol) finds promoter
31. 2. Elongation - Template/antisense DNA strand is read and
complementary RNA synthesized in 5' → 3' direction (same as DNA
synthesis); DNA is read in 3' → 5' (also same as DNA synthesis)
32. 3. Termination - temination sequence marks end, special
proteins dissociate RNA pol from DNA
33. Gene regulation
- ANS - Most occurs at transcription via repressors and activators,
which bind near promoter and affect activity of RNA polymerase
2026/2027 Updated Verified
Questions and Solutions A+
Pass Guaranteed
1. Central Dogma
- ANS - DNA → RNA → Protein
2. Purines
- which bases?
- how many rings?
- ANS -
3. Pyrimidines
- which bases?
- how many rings?
- ANS - Remember: "Pyrimidine" has a "y" in it; so does
"cytosine" and "thymine."
4. Phosphodiester Bond
- ANS - Joins one nucleotide to the next; between the 3rd C of one
ribose and the 5th C of the other to create the sugar-phosphate
backbone
,5. Directionality of DNA (convention)
- ANS - 5' → 3'
6. (but strands are antiparallel, so other strand is opposite)
7. 3' of DNA attached to ...
- ANS - OH
8. 5' of DNA attached to ...
- ANS - Phosphate group
9. DNA composition
- ANS - 1. Phosphate group
10. 2. 5-Carbon sugar
11. 3. Nitrogenous base (A, T, G, C)
12. Which nitrogenous bases form 2 hydrogen bonds?
- ANS - A, T
13. Which nitrogenous bases form 3 hydrogen bonds?
- ANS - G, C
14. Replisome
- ANS - Proteins that govern the replication process
15. Origin of replication
- ANS - Where replication begins. Prokaryotes have 1; eukaryotes
have many on each chromosome
,16. DNA synthesis: direction of synthesis
- ANS - 5' → 3'
17. (the DNA is read 3' → 5')
18. Steps of replication (5)
- ANS - 1. Helicase unzips double helix
19. 2. RNA polymerase builds a primer
20. 3. DNA polymerase adds leading/lagging strands
21. 4. Primers removed
22. 5. Okazaki fragments joined
23. RNA vs. DNA: differences
- ANS - RNA:
- C2 is oxygenated (has OH)
- Single stranded
- Uses uracil instead of thymine
- Can move through nuclear pores out of nucleus
24. DNA
- C2 is deoxygenaged (has H)
- Double stranded (double helix)
- Uses thymine
- Stuck in the nucleus
25. Transcription
- ANS - Process of making RNA (rRNA, mRNA, tRNA)
, 26. Promoter
- ANS - Required for transcription. Sequence of DNA nucleotides
that signals beginning point for transcription.
27. Primer
- ANS - Required for DNA replication
28. Consensus sequence
- ANS - Most common promoter sequences; closer the DNA
nucleotides are to the consensus sequence, the more tightly the
RNA polymerase can bind, which leads to more frequent
transcription (and vice versa)
29. RNA polymerase
- ANS - Synthesizes RNA in transcription
30. Transcription: Steps
- ANS - 1. Initiation - transcription factors, transcription initiation
complex (including RNA pol) finds promoter
31. 2. Elongation - Template/antisense DNA strand is read and
complementary RNA synthesized in 5' → 3' direction (same as DNA
synthesis); DNA is read in 3' → 5' (also same as DNA synthesis)
32. 3. Termination - temination sequence marks end, special
proteins dissociate RNA pol from DNA
33. Gene regulation
- ANS - Most occurs at transcription via repressors and activators,
which bind near promoter and affect activity of RNA polymerase
