Question 1 of 10
Which class of biomolecule is built from nucleotide monomers?
ACarbohydrates
BProteins
CLipids
DNucleic acids (DNA and RNA)
Explanation
Nucleic acids (DNA, RNA) are polymers of nucleotide monomers — each nucleotide is a phosphate + sugar + nitrogenous base. Distractors: Proteins are polymers of *amino acids*. Carbohydrates are polymers of *monosaccharides* (e.g., glucose). Lipids are not true polymers — they assemble from fatty acids and glycerol but don't repeat a single monomer.
Question 2 of 10
During which phase of the cell cycle does DNA replication occur? 
AG2 phase
BM phase
CG1 phase
DS phase
Explanation
📌 DNA replication occurs during S phase (Synthesis) of interphase.
Interphase: G1 → S → G2, then Mitosis.
Interphase: G1 → S → G2, then Mitosis.
Question 3 of 10
Alternative splicing allows:
Achromosomes to separate
Bone gene to code for multiple proteins
CDNA to be repaired
Dmutations to be prevented
Explanation
📌 One gene → multiple proteins by including/excluding different exons. Increases protein diversity without needing more genes.
Question 4 of 10
Epigenetics studies how:
ADNA sequence changes
Bcells divide
Corganisms evolve
Dgene expression changes without altering DNA sequence
Explanation
📌 Epigenetics = changes in gene expression WITHOUT changing DNA sequence.
Mechanisms: DNA methylation, histone modification.
Affected by environment, diet, stress.
Mechanisms: DNA methylation, histone modification.
Affected by environment, diet, stress.
Question 5 of 10
Which molecule carries energy from glucose breakdown to the electron transport chain?
ACO2
BH2O
CNADH
DATP
Explanation
📌 NADH and FADH2 are electron carriers. They transport high-energy electrons from glycolysis and Krebs cycle to the ETC.
Question 6 of 10
The graph shows the change in a moth population over time. Dark moths increased after industrial pollution darkened tree bark. This is an example of:
AGenetic engineering
BArtificial selection
CNatural selection
DSpontaneous generation
Explanation
📌 This is the classic peppered moth example of natural selection.
Before pollution: light bark → light moths camouflaged → survived
After pollution: dark bark → dark moths camouflaged → survived
The environment selected for the trait that provided camouflage.
Before pollution: light bark → light moths camouflaged → survived
After pollution: dark bark → dark moths camouflaged → survived
The environment selected for the trait that provided camouflage.
Question 7 of 10
A student designed an experiment to test how light affects plant growth. Identify the components of this experiment. 
AIndependent: water; Dependent: soil
BIndependent: light; Dependent: plant height
CIndependent: plant height; Dependent: light
DIndependent: temperature; Dependent: light
Explanation
📌 Independent variable = what you change (light)
Dependent variable = what you measure (plant height)
Control group = no light (to compare against)
Constants = same soil, water, temperature, pot size
Dependent variable = what you measure (plant height)
Control group = no light (to compare against)
Constants = same soil, water, temperature, pot size
Question 8 of 10
In a DNA nucleotide, which component carries the genetic code through its specific sequence?
APhosphate group
BDeoxyribose sugar
CHydrogen bond
DNitrogenous base
Explanation
The nitrogenous base (adenine, thymine, guanine, or cytosine) is the part of a DNA nucleotide that varies — its sequence along the strand IS the genetic code. The phosphate and deoxyribose sugar are identical in every nucleotide and form the structural 'backbone' of the DNA strand; they don't store information. Hydrogen bonds hold the two strands together at the bases but are not part of a single nucleotide.
Question 9 of 10
The carbon cycle involves:
Athe movement of carbon through living and non-living systems
Bonly the ocean
Conly the atmosphere
Donly living organisms
Explanation
📌 Carbon moves through: atmosphere (CO₂) → photosynthesis → organisms → respiration/decomposition → atmosphere.
Also: fossil fuels → combustion → atmosphere.
Also: fossil fuels → combustion → atmosphere.
Question 10 of 10
Use the Punnett square to determine the probability of offspring with the homozygous recessive (aa) genotype.
A0
B3/4 (75%)
C1/4 (25%)
D1/2 (50%)
Explanation
Aa × Aa cross: AA, Aa, Aa, aa. Only one box (aa) shows the homozygous recessive: 1/4 = 25%.