Biology Practice Question

Fall 2025

Q: Which characteristic is required for something to be considered alive?
A. Photosynthesis
B. Ability to evolve
C. Having a nucleus
D. Multicellularity

A: B
~
Explanation: All living organisms must evolve; the others are not universal traits.

Q: According to the Cell Theory, where do new cells come from?
A. Spontaneous generation
B. DNA replication alone
C. Pre-existing cells
D. Abiotic synthesis

A: C
~
Explanation: Pasteur’s experiment showed cells arise only from other cells.

Q: What defines a nonpolar amino acid?
A. It has oxygen in the R-group
B. It carries a charge
C. It lacks charge and has no polar atoms
D. It is extremely reactive

A: C
~
Explanation: Nonpolar R-groups contain mostly hydrocarbons and do not hydrogen-bond with water.

Q: Which bond forms between amino acids during protein synthesis?
A. Glycosidic
B. Hydrogen
C. Peptide
D. Ionic

A: C
~
Explanation: Peptide bonds link amino acids through condensation reactions.

Q: Secondary protein structure is stabilized mostly by:
A. Peptide bonds
B. Hydrogen bonds
C. Hydrophobic interactions
D. Disulfide bridges

A: B
~
Explanation: Hydrogen bonds between backbone groups form α-helices and β-sheets.

Q: What forms the sugar-phosphate backbone of DNA?
A. Peptide linkages
B. Phosphodiester bonds
C. Ionic attractions
D. Van der Waals forces

A: B
~
Explanation: Nucleotides are linked by phosphodiester bonds during polymerization.

Q: Why is RNA more reactive than DNA?
A. It uses uracil
B. It has a 2’ OH group
C. It has more phosphates
D. It is double stranded

A: B
~
Explanation: The 2' hydroxyl makes RNA more susceptible to hydrolysis.

Q: What structure forms spontaneously when phospholipids contact water?
A. Two DNA helices
B. Micelles or bilayers
C. Peptide chains
D. Ribosomes

A: B
~
Explanation: Amphipathic molecules assemble to shield hydrophobic tails from water.

Q: Which molecule crosses a membrane most easily?
A. Na⁺
B. Glucose
C. Water
D. O₂

A: D
~
Explanation: Small nonpolar molecules diffuse rapidly across membranes.

Q: What happens to an animal cell in a hypertonic solution?
A. It swells
B. It bursts
C. It shrinks
D. Nothing changes

A: C
~
Explanation: Water exits the cell, causing it to shrivel.

Q: What type of membrane protein allows facilitated diffusion of ions?
A. Pumps
B. Channels
C. Ribosomes
D. Enzymes

A: B
~
Explanation: Ion channels permit passive movement along electrochemical gradients.

Q: Where is DNA found in prokaryotic cells?
A. Nucleus
B. Lysosome
C. Nucleoid region
D. Mitochondria

A: C
~
Explanation: Prokaryotes lack membrane-bound nuclei.

Q: What happens during anaphase of mitosis?
A. Nuclear envelope reforms
B. Sister chromatids separate
C. Chromosomes condense
D. Spindle breaks down

A: B
~
Explanation: Cohesin proteins are cleaved and chromatids move to opposite poles.

Q: What activates Cdk in MPF?
A. Removal of an inhibitory phosphate
B. Binding of ubiquitin
C. High levels of glucose
D. Formation of Okazaki fragments

A: A
~
Explanation: Cdk activation requires cyclin binding + dephosphorylation.

Q: What separates in meiosis I?
A. Sister chromatids
B. Homologous chromosomes
C. DNA strands
D. Ribosomes

A: B
~
Explanation: Meiosis I reduces ploidy by separating homologs.

Q: Crossing over occurs during:
A. Prophase I
B. Metaphase II
C. Anaphase I
D. Cytokinesis

A: A
~
Explanation: Synapsis and recombination occur only in prophase I.

Q: Which of the following is an example of incomplete dominance?
A. Blood type AB
B. Pink snapdragons from red + white parents
C. Coat color in labs
D. Height in humans

A: B
~
Explanation: Intermediate phenotypes indicate incomplete dominance.

Q: What type of mutation creates a premature stop codon?
A. Silent
B. Missense
C. Nonsense
D. Frameshift

A: C
~
Explanation: Nonsense mutations introduce STOP codons.

Q: What is the function of helicase?
A. Adds RNA primers
B. Unwinds the DNA helix
C. Repairs mutations
D. Removes Okazaki fragments

A: B
~
Explanation: Helicase disrupts hydrogen bonds to open the replication fork.

Q: What enzyme removes RNA primers and replaces them with DNA?
A. DNA pol III
B. Ligase
C. DNA pol I
D. Primase

A: C
~
Explanation: DNA polymerase I excises primers and fills gaps.

Q: What is PCR used for?
A. Protein folding
B. DNA amplification
C. Chromosome segregation
D. Translation initiation

A: B
~
Explanation: PCR exponentially increases DNA quantity via cycles of heating/cooling.

Q: What recognizes promoters in bacteria?
A. General transcription factors
B. Sigma factor
C. TBP
D. Ribosomes

A: B
~
Explanation: Sigma binds bacterial promoters and recruits RNA polymerase.

Q: Where does translation occur in eukaryotes?
A. Nucleus
B. Mitochondria only
C. Cytoplasm
D. Golgi apparatus

A: C
~
Explanation: Ribosomes read mRNA in the cytoplasm (or on rough ER).

Q: Which site of the ribosome holds the growing polypeptide?
A. A site
B. P site
C. E site
D. G site

A: B
~
Explanation: The P site contains the tRNA attached to the elongating protein.

Q: What causes termination of translation?
A. Stop codon + release factor
B. Ribosome running out of amino acids
C. 5' cap removal
D. Poly(A) tail shortening

A: A
~
Explanation: Release factors bind stop codons and free the polypeptide.

Q: Which gene acts as a tumor suppressor?
A. Ras
B. MyoD
C. p53
D. CAP

A: C
~
Explanation: p53 halts the cell cycle when DNA damage is detected.

Q: What is chromatin remodeling required for?
A. Allowing transcription factors access to DNA
B. Enhancing glycolysis
C. Breaking peptide bonds
D. DNA methylation

A: A
~
Explanation: Open chromatin is necessary for transcription initiation.

Q: What binds enhancers?
A. Repressors
B. Activators
C. Sigma
D. tRNA

A: B
~
Explanation: Enhancers increase transcription when activators bind.

Q: RNA interference (RNAi) leads to:
A. DNA replication
B. mRNA destruction or translation blockade
C. Protein folding
D. Transcriptional activation

A: B
~
Explanation: miRNA-loaded RISC targets specific mRNAs.

Q: CRISPR-Cas9 requires what molecule to target specific DNA?
A. DNA polymerase
B. Guide RNA
C. Helicase
D. Ligase

A: B
~
Explanation: sgRNA directs Cas9 to the complementary DNA sequence.

Q: What is a morphogen?
A. A DNA repair enzyme
B. A molecule that patterns tissues based on concentration
C. A spliceosome component
D. A type of tRNA

A: B
~
Explanation: Morphogens form gradients that specify positional information.

Q: Bicoid protein specifies which part of the Drosophila embryo?
A. Posterior
B. Ventral
C. Dorsal
D. Anterior

A: D
~
Explanation: Bicoid concentration highest at the anterior controls head formation.

Q: Hox genes encode:
A. Ribosomes
B. Repressors only
C. Transcription factors controlling segment identity
D. DNA polymerases

A: C
~
Explanation: Hox proteins regulate developmental patterning.

Q: What are somites?
A. Regions producing RNA polymerase
B. Mesodermal blocks forming muscle and bone
C. Stem cell clusters in the brain
D. Pluripotent apoptotic cells

A: B
~
Explanation: Somites differentiate into vertebrae, ribs, and skeletal muscle.

Q: What is an operon?
A. A single enhancer sequence
B. A cluster of genes transcribed together
C. A protein complex
D. A section of introns

A: B
~
Explanation: Operons allow bacteria to regulate multiple genes as a unit.

Q: What activates CAP in the lac operon?
A. Lactose
B. Glucose
C. cAMP
D. Allolactose

A: C
~
Explanation: cAMP binds CAP when glucose is low, enhancing transcription.

Q: The trp operon is turned off when tryptophan is:
A. Low
B. Medium
C. High
D. Absent

A: C
~
Explanation: Tryptophan binds the repressor, which then blocks transcription.

Q: What is a regulon?
A. A single bacterial gene
B. A 3' UTR region
C. A set of genes regulated by the same protein
D. A mutated operon

A: C
~
Explanation: Regulons allow global response to stress (e.g., SOS system).

Q: What are induced pluripotent stem cells (iPSCs)?
A. Fertilized eggs
B. Reprogrammed adult cells
C. Cancer cells
D. Mutant muscle cells

A: B
~
Explanation: iPSCs regain embryonic-like potency when master regulators are expressed.

Q: What causes limb loss in snakes evolutionarily?
A. Changes in Hox genes
B. Loss of Shh enhancer activity
C. Extra apoptosis
D. Errors in mitosis

A: B
~
Explanation: The ZRS enhancer controlling Shh limb expression is nonfunctional in snakes.

Q: Which experiment disproved spontaneous generation?
A. Hershey–Chase
B. Griffith
C. Pasteur's swan-neck flask
D. Watson & Crick

A: C
~
Explanation: Pasteur showed that microbes did not appear when broth was protected from airborne cells.

Q: Which level of protein structure involves interactions between R-groups?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary

A: C
~
Explanation: Tertiary structure arises from side chain interactions like ionic bonds, hydrophobic forces, and disulfide bonds.

Q: Phospholipids are amphipathic because they contain:
A. Two polar tails
B. One hydrophilic head and hydrophobic tails
C. Only hydrocarbons
D. Only charged groups

A: B
~
Explanation: Their structure gives them the ability to form bilayers in water.

Q: What determines membrane fluidity?
A. DNA methylation
B. Fatty acid saturation
C. Ribosome size
D. ATP levels

A: B
~
Explanation: More saturated tails make membranes less fluid and less permeable.

Q: Which of the following would most quickly increase gene expression in eukaryotes?
A. DNA methylation
B. Histone deacetylation
C. Histone acetylation
D. Addition of introns

A: C
~
Explanation: Acetylation opens chromatin, allowing transcription factors access to DNA.

Q: Which organelle contains digestive enzymes and breaks down waste?
A. Rough ER
B. Lysosome
C. Golgi
D. Mitochondria

A: B
~
Explanation: Lysosomes contain acid hydrolases for digestion and recycling.

Q: What is the function of the Golgi apparatus?
A. DNA replication
B. Protein sorting and modification
C. ATP synthesis
D. Protein translation

A: B
~
Explanation: Proteins are glycosylated and packaged into vesicles in the Golgi.

Q: How do molecules move in passive transport?
A. Against the gradient
B. Using ATP
C. Down their concentration gradient
D. Using motor proteins

A: C
~
Explanation: Passive transport requires no energy input.

Q: During mitosis, chromosomes first become visible during:
A. G1
B. Prophase
C. Anaphase
D. Telophase

A: B
~
Explanation: Chromatin condenses at the beginning of mitosis.

Q: Which checkpoint ensures DNA is undamaged before replication?
A. G1
B. S
C. G2
D. M phase

A: A
~
Explanation: G1 checkpoint checks cell size, nutrients, growth signals, and DNA integrity.

Q: Homologous chromosomes pair during:
A. Mitosis
B. Prophase I
C. Prophase II
D. Anaphase II

A: B
~
Explanation: Synapsis only occurs in prophase I.

Q: Independent assortment is a result of:
A. Crossing over
B. Random alignment of homologous pairs
C. Cytokinesis
D. Translation

A: B
~
Explanation: Homologous chromosomes align independently at metaphase I.

Q: In Mendel’s experiments, the F1 generation from pure lines was always:
A. Blended
B. Heterozygous and showing the dominant trait
C. Showing both traits
D. Homozygous recessive

A: B
~
Explanation: Dominant alleles mask recessive ones in heterozygotes.

Q: A mutation that changes one amino acid to another is:
A. Silent
B. Missense
C. Nonsense
D. Frameshift

A: B
~
Explanation: Missense mutations alter a single amino acid in the protein.

Q: Which enzyme seals DNA fragments together?
A. DNA polymerase
B. Ligase
C. Helicase
D. Primase

A: B
~
Explanation: Ligase forms phosphodiester bonds between DNA fragments.

Q: What prevents re-annealing of DNA strands during replication?
A. Topoisomerase
B. Single-strand binding proteins (SSBs)
C. RNA polymerase
D. Telomerase

A: B
~
Explanation: SSBPs stabilize open DNA strands.

Q: Telomerase is active in:
A. Somatic cells
B. Stem cells and cancer cells
C. Red blood cells only
D. Bacteria

A: B
~
Explanation: Most somatic cells lack telomerase, leading to telomere shortening.

Q: What enzyme synthesizes mRNA?
A. DNA pol III
B. RNA polymerase
C. Primase
D. Reverse transcriptase

A: B
~
Explanation: RNA polymerase transcribes DNA into RNA.

Q: What structure on mRNA helps ribosomes bind?
A. Poly-A tail
B. Intron loop
C. 5’ cap
D. Anticodon

A: C
~
Explanation: The 5’ cap stabilizes mRNA and initiates translation.

Q: A tRNA carries an amino acid to the ribosome at which site first?
A. E site
B. Q site
C. P site
D. A site

A: D
~
Explanation: Aminoacyl-tRNAs enter at the A site.

Q: What catalyzes peptide bond formation?
A. DNA
B. Ribosomal RNA
C. Lipids
D. RNA polymerase

A: B
~
Explanation: The ribosome is a ribozyme.

Q: Which molecule binds to a repressor to activate the lac operon?
A. Glucose
B. Allolactose
C. ATP
D. cAMP

A: B
~
Explanation: Lactose derivative allolactose inactivates the lac repressor.

Q: When tryptophan levels are high, the trp operon is:
A. Activated
B. Repressed
C. Mutated
D. Transcribed excessively

A: B
~
Explanation: Tryptophan acts as a co-repressor to block transcription.

Q: What is DNA methylation associated with?
A. Increased transcription
B. Decreased transcription
C. Faster replication
D. Alternative splicing

A: B
~
Explanation: Methyl groups silence genes by tightening chromatin.

Q: Enhancers can be located:
A. Only immediately upstream
B. Anywhere: upstream, downstream, or in introns
C. Only in promoters
D. Only in coding regions

A: B
~
Explanation: Enhancers function independent of distance or orientation.

Q: Alternative splicing allows:
A. Multiple proteins from one gene
B. Faster translation
C. More introns
D. More DNA replication

A: A
~
Explanation: Exons can be included or excluded to produce variant proteins.

Q: MicroRNAs regulate gene expression by:
A. Increasing ribosome number
B. Binding mRNA and preventing translation
C. Amplifying DNA
D. Inactivating enhancers

A: B
~
Explanation: miRNAs guide RISC to target mRNA.

Q: Which technique is used to amplify DNA?
A. Western blot
B. Southern blot
C. PCR
D. ELISA

A: C
~
Explanation: PCR cycles replicate DNA exponentially.

Q: CRISPR-Cas9 cuts DNA at sequences determined by:
A. DNA polymerase
B. sgRNA
C. Ligase
D. Helicase

A: B
~
Explanation: The guide RNA provides complementarity to the target.

Q: What is meant by “genetic equivalence”?
A. Each cell contains different genes
B. All cells contain the same genes
C. Only stem cells contain DNA
D. Genes change depending on tissue

A: B
~
Explanation: Differences in cell type arise from gene expression, not gene content.

Q: Cytoplasmic determinants influence early development by:
A. Triggering apoptosis
B. Unevenly distributing regulatory molecules
C. Activating translation
D. Breaking down mRNA

A: B
~
Explanation: Determinants are localized molecules in the egg.

Q: Bicoid mRNA is localized to which end of the egg?
A. Posterior
B. Ventral
C. Anterior
D. Dorsal

A: C
~
Explanation: Bicoid gradient determines the head region.

Q: Hox genes are conserved because they:
A. Mutate quickly
B. Control essential body patterning
C. Are not expressed
D. Do not bind DNA

A: B
~
Explanation: Hox transcription factors set segment identity across animals.

Q: During gastrulation, germ layers form by:
A. DNA replication
B. Cell movements and rearrangements
C. Mutation
D. Apoptosis

A: B
~
Explanation: Gastrulation creates ectoderm, mesoderm, and endoderm.

Q: Which germ layer becomes muscle and bone?
A. Ectoderm
B. Mesoderm
C. Endoderm
D. Epidermis only

A: B
~
Explanation: Mesoderm forms muscle, bone, blood, and many organs.

Q: What are somites?
A. Neural stem cells
B. Mesoderm segments forming vertebrae and muscles
C. Brain neurons
D. Germ cells

A: B
~
Explanation: Somites differentiate into skeletal muscles, ribs, and vertebrae.

Q: Evolution of limb loss in snakes is linked to:
A. Loss of the Shh enhancer
B. Gain of Hox genes
C. Loss of mitosis
D. Change in ECM structure

A: A
~
Explanation: The ZRS enhancer fails to activate Shh in limb buds.

Q: What does the SOS response do?
A. Stops translation
B. Repairs DNA damage with multiple genes
C. Activates apoptosis
D. Blocks replication

A: B
~
Explanation: The SOS regulon triggers wide-scale DNA repair.

Q: Which gene type drives uncontrolled cell division when mutated?
A. Tumor suppressor
B. Proto-oncogene
C. Hox gene
D. Operon gene

A: B
~
Explanation: When proto-oncogenes mutate, they become oncogenes.

Q: What does ubiquitin do?
A. Initiates transcription
B. Tags proteins for degradation
C. Activates enhancers
D. Forms phospholipid bilayers

A: B
~
Explanation: Ubiquitin marks proteins to be destroyed by the proteasome.

Q: The fluid mosaic model describes membranes as:
A. Static structures
B. Solid lipid layers
C. Dynamic phospholipid bilayers with proteins
D. Purely protein structures

A: C
~
Explanation: The model emphasizes lateral movement of lipids and embedded proteins.

Q: Which fatty acid increases membrane permeability the most?
A. Saturated, long-chain
B. Saturated, short-chain
C. Unsaturated
D. Trans-fatty acids

A: C
~
Explanation: Unsaturated fats have kinks that reduce packing and increase permeability.

Q: The nucleolus is the site of:
A. DNA replication
B. Ribosomal RNA synthesis
C. Protein synthesis
D. Transcription factor storage

A: B
~
Explanation: rRNA is produced and ribosome subunits assemble in the nucleolus.

Q: Which organelle is responsible for detoxifying alcohols and reactive oxygen species?
A. Lysosome
B. Peroxisome
C. Golgi
D. Chloroplast

A: B
~
Explanation: Peroxisomes contain enzymes like catalase to break down peroxides.

Q: Why do cells use compartmentalization?
A. To increase membrane rigidity
B. To separate incompatible chemical reactions
C. To promote DNA methylation
D. To store extra ATP

A: B
~
Explanation: Organelles create specialized environments that optimize reactions.

Q: Chromosomes line up at the metaphase plate due to tension from:
A. Cohesin destruction
B. Microtubules pulling equally from both poles
C. DNA polymerase activity
D. Centrosome duplication

A: B
~
Explanation: Equal tension ensures proper alignment before separation.

Q: What would happen if separase failed to function during mitosis?
A. DNA would not replicate
B. Chromatids would not separate
C. Nuclear envelope would not break down
D. Spindles would not form

A: B
~
Explanation: Separase cleaves cohesin; without it, chromatids remain stuck together.

Q: A cell permanently stopped in G1 is said to be in:
A. G2
B. S phase
C. G0
D. M phase

A: C
~
Explanation: G0 is a resting, non-dividing state.

Q: A cell permanently stopped in G1 is said to be in:
A. G2
B. S phase
C. G0
D. M phase

A: C
~
Explanation: G0 is a resting, non-dividing state.

Q: What is codominance?
A. One allele completely masks another
B. Both alleles influence the heterozygote phenotype
C. A single allele controls multiple traits
D. Two genes blend together

A: B
~
Explanation: In codominance, both alleles express equally (e.g., AB blood).

Q: Which of the following is an example of polygenic inheritance?
A. Blood type
B. Widow’s peak
C. Skin color
D. Cystic fibrosis

A: C
~
Explanation: Many genes contribute to a quantitative trait like skin pigmentation.

Q: What is the complement of the DNA sequence 5’-AGTCCG-3’?
A. TCAGGC
B. AGTCCG
C. GGCATC
D. UCAGGC

A: A
~
Explanation: DNA complements pair A–T and C–G.

Q: What is the role of topoisomerase?
A. Unzips DNA
B. Relieves tension from supercoiling
C. Forms Okazaki fragments
D. Synthesizes primers

A: B
~
Explanation: Topoisomerase prevents DNA from overwinding during replication.

Q: Which RNA processing event is required for nuclear export of mRNA?
A. Polyadenylation
B. Introns inserted
C. Removal of the 5’ cap
D. Frameshifting

A: A
~
Explanation: Poly(A) tails help stabilize, transport, and translate mRNAs.

Q: A ribozyme is:
A. A ribosome-bound enzyme
B. RNA with catalytic activity
C. A mutated ribosome
D. A viral protein

A: B
~
Explanation: Certain RNAs (including rRNA) catalyze biochemical reactions.

Q: Wobble pairing allows:
A. More amino acids to be synthesized
B. Fewer tRNAs to recognize many codons
C. Faster DNA replication
D. Alternative splicing

A: B
~
Explanation: Flexibility at the third codon base reduces the number of tRNAs required.

Q: A repressor that cannot bind the operator will cause an operon to be:
A. Always off
B. Always on
C. Only on during mitosis
D. Able to translate but not transcribe

A: B
~
Explanation: Without repressor binding, transcription proceeds constantly.

Q: If glucose is high in the environment, cAMP levels are:
A. High
B. Low
C. Unchanged
D. Unstable

A: B
~
Explanation: Glucose inhibits adenylyl cyclase, lowering cAMP, and reducing CAP activity.

Q: What protein binds to the TATA box in eukaryotes?
A. Sigma
B. TBP
C. CAP
D. RISC

A: B
~
Explanation: TBP (TATA-binding protein) initiates pre-initiation complex formation.

Q: What happens when DNA is highly methylated?
A. Transcription increases
B. Transcription decreases
C. DNA replication accelerates
D. Alternative splicing increases

A: B
~
Explanation: Methylation condenses chromatin, reducing gene expression.