TEAS Biology practice questions

Cells, macromolecules, DNA and protein synthesis, cell division, genetics and microorganisms. Biology is 9 of the 44 scored questions in TEAS Science.

scored questions

9

of Science's score

20%

for all of Science

60 min

1. 01Science · BiologyA single primary spermatocyte with genotype AaBb, in which the A and B genes lie on different chromosome pairs, completes meiosis without any crossing over. Which set of four sperm could result from this one cell?+−

   • A. AB, Ab, aB, ab
   • B. AB, AB, aB, aB
   • C. AB, Ab, AB, Ab
   • D. AB, AB, ab, ab (correct)

   Without crossing over, one cell produces only two kinds of sperm, two of each: either AB and ab, or Ab and aB, depending on how the homologous pairs lined up. Four different types would need independent assortment across many cells, and the other sets lack a or b entirely.

2. 02Science · BiologyA woman with type A blood, whose father had type O blood, has a child with a man who has type B blood, whose mother had type O blood. What is the probability that their child has type O blood?+−

   • A. 1/2
   • B. 1/8
   • C. 0
   • D. 1/4 (correct)

   Each parent must have received an O allele from the type O parent, so the woman is AO and the man is BO. Their child can be AB, AO, BO or OO with equal probability, so type O has a probability of 1/4. Type O is possible even though neither parent has it, because both are carriers of the recessive O allele.

3. 03Science · BiologyA mature protein is 150 amino acids long. After translation, its N-terminal methionine, which was encoded by the start codon, was removed. The coding region of the gene, from the start codon through the stop codon, contains no introns. How many nucleotides long is this coding region?+−

   • A. 450
   • B. 453
   • C. 456 (correct)
   • D. 459

   The original polypeptide had 150 + 1 = 151 amino acids, so there were 151 codons plus 1 stop codon, which is 152 codons × 3 = 456 nucleotides. The value 453 leaves out the stop codon, and 450 also leaves out the removed methionine.

4. 04Science · BiologyIn primary ciliary dyskinesia, the cilia lining the airways cannot beat, so mucus is not cleared from the lungs. Which cytoskeletal element forms the internal framework of cilia and is therefore the most likely site of the defect?+−

   • A. Microtubules (correct)
   • B. Actin microfilaments
   • C. Intermediate filaments
   • D. Extracellular collagen fibers

   The core of a cilium is built of microtubules with motor proteins that produce bending. Actin microfilaments are tempting because they support cell movement and microvilli, but they do not form the ciliary core.

5. 05Science · BiologyArrange the following events of the lytic cycle of a bacteriophage in the order in which they occur, from first to last.+−

   Correct order:

   1. The phage attaches to receptors on the bacterial surface
   2. The phage injects its DNA into the bacterium
   3. The host cell's machinery copies phage DNA and makes phage proteins
   4. New virus particles are assembled inside the host cell
   5. The host cell bursts and releases new phages

   The phage attaches, injects its genome, and takes over the host's machinery to make its components. These are assembled into new particles, and the cell then lyses to release them. Assembly cannot come before the components have been made.

6. 06Science · BiologyWhich of the following statements about nucleotides and nucleic acids are correct? Select all that apply.+−

   • A. ATP contains the sugar deoxyribose.
   • B. In a DNA strand, the phosphate group of one nucleotide is covalently linked to the sugar of the next nucleotide. (correct)
   • C. The two strands of a DNA double helix are held together by covalent bonds between the bases.
   • D. Adenine and guanine each have a double-ring structure. (correct)
   • E. In a double helix, each purine pairs with another purine so the strands stay evenly spaced.
   • F. RNA uses uracil in place of thymine. (correct)

   The sugar-phosphate backbone is built from phosphodiester links, adenine and guanine are double-ring purines, and RNA has uracil instead of thymine. ATP contains ribose, base pairs are joined by hydrogen bonds (not covalent bonds), and each purine pairs with a single-ring pyrimidine.

7. 07Science · BiologyIn a breed of dogs, coat color depends on two genes on different chromosomes. At the E gene, a dog with at least one E allele can deposit pigment, but a dog with genotype ee has a yellow coat regardless of its genotype at the B gene. In dogs with at least one E allele, B_ produces a black coat and bb produces a brown coat. A BbEe dog is mated with a Bbee dog. What proportion of the puppies is expected to be brown?+−

   • A. 1/16
   • B. 1/8 (correct)
   • C. 3/16
   • D. 1/4

   A brown puppy must be bb (1/4 from Bb × Bb) and have at least one E (1/2 from Ee × ee), so 1/4 × 1/2 = 1/8. The value 3/16 is tempting but applies to a BbEe × BbEe cross, not this one.

8. 08Science · BiologyThe template strand of a DNA segment reads 3'-TACGGATC-5'. Which mRNA sequence is transcribed from it?+−

   • A. 5'-GAUCCGUA-3'
   • B. 5'-ATGCCTAG-3'
   • C. 5'-AUGCCUAG-3' (correct)
   • D. 5'-UACGGAUC-3'

   RNA polymerase pairs bases complementary and antiparallel to the template, using uracil in place of thymine, which gives 5'-AUGCCUAG-3'. Option A has the correct bases but reads them in the wrong direction (this is the same sequence written 3' to 5'), and B contains thymine, which is not found in RNA.

9. 09Science · BiologyCardiac muscle cells have a very high demand for ATP. Which organelle would be expected in especially large numbers in these cells?+−

   • A. Lysosomes
   • B. Golgi apparatus
   • C. Ribosomes
   • D. Mitochondria (correct)

   Mitochondria are the main site of ATP production by aerobic respiration, so cells with high energy needs contain many of them. Lysosomes digest materials and do not produce ATP.

10. 10Science · BiologyA double-stranded DNA sample contains 22% thymine. What percentage of its bases is guanine?+−

    Answer: 28 %

    Thymine pairs with adenine, so A = T = 22%, together 44%. The remaining 56% is split equally between guanine and cytosine, giving 28% each.

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Sources

1. ATI: ATI TEAS exam details (sections, questions, sub-areas)

Updated November 6, 2026