Biology — Genetics, Molecular Biology & Evolution for the NEET Exam — Texas candidates

Common failure modes

These are the patterns that cause most candidates to lose marks on this topic. Recognising them in advance is half the work.

• !Punnett square errors in dihybrid crosses — forgetting to apply independent assortment (9:3:3:1 ratio for two independent traits)
• !Confusing co-dominance (both alleles expressed, e.g., AB blood type) with incomplete dominance (blended phenotype, e.g., pink snapdragons)
• !Misidentifying the steps of DNA replication vs transcription (which enzyme makes what)
• !Forgetting Hardy-Weinberg equilibrium conditions — mutation, selection, gene flow, non-random mating, and genetic drift ALL violate the equilibrium
• !Confusing convergent evolution (analogous organs, unrelated species) with divergent evolution (homologous organs, common ancestry)

Study tips

• 1Practise Punnett squares for monohybrid (3:1 ratio), dihybrid (9:3:3:1), and test cross scenarios. NEET tests all three.
• 2For molecular biology, memorise the central dogma: DNA → (transcription) → mRNA → (translation) → Protein. Know the enzyme: DNA polymerase (replication), RNA polymerase (transcription), ribosome (translation).
• 3Learn the genetic code features from NCERT: it is universal, degenerate (multiple codons per amino acid), non-overlapping, and unambiguous. AUG is start (methionine), UAA/UAG/UGA are stop codons.
• 4Memorise Hardy-Weinberg equation: p² + 2pq + q² = 1 (genotype frequencies) and p + q = 1 (allele frequencies). NEET uses these directly in numerical questions.
• 5For evolution, know the evidence types: comparative anatomy (homologous vs analogous structures), embryology, fossil record, molecular biology. Darwin's natural selection vs Lamarck's inheritance of acquired characteristics.
• 6For CDL: book your skills test at a TxDPS megacenter (Houston, Dallas, San Antonio, Austin) or one of the 200+ third-party testers; megacenter wait times average 4–6 weeks.
• 7For NCLEX-RN: the Texas Board of Nursing requires fingerprinting via IdentoGO before authorization-to-test (ATT) is issued — start that process the same day you submit your application.
• 8Spanish-language CDL written tests are offered in Texas; the skills/road portion is conducted in English. Many CDL training programs in the Rio Grande Valley teach a bilingual track.

Sample NEET Biology — Genetics, Molecular Biology & Evolution questions

These sample items mirror the format and difficulty of real NEET questions. Practice with thousands more on the free Koydo question bank.

1. 1

   In a monohybrid cross between two heterozygous parents (Tt × Tt), the expected phenotypic ratio is:

   • A1:2:1
   • B3:1Correct
   • C1:1
   • D2:1
   Why this answer?

   Cross Tt × Tt → TT : 2Tt : tt = 1:2:1 genotypic ratio. If T is dominant over t, then TT and Tt both show the dominant phenotype. Phenotypic ratio = 3 dominant : 1 recessive = 3:1.

2. 2

   The enzyme responsible for DNA replication is:

   • ARNA polymerase
   • BDNA ligase only
   • CDNA polymerase IIICorrect
   • DHelicase only
   Why this answer?

   DNA polymerase III (in prokaryotes) is the primary enzyme that synthesises new DNA strands by adding nucleotides complementary to the template strand. Helicase unwinds the double helix; DNA ligase joins Okazaki fragments; RNA polymerase makes RNA, not DNA.

3. 3

   Homologous organs are evidence for:

   • AConvergent evolution
   • BDivergent evolution (common ancestry)Correct
   • CParallel evolution
   • DCo-evolution
   Why this answer?

   Homologous organs have the same basic structural plan and evolutionary origin but may perform different functions (e.g., forelimbs of humans, whales, bats, horses). They indicate divergent evolution — common ancestry with adaptation to different environments. Analogous organs (wings of insects vs birds) indicate convergent evolution from different ancestry.

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