CBSE Class 12 Biology Paper Sample 2023
This sample paper covers the breadth of CBSE Class 12 Biology in a single sitting, testing both conceptual depth and your ability to apply knowledge under timed pressure — exactly what the board exam demands. You'll encounter questions spanning reproduction and development, the molecular basis of inheritance, and the ecology–biotechnology interface: all three are high-frequency in recent CBSE papers. The mix includes multiple-choice questions that test recall and reasoning, a few true-false statements to catch common misconceptions, and fill-in-the-blank items that demand precision. By completing this paper, you'll not only identify your knowledge gaps but also calibrate how much time you can afford per question without rushing through the genetics or ecology sections where students most often stumble.
Questions in this quiz
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- Question 1
During oogenesis in human females, the secondary oocyte is arrested at which stage of meiosis until the surge of luteinizing hormone (LH) just before ovulation?
- Question 2
The corpus luteum secretes which hormone to maintain the endometrium during the luteal phase of the menstrual cycle?
- Question 3
In human male reproduction, Leydig cells (interstitial cells) are responsible for producing testosterone. These cells are stimulated by which pituitary hormone?
- Question 4
In Mendel's experiments, when a homozygous dominant pea plant (TT) is crossed with a homozygous recessive plant (tt), all F₁ offspring are heterozygous (Tt) and express the dominant phenotype. What would be the genotypic ratio in the F₂ generation if F₁ plants self-pollinate?
- Question 5
The process by which a segment of DNA is synthesized in a 5' to 3' direction using RNA as a primer is called DNA replication. The strand synthesized continuously in this direction is called the leading strand. True or False?
- Question 6
During transcription in eukaryotes, the enzyme RNA polymerase II synthesizes mRNA by reading the DNA template in the 3' to 5' direction. The newly synthesized mRNA strand grows in which direction?
- Question 7
A codon is a sequence of three nucleotides on mRNA that corresponds to one amino acid during translation. What is the name of the tRNA component that binds to the codon on the mRNA ribosome?
- Question 8
According to Darwin's theory of evolution by natural selection, organisms with traits best adapted to their environment are more likely to survive and reproduce. Which of the following statements is NOT a key premise of Darwinian evolution?
- Question 9
In population genetics, the Hardy–Weinberg equilibrium describes a population in which allele frequencies do not change across generations. Which of the following conditions is NOT required for Hardy–Weinberg equilibrium to hold?
- Question 10
Recombinant DNA technology allows scientists to insert genes from one organism into another. The plasmid DNA isolated from bacteria and used as a vector is cut at specific sites by restriction endonucleases. What do we call the short single-stranded DNA segments that extend from the ends of cut DNA?
- Question 11
The polymerase chain reaction (PCR) is a molecular technique used to amplify a specific segment of DNA in vitro. The reaction is cycled repeatedly through three temperature-dependent steps. The step at approximately 94–95°C is called denaturation and causes double-stranded DNA to separate into single strands. True or False?
- Question 12
Ecosystem productivity refers to the rate at which biomass is accumulated in an ecosystem. The total energy (or biomass) accumulated by plants through photosynthesis is called gross primary productivity (GPP). Net primary productivity (NPP) is the energy available for herbivores after plants have used some of the GPP for their own respiration. Which of the following statements correctly describes the relationship between GPP and NPP?
- Question 13
Bt cotton is a genetically modified crop that carries the gene from Bacillus thuringiensis, a bacterium that produces a toxin lethal to insect pests. Bt cotton has revolutionized agriculture in several countries by reducing the need for chemical insecticides. However, repeated exposure to Bt crops can lead to the evolution of insect-resistant populations. This phenomenon is best explained by which evolutionary concept?