All Free Biology MCQs with Answers

1581. The term 'gene' was first used by _______?

• A. Johannsen
• B. Mendel
• C. Lemark
• D. Cuvier

Explanation: Wilhelm Johannsen introduced the term gene in 1909 for the hereditary unit responsible for a trait. Mendel established the principles of inheritance but used terms such as factors rather than the word gene, making him the likely mistaken choice.

1582. The place of centromere where spindle fibres get attached is_________?

• A. Kinetochore
• B. Kinochore
• C. Centromere region
• D. all of these

Explanation: The kinetochore is a protein-containing structure assembled at the centromere, and spindle-fibre microtubules attach to it during cell division. Students may choose the centromere region because the kinetochore is located there, but the centromere itself is the DNA region, not the direct spindle attachment structure.

1583. Division of nucleus is termed as___________ ?

• A. Karyokinesis
• B. Cytokinesis
• C. Anaphase
• D. Meiosis

Explanation: Karyokinesis is the division of the nucleus, during which duplicated chromosomes are separated into daughter nuclei. Cytokinesis is the division of the cytoplasm, while anaphase is only one stage of nuclear division.

1584. Zygote with three copies chromosome 21, is known to cause _________?

• A. Hay fever
• B. Scurvy
• C. Parkinson Disease
• D. Downs syndrome

Explanation: A zygote with three copies of chromosome 21 has trisomy 21, which causes Down syndrome and is associated with characteristic developmental and physical features. Students may choose Parkinson disease because both can involve neurological effects, but Parkinson disease is not caused by chromosome 21 trisomy.

1585. Trisomy 21 is most common in mothers of the ________ age group.

• A. 15 to 19
• B. 20 to 34
• C. 35 to 39
• D. 40 to 45

Explanation: The risk of nondisjunction and therefore trisomy 21 rises markedly with maternal age, with the highest risk among the listed groups at 40 to 45 years. Students may choose 35 to 39 because risk begins increasing substantially after 35, but the older group has the greater incidence.

1586. in animals meiosis produces____________?

• A. spores
• B. gametes
• C. both a & b
• D. all the above

Explanation: In animals, meiosis occurs in reproductive organs and produces haploid gametes, such as sperm or ova, from diploid precursor cells. The likely mistake is spores, which are commonly produced by meiosis in plants and fungi rather than being the usual animal product.

1587. which of the following gives to rise two daughter cell during cell division?

• A. meiosis
• B. mitosis
• C. both a & b
• D. none of these

Explanation: Mitosis involves one nuclear division and produces two genetically similar daughter cells with the same chromosome number as the parent cell. Students may choose meiosis because it is also a type of cell division, but meiosis normally produces four haploid cells after two successive divisions.

1588. four daughter cells are given to rise during the process of____________?

• A. meiosis
• B. mitosis
• C. cell division
• D. none of these

Explanation: Meiosis has two successive divisions, meiosis I and meiosis II, and therefore produces four haploid daughter cells from one starting cell. The likely alternative is mitosis, but mitosis has only one division and produces two daughter cells.

1589. The number of chromosomes in human cell is_____________?

• A. 48
• B. 44
• C. 46
• D. 26

Explanation: A normal human somatic cell contains 46 chromosomes arranged in 23 pairs, including 22 pairs of autosomes and one pair of sex chromosomes. Students may choose 44 because they count only the autosomes and omit the two sex chromosomes.

1590. Genes will not be found in gene pairs in the_____________?

• A. Muscle cell of worm
• B. Uterine cells of dog
• C. Sperm cells of frog
• D. Guard cells of leaf

Explanation: A sperm cell is haploid, so it contains one chromosome from each homologous pair rather than genes in pairs. Muscle cells, uterine cells and leaf guard cells are generally diploid and contain homologous chromosome pairs. Students may choose a muscle or guard cell because these cells are specialized, but specialization does not normally remove their chromosome pairs.