All Free Biology MCQs with Answers

• A. Actin
• B. Myosin
• C. Tubulin
• D. Myoglobin

Explanation: Spindle fibres consist of microtubules that are polymeric chains synthesized from the protein Tubulin.

• A. Anther
• B. Root tip
• C. Animal tissues
• D. Ovary

Explanation: Mitosis occurs both in somatic cells as well as in germ cells of the gonads. In plants, mitosis occurs in the meristematic cells of the root tip or shoot tip. These cells divide at a faster rate. So the root tip shows active cell division and is used in the laboratory to study mitosis. For studying meiosis, young anthers are used.

• A. Chromocentre
• B. Chromomere
• C. Kinetochore
• D. Centriole

Explanation: Spindle is microtubular apparatus that appears in many eukaryotic cells at the beginning of nuclear division and is responsible for the ordered separation of the chromosomes, chromosomes being attached to the spindle fibres by their centromeres. Two types of spindle fibres can be distinguished as the interpolar fibre, which stretches continuously from pole to pole of the spindle; the kinetochore fibre, which stretches from the pole to the centromere (kinetochore) of an individual chromosome. The mechanism by which the chromosomes move and the spindle fibres contract remains unclear. Cells of animals and lower plants possess centrioles, which act as organizer regions for spindle microtubule formation, but centrioles are absent from the cells of higher plants.

• A. Muscle contraction
• B. Membrane architecture
• C. Cell division
• D. DNA recognition

Explanation: Microtubules are unbranched, hollow, submicroscopic tubules of the wwprotein tubulin which develop on specific nucleating regions and can undergo quick growth or dissolution at their ends by assembly or disassembly of monomers. Microtubules form the spindle during cell division. Centrioles help in cell division by forming spindle poles or microtubules. In animal cells, microfilaments collect in the middle region of the cell below the cell membrane. They induce the cell membrane to invaginate. In plant cells, a cell plate is formed to separate the two daughter cells. Some of the spindle fibres called interzonal microtubules are deposited around the phragmoplast. Vesicles from the Golgi apparatus are deposited and coalesce on the phragmoplast to form a cell plate.

• A. 28
• B. 32
• C. 7
• D. 14

Explanation: (c) : Mitosis is an equational division where after division each cell produces two daughter cells, therefore after 7 divisions one cell will give 128 cells in case of mitosis. 1 1 ➡ 2 2➡ 4 3➡ 8 4➡ 16 5➡ 32 6➡ 64 7➡ 128

• A. Telophase
• B. Cytokinesis
• C. Metaphase
• D. Anaphase

Explanation: In apical meristems, mitotic divisions occur at a rapid rate. In the late telophase of mitosis, a nuclear membrane appears on the outside from either pieces of the nuclear envelope or endoplasmic reticulum. The telophase may last as long as prophase.

• A. Bivalent-forming
• B. Dyad-­forming
• C. Synapsis
• D. Crossing-­over

Explanation: Crossing over is responsible for inducing variability. It involves an exchange of equal segments of non­ sister chromatids belonging to two different but homologous chromosomes. Crossing over takes place at the four-stranded stage. Only two of the four chromatids take part in crossing over. The other two are called non-crossovers. Zygotene is characterized by the pairing of homologous chromosomes which is called synapsis. The first meiotic division which is completed at first telophase may be followed by cytokinesis giving rise to a dyad.

• A. Meiosis is necessary for sexual reproduction
• B. Genetic recombinations are possible from generation to generation
• C. Meiosis alternates with mitosis from generation to generation
• D. The same genetic system is passed on from generation to generation

Explanation: Meiosis involves the exchange of genes between homologous chromosomes. So the gametes produced are genetically different from each other. Offsprings produced by the fusion of gametes therefore also show recombinations or genetic variations. These variations in the offsprings make organisms more adaptable to the environment and these have a definite role in evolution.

• A. Separation of sex chromosomes
• B. DNA replication and centromere
• C. Separation of homologous chromosomes
• D. Separation of chromatids

Explanation: Meiosis II is shorter than the typical mitotic division because of the shortening of the prophase of this division. The division maintains the number of chromosomes produced at the end of reduction division. Hence, it is called homotypic or equational division, though it is similar to mitosis. The main function of homotypic division or meiosis II is to separate the chromatids of univalent chromosomes which differ from each other in their linkage groups due to crossing over.

• A. Two each in mitosis and meiosisq
• B. Two in mitosis and one in meiosis
• C. Two in mitosis and four in meiosis
• D. One in mitosis and two in meiosis

Explanation: The number of chromatids at metaphase is two each in mitosis and meiosis. Chromatid is a half chromosome during duplication in early prophase and metaphase of mitosis and between diplotene and the second metaphase of meiosis. After these stages, chromatids are called daughter chromosomes.