All Free Biology MCQs with Answers

• A. Interphase
• B. Prophase
• C. Metaphase
• D. Anaphase
• E. Telophase

Explanation: The mitotic apparatus, also known as the mitotic spindle, is formed during the **Prophase** stage of cell division. Here's an explanation of each of the stages you mentioned:1. **Interphase**: This is the stage before cell division where the cell prepares for division by growing, replicating its DNA, and carrying out normal cellular functions. The mitotic apparatus is not formed during interphase.2. **Prophase**: During prophase, the chromatin in the nucleus condenses into visible chromosomes, and the mitotic spindle, consisting of microtubules, begins to form. The spindle fibers extend from the centrosomes and play a crucial role in separating chromosomes during cell division.3. **Metaphase**: In metaphase, the mitotic spindle is fully formed and the chromosomes align at the cell's equator, known as the metaphase plate. The spindle fibers help hold the chromosomes in place during this alignment.4. **Anaphase**: In anaphase, the spindle fibers start to shorten, pulling the sister chromatids of each chromosome apart and moving them towards opposite poles of the cell. This is a key step in chromosome segregation.5. **Telophase**: In telophase, the separated chromatids reach the opposite poles of the cell, and new nuclear envelopes begin to form around them. The mitotic apparatus begins to disassemble as cell division nears completion.So, the formation of the mitotic apparatus primarily occurs during prophase.

• A. Spermatogonia to primary spermatocytes
• B. Secondary spermatocytes to spermatids
• C. Primary spermatocytes to secondary spermatocyte
• D. Spermatids to sperms

Explanation: Explanation for this question will be added soon.

• A. Spermatogonia
• B. Secondary spermatocyte
• C. Primary spermatocyte
• D. Spermatid

Explanation: Remember that these stages are part of spermatogenesis, the process of sperm cell formation in the testes. The reduction division (meiosis) primarily occurs in primary spermatocytes, leading to the generation of haploid secondary spermatocytes and, ultimately, spermatids.

• A. Stops the functioning of centriole
• B. Prevents attaching of centromeres with rays
• C. Prevents the spindle formation in mitosis
• D. Prevents the formation of equatorial plane

Explanation: Colchicine is an alkaloid that inhibits spindle fiber formation during mitosis, preventing proper chromosome segregation during anaphase. This disruption can result in cells with multiple sets of chromosomes, a condition utilized in research and therapy. While centrioles and centromeres are involved in the mitotic process, colchicine's primary action is on the spindle fibers themselves, not directly on these structures, which is why Option C is correct. Other options incorrectly attribute its action to different cellular structures or processes.

• A. Two chromatids and one centromere
• B. Two chromatids and two centromeres
• C. Four chromatids and two centromeres
• D. Four chromatids and four centromeres

Explanation: A bivalent, also known as a tetrad, forms during meiosis when two homologous chromosomes pair up. Each homologous chromosome consists of two sister chromatids, resulting in a total of four chromatids. These chromatids are organized into two pairs, each connected by a centromere, thus giving us two centromeres in a bivalent. This configuration facilitates the process of genetic recombination and ensures accurate segregation of chromosomes during cell division. Options A and B incorrectly describe the number of chromatids, while Option D incorrectly states the number of centromeres.

• A. Fibroblasts
• B. Circulatory system
• C. Immune system
• D. Epithelial cells

Explanation: Fibroblasts are the cells present in connective tissue. Sarcomas are cancers that are located in connective and muscular tissues derived from mesoderm. Thus, they include the cancers of bones, cartilages, tendons, adipose tissue, lymphoid tissue and muscles.

• A. 5 x 10^5 cells
• B. 35 x 10^5 cells
• C. 32 x 10^5 cells
• D. 174 x 10^5 cells

Explanation: The bacteria divide every 35 minutes. Over 175 minutes, the bacteria will divide 5 times (175 / 35 = 5). Each division doubles the number of bacteria, so after 5 divisions, the number of bacteria is 25 = 32 times the initial count. Starting with 105 cells per mL, the concentration becomes 32 x 105 cells per mL.Other options do not correctly calculate the number of divisions or misunderstand the relationship between time and cell doubling.

• A. Cleft lip and Palate
• B. Polydactyly
• C. Turner's Syndrome
• D. Klinefelter's Syndrome
• E. Down's Syndrome

Explanation: Mental and physical retardation is down syndrome. Down syndrome, also known as Down's syndrome or trisomy 21, is a genetic disorder that occurs when there is an extra copy of chromosome 21. Typically, humans have 46 chromosomes in each cell, but individuals with Down syndrome have 47 chromosomes because they have three copies of chromosome 21 instead of the usual two. This extra genetic material can lead to a range of developmental and physical characteristicsPeople with Down syndrome often have intellectual and developmental disabilities of varying degrees. Their cognitive and learning abilities may be below average, but there is a wide range of cognitive functioning within the Down syndrome population.Down syndrome is associated with an increased risk of certain medical conditions, including heart defects, respiratory issues, hearing problems, and thyroid disorders. Regular medical check-ups are essential to monitor and address these conditions.It's important to note that the impact of Down syndrome can vary widely from one individual to another, and many individuals with Down syndrome lead fulfilling and meaningful lives with the support of their families and communities.Down syndrome is typically diagnosed before or at birth through genetic testing, such as chorionic villus sampling (CVS) or amniocentesis during pregnancy, or through a blood test (karyotype analysis) shortly after birth. Early diagnosis allows for early intervention and support.People with Down syndrome can benefit from a supportive and inclusive environment that helps them reach their potential and lead happy, fulfilling lives. Many advocacy organizations and support networks are available to assist individuals with Down syndrome and their families.

• A. Microfilaments
• B. Microvilli
• C. Microtubules
• D. Intermediate filaments

Explanation: Typical centrioles are made of 9 triplets of microtubules organized with radial symmetry. Microfilaments, also called actin filaments, are polymers of the protein actin that are part of a cell's cytoskeleton. Microvilli are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions. Intermediate filaments are important components of the cell's cytoskeletal system. They may stabilize organelles, like the nucleus, or they may be involved in specialized junctions. They are distinguished from "thin filaments" by their size (8-10 nm) and the fact that thin filaments are motile.

• A. 100 S
• B. 90 S
• C. 80 S
• D. 70 S

Explanation: The S in the ribosomal subunits stands for svedberg units. It represents the different sedimentation rates of the ribosomes during centrifugation. The 60s and 40s ribosomal subunits join to form an 80S ribosome found in eukaryotes.