NEET Practice Questions (MCQs) with Answers & Solutions

In G1, the cell has 2n chromosomes and 2C DNA. After S phase and until metaphase, the cell maintains 2n chromosomes (each with two chromatids) and 4C DNA. During anaphase, the centromeres split, and sister chromatids separate, moving to opposite poles. At this point, each chromatid is considered an individual chromosome. Therefore, temporarily, the chromosome number doubles to 4n, and the DNA content remains 4C in the entire cell during anaphase, before cytokinesis fully separates them.

According to the NCERT text, 'The eukaryotic ribosomes are 80S while the prokaryotic ribosomes are 70S. Each ribosome has two subunits, larger and smaller subunits (Fig 8.9). The two subunits of 80S ribosomes are 60S and 40S while that of 70S ribosomes are 50S and 30S.' Therefore, the statement that 80S ribosomes have 50S and 30S subunits is incorrect.

The NCERT text states: 'Here ‘S’ (Svedberg’s Unit) stands for the sedimentation coefficient; it is indirectly a measure of density and size.'.

The NCERT text mentions: 'They [ribosomes] are composed of ribonucleic acid (RNA) and proteins and are not surrounded by any membrane.'.

The NCERT text states: 'Within the cell, ribosomes are found not only in the cytoplasm but also within the two organelles – chloroplasts (in plants) and mitochondria and on rough ER.' Lysosomes are membrane-bound organelles that contain digestive enzymes and do not inherently contain ribosomes.

NCERT states: 'RER is frequently observed in the cells actively involved in protein synthesis and secretion.' This is directly linked to the function of ribosomes in protein synthesis.

As per the NCERT text: 'In prokaryotes, ribosomes are associated with the plasma membrane of the cell. They are about 15 nm by 20 nm in size...'

The NCERT text specifies: 'The ribosomes of the chloroplasts are smaller (70S) than the cytoplasmic ribosomes (80S).'

The NCERT states: 'Since the functions of the mitochondria, chloroplast and peroxisomes are not coordinated with the above components (ER, golgi, lysosomes, vacuoles), these are not considered as part of the endomembrane system.' Mitochondria are known to contain 70S ribosomes.

NCERT text states: 'The outer membrane usually remains continuous with the endoplasmic reticulum and also bears ribosomes on it.'