Tag: botany

'L' shaped chromosomes that appear during anaphase are sub-metacentric. According to the position of the centromere, the metacentric chromosomes are X shaped and due to the unequal length of the arms of the chromosomes, they become L shaped and are called sub-metacentric.

The arm ratio in metacentric condition is 1:1. These are X-shaped chromosomes, with the centromere in the middle, so that, the two arms of the chromosomes are almost equal. A chromosome is metacentric, if its two arms are roughly equal in length. In a normal human karyotype, two chromosomes are considered metacentric: chromosomes 1 and 3. In some cases, a metacentric chromosome is formed by balanced translocation: the fusion of two acrocentric chromosomes to form one metacentric chromosome.

Chromosome with centromere at one end is telocentric. A telocentric chromosome's centromere is located at the terminal end of the chromosome. Telomeres may extend from both ends of the chromosome. Humans do not possess telocentric chromosomes.

A chromosome present in addition to the normal chromosome complement is called as a supernumerary chromosome, also known as accessory chromosome. These chromosome does not produce any detectable phenotypic expression in an organism. These chromosomes are not essential for the life of a species, and are lacking in some (usually most) of the individuals. Thus a population would consist of individuals with 0, 1, 2, 3 (etc.) supernumeraries.

The rod-like chromosomes which have the centromere on the proximal end are known as the telocentric chromosomes. Humans do not possess telocentric chromosomes but they are found in other species such as mice. Thus, the correct answer is option A.

Vacuoles are storage bubbles found mostly in plant cells. These are used for storage of food or water. The vacuolar membrane is a single layered and is called as tonoplast. Osmotic pressure and turgidity is maintained by vacuoles. They store toxic metabolic by-products or end products of plant cells. Such vacuoles are thrown out of the cell by exocytosis. Thus, the correct answer is option D.

A chromosome with the median centromere and two equal arms are called as metacentric chromosomes. The presence of centromere at the terminal end makes telocentric chromosome. Acentric chromosomes lack centromere and therefore have a single arm. The presence of centromere in diffused state makes the polycentric chromosomes as if they have multiple centromeres Thus, the correct answer is option A.

In a plant cell, the vacuoles are large and centrally placed organelle. Vacuoles typically contain salts, sugars and sometimes proteins and have a variety of secretory, excretory and storage functions. The vacuole may also be involved in the breakdown of old organelles or macromolecules and then recycling the products back to the rest of the cell. Thus, they are in large number in a cell adapted for waste storage and disposal.
So, the correct answer is option A.

• The cell sap is a non-living content of the vacuole. Cell sap is the fluid manufactured by the cytoplasm of the living plant cell.
•  Cell sap consists of water and various substances that are often in the form of a colloidal suspension. 
• On average, cell sap has twice the viscosity of water. 
• The cell sap contributes to the osmotic properties and turgor of the cell, and consequently, to the elasticity of plant tissues and organs.