DNA model given by Watson and Creek in the year of 1953 gave a very detailed study regarding the structure of B DNA which is valid till date and is essentially corroborating with Chargaff's data and Xray diffraction pattern.
<h3><u>Explanation:</u></h3>
The DNA is the most common nucleic acid found in the living organisms as a genetic material. As stated by Watson and Creek, this DNA contains a double helical structure with two sugar phosphate backbones and the nitrogen bases getting projected from it inwards. The backbones are formed of ribose sugar and phosphate and joined together with a phosphodiester bond. The ribose sugar is attached to phosphates at its 3' and 5' Carbon atoms. The nitrogen bases found in DNA are Adenine, Guanine, Thymine and Cytosine. The Adenine has two hydrogen bonds with thymine and guanine has 3 hydrogen bonds with cytosine.
Each full turn of a helix is 34A and each base pair is 3.4A apart. The distance between two strands of DNA is 20A.
Chargaff's rule regarding the equal amount of adenine and thymine as well as guanine and cytosine is matching with this structure. All the other rules also do match with this DNA structure.
Surface area is an important factor in limiting cell growth because
a. the cell can burst if the membrane becomes too large.
b. materials cannot enter the cell if the surface is too large.
c. the cell may become too large to take in enough food and to remove enough wastes.
d. waste products cannot leave the cell if the cell is too small.
Answer:
c. the cell may become too large to take in enough food and to remove enough wastes.
Explanation:
The exchange of substances with surroundings is done by cells by the process of diffusion. The rate of diffusion of substances requires the presence of a higher surface area than volume. As the cells become larger, their surface area is reduced with respect to the volume. Therefore, larger cells can not support the diffusion of substances in and out as required for its proper functioning. If cells are allowed to grow continuously, they will not be able to intake the requires materials such as food and to release the waste outside.
Answer:
invertebrates. animal's without backbone.
verterbrates- animals with backbone
