Biology Test - 11

The correct pair is: Ligases - are the enzymes that join the two DNA molecules.

Ligase will join two pieces of DNA with matching ends to form a single, unbroken molecule of DNA. Restriction enzymes and DNA ligase are used in DNA cloning to inject genes and other DNA fragments into plasmids.

Other option is:

Polymerase - synthesize the DNA strand.

Nucleases - Break the DNA into fragments.

Exonucleases - a special type of nucleases enzymes that make cut at the end of the DNA.

The false sentence about cycas is: seeds are borne in seed cones.

• Cycas is a genus of plants belonging to a very ancient lineage, the Cycadophyta, which are not closely related to palms, ferns, trees or any other modern group of plants.
• Cycas, genus of 115 species of palmlike cycads in the family Cycadaceae native to tropical and subtropical areas of the Old World. The leaves of sago palm (Cycas revoluta) are widely used as ceremonial “palms” and in floriculture. The pithy stems of this and other species are a source of sago, a food starch.

Blood group AB contains no antibodies.

People with blood group AB have both antigen A & B present in their bloodstream, they do not have any antibodies present.Due to the absence of antibodies in the blood, they are called universal recipients as they can receive blood from any other type.

UAG is a nonsense codon in universal code.

There are three nonsense codons are called amber (UAG) ochre (UAA) and opal (UGA). They encode no amino acid. The ribosome pauses and falls off the mRNA.

• UGG code for tryptophan
• UGC code for cysteine
• UAC code for tyrosine

Diploid endosperm is found in Oenothera.

The Endosperm is the tissue produced inside the seeds of most flowering plants following fertilization.It is a product of triple fusion, develops from the central cell of the embryo sac.It is generally Triploid tissue.Date palm, Ivory palm and Castor have triploid endosperm.Diploid endosperm is found in Oenothera.

Osteoblasts are bone forming cells. It produces matrix which later becomes mineralized. Osteoclasts are cells that break bone. Bone mass is maintained by balancing osteoblasts and osteoclasts process. Chondroblasts are cells which form chondrocytes in the cartilage matrix. Chondroclasts are cells which reabsorb calcified cartilage.

Azolla forms a symbiotic relationship with Anabaena. The cyanobacterium fixes atmospheric nitrogen, giving the plant access to nitrogen whereas the fern provides a habitat for the cyanobacterium.

Polyblend is a fine powder of recycled modified plastic waste. The mixture is mixed with bitumen that is used to lay roads.

Polyblend is a fine powder of recycled modified plastic. It was produced by plastic manufacturers in order to recycle plastic waste. When blended with bitumen, polyblend can be used to lay roads which have increased road life.

Sunken stomata are not directly visible to the leaf surface. They are found beneath the epidermis and beneath the leaves of plants. Xerophytes have sunken stomata to prevent water loss from the plant. They are often enclosed and partially covered by cuticles and are sunken within the leaf rather than on the surface. Therefore statement (A) is not true.

The stem of the aquatic plants is flexible because it helps the leaves to float. They bend with the flow of water so the plants do not get damaged by strong current. Therefore statement (B) is true.

Heterophylly is one of the methods of plasticity in which plant follow several pathways in response to the external environment. Plants like cotton, coriander, larkspur and buttercup have leaves in juvenile phase which are entirely different from the mature phase. Also, differ in either the plant is aquatic or terrestrial.  Therefore statement (C) is true.

Generally, hydrophytes have poorly developed root systems. This is because their other adaptations allow them to gain all the nutrients they need from their aquatic environment. Therefore statement (D) is true.

No waxy cuticle, or a very thin one, can be found on the leaves of hydrophytes . Due to the excess of water available to them, there is no need for a waxy cuticle, since reducing water loss is not a factor these plants have needed to adapt to. Therefore statement (E) is not true.

Root pressure introduced by Stephen Hales and it is absent in gymnosperms.

When a plant is carefully cut close to the base of the stem, the sap oozes from the stump. The fluid comes out forcibly, that pressure is known as root pressure.Root pressure is a vital significance in plants, for it forces up water against the gravity to the tip of even the tallest plant.