Answer:
d. DNA polymerase begins adding nucleotides at the 5' end of the template
Explanation:
Polymerase DNA always works in one direction, synthesizing the new 5' to 3' oriented chains and adding nucleotides to the 3' end of a new synthesis chain by forming phosphodiester bonds between the phosphate of a nucleotide and the sugar of the anterior nucleotide.
Because DNA polymerase only acts in a 5' to 3' direction, replication along a chain, the leading chain, occurs continuously. The synthesis of the opposite chain, the delayed chain, occurs discontinuously because the DNA polymerase must wait for the replication fork to open. Over the delayed chain, short segments of DNA called Okazaki fragments (named after Reiji and Tsuneko Okazaki, the scientists who discovered these fragments) are synthesized as polymerase DNA works out of the replication fork. Ligase DNA catalyzes the covalent bonds between Okazaki fragments in the delayed chain to ensure there are no gaps in the phosphodiester skeleton. Finally, the first ones are removed and these gaps are filled by the DNA polymerase.
Answer is labyrinthodont
About 110 million years ago, labyrinthodonts ( maze-toothed), a group of extinct amphibians. They were evolved from lobed-finned fish in the Devonian period. They were dominant animals in the rift valley was present at that time between Antarctica and Australia.
Answer:
Watson and Crick proposed the double helical model of DNA.
Explanation:
- This model says that DNA exist as double helix. It has two polynucelotide strands running in opposite direction i.e the strands are anti-parallel.
- Each polynucleotide strand is made up of several nucleotide liknked together by phophodiester bonds.
- The two strands are not coiled upon each other but the double strand is coiled upon itself around a common axis like the spiral stair case. Here base pairs forms the stairs and backbone of two strands form railing. Back bone contains sugar and phosphate.
- The base pairing is specific, adenine always pairs with thymine and guanine always pairs with cytosine. Thus if we see any base pair, it consists of one purine and one pyrimidine.
- The two strands of DNA thus show complementary base pairing.
- The strands are held together because of hydrogen bonding between the bases in opposite strand.
- One full helical turn involves ten base pairs and the base pairs are stacked 3.4 A apart.
- This form is called as B-form of DNA.
Biomolecules are organic compounds that are present as essential components of living things. There are four major biomolecules namely lipids, proteins, carbohydrates and nucleic acids. Proteins, lipids and glucose are usually used by organisms as energy sources as well as structural components among other functions in living organisms. Nucleic acids are important components that bring about heredity. In this case the appropriate molecule to be chosen by the long distance learner would be carbohydrate because it stores and may be used as a source of energy.
