Structure of Nucleotides and DNA

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Structure of nucleotides and DNA.

Deoxyribonucleic (DNA) is the molecule that hold the genetic information of living things. In our body every cell contains about 2 meters of DNA. DNA is copied every time a cell divides. Deoxyribonucleic (DNA) is made up of two polynucleotide strands. Polynucleotide strands twist around each other, forming a shape that looks like a ladder called a double helix. The two polynucleotide strands run antiaparallel to each other with nitrogenous bases this means that the stands run in opposite directions, parallel to one another. The DNA molecule consists of two backbones chains of sugars and phosphate groups. The organic bases held together by hydrogen bonds. Although bases bonded together are termed paired and specific way as to which base they join to. An Adenine with only pair with thymine and Cytosine with only pair with guanine.

Deoxyribonucleic (DNA) and ribonucleic acid (RNA) both carry genetic information, although they have a few differences between them. DNA contains a sugar called deoxyribose, whilst RNA contains a sugar called ribose. Also DNA is a double polynucleotide chain while RNA is a single polynucleotide chain as well DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses adenine, uracil, cytosine, and guanine. Uracil is different from thymine in that it lacks a methyl.

• Replication

DNA replicates by the semi- conservative method. When the cell divides throughout a part of the interphone recognized as the S phase then each DNA molecule replicates. The new molecules contain one stand of the original and one new stand, and this type of replication. DNA must copy when cells divide. This is called replication this process take place during i...

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...and begin to move to chromosomes towards the midline of diving cell.

- Metaphase 2: The chromosome moves to the midline to the dividing cell, facing opposite poles of the dividing cell.

- Anaphase 2: the centromeres divide and the chromatide separate and move towards opposite poles of the cell.

- Telophase 2: Nuclear envelopes reform around the four daughter haploid nuclei. A nuclear membrane forms around the chromosomes in each of the 4 new cells.

• Chromosomal abnormalities

Non disjunction is improper segregation of chromosomes during meiosis cell divisions during meiosis stage 1 or stage 2, both go into the same gamete. This is known as non – disjunction. As an effect of non- disjunction some gametes have two copies of chromosome. No disjunction at the first meiotic division results in both homologs travelling towards the same spindle pole.

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