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Structure of a DNA Molecule


 Introduction

Deoxyribonucleic acid (DNA) is said to be a nucleic acid that contains genetic material. DNA molecules store information that is used in development of other molecules like protein molecules and RNA molecules. Genes are DNA components that carry the genetic material.


 Structure of DNA molecule

DNA has a double helix structure. A DNA molecule has two chains of nucleotides that are polymers of nucleic acid. The polymers are made up of different components. They contain a phosphate, a five carbon sugar and a nitrogen base. The nucleotides coil to form the double helix structure of the DNA molecule (Bates, &Maxwell, 2005). The nucleotides forming the DNA structure are arranged in a way that their sugar phosphate components face outside to form the backbone of the DNA structure. The nitrogenous bases face inward. There are four types of bases in a DNA structure. They include Adenine, Thymine, Guanine and Cytosine. When two chains of a DNA strand come together to form the helix shape of DNA structure the base in one strand binds with another base from another strand. The bases have different behaviors of binding. Adenine binds with Thymine and Guanine binds with Cytosine. The DNA molecules are composed of long strands of nucleotides.


Nucleotides are grouped together to form genes in the DNA structure. The genes are further grouped to form chromosomes. Human beings have 23 pairs of chromosomes. The DNA molecule has various functions. First the DNA molecule stores genetic information of the organism (Bates, &Maxwell, 2005). The DNA molecules have genes that are designed to perform specific functions in the body of human beings. The genes code for a specific proteins that carry out specific functions in the body. The DNA molecule is also used to transfer genetic information from one generation to another. The structure of DNA helps in inheritance because it contains genes and chromosomes that are used in inheritance. The structure of a DNA molecule contains a chain of nucleotides that are grouped into four. That is the Adenine (A), Cytosine (C), Guanine (G) and Thymine (T). The genetic material that is used in inheritance exists in the series of the nucleotides in the DNA and genes are also found in the DNA.


The genetic material is duplicated by splitting the strands in a DNA and using the strands to form a new partner strands. The duplication of genetic material is called DNA replication. Genes in the DNA store materials that are used to form proteins that form cells in the body. During inheritance chromosomes are also passed to the offspring by their parents. Each parent passes 23 chromosomes to the offspring so that the offspring has 46 chromosomes. These chromosomes contain genetic material from both parents thus giving the offspring the characteristics of the parents (Hagiya, &Ohuchi, 2003).


Meiosis is a process of cell division in sexually reproducing organisms. Meiosis reduces the number of chromosomes in a cell from diploid into haploid. This process leads to the development of gametes in animals and spores in plants. During meiosis each of the chromosomes duplicates its DNA and it carries the two copies of the DNA molecules that are identical. This strands are viewed as sister chromatids and they are connected by a Centro mere (Hagiya, &Ohuchi, 2003). During meiosis the homologous pairs of chromosomes are determine and matched. This process is called pairing. After that the two pairs which are matched are interlocked through recombination. This is known as crossover. After cross over the homologous chromosomes separate from each other and are divided into different nuclei in the first meiotic division. During second meiotic division the sister chromatids of each chromosome are separated and move to form different daughter cells so as to produce gametes (Hagiya, &Ohuchi, 2003).Meiosis is related to Mendel inheritance pattern because it leads to production of gametes in animals and spores in plants that are useful for inheritance. In Mendel experiment using peas. The peas have different genes that combine to form the offsprings. The different genes are called alleles and Mendel experiment has different genes that give different results. The alleles in the peas are passed to gametes through meiosis so as to form offsprings. This offsprings formed have almost similar characteristics with the parent pea plant.


Meiosis is applicable in Mendel’s plant as it has lead to formation of spores that are used for fertilization of the plants. The structure of DNA allows genetic materials to be copied and this supports Mendel’s observations using a pea plant. This is because the materials from DNA molecules are copied during meiosis to form gamates. The purpose of meiosis is to transfer genetic material from parents to offsprings and this is evidenced in Mendel experiment. The cells formed during meiosis have genetic material half the DNA and this allows the cell to combine with new cell with half genetic material to form a new offspring which is almost similar to the parents but slightly different( Bates,&Maxwell,2005).


 Conclusion

DNA molecules are important as they contain genes that store genetic materials and contain chromosomes that are used for replication. Cells undergo meiosis to produce gametes that have half the number of chromosomes from the parent. The structure of the DNA molecule is important as it helps in inheritance because of the genes and chromosomes.


 Reference

Bates, A., &Maxwell, A. (2005).DNA topology.Edition2.Oxford University Press, page 1

Hagiya, M., &Ohuchi, A. (2003).DNA computing: 8th International Workshop on DNA-Based Computers, DNA8, Sapporo, Japan, June 10-13, 2002: revised papers, Volume 2002.Springer, page 1

 
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