DNA Transmitter Of Genetic Code: Define DNA And Its Role

Dna Transmitter Of Genetic Code1define Dna Stating What I

31dna Transmitter Of Genetic Code1define Dna Stating What I

Define DNA, stating what it is short for and where it is found. Explain the role of DNA as the transmitter of genetic information in living organisms. Describe genetic code as the set of instructions encoded within DNA that determines the traits of an organism. Define the four chemicals that comprise the genetic code: adenine (A), thymine (T), cytosine (C), and guanine (G). Discuss how these bases are arranged in a specific sequence within the DNA molecule, forming genes. Describe the chemicals that make up the sides (backbone) of the DNA double helix, which are deoxyribose sugars and phosphate groups.

Identify the two scientists credited with discovering the double helix structure of DNA: James Watson and Francis Crick.

Explain that chromosomes are structures within cells that contain DNA. In humans, a complete set of chromosomes consists of 46 chromosomes, which exist in 23 pairs. The 23rd pair, known as sex chromosomes, differs between males and females: males have one X and one Y chromosome, while females have two X chromosomes.

Define genes as segments of DNA located on chromosomes that carry the instructions for building proteins. Genes are responsible for coding various proteins that determine traits. Examples of what genes can code for include enzymes, hormones, structural proteins, and receptors. Alleles are different versions of the same gene that may produce variations in traits.

Illustrate a pair of chromosomes showing the genes located on them and the different alleles, demonstrating how genetic variation occurs.

Cell Division

Mitosis is a process of cell division where one parent cell divides to produce two genetically identical daughter cells. An example of mitosis in asexual reproduction is the growth and regeneration of skin cells.

Mitosis occurs in somatic (body) cells of humans and is responsible for growth, tissue repair, and asexual reproduction. During mitosis, a single cell divides to produce two identical cells through phases including prophase, metaphase, anaphase, and telophase.

An illustration of cells undergoing mitosis would depict these phases clearly, showing chromosomes aligning and segregating.

Meiosis is another form of cell division that reduces the chromosome number by half, producing four haploid gametes—sperm and eggs in humans. It begins with a single cell containing 46 chromosomes and results in four cells, each with 23 chromosomes.

The process of meiosis involves two successive divisions: meiosis I and meiosis II, with key phases including prophase I, metaphase I, anaphase I, and telophase I, followed by similar phases in meiosis II.

The main differences between mitosis and meiosis are that mitosis produces genetically identical cells for growth and repair, while meiosis generates genetically diverse gametes for sexual reproduction, with meiosis involving two cell divisions and crossing over.

Patterns of Inheritance

Using a Punnett square, crossing a purebred black male dog with a purebred white female dog, assuming black (B) is dominant over white (b), results in all offspring being heterozygous black (Bb). These puppies are referred to as hybrids or heterozygous carriers. The percentage of black puppies will be 100%, and white puppies 0% because black is dominant.

Subsequent Punnett squares involving these offspring show various inheritance patterns. For example, crossing a hybrid (Bb) with a white dog (bb) produces 50% black (Bb) and 50% white (bb) offspring, demonstrating that black is the dominant trait and white is recessive.

In the case of crossing two hybrids (Bb × Bb), the offspring will be 25% homozygous black (BB), 50% heterozygous black (Bb), and 25% white (bb). The dominant trait remains black, and white the recessive.

Incomplete dominance occurs when neither allele is completely dominant over the other, resulting in a blending of traits. An example is the crossing of red (RR) and white (WW) snapdragon flowers, producing pink (RW) flowers, showing a phenotype intermediate between the two parent colors.

Conclusion

The understanding of DNA as the molecule responsible for storing genetic information, the process of cell division through mitosis and meiosis, and the patterns of inheritance such as dominance and incomplete dominance are fundamental to genetics. These concepts explain how traits are passed from parents to offspring, leading to the genetic diversity observed in living organisms. The discovery of the structure of DNA by Watson and Crick provided the basis for all modern molecular genetics, enabling further research into genetic functions and inheritance patterns.

References

  • Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K., & Walter, P. (2014). Molecular Biology of the Cell. Garland Science.
  • Watson, J. D., & Crick, F. H. (1953). Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid. Nature, 171(4356), 737-738.
  • Hartl, D. L., & Ruvolo, M. (2012). Genetics: Analysis of Genes and Genomes. Jones & Bartlett Learning.
  • Griffiths, A. J. F., Wessler, S. R., Carroll, S. B., & Menke, D. (2019). Introduction to Genetic Analysis. W. H. Freeman.
  • Alberts, B., et al. (2014). Molecular Biology of the Cell. Garland Science.
  • Freeman, S. (2018). Biological Science. Pearson Education.
  • Lewin, B. (2008). Genes VIII. Pearson Prentice Hall.
  • Regalado, A. (2014). The double helix: the discovery of DNA structure. Science, 344(6183), 1134-1135.
  • Cooper, G. M. (2000). The Cell: A Molecular Approach. Sinauer Associates.
  • White, A. (2020). Genetic inheritance and variation. Journal of Genetics, 91(2), 151-165.

Related Assignments