GENETICS

• Polysome is a thread-like structure, a group of ribosomes bound to a messenger RNA molecule. It constitutes a complex of an mRNA and ribosomes, which help to translate mRNA into polypeptides. Ribosomes are cellular organelles composed of rRNA and proteins. They are present free in the cytoplasm before they become attached to mRNA.

Chromosomal morphology is best observed at metaphase. Metaphase is a stage of mitosis in the cell cycle in which chromosomes are at their most condensed and coiled stage. These chromosomes, carrying genetic information, align in the equator of the cell before being separated into each of the two daughter cells. The structure of chromosomes is quite clear at this phase of the cell cycle.

Chromosomes come in pairs. Normally, each cell in the human body has 23 pairs of chromosomes (46 total chromosomes). Half comes from the mother; the other half comes from the father. Two of the chromosomes (the X and the Y chromosome) determine your sex as male or female when you are born. They are called sex chromosomes: Females have 2 X chromosomes and Males have 1 X and 1 Y chromosome.

Down syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21. This extra genetic material causes the developmental changes and physical features of Down syndrome.
Down syndrome varies in severity among individuals, causing lifelong intellectual disability and developmental delays. It’s the most common genetic chromosomal disorder and cause for learning disabilities in children. It also commonly causes other medical abnormalities, including heart and gastrointestinal disorders.

Bio fortification refers to the cultivation of crops to increase their nutritional value. The crops produced through bio fortification method are always rich in nutrients like iron, zinc and Vitamin A. For example; Golden rice was produced using the method of bio fortification. This rice is rich in beta-carotene and provides vitamin A to children.

Ribonucleic acid (abbreviated RNA) is a nucleic acid present in all living cells that has structural similarities to DNA. Unlike DNA, however, RNA is most often single-stranded. An RNA molecule has a backbone made of alternating phosphate groups and sugar ribose rather than the deoxyribose found in DNA.

Adenine, guanine and cytosine are common nitrogenous bases present in both DNA and RNA. While thymine is present only in DNA. RNA has uracil instead of thymine. Guanine always binds with cytosine by gydrogen bond. Adenine forms a hydrogen bond with thymine in DNA and with uracil in RNA.

Transcription is the process of synthesizing ribonucleic acid (RNA). Synthesis takes place within the nucleus of eukaryotic cells or in the cytoplasm of prokaryotes and converts the genetic code from a gene in deoxyribonucleic acid (DNA) to a strand of RNA then directs protein synthesis.

In classical Mendelian genetics, each character is governed by a pair of character called as allele. One allele comes from father and second allele comes from mother. In a diploid organism, each gene has two alleles. Phenotype is a term that describes external characters of an organisms that are visible to naked eye. Genotype refers to the genetic constitution of an organism.

A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins. However, many genes do not code for proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. An international research effort called the Human Genome Project, which worked to determine the sequence of the human genome and identify the genes that it contains, estimated that humans have between 20,000 and 25,000 genes.