Genetics

The role of ribosomes in a polysome is to Translate the mRNA into proteins.

• A polysome (or polyribosome) is a complex of an mRNA molecule and two or more ribosomes that are actively translating the mRNA into protein.
• Each ribosome synthesizes a polypeptide chain based on the mRNA sequence.

The morphology of chromosomes can be best studied at Metaphase.

During metaphase of cell division, chromosomes are highly condensed and aligned at the metaphase plate, making them most visible and distinct under a microscope.

stages of cell division, specifically focusing on mitosis, which is the process of nuclear division in eukaryotic cells:

1. Interphase (Preparation phase, not part of mitosis but essential)

   • Cell grows and prepares for division.

   • DNA is replicated.

2. Prophase

   • Chromatin condenses into visible chromosomes.

   • Each chromosome has two sister chromatids joined at the centromere.

   • Nuclear membrane starts to break down.

   • Spindle fibers begin to form from centrioles.

3. Metaphase

   • Chromosomes align at the cell’s equator (metaphase plate).

   • Spindle fibers attach to centromeres of chromosomes.

4. Anaphase

   • Sister chromatids are pulled apart toward opposite poles of the cell by spindle fibers.

5. Telophase

   • Chromatids reach the poles.

   • Nuclear membranes reform around each set of chromosomes.

   • Chromosomes begin to uncoil back into chromatin.

6. Cytokinesis (Division of the cytoplasm)

   • Cell membrane pinches in, dividing the cytoplasm and creating two daughter cells.

   • Occurs concurrently with telophase or right after.

A human cell typically contains 46 chromosomes.

These are arranged in 23 pairs, with 22 pairs of autosomes and one pair of sex chromosomes (XX for females, XY for males).

Down Syndrome, which causes learning difficulties and physical health development delays and disabilities, is a Genetic disease.

• It is caused by an extra copy of chromosome 21, also known as Trisomy 21.

In Biofortification Technique, plant breeders use breeding to overcome Deficiency of micronutrients and vitamins.

• Biofortification aims to increase the nutritional value of crops by breeding varieties that are richer in essential vitamins and minerals.

  Examples:

  • Golden Rice enriched with vitamin A.

  • Iron-rich beans and zinc-rich wheat.

• It is a polymeric molecule essential in various biological roles in coding, decoding, regulation, and expression of genes.

The nitrogenous base absent in ribonucleic acid (RNA) is Thymine.

In RNA, thymine is replaced by uracil (U).

So, RNA contains

1. Adenine (A),
2. Guanine (G),
3. Cytosine (C),
4. and Uracil (U).

he nitrogenous bases of DNA are the molecules that form the building blocks of the genetic code. There are four main nitrogenous bases in DNA:

1. Adenine (A)

2. Thymine (T)

3. Guanine (G)

4. Cytosine (C)

In eukaryotic cells, the synthesis of RNA (transcription) takes place in the nucleus.

• The DNA, which serves as the template for RNA synthesis, is located within the nucleus.

A pair of contrasting characters controlling the same trait is called allele.

• Alleles are different forms of a gene located at the same locus on homologous chromosomes.

• 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.