Major highlights of Human Genome Project

 Major highlights of Human Genome Project:-

The most important feature of a DNA molecule are the nucleotide sequences, and the identification of genes and their activities. 

• Approximately 1.1% to 1.5% of the genome codes for proteins.
• The number of protein coding genes is in the range of 30,000-40,000.
• An average gene consists of 3000 bases, the sizes however vary greatly. Dystrophin gene is the larget known human gene with 2.4 million bases.
• Approximately 24% of the total genome is composed of introns that split the coding regions (exons), and appear as repeating sequences with no specific functions.
• The draft represents about 90% of the entire human genome. It is believed that most of the important parts have been identified.
• The remaining 10% of the genome sequences are at the very ends of chromosomes (i.e. telomeres) and around the centromeres.
• Chromosome 1 contains the highest number of genes (2968), while the Y chromosome has the lowest. Chromosomes also differ in their GC content and number of transposable elements.
• About 100 coding regions appear to have been copied and moved by RNA-based transposition (retro transposons).
• A vast majority of the genome (~97%) has known functions.
• More than 3 million single nucleotide polymorphisms (SNPs) have been identified.
• About 200 genes are close to that found in bacteria.
• Genes and DNA sequences associated with many diseases such as breast cancer, muscle diseases, deafness and blindness have been identified.
• Human genome is composed of 3200 Mb (or 3.2 Gb) i.e. 3.2 billion base pairs (3,200,000,000).
• Human DNA is about 98% identical to that of chimpanzees.
• Repeated sequences constitute about 50% of the human genome.
• Between the humans, the DNA differs only by 0.2% or one in 500 bases.

special properties of plant cells

 Special Properties of Plant Cells:-

Among eukaryotic cells the most striking difference is between those of animals and plants. Plants have evolved a sedentary lifestyle and a mode of nutrition that means

they must support a leaf canopy. Their cells are enclosed within a rigid cell wall that gives

shape to the cell and structural rigidity to the organism. This is in contrast to the flflexible boundaries of animal cells. Plant cells frequently contain one or more vacuoles

that can occupy up to 75% of the cell volume. Vacuoles accumulate a high concentration

of sugars and other soluble compounds. Water enters the vacuole to dilute these sugars,

generating hydrostatic pressure that is counterbalanced by the rigid wall. In this way the

cells of the plant become stiff or turgid, in the same way that when an inner tube is inflflated

inside a bicycle tire the combination becomes stiff. Vacuoles are often pigmented, and

the spectacular colors of petals and fruit reflflect the presence of compounds such as the

purple anthocyanins in the vacuole. Cells of photosynthetic plant tissues contain a special

organelle, the chloroplast, that houses the light-harvesting and carbohydrate-generating

systems of photosynthesis. Plant cells lack centrosomes although these are found in many algae.