Entire Human Genome Has Been Sequenced

June 20, 2021
by rajeev
0

Researchers have finally sequenced the complete human genome, filling the gaps in the Human Genome Project’s (HGP) historic first draft; which could serve as a more accurate reference guide for future genomic research, giving scientists a way to study the 0.1% of the genome that varies across our species. The new human genome study has yet to be peer-reviewed.

LEARNING FROM HOME/WITHOUT CLASSES/BASICS

The human genome: A genome is like a genetic instruction manual — it contains all the information an organism needs to grow and function. The human genome is written in DNA, and while your exact genome is unique to you, about 99.9% of it is identical across all people.

When we talk about “sequencing” the genome, we mean writing out the DNA bases (C, G, T, and A) in the order they appear in most people. This sequence can then serve as a reference guide for research into human biology, evolution, diseases, and more.

What is DNA

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA). Mitochondria are structures within cells that convert the energy from food into a form that cells can use.

The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. An important property of DNA is that it can replicate, or make copies of itself.

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.

In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females.

The 23rd pair, the sex chromosomes, differ between males and females. Females have two copies of the X chromosome, while males have one X and one Y chromosome.

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. Every person has two copies of each gene, one inherited from each parent.

Ribonucleic acid (RNA): A nucleic acid molecule similar to DNA but containing ribose rather than deoxyribose. RNA is formed upon a DNA template. There are several classes of RNA molecules.

They play crucial roles in protein synthesis and other cell activities.

DNA COMPARISON WITH RNA

Comparison	DNA	RNA
Full Name	Deoxyribonucleic Acid	Ribonucleic Acid
Function	DNA replicates and stores genetic information. It is a blueprint for all genetic information contained within an organism	RNA *converts the genetic information contained within DNA to a format used to build proteins*, and then moves it to ribosomal protein factories.
Structure	DNA consists of two strands, arranged in a double helix. These strands are made up of subunits called nucleotides. Each nucleotide contains a phosphate, a 5-carbon sugar molecule and a nitrogenous base.	RNA only has one strand, but like DNA, is made up of nucleotides. RNA strands are shorter than DNA strands. RNA sometimes forms a secondary double helix structure, but only intermittently.
Length	DNA is a much longer polymer than RNA. A chromosome, for example, is a single, long DNA molecule, which would be several centimetres in length when unravelled.	RNA molecules are variable in length, but much shorter than long DNA polymers. A large RNA molecule might only be a few thousand base pairs long.
Sugar	The sugar in DNA is deoxyribose, which contains one less hydroxyl group than RNA’s ribose.	*RNA contains ribose sugar molecules,* without the hydroxyl modifications of deoxyribose.
Bases	The bases in DNA are Adenine (‘A’), Thymine (‘T’), Guanine (‘G’) and Cytosine (‘C’).	RNA shares Adenine (‘A’), Guanine (‘G’) and Cytosine (‘C’) with DNA, but contains Uracil (‘U’) rather than Thymine.
Base Pairs	Adenine and Thymine pair (A-T) Cytosine and Guanine pair (C-G)	Adenine and Uracil pair (A-U) Cytosine and Guanine pair (C-G)
Location	DNA is found in the nucleus, with a small amount of DNA also present in mitochondria.	RNA forms in the nucleolus, and then moves to specialised regions of the cytoplasm depending on the type of RNA formed.
Reactivity	Due to its deoxyribose sugar, which contains one less oxygen-containing hydroxyl group, DNA is a more stable molecule than RNA, which is useful for a molecule which has the task of keeping genetic information safe.	RNA, containing a ribose sugar, is more reactive than DNA and is not stable in alkaline conditions. RNA’s larger helical grooves mean it is more easily subject to attack by enzymes.