1.
Humans have roughly
100,000,000,000,000 (100 trillion cells). Each cell (except red blood cells)
has a nucleus. Each nucleus contains 46 (23 pairs) of chromosomes (in gametes
such as sperm and ovum only 23 chromosomes are present). These chromosomes contain
the amazing molecule, the DNA (Deoxyribo Nucleic Acid).
2.
DNA is considered as the
“blueprint” of life.
3.
DNA is found in all living
things except some RNA viruses.
4.
Generally a cell is microscopic.
Its size is at micron (10-6 m) level. The diameter of nucleus inside
in it is about 6 micrometers (μm). What will be the length of DNA present in such
a nucleus? If we unwound and tied together, the DNA strands in a cell nucleus would
be about 2 metre (6 feet)!!! But its width would be only 50 trillionths of an
inch.
5.
If you unraveled your
entire DNA from all of your cells and laid out the DNA end to end, the strand can
be stretched from the Earth to the Sun hundreds of times!!
6.
If you uncoil the entire
DNA in all your cells, you could reach the moon 6000 times!
7.
You can accommodate about 25,000
DNA strands side by side in the width of a single adult hair. (The diameter of
human hair ranges from 17 to 181 µm whereas it is 20 Å for DNA).
8.
Do you know what a gene is?
It’s a functional segment of DNA that controls a particular character.
9.
The entire DNA in 23
chromosomes of a human cell is called human genome. It means we have 2 genomes in
each cell. Such cells are known as diploid cells. But the sperm and ovum have only
one genome (remember they have only 23 chromosomes). Such cells are known as haploid cells.
10.
In a human cell there are about
30,000 genes.
11.
Average gene consists of 3000
bases.
12.
Largest known human gene is
dystrophin on X-chromosome. It contains 2.4 million bases.
13.
Functions
of over 50% of discovered genes are unknown.
14.
Chromosome I has most
genes (2968 genes) and Y chromosome has the fewest (231 genes).
15.
What is the chemical content
of a DNA? DNA is made up of millions of chemical building blocks called
nucleotides. Each nucleotide contains 3 types of chemicals- a nitrogen base, a
deoxyribose sugar and a phosphate group. There are 4 types of nitrogen bases in DNA- Adenine
(A), Thymine (T), Cytosine (C) and Guanine (G). So the types nucleotides are
also vary based on the type of nitrogen base in it.
16.
Human
genome, i.e. DNA in 23 chromosomes of a cell, contains about 3165 million
nucleotides!!
17.
In DNA, there are millions of
steps formed of a pair of nitrogen bases. Adenine always pairs with thymine and
Cytosine always pairs with cytosine. It means the amount of adenine is equal to
thymine. Similarly the amount of cytosine is equal to guanine.
18.
99.9% nucleotide bases are
identical in all people i.e. 99.9% of our DNA sequence is the same as other
humans. 0.1% is what makes each of us unique. Identical twins share 100% of
their genes. Siblings share 50% of their genes. A parent and child share 50% of
their genes.
19.
Our DNA has very close
similarity with the DNA of other species. See them below:
Species
|
How many genes do we share with them?
|
Chimpanzee
|
98%
|
Mouse
|
92%
|
Zebra fish
|
76%
|
Fruit fly
|
51%
|
Weed (thale cress)
|
26%
|
Bacteria (E. coli)
|
18%
|
20.
Human DNA is closer to a rat
than a cat.
21.
Less than 2% of the genome
codes for proteins. i.e., Genes make up only about 2-3% of our genome.
22.
The 4 nitrogen bases are considered as
the letters in the genetic language. The sequence of nitrogen bases (in nucleotides)
forms the genetic codes as the letters form the words in a language. In a
genetic code there will be only 3 bases. Each code is responsible for the
production of a particular amino acid. Many amino acids are linked in a
specific sequence to form a protein. This protein is expressed as a particular
character of the individual. On the other hand, the four letters in
the DNA alphabet - A, C, G and T - are used to carry the instructions for
making all organisms.
23. There are approximately 3 billion chemical letters (bases)
in the DNA code in every cell in your body.
24.
If you tried typing the whole genetic code continuously at
the speed of 200 letters per minute it would take 29 years to finish!
25.
One million bases of DNA sequence data is equivalent to 1
megabyte (MB) of computer data storage space.
26.
James Watson and Francis
Crick explained the structure of
DNA. According to them, DNA is a double helix i.e. like a twisted ladder.
27.
A complete 3 billion base
genome would take 3 gigabytes of storage space.
28.
DNA can self-replicate
using cellular machinery made of proteins.
29.
The segment of DNA
designated a gene is made up of exons and introns. Exons have the code for
making proteins. Introns (junk DNA) are intervening sequences that do not code
for making proteins.
30.
The human genome sequence
generated by the private genomics company Celera was based on DNA samples
collected from five donors who identified themselves only by race and sex.
31.
If
all three billion letters in the human genome were stacked one millimeter
apart, they would reach a height 7,000 times the height of the Empire State
Building.
32.
Changes in the DNA
sequence are called mutations.
Many thing can cause mutations, including UV irradiation from the sun,
chemicals like drugs, etc.
33.
DNA is affected by the
environment; environmental factors can turn genes on and off.
34. The technique to identify
the similarities of the DNA fragments of 2 individuals are called DNA
fingerprinting. It is developed by Alec Jeffreys (1985). It is used as a forensic
tool to solve paternity, rape, murder etc. it can also be used for the
diagnosis of genetic diseases and to determine phylogenetic status of animals.
35.
DNA can be extracted from many different types of
samples: blood, cheek cells, urine. You can extract DNA at home from fruit and
even your own cheek cells.
36.
DNA can be stored either
as cells on a cotton swab, buccal brush, or frozen blood or in extracted form.
37.
In forensics, DNA analysis
usually looks at 13 specific DNA markers (segments of DNA).
38.
A DNA fingerprint is a set
of DNA markers that is unique for each individual except identical twins.
39.
Many countries, including
the US and UK, maintain a DNA database of convicted criminals.
40.
Polymerase chain reaction
(PCR) is used to amplify a sample of DNA so that there are more copies to
analyze.
41.
We eat DNA every day because
the vegetables, fruits, meat, fish etc contain DNA.
42.
DNA testing is used to
authenticate food like caviar and fine wine.
43.
Genetically modified crops
have DNA from another organism inserted to give the crops properties like pest
resistance.
DNA is like an engineer! It draws a plan known as RNA. It constructs a building called Protein!! A mistake made by an engineer results in the mistake in his plan which in turn affects the building. Thus any mutation (change or mistake) in DNA results in change in RNA which synthesizes wrong protein leading to genetic disorders.