Download Unzipping DNA - School Science

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HUMAN BODY
DNA is found in every single cell of
the human body (except red blood
cells), and in every living organism
and is stored in a special compartment
called the nucleus. There is also a
little DNA in the mitochondria.
Chromosomes
An average size protein molecule may contain 6000 atoms.
Chains of 50 - 2000 amino acids make up larger molecules
called proteins.
Amino acids are the basic building blocks of proteins and are
made up of molecules containing 10 - 40 atoms.
Proteins which cause chemical reactions are called enzymes.
There are over 2000 known different proteins and a typical
cell may contain up to a million copies.
The DNA in every human
cell contains all the
instructions (genetic code)
to make a complete body.
CELL
Metaphase
chromosome
NUCLEUS
The sides of the ladder are
made up of chains of sugar
(ribose) and phosphate.
DNA strand
wound around
histone protein
TARGET DNA
SEQUENCE
Chromatids
Protein scaffold
(non-histone protein)
Histone protein
The beads are
nucleosomes
POSSIBLE STRUCTURE
OF CHROMATID IN
CHROMOSOME
(ENLARGED VIEW)
DNA in the cell is not continuous but split into shorter
strands called chromosomes.
Humans have 46 chromosomes
(23 pairs - one chromosome in each pair is always
inherited from the mother and one from the father).
In humans 22 pairs of chromosomes always match if the 23rd pair matches then the individual is female,
if not they are male.
The sequence of base pairs on the DNA which
contains the information to make a protein is called
a gene. A gene is the blueprint for a protein.
One gene assembles only one protein. A specific
gene is always found in a particular site on a
particular chromosome.
Although there are only 4 different nucleotide
bases present in DNA - A,T,G and C these can be combined in many ways to
generate thousands of different genes.
DNA Double Helix
DeoxyriboNucleic Acid is a very long
molecule in the form of a double helix.
The best way to think of this is to
imagine a ladder twisted to make a
right-handed spiral.
The rungs of the ladder are made up of
four nucleic acids, Adenine (A), Thymine (T),
Guanine (G) and Cytocine (C) known as
the base pairs. A always pairs with T and C
with G. The sequence of pairing is known
as the genetic code.
Schools Liaison Office, CCLRC Daresbury Laboratory, Keckwick Lane, Daresbury, Warrington, WA4 4AD.
www.cclrc.ac.uk
1. Our bodies contain more than a million million cells, 5. DNA has been extracted from some strange sources
each containing about 1.5 metres of DNA - there are
including a cashmere jumper, powdered soup, stock
‘only’ 100 billion stars in our galaxy.
cubes, crisps, bones (e.g. the Tzar’s family) and a
tooth (from the body believed to be Luke).
2. Laid end to end the cells in a human body would
measure 27 million miles.
DNA DOUBLE HELIX
DNA replicates itself by ‘unzipping’ along the base
pairs so that there are two single strands. The cell also
contains ‘free’ nucleotides that attach themselves to the
single strands following the rule that A always attaches
to T and C to G. When the process is complete there
are now two identical strands of DNA where before
there was one. DNA replicates itself before cell division
or to produce proteins
3. The coding of the human genome (the complete
genetic code) contains enough letters to occupy
three sets of Encyclopedia Britannica, a total of 90
volumes in all, whereas the genome for a lily seed
the equivalent of 1800 volumes.
4. The total DNA from a whole human body is over a
million million metres long.This is enough to stretch
from the earth to the moon and back over 800 times.
6. Our genetic overlap with a chimpanzee is roughly
98.4%, with another human 99.9% with a sibling
99.95% and 100% with an identical twin. We also
share half our genes with an iguana.
ST RA NGE
DNA FACTS