Download DNA DNA Structure ~ The Specifics

DNA
DNA (deoxyribonucleic acid) - molecule that encodes genetic information of
living thingsFrancis Crick and James Watson are credited for discovering the
structure of DNA and ultimately how it works. However, it was largely the
work of Franklin Rosalind that led to this important discovery.
Genetics is the study of heredity and variation (differences) of inherited
characteristics. The genetic material inside is held in the nucleus on
chromosomes Chromosomes will contain all the genetic material in a
molecule of deoxyribonucleic acid (DNA). DNA is made of a set of chemical
instructions for the cell. The sequence of chemicals is unique for every
individual.
DNA
Chromosome
If we were to look at a distinct set of chemicals on the DNA molecule for
instructions this is called a gene. Each one of these genes will be located at a
specific location called a locus on a chromosome. One chromosome can carry
hundreds or thousands of genes. The complete set of an organism’s
hereditary information is called it’s Genome
DNA Structure ~ The Specifics
DNA has 3 main components: A pentose sugar (cyclic 5-carbon sugar), A phosphate
group that has a negative charge, A nitrogenous base. These 3 components together are
called nucleotides. (Be able to draw a nucleotide!)
The nitrogenous base is attached to the carbon ring in 1’ (prime) position by a glycosyl
bond. The phosphate group is attached to the 5’ carbon by an ester bond. There are 4
possible bases for nucleotides of DNA:_______________________________________________.
These 4 nitrogenous bases have a key relationship. The bases of one strand are paired
with the bases in the other strand.
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This type of pairing is called Complementary Base Pairing. Chargaff’s Rule- means that
if you know the nucleotide sequence of one strand you can deduce the sequence of the
other strand.
The base pairs are held together by hydrogen bonds. Each nucleotide piece is attached to
the next nucleotide in order by a phosphodiester bond… creating the “backbone” of the
DNA molecule or the “ladder sides”. The two sides of the DNA molecule are bonded
together in the middle by hydrogen bonds holding together the nitrogenous bases…
creating the “steps” of the ladder. Two strands twist together to form a helix shape…
cork screw shape. DNA consists of 2 antiparallel (parallel but running in opposite
directions) strands of nucleotides. These two strands have the 5’ end of one strand of
DNA aligning with the 3’ end of the other strand in the double helix. Thus each DNA
molecule has an intrinsic directionality.
That is, the fifth carbon in deoxyribose points upward in one strand and downward in
the other. These 2 strands of nucleotides are twisted into a right-handed helix that
makes one complete turn every 10 nucleotides (a distance of 3.4 nm).