DNA: Intro to structure and function
ppt notes
DNA by the numbers
• A human has _____ chromosomes (coiled DNA), a plum tree has 48, a chicken has 78 and an
an t has 2
• Each human cell has about ______ of DNA. About 6 billion bases, or ___ billion pairs of bases.
• The average human has 75 trillion cells.
• DNA has a diameter of only 0.000000002 m
Why do we study DNA?
• Importance to _________________________________________• Medical benefits such as cures for ____________________
• _____________________ Engineering
Chromosomes and DNA
• DNA makes up the ____________________________
• Genes are stretches of __________ found in different regions in the chromosomes.
• More about this soon!!
DNA
• DNA is often called the blueprint of life - Why?
• In simple terms, DNA contains the
_________________________
for
making
__________________ within the cell.
The Shape of the Molecule
• DNA is a very long polymer.
• The basic shape is like a twisted __________________.
W hat other objects, if we twist them,
might resemble DNA?
• Double helix
The Double Helix Molecule
• The DNA double helix has _______ strands twisted together
• Need to look at the structure of one strand
One Strand of DNA
• Backbone is alternating ____________________ and __________________________, a sugar
• The teeth are nitrogenous _______________
Nucleotides
One deoxyribose together with its phosphate and base make a _______________________.
The Structure of DNA
• One strand of DNA is a ______________________ of nucleotides
• One strand of DNA has many millions of nucleotides
Four nitrogenous bases
•
Cytosine ___
• Thymine
• Adenine
• Guanine
___
___
___
Two Kinds of Bases in DNA
• Pyrimidines are single ring bases
• Purines are double ring bases
Pyrimidines:
Thymine and Cytosine
• Thymine and cytosine each have one ring of carbon and nitrogen atoms
Purines:
Adenine and Guanine
• Adenine and guanine each have two rings of carbon and nitrogen atoms
Two Stranded DNA
• DNA has two strands that fit together something like a ___________________
• The teeth are the nitrogenous bases but why do they stick together?
Hydrogen Bonds
• The bases attract each other because of ____________________ bonds
• Hydrogen bonds are weak but there are millions and millions of them in a single molecule of
DNA………W here else do we find millions and millions of hydrogen bonds? ________________
Hydrogen Bonds, cont.
• When making hydrogen bonds, thymine always pairs up with adenine
• And cytosine always pairs up with guanine
Important:
• Adenine and Thymine always join together
So ‘A’ bonds with ____
• Cytosine and Guanine always join together
So ‘C’ bonds with ____