DNA Composition and Structure Flashcards
DNA structure
What does DNA consist of what does this form?
What is a molecule of DNA made up of?
DNA consists of two molecules (polynucleotide stands) that form a double helix structure
A molecule of DNA is made up of millions of tiny subunits called nucleotides.
What does each nucleotide consist of?
Each nucleotide consists of:
- Phosphate group
- Pentose sugar
- Nitrogenous base
(Diagram of a nucleotide on OneNote)
What forms the backbone of the DNA molecules and what forms the rungs?
The phosphate and sugar form the backbone of the DNA molecule
(sugar - phosphate backbone)
The bases form the rungs
What are the four types of nitrogenous bases in DNA?
Adenosine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Each base will only bond with one other specific base.
Which bases pair?
Adenine and Thymine
Cytosine and Guanine
This is complementary base pairing
(so %A = %T and %G = %C)
Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.
(Diagram on OneNote)
(Diagram to show this on OneNote)
How are the 2 DNA strands held together?
The strands are held together by complementary base - pairing.
The bases are joined by hydrogen bonds.
How many Hydrogen bonds are Adenosine and Thymine held together by?
How many Hydrogen bonds are Guanine and Cytosine held together by?
Adenosine and Thymine are held together by 2 hydrogen bonds
Guanine and Cytosine are held together by 3 hydrogen bonds
What does Chargaff’s Rule tell us?
% of Guanine and Cytosine are equal
% of Adenine and Thymine are equal
So Purines = pyrimidines
Which bases are Purines and which are Pyrimidines?
Purines = Adenine and Guanine (Large bases/ double rings)
Pyrimidines= Cytosine and Thymine (smaller bases/ single ring)
Remembering the Base Pairings
Mnemonic Device
AT the Grand Canyon
A to T
G to C
What is a codon?
What does each codon code for?
Codon is a sequence of 3 bases.
Each codon codes for a specific amino acid
What is a gene?
What does each unique gene contain?
A gene is a section of DNA that codes for a protein.
Each unique gene has a unique sequence of bases.
What does the unique sequence of bases code for?
What gives us a unique phenotype?
This unique sequence of bases will code for the production of a unique protein.
It is these proteins and combination of proteins that give us a unique phenotype.
Central Dogma
What is it?
Theory stating that genetic information flows only in one direction, from DNA, to RNA, to protein, or RNA directly to protein.
Double-stranded DNA is the cellular target of several anticancer drugs
(Many anticancer drugs act on DNA)
Example 1
Anticancer Drug Cisplatin
This forms covalent adducts to Guanine bases
Example 2:
Anticancer Drug: Doxorubicin
Acts as an intercalating agent
i.e. it slides in between the stacked bases
Mitosis
All cells replicate and divide through mitosis.
This involves all parts of the cell.
When a cell replicates and divides, the DNA replicates and divides too.
What are the 2 main functions of mitosis?
The functions include growth and replacing aging cells
How does DNA replicate?
The two strands of DNA must be separated and be copied.
One protein separates the two strands of DNA.
Another protein brings the correct new base to pair with the existing base, thus using it as a template.
- A with T, and G with C
In this way, two DNA strands are formed from one.
Each new DNA double helix has one old strand (the parent strand) and one new strand (the daughter strand).
What is the human genome?
How many base pairs are in the human genome?
The human genome is all of the DNA in a cell of a human
The human genome has over 3.2 billion base pairs.
What can DNA condense to form?
DNA can condense to form a chromosome
(DNA tightly wraps around a spool just like kite string. This is a chromosome.)
(Condensing a strand of DNA is like taking a very long string, sewing it into a shirt and balling up the shirt into a very tight wad. The string is the DNA.)
(Diagram to show this on OneNote)
Viral DNA replication can be targeted to prevent viral replication
Acyclovir
Inhibits viral DNA polymerase
Acyclovir is primarily used to treat herpes simplex virus infections, chickenpox and shingles.
It is also used to prevent cytomegalovirus infection following transplant and severe complications of Epstein–Barr virus infection.
