Biological Molecules - DNA + RNA Flashcards
What is DNA?
DeoxyriboNucleic Acid is a double stranded polynucleotide that contains all the genetic information for a living organism. It is a hereditary molecule
What are nucleic acids composed of?
Nucleotides
What is the structure of a nucleotide?
Phosphate
Pentose sugar
Nitrogenous base
What are the 4 nitrogenous bases found in DNA?
Adenine Cytosine Guanine Thymine
What are the 4 nitrogenous bases found in RNA?
Adenine Cytosine Guanine Uracil
What bond links nucleotides?
Phosphodiester bond
What is RNA?
RiboNucleic Acid is a single stranded polynucleotide chain
What are the 3 forms of RNA?
transfer -> tRNA
messenger -> mRNA
ribosomal -> rRNA
What is the pentose sugar in DNA?
Deoxyribose
How are the 2 strands of DNA held together?
By the complementary base pairs and hydrogen bonds
What factors ensure that DNA is a very stable molecule?
The phosphodiester backbone is unreactive, protecting the reactive bases
The strands are bonded together by complementary base pairing and hydrogen bonds
What are the complementary base pairs in DNA?
Adenine pairs with Thymine
Guanine pairs with Cytosine
Why is RNA less stable than DNA?
It only has one strand to protect the reactive bases
How does complementary base pairing help DNA’s function?
It makes DNA and RNA sequences compatible, allowing RNA to transfer information from the DNA
What feature of DNA allows it to be separated easily during copying?
the strands are held together by relatively weak hydrogen bonds
Who discovered the structure of DNA?
Watson and Crick
Why did people originally doubt that DNA was a hereditary molecule?
It is a simplistic molecule
What is the main function of DNA?
To be replicated
How is DNA replicated?
Semi-conservatively: Each time it is copied, only half the information is made new
Describe the process of DNA replication
The strand ‘unzips’ and new nucleotides attach to each half of the strand, forming two new, identical strands
Name the enzymes present in DNA replication and their funtions
Helicase -> unzips strands
Polymerase -> attaches new nucleotides
Why do the polymerase enzymes run in opposite directions?
The active site of polymerase only bonds with the 3’ end of the strands.
For one strand, the polymerase works normally but for the other it works in sections but skipping backwards as it can only attach to the 3’ not the 5’
