DNA Structure Flashcards
DNA consists of basic units known as _____
Nucleotides
A DNA nucleotide consists of _____
Deoxyribose sugar, a base and and a phosphate group
The deoxribose sugar bonds with the base via a ____ reaction that occurs when the base forms a _____ bond with the C’____ of the deoxribose sugar.
The deoxribose sugar bonds with the base via a condensation reaction that occurs when the base forms a N-glycosidic bond with the C’1 of the deoxribose sugar.
The term for the unit formed between the deoxribose sugar and the base (before the phosophate has bonded) is _____
A nucleoside.
The bond formed between the phosphate group and the deoxribose sugars C’___ is known as a ____ and is formed via a ____ reaction.
The bond formed between the phosphate group and the deoxribose sugars C’5 is known as a phosphoester bond and is formed via a condensation reaction.
Two bases are purines, meaning they are _____ structures. The purine bases are _____
Two bases are purines, meaning they are “two ringed” structures. The purine bases are adenine and guanine.
Two bases are pyrimidines, meaning they are ____ structures. The pyrimidine bases are ____
Two bases are pyrimidines, meaning they are “single ring” structures, The pyrimidine bases are thymine and cytosine.
Both the bond between deoxyribose sugar and the base, and the bond between the phosphoric acid and deoxyribose sugar are examples of strong ____ bonds.
Both the bond between deoxyribose sugar and the base, and the bond between the phosphoric acid and deoxyribose sugar are examples of strong covalent bonds.
A DNA strand is a ____ of deoxyribonucleotides. The nucleotides are joined by bonds between the C’ ___ of the sugar of one nucleotide and the ____ of the next nucelotide.
A DNA strand is a polymer of deoxyribonucleotides. The nucleotides are joined by bonds between the C’ 3 of the sugar of one nucleotide and the phosphate group of the next nucelotide.
The bond formed between two nucelotides is known as _____. It is formed via a ___ reaction.
A phosphodiester bond (covalent). Condensation reaction.
A long DNA strand consists of an array of bases and a _____
Sugar-phosphate backbone.
DNA forms in a ______ direction. Because the strand is elongated by ____
DNA forms in a 5’ to 3’ direction. Because the strand is elongated by the addition of nucelotides to the 3’ end.
What is the difference between the 5’ end and the 3’end of a DNA strand?
A 5’ end consists of a hydroxl group attached via the phosphate group to the 5’ of the deoxribose sugar. The 3’ end has an unbound OH group attached to the 3’ of the deoxribose sugar.
How is the orientation of two DNA strands described?
Anti-parallel
What holds two DNA strands together
The bases of each DNA strand form hydrogen bonds with their complimentary base on the other strand.
- Why don’t pyrimidines pair with each other?
2. Why don’t purines paor with each other?
- Two pyrimidines can’t pair as they wouldn’t be able to get close enough to form a hydrogen bond
- Two purines would be too bulky to fit inside the double helix
Why doesn’t Adenine ever pair with Cytosine?
Cytosine does not contain groups which can form hydrogen bonds with Adenines hydrogen bond forming groups. Steric hindrance occurs.
Why doesn’t Thymine ever pair with Guanine?
Thymine only contains one group which can form a hydrogen bond with Guanine. Steric hindrance occurs.
How many hydrogen bonds does a Adenine - Thymine pair have?
2
How many hydrogen bonds does a Guanine - Cytosine pair have?
3
State the four key facts of arrangement between two DNA strands.
- The strands are anti-parallel to each other
- The bases point toward the center
- The sugar-phosphate backbone forms on the outside
- The strands form a double helix.
