dna structure and replication Flashcards
it is the different building blocks combine in sequences which enables to carry information
nucleic acids
what are the 2 classes of nucleic acids
DNA and RNA
it is the single building block of DNA
nucleotide
nucleotide consist of
1 deoxyribose sugar (5 carbon sugar)
1 phosphate group (phosphorus atom bonded to 4 oxygen atoms)
1 nitrogenous base
- purines: adenine and guanine
- pyrimidines: cytosine and thymine
it forms the “rails” of the DNA helix, providing structure
sugar-phosphate backbone
purines vs pyrimidine
purines: 2 ring structure
pyrimidine: 1 ring structure
their pairing (1 big and 1 small) ensures that the DNA helix maintains a consistent width throughout
phosphodiester bond vs hydrogen bond
phosphodiester bond:
Link the sugar of one nucleotide to the phosphate group of the next in the DNA backbone.
hydrogen bond:
Hold the complementary nitrogenous bases (A-T, G-C) together between the two DNA strands.
why must dna be replicated
To ensure that genetic information is passed to daughter cells during cell division, maintaining the continuity of genetic information across generations.
dna sequences are measured in
measured in numbers of base pairs
- kilobase (kb): thousands
- mega base (mb): millions
it is the information-containing parts of DNA because they form sequences
nitrogenous bases
it is a chain that forms when nucleotides link together that held together phosphodiester bons
polynucleotide chains
what are phosphodiester bonds
they are formed between deoxyribose sugars and the phosphate groups
it is a continuous link that are formed between deoxyribose sugars and the phosphate groups
sugar-phosphate backbone
it is when in a DNA molecule, the two polynucleotide chains run in opposite directions
antiparallelism
briefly explain antiparallelism
One chain runs from the 5′ end (5 prime) to the 3′ end (3 prime)
while the other runs from the 3′ end to the 5′ end
= head-to-toe alignment.
5’ -
3’ -
*structure of sugar-phosphate backbone structure
5’ - have phosphate group attached to 5th C
3’ - end w hydroxyl grp attached to 3rd C
explain how the sugar-phosphate backbone is formed
These carbons are numbered from 1 to 5, starting from the carbon next to the nitrogenous base and moving
clockwise
nucleotides and pairing
adenine pairs w thymine
guanine pairs w cytosine
A & T - 2 hydrogen bonds
G & C - 3 hydrogen bonds
true or false:
a single strand of DNA will form a helix
flase - will not
purine-pyrimidine couples are called
complementary base pairs
why is the hydrogen bonds are weak individually but strong collectively
the bonds are between base pairs
that maintains the stability of the DNA structure
they are strong collectively butt weak enough to allow the strands to separate when needed
this is formed when the DNA strands twist and when they are antiparallel
double helix structure
true or false:
DNA molecules are extremely long
true
how long is the the DNA of the smallest human chromosome, if stretched out
14 millimeters (thousandths of meter)
*but it is packed into a chromosomes that during cell division, its only 2 micrometers (millionths of a meter)