DNA (+ replication) Flashcards
name 2 polynucleotides
DNA
RNA
describe the structure of DNA
DNA is a polynucleotide that is made up of many nucleotide monomers
a nucleotide consists of a phosphate group bonded to a deoxyribose sugar (pentose) and a base (adenine, thymine, guanine, cytosine)
the nucleotides undergo a condensation reaction so they can form phosphodiester bonds
DNA has a double-helix structure
describe how a phosphodiester bond is formed between 2 nucleotides within a molecule
2 nucleotides undergo a condensation reaction which is catalysed by DNA polymerase and a phosphodiester bond forms between the phosphate group of 1 nucleotide and the sugar of another
why is having a sugar-phosphate backbone an advantage for DNA
it protects more chemically reactive bases that are inside of the double helix
why is having a double helix an advantage for DNA
increases the stability of the molecule
tightly coils to store a lot of information in a small space
name 2 nucleic acids
DNA
RNA
what is the function of DNA
carry/store genetic information
what does DNA stand for
Deoxyribonucleic acid
how is hereditary information passed on
from cell to cell (mitosis)
passed on from generation to generation
what does RNA stand for
Ribonucleic acid
what is the function of RNA
transfers genetic information from DNA in the nucleus to ribosomes in the cytoplasm
why does A always have to be paired with T
they are complimentary base pairs therefore hydrogen bonds can form between them
how many hydrogen bonds form between A and T
2 hydrogen bonds
how many hydrogen bonds form between C and G
3 hydrogen bonds
how do you describe that 2 polynucleotide strands run in opposite directions
anti parallel
what is an advantage of hydrogen bonds
they make DNA stable especially in areas of high G - C pairings
if there are equal percentages of A + T what type of cell are you looking at
human body cell
(it is double-stranded due to same percentages)
what is the name of the sugar in RNA
ribose sugar
name the bases of RNA
Adenine (A)
Guanine (G)
Cytosine (C)
Uracil (U)
what are the 3 types of RNA and what are their functions
mRNA - made in transcription
tRNA -role in translation as it carries the amino acid to the ribosome
rRNA - proteins that make up ribosomes
list all of the similatires between DNA and RNA
both have the bases of cytosine, adenine, guanine
both have a phosphate group
both have a phosphate sugar backbone
both have phosphodiester bonds
list 2 difference of RNA compared to DNA
RNA
- much shorter
- single-stranded
DNA
- 2 strands are anti-parallel
- double helix
- lots of hydrogen bonds
how is DNA adapted for it’s function (6 marks)
stable
- many hydrogen bonds between bases and these are protected by sugar-phosphate backbone
- can pass information between generations without changing
A binds to T
G binds to C
- protects the genetic code from being changed by chemical/physical forces
- allows for successful DNA replication and transcription
very large
- carries a lot of information
(double helix makes DNA compact)
hydrogen bonds between bases are individually weak
- strands are easily separated during DNA replication and transcription
describe the process of semi conservative DNA replication
- DNA helicase breaks the hydrogen bonds which separates the strands
- both strands act as templates
- free nucleotides attach to the template strands on their complimentary base (A T C G)
- DNA polymerase joins nucleotides together in a new strand
hydrogen bonds form between the complementary base pairs
semi conservative DNA replication is when a new DNA molecule contains 1 new and 1 original strand
why does DNA replication go from the 3 prime to the 5 prime direction
DNA polymerase has an active sit that is only complementary to the 3 prime end of the new DNA strand so DNA polymerase can only add nucleotides to the 3 prime end of a new DNA strand
what did the meselson and stahl experiment prove
that dna replication is semi conservative
what 2 isotopes of nitrogen was used in meselson and stahls experiment
15N
14N
