2.1 Structure of DNA and RNA Flashcards
What does RNA stand for
How many strands does it have
Ribonucleic acid
One strand
What does DNA stand for
deoxyribonucleic acid
What is DNA made up of and what is the structure of DNA called
Its double helix structure
Nucleotides that have 3 basic components
What is the nucleotide structure
. A pentose sugar (so called because it has 5 carbon atoms)
. A phosphate group
. A nitrogen containing organic base (ATCG)
What are the names of the bases
A
T
C
G
Adenine
Thymine
Cytosine
Guanine
What base is In RNA that isn’t in DNA
Uracil (U)
What type of reaction occurs between a pentose sugar, phosphate group, and organic base
Condensation reactions to form a single nucleotide
(mononucleotide)
How are mononucleotides joined and what’s the new name
What’s the bond called
Condensation reactions also between the deoxyribose sugar of one mononucleotide, and phosphate group of another
Dinucleotide
A phosphodiester bond is formed
What is a polynucleotide
Multiple mononuclotides joined together forming a long chain
What is the shape of the symbol for…
Phosphate
Pentose sugar
. Circle
. Pentagon
What base does uracil replace in RNA from DNA
Thymine
Describe the structure of ribonucleic acid
. Ribonucleic acid is a polymer made up of nucleotides
. Single, short chain where the pentose sugar is ALWAYS ribose
. Bases are always Adenine, Cytosine, Guanine, and Uracil
so they have no thymine
What are the 3 types of RNA
MRNA
Ribosomal RNA
Transfer RNA
. Messenger RNA: Transfers genetic info from nucleus to ribosomes
. Ribosomal RNA: Ribosomes are made from this type of RNA
. Transfer RNA: Involved in protein synthesis
Who worked out the structure of DNA and when
1953
James Watson and Francis Crick worked out the structure
Rosalind Franklin also found X ray diffraction patterns of DNA
What is the pentose sugar in DNA
What are the bases
Deoxyribose
Adrenine
Thymine
Cytosine
Guanine
Structure of DNA
Made up of two strands of nucleotides (polynucleotides).
Each strand is extremely long
Strands are joined together by hydrogen bonds formed between certain bases
What does Adenine pair to
What does Guanine pair to
Thymine
Cytosine
What is complimentary base pairing
. The bases attach to a specific one with hydrogen bonds, that hold the two strands together.
How do the quantities of bases vary in DNA
The quantities of A and T in DNA are always the same, and so are the quantities of C and G
However, the ratio of AT to CG varies between species
What is the name of the structure of DNA
Explain it
Double helix
Ladder like arrangement of two polynucleotide chains being twisted
Uprights of phosphate and deoxyribose wind around each other to form double helix
It forms the backbone of the DNA molecule
What ways do the uprights run in DNA
They go different directions ( Antiparallel)
How is DNA a stable molecule
. Phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
. hydrogen bonds link the organic base pairs forming bridges between the phosphodiester uprights.
As there are three hydrogen bonds between C and G, the higher the proportion of these pairings, the more stable the DNA molecule
There are other interactive forces between base pairings, holding molecule together
How many hydrogen bonds are there between cytosine and guanine
What about between adenine and thymine
What do these bonds do
3 between c and g
2 between a and t
They hold the two chains together forming bridges.
What is the function of DNA
. To contain Hereditary material responsible for passing genetic info from cell to cell and generation to generation
There are around 3.2 billion base pairs in the DNA of a typical mammal cell
What does this mean
There is an almost infinity variety of sequences of bases along the length of a DNA molecule
Why is DNA being stable very important for its function
. It’s a very stable structure which passes down generations without significant change.
Most mutations are repaired, so persistent mutations are rare
Why is it good that DNA has only hydrogen bonds joining the two strands together
Its two strands are joined only by hydrogen bonds between the nitrogenous based which allow them to separate during DNA replication and protein synthesis
How is the DNA molecule adapted to carry out it’s function:
Its large
Its an extremely large molecule so carries an immense amount of genetic info
How is the DNA molecule adapted to carry out it’s function:
Has base pairs within helical cylinder of the deoxyribose phosphate backbone
By having base pairs within the helical cylinder of deoxyribose phosphate backbone, the genetic info is to some extent protected from being corrupted by outside chemical and physical forces
How do base pairings help DNA transfer information
Base pairings lead to DNA being able to replicate and to transfer information as MRNA
How are carbon atoms in pentose molecules numbered
. Labelled from 1 to 5
3 prime carbon has hydroxyl group
5 prime carbon has the attached phosphate group
They are labelled starting from 1, from the clockwise direction from the O in it.
What ways do the strands run in DNA
. One strand runs in 5’ to 3’ direction, whilst the other runs in the opposite 3’ to 5’ direction.
The two strands are said to be antiparallel
Why can nucleic acids only be synthesised in Vivo
This is the 5’ to 3’ direction, because the enzyme DNA polymerase that assembles nucleotides into a DNA molecule can only attach nucleotides to the hydroxyl group on 3’ carbon molecule.
