3.1.5 Nucleic Acids and DNA Replication (C2) Flashcards
DNA is made from which monomer?
Mononucleotides (or just nucleotides)
Name the 3 components of a nucleotide
Phosphate group
Pentose sugar (ribose RNA or deoxyribose DNA)
Organic base (containing nitrogen)
In DNA, which base complements guanine?
cytosine
In RNA, which base complements adenine?
uracil
In DNA, which base complements thymine?
adenine
Idenitfy the 5’ and 3’ carbon atoms of the deoxyribose molecule.
Idenitfy the 5’ and 3’ carbon atoms of the deoxyribose molecule.
Identify the molecule.
Ribose
In RNA, which base complements guanine?
cytosine
In DNA, which base complements cytosine?
guanine
In RNA, which base complements uracil?
adenine
Which atoms will react to join the two nucleotides?
Which atoms will react to join the two nucleotides?
What shape does a molecule of DNA take?
A double helix
In DNA, which base complements adenine?
thymine
DNA is a stable molecule because…
- The phosphodiester backbone protects the chemically reactive base pairs.
- C-G base pairs contain 3 hydrogen bonds, so the more C-G base pairs in a DNA molecule the more stable it is.
- Interactive forces between base pairs add further stability
How many hydrogen bonds are formed between Cytosine and Guanine in a DNA molecule?
3
Name the bond that forms between the 2 adjacent nucleotides of a dinucleotide.
Phosphodiester bond
What is the function of RNA?
To transfer genetic information from DNA to the ribosomes.
How is DNA adapted to carry out its function as a means of passing genetic information from generation to generation?
- Very stable - rarely mutates
- Hydrogen bonds between strands easy to separate for replication and protein synthesis.
- Very long - carries a lot of genetic information.
- Base pairs protected from chemical/physical forces by phosphodiester backbone.
Describe how are 2 DNA nucleotides form a dinucleotide
A condensation reaction occurs between the hydroxyl (OH) group on the 3’ carbon of Deoxyribose on 1 nucleotide and the hydroxyl group of the phosphate group on another nucleotide.
In RNA, which base complements cytosine?
guanine
How many hydrogen bonds are formed between Adenine and Thymine in a DNA molecule?
2
How are the 2 strands of DNA that make up the double helix held together?
Hydrogen bonds between complementary organic bases
What is the function of DNA
To carry genetic information and code for protein
Name the 2 nucleic acids
Deoxyribonucleic acid (DNA)
Ribonucleic Acid (RNA)
Identify the molecule.
Phosphoric Acid/phosphate
Name the organic bases that can become part of a DNA nucleotide
Adenine
Thymine
Cytosine
Guanine
The phosphate group, pentose sugar and organic base of a DNA or RNA nucleotide are joined through which type of reaction?
Condensation reaction
The phosphate group attaches to which carbon atom of a ribose or deoxyribose molecule when forming a nucleotide?
The 5’ carbon atom (pronounced 5 prime)
Name the organic bases that can become part of a RNA nucleotide
Adenine
Uracil
Cytosine
Guanine
Identify the molecule.
Deoxyribose
Describe how 2 RNA nucleotides form a dinucleotide
A condensation reaction occurs between the hydroxyl (OH) group on the 3’ carbon of Ribose on 1 nucleotide and the hydroxyl group of the phosphate group on another nucleotide.
Which type of bond are the arrows pointing at?
Phosphodiester bond
What is meant by degenerate when talking about the genetic code?
more than one triplet for each amino acid
What is meant by the term non overlapping when talking about the genetic code?
each base is only part of one triplet/codon
How do the organic bases help to stabilise structure of DNA?
- Hydrogen bonds between the base pairs holds two strands together;
- Many hydrogen bonds provides strength;
Function of DNA helicase?
break H bonds between bases
Function of DNA polymerase?
forms phosphodiester bonds between adjacent nucleotides in DNA
Give 2 differences between the nucleotide in ATP (nucleotide derivative) and the nucleotides in DNA
- ATP has 3 phosphates DNA 1 phosphate group per nucleotide
- ATP has ribose, DNA deoxyribose
- ATP - base always adenine, DNA it varies
Name the bond between the deoxyribose and the phosphate in a nucleotide
phosphodiester
What is meant by the DNA code being Universal?
The same codon/triplet always codes for the same amino acid
Name the accepted method of DNA Replication
Semi-conservative replication
Describe the experiment that Meselson and Stahl carried out to confirm the semi-conservative method of DNA replication
- Grow E. coli bacteria in 15N (heavy isotope), which is assimilated into its base pairs, causing it to have heavy DNA. Take a sample of this and ‘normal’ 14N grown E.coli
- Allow ‘heavy DNA’ E. Coli to divide once in 14N growth medium and take a sample.
- Allow E. Coli to divide once more in 14N growth medium and take another sample.
- Remove DNA from each sample and perform gradient density centrifugation.
- Check the mass of DNA present in each sample.
Describe the process of semi-conservative DNA replication.
DNA helicase breaks the hydrogen bonds causing the strands to separate
Both strands act as a template
Free nucleotides complementary base pair to the template A-T and G-C
DNA polymerase joins adjacent nucleotides together forming a phosphodiester bond
Hydrogen bonds form between the old strand and the newly synthesised strand
DNA replication is semi-conservative replication
What is the function of free DNA nucleotides in DNA replication?
To bind to a separated strand of parent DNA to form a new complementary strand of daughter DNA.
What is the function of DNA Polymerase?
An enzyme that joins the free daughter nucleotides bound to the parent template strands by creating phosphodiester bonds between nucleotides.
What is required for DNA replication to take place?
DNA to be copied
Free DNA nucleotides
DNA Polymerase
DNA Helicase
Energy to drive the process
What is meant by ‘semi-conservative’ DNA replication
DNA replication whereby each new DNA molecule contains one of the original DNA strands.
Name 2 enzymes involved in semi conservative replication of DNA
DNA helicase
DNA polymerase
Describe the ROLE of the 2 enzymes in DNA replication
- Helicase - breaks H binds
- DNA polymerase joins DNA nucleotides together to reform phosphodiester bond
Give 2 features of DNA and explain how each is important for semi conservative replication
- weak H bonds to allow unzipping of 2 strands
- Two strands so both can act as template
