Nucleic Acids Flashcards
What makes up a Nucleotide?
A phosphate group,
A pentose sugar
Nitrogenous base
What is the pentose sugar in DNA?
Deoxyribose
What is the pentose sugar in RNA?
Ribose
How are polynucleotide strands formed and broken down?
Condensation reactions between nucleotides form strong phosphodiester bonds. Hydrolysis reactions use a molecule of water to break these bonds. Enzymes catalyse these reactions.
What is the structure of DNA?
Molecules twist to form a double helix of 2 deoxyribose polynucleotide strands ( so there are 2 sugar-phosphate backbones). H-bonds form between complementary base pairs (AT & GC) on strands that run antiparallel.
What are purine bases?
Adenine and Guanine
What are pyrimidine bases?
Thymine
Cytosine
Uracil
Why is DNA replication described as semi conservative?
Strands from original DNA molecule act as templates.
New DNA molecule contains 1old strand and 1 new strand (specific base pairing enables genetic material to be conserved accurately)
Was is the role of DNA helicase in semi conservative replication?
Breaks the hydrogen bonds between base pairs to form 2 single strands, each of which can act as a template.
How is a new strand formed during semi conservative replication?
Free nucleotides from nuclear sap to attach to exposed bases by complementary base pairing.
DNA polymerase joins adjacent nucleotides on new strand in a 5->3 direction via condensation reactions to form phosphodiester bonds.
Hydrogen bonds reform
What are features of the genetic code?
Non-overlapping- each triplet is only read once
Degenerate- more than one triplet codes for the same amino acid (64 possible triplets for 20 amino acids)
Universal- same bases and sequences used by all species
How does a gene determine the sequence of amino acid in a protein?
Consists of base triplets that code for a specific amino acid
How can DNA be purified by precipitation?
Add ethanol and a salt to aqueous solution. Nucleic acids precipitate out if the solution.
Centrifuge to obtain pellet of nuclei acid. Wash pellet with ethanol and centrifuge again
What does transcription produce?
mRNA
Where does transcription occur?
In the nucleus
What is the process of transcription?
RNA polymerase bind to potometer region on a gene.
Section of DNA uncoils into 2 strands with exposed bases. Antisense stand acts as a template.
Free nucleotides are attracted to their complementary bases.
RNA polymerase joins adjacent nucleotides to form phosphodiester bonds.
What happens after a strand of mRNA is transcribed?
RNA polymerase detaches at terminator region.
Hydrogen bonds reform and DNA rewinds.
Splicing removes introns from pre-mRNA in eukaryotic cells.
mRNA moves out of nucleus via nuclear pore and attaches to ribosomes
What does translation produce?
Proteins
Where does translation occur?
In the cytoplasm on ribosomes (which are made of proteins and rRNA)
What is the process of translation?
Ribosomes moves along mRNA until the ‘start’ codon.
tRNA anticodon attatches to complementary bases on mRNA.
Condensation reactions between amino acids on tRNA form peptide bonds. Requires energy from ATP hydrolysis.
Process continues to form polypeptide chain until the ‘stop’ codon is reached
What is a mutation?
An alteration to the DNA base sequence. Mutations often arise spontaneously during DNA replication
What is semi-conservative repliaction?
How DNA replicates, resulting in two new molecules, each of which contains one old strand and one new strand. One old strand is conserved in each new molecule.
What are genes?
A length of DNA that codes for a polypeptide or for a length of RNA that is involved in regulating gene expression.
What are polypeptide?
A polymer made of many amino acid units joined together by peptide bonds. Insulin is a polypeptide of 51 amino acids.
