DNA Flashcards
What does DNA stand for?
Deoxyribonucleic acid
What are the four nitrogenous bases found in DNA?
Adenine, Thymine, Guanine, Cytosine
What are the four nitrogenous bases found in RNA?
Adenine, Uracil, Guanine, Cytosine
What type of bond holds the nitrogenous bases together in DNA?
Hydrogen bond
What is the structure of DNA often described as?
Double helix
What is the sugar component in DNA?
Deoxyribose
What is the purpose of proofreading by DNA polymerase during replication?
To correct errors in nucleotide sequence
What is the overall result of DNA replication?
Two identical DNA molecules
During DNA replication, what enzyme is responsible for unwinding the double helix?
Helicase
Function of DNA helicase?
break Hydrogen bonds between bases
What is the role of DNA in protein synthesis?
DNA contains the genetic information that determines the sequence of amino acids in proteins
What is the function of mRNA in protein synthesis?
To carry the genetic information from DNA to the ribosome for protein synthesis
What is the function of tRNA in protein synthesis?
To bring amino acids to the ribosome during protein synthesis
What are the short pieces of DNA made on the lagging strand called?
Okazaki fragments
What enzyme is responsible for adding complementary nucleotides during DNA replication?
DNA polymerase
What is the role of ribosomes in protein synthesis?
To catalyze the formation of peptide bonds between amino acids
What is a codon?
A three-nucleotide sequence on mRNA that codes for a specific amino acid
What is an anticodon?
A three-nucleotide sequence on tRNA that is complementary to a codon on mRNA
What is the start codon in protein synthesis?
AUG (methionine)
What is the role of primase in DNA replication?
To synthesize RNA primers for DNA polymerase to start replication
What is the purpose of DNA ligase during replication?
To join Okazaki fragments on the lagging strand
What is the function of the lagging strand during DNA replication?
To synthesize discontinuously in short Okazaki fragments
What is the function of the leading strand during DNA replication?
To synthesize continuously in the 5’ to 3’ direction
What is the function of DNA helicase in protein synthesis?
To unwind the DNA double helix during transcription and replication
What is the replication fork?
The point at which the double helix is unwound during replication
What is the role of RNA polymerase in protein synthesis?
To synthesize RNA from a DNA template during transcription
What is the function of the 5’ cap and poly-A tail in mRNA?
To facilitate mRNA transport, stability, and translation
What is the genetic code?
The set of rules by which information encoded in mRNA is translated into proteins
Which bases are Purine?
Adenine & Guanine
Which bases are Pyrimidine?
Thymine & Cytosine
Why does DNA replication make an exact copy?
To have the correct genetic information, DNA in the daughter cell must be the exact same as the parent cell
What is a nucleotide?
The basic building block of nucleic acids
- RNA and DNA are made of long chains of nucleotides.
- Consists of a sugar molecule (ribose in RNA or deoxyribose in DNA) attached to a phosphate group and a nitrogen-containing base.
Name the 3 components of a nucleotide
Phosphate group
Pentose sugar
Organic base (containing nitrogen)
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 (‘base stacking’)
Name the 3 Scientists who discovered the structure of DNA
James Watson
Francis Crick
Rosalind Franklin
What are the 3 main differences between RNA and DNA?
- sugar in RNA has an extra group called ribose (not deoxyribose)
- DNA contains nitrogen base thymine, RNA contains nitrogen base uracil instead
- RNA is single stranded, DNA is double stranded
Name the bond between the deoxyribose and the phosphate in a nucleotide
phosphodiester
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.
What is a leading strand?
New strand of DNA that is synthesized around the replication fork
What is a lagging strand?
A lagging strand is one of two strands of DNA found at the replication fork, or junction, in the double helix; the other strand is called the leading strand
Phosphate and sugar join with what bond?
Ester bond
A base and sugar join with what bond?
Glycosidic bond
What is the nitrogen and carbon containing molecule comprising a one ring structure?
Pyrimidine
What is the nitrogen and carbon containing molecule comprising two ring structures?
Purine
What are the strong bonds formed between adjacent nucleotides in a polynucleotide?
Phosphodiester
What is the general name for a five carbon sugar?
Pentose sugar
The phosphate group, pentose sugar and organic base of a DNA or RNA nucleotide are joined through which type of reaction?
Condensation reaction
What enzyme prevents DNA from supercoiling during replication
Topoisomerase
What is the function of ligase?
Glue okazaki fragments together
Why is the replication process semi-conservative
One strand in each new dna is old and one is new
Primase function
Makes primers on the DNA so that DNA polymerase can start building
Which direction does DNA polymerase build in
5’ to 3’
(Complementary to 3’ to 5’ on the original strand)
When does replication happen in a cell?
During interphase - before cell division
DNA Polymerase
Replicates existing DNA molecules to build new strands of DNA
Which protein binds to the DNA strands to keep them separated
SSB protein
