Topic A: DNA and Replication Flashcards
What are the 4 key criteria genetic material must possess?
- Must encode information. As in it must contain the information necessary to make an entire organism
- Transmission. Must be passed from parent to offspring
- Replication. Must be copied in order to be passed from parent to offspring, and must be able to self-replicate.
- Variation. must be able to adapt to changing environments.
what are the 4 nitrogenous bases DNA is comprised of? RNA? How do they match?
DNA: Adenine and Thymine, and Cytosine and Guanine
RNA: Adenine and Uracil, Cytosine and Guanine.
What are the Purines? Pyrimidines?
Purines: Double ringed, Adenine and Guanine
Pyrimidines: single ringed, cytosine and Thymine (in DNA) or Uracil (in RNA)
What are the 3 major components of DNA?
- nitrogenous bases
- pentose/5-carbon sugar
- phosphate group
What is the pentose sugar in DNA? RNA?
DNA: Deoxyribose
RNA: Ribose
What does it mean when DNA has directionality?
Nucleic acid synthesis always happens from 5’ to 3’. The 5’ end starts with the phosphate group, and the 3’ end starts with the hydroxide (OH) group.
What are the main differences between DNA and RNA?
DNA (deoxyribonucleic acid):
- Double stranded sugar phosphate, whose base pairs are cytosine and guanine, and thymine and adenine.
- DNA also has a single hydrogen at the 2’ location on the pentose sugar
RNA (ribonucleic acid):
- Single stranded sugar phosphate whose base pairs are cytosine and guanine, and uracil and adenine.
- RNA has an OH in the 2’ location on the pentose sugar.
What did Rosalind Franklin determine about the structure of DNA?
- determined DNA must have a helical structure and that it must be double stranded
- also that the diameter of the helix is 20 angstroms wide and there are 10 bases per 360 degree turn of the helix.
What did Erwin Chargaff determine about the structure of DNA? What is Chargaffs rule?
- determined that Adenine and Thymine percentages in a variety of organisms were the same, and guanine and cytosine where the same.
- thus he determines that the amount of Guanine must be the same amount as cytosine, and the amount of thymine must be the same amount as adenine, and thus G+A=C+T, because A=T and G=C.
What are the 3 models of DNA replication?
- Conservative model
- takes the parental model and forms newly synthasized DNA, one daughter which is formed from the parental and one daughter that is all new. - Semiconservative model
- takes the original model, separates the two strands by breaking the hydrogen bonds, creating daughter DNA that is half old half new. - Dispersive model:
- breaks the phosphodiester bonds within a strand, making daughter DNA that is fragmented half old half new.
what model of DNA replication was accepted? Why?
Semiconservative model!
- this is because splitting the bonds between the two strands is easer, as the base pairs are only held together with weak hydrogen bonds, and not the strong phosphodiester bonds that hold adjacent nucleotides together on the same strand.
What is DNA composed of? How are the strands orientated?
Two polynucleotide strands/chains that form a double helix, and are anti-parallel to each other.
“The deoxyribose sugar and the phosphate groups form the ______ of the helix, while the nitrogenous bases are orientated towards the _____ of the helix”
“The deoxyribose sugar and the phosphate groups form the BACKBONE of the helix, while the nitrogenous bases are orientated towards the INTERIOR of the helix”
Nitrogenous bases on opposing pairs hold each other via what kind of bond? How many are between adenine and thymine? Guanine and cytosine?
Hydrogen bonds!
- there are 2 hydrogen bonds between adenine and thymine, and 3 hydrogen bonds between guanine and cytosine.
Adjacent nucleotide on the same polynucleotide strand are joined to each other by what kind of bonds?
- phosphodiester bonds