Chapter 8: The Molecular Basis of Inheritance Flashcards
Griffith
Discovered that bacteria have the ability to turn harmless cells into virulent ones by transferring some of its genetic factors (bacterial transformation).
Avery, McLeod, McCarty
Proved that DNA was the genetic material, not proteins. Proved that the “transformation factor” from Griffith’s work was DNA.
Hershey and Chase
Provided further evidence that DNA was the genetic material, not proteins.
Rosalind Franklin
Did DNA imagine through X-ray crystallography. Worked alongside Maurice Wilkins.
Watson and Crick
Identified the double helix shape of DNA. Depended on the use of Franklin and Chargaff’s work.
Meselsohn and Stahl
DNA replication is semi-conservative.
Structure of DNA
DNA is a double helix, in which the two strands run in opposite directions (5’ to 3’, and 3’ to 5’). Each nucleotide is made up of a nitrogenous base, a 5-Carbon sugar, and a phosphate group, where the nitrogenous bases are A, G, T, C. The nitrogenous bases are held together through hydrogen bonding.
Nitrogenous Base Pairing
A bonds with T
C bonds with G
RNA Structure
A single stranded helix consisting of four nucleotides: C, U, A, and G. The sugar in RNA is ribose.
Semiconservative Replication
When the DNA replicates, it uses one strand as a template for the new strand composed of complementary nucleotides. Thus, new DNA consists of one old strand and one new strand: semiconservative.
DNA Replication in Eukaryotes
1.
Avery, McLeod, McCarty
Proved that DNA was the genetic material, not proteins. Proved that the “transformation factor” from Griffith’s work was DNA.
Hershey and Chase
Provided further evidence that DNA was the genetic material, not proteins.
Rosalind Franklin
Did DNA imagine through X-ray crystallography. Worked alongside Maurice Wilkins.
Watson and Crick
Identified the double helix shape of DNA. Depended on the use of Franklin and Chargaff’s work.
Meselsohn and Stahl
DNA replication is semi-conservative.
Structure of DNA
DNA is a double helix, in which the two strands run in opposite directions (5’ to 3’, and 3’ to 5’). Each nucleotide is made up of a nitrogenous base, a 5-Carbon sugar, and a phosphate group, where the nitrogenous bases are A, G, T, C. The nitrogenous bases are held together through hydrogen bonding.
Nitrogenous Base Pairing
A bonds with T
C bonds with G
RNA Structure
A single stranded helix consisting of four nucleotides: C, U, A, and G. The sugar in RNA is ribose.
Semiconservative Replication
When the DNA replicates, it uses one strand as a template for the new strand composed of complementary nucleotides. Thus, new DNA consists of one old strand and one new strand: semiconservative.
Process of DNA Replication in Eukaryotes
- Replication begins at the origin of replication. Here, there are replication bubbles to separate the DNA, and replication forks where the DNA physically separates.
- DNA polymerase elongates the DNA in the antiparallel direction.
- DNA polymerase always builds DNA in the 5’ to 3’ direction, and adds nucleotides to the 3’ end.
- One strand, called the leading strand, is replicated linearly and in one string, while the lagging strand is replicated in short Okazaki fragments.
- The DNA ligase seals up the Okazaki fragments.
Other proteins and enzymes that assist in DNA replication:
- Helicases: Helps untwist the original strand of DNA at the replication fork.
- Single-stranded binding proteins: Keeps the DNA from retesting back together during DNA replication.
- Topoisomerase: takes away the tension the DNA goes through.
- DNA nuclease: Gets rid of broken and bad pieces of DNA.
- Telomeres: Repetitive strands of DNA added on by telomerase to keep from the erosion of DNA that occurs with ever replication of DNA.
Translating between DNA, mRNA, and tRNA
Going from DNA to mRNA, use GATC -> CUAG
Going from mRNA to tRNA, use the original DNA sequence, but replace all T’s with U’s.
Steps from DNA to Protein
- Transcription
- RNA processing
- Translation
The three types of RNA in protein synthesis
- mRNA: DNA is copied into mRNA in transcription, using CUAG.
- rRNA: for structural purposes. Makes up the ribosome and the two ribosomal subunits.
- rRNA: Carries the amino acid from the cytoplasmic pool to the mRNA at the ribosome. It has a binding site for the amino acid and the anticodon.
Transcription
Process from DNA to mRNA. It has 3 stages: initiation, elongation, and termination.
Initiation:
- RNA binds to the promoter region.
- The transcription factors recognize the TATA box.
- The RNA polymerase binds to the promoter, and the next stage begins.
Elongation:
- the RNA polymerase adds nucleotides to the 3’ end.
- Transcription unit: the length of DNA that gets turned into mRNA.
Termination: Elongation occurs for a little while longer after the RNA polymerase transcribes the termination sequence, which the mRNA is cut off from the DNA template.