Molecular Genetics Flashcards
What are nucleic acids?
Macromolecules that make up DNA and RNA.
Who discovered nucleic acids?
Friedrich Miescher in 1869
Who discovered that DNA and RNA were two groups of macromolecules?
Phoebus Levene in 1900
What were Phoebus Levene’s findings?
Levene discovered that DNA and RNA are polymers made up of monomers called nucleotides.
How are nucleotides broken up?
Each monomer in D A and RNA contains a five-carbon sugar, a phosphate group, and a 5 nitrogen-containing base.
How are the 5 nitrogen-bases divided?
Purines, which are double ringed structures including guanine(G) and adenine(A), and pyrimidines, which are single ringed structures including cytosine(C), thymine(T) and uracil(U).
Where are each nitrogen bases found?
Adenine, guanine, and cytosine are all found in both DNA and RNA, while thymine is found in DNA only and replaced by uracil which is found in DNA only.
Who discovered genes?
Thomas Hunt Morgan in the 1900’s
How did Morgan discover genes?
He was doing experiments on fruit flys after Levene made his findings, he discovered that genes are found on chromosomes but could not figure out if DNA or proteins where the basis for genes.
Who accidentally discorde how genes are passed down? How? Did this discovery prove is genes were passed through DNA or proteins?
Frederick Griffith in 1928 by experimenting on mice during a pneumonia outbreak. He discovered that dead pathogenic bacteria could pass on disease causing properties to living, non-pathogenic bacteria strains. This still did not prove whether genes were passed through DNA or proteins.
What were Frederick Griffith’s findings called?
The transforming principle
How was it first proven that genes are found in nucleic acids?
Heat killed pathogenic bacteria was treated with proteases and nucleases. When proteases were only used, griffith’s process continued successfully. When nucleases were used, the transformation was not able to occur.
How was it further proved that chromosomes are found in DNA?
Alfred Hershey and Martha Chase used bacteriophage viruses in two batches. One contained radioactive phosphorus tagged on the nucleic acids, and the other was tagged with radioactive sulfur on its protein coat. Once the bacteriophage injected its virus into the bacterial cells, only radioactive phosphorus was found inside the bacteria, proving that DNA is what contains the genes.
What did Erwin Chargaff discover?
He discovered that not each of the 4 nucleotides present in DNA are found in equal amounts, and then the amount of A=T, and C=G.
What are Chargaffs discoveries called?
Chargaff’s rule.
What did Rosalind Franklin discover?
Franklin took c-ray picture of DNA to analyze its structure, and discovered that DNA is wrapped in a helical structure with 2 strands of a repeating pattern called the double helix. She also realized that the nitrogen bases are found within DNA while the phosphate and sugars are in the outside.
What did Watson and Crick discover?
Using the same pictures that Rosalind Franklin took, they discovered that DNA contains a double helix structure, like a ladder. They took the credit for the discovery.
What are complementary base pairs?
The handrails of the double helix which are always opposing. A is always opposite T, and G is always opposite C.
What does it mean that DNA is antiparrallel?
The strands run in opposite directions, where the 5’ and 3’ ends are opposite and flipped.
How do you find where the 5’ end is?
The phosphate group will point to it.
What is mitochondrial DNA?
mtDNA is found outside of the nucleus in the mitochondria.
What is unique about mtDNA?
It is genetically identical to the mother’s DNA, which means mtDNA dates back thousands of years.
How do scientists use mtDNA?
It is used to trace ancient lineage patterns, to discover where people originated from.
How did DNA get into the mitochondria?
DNA got into the mitochondria as it was once a free living bacteria, engulfed by the cell.
What is endosymbiosis?
When a free living organism is engulfed by cells which will gain a mutualistic relationship.
What are 3 major differences between DNA and RNA?
The sugar in RNA is ribose while in DNA it’s deoxyribose. RNA is single stranded while DNA is double stranded. RNA contains uracil instead of thymine.
What are the three main types of RNA?
Messenger mRNA, transfer tRNA, and ribosomal rRNA.
What is a genome?
The sum of all the DNA in an organisms cell.
What are genomes made up of?
Genes that code for specific traits .
How is a genome discovered?
Using DNA sequencing, where each nucleotide is noted in precise sequences.
What is DNA replication?
The process DNA undergoes to make a copy of itself during the S-phase.
What does semi-conservatively mean?
The new DNA molecule contains one strand from its parent and one strand that is newly formed called the complementary daughter strand.
What are the 3 stages of DNA replication?
Initiation, elongation, termination.
How does initiation begin in DNA replication?
The DNA strands unravel in more than one spot at replication origins due to DNA helicase. This enzyme opens the DNA at 2 y-shaped ends called replication forks of the replication bubble; the unwound area.
What is the process of elongation in DNA replication?
An RNA primer is placed as a starting point for daughter strands to be built. The primer is later by an enzyme called primase. A second enzyme called DNA polymerase III places itself next to the RNA primer and begins the contradiction of the daughter strand, 1 nucleotide at a time. After copying is complete, DNA polymerase I removes any RNA primers and checks the code of the daughter strands to ensure no mistakes were made, and fixes any that occurred. The gaps created by RNA primers are sealed using the enzyme ligase.
In which direction does DNA replication occur?
In the 5’ to 3’ direction only along a forming daughter strand.
What is a leading strand?
The daughter strand that is continuously built as the DNA double helix unravels and only requires one RNA primer.
What is a lagging strand?
A daughter strand created in fragments as it replicates in the opposite direction of DNA unraveling. It requires multiple RNA primers .
