DNA Structure Flashcards
What are some of the general characteristics that differ bacteria from eukaryotes?
- DNA forms an tangle known as a nucleid;which contains no membrane and is not bound to proteins.
- Contain plasmids; small loops of DNA that can be transmitted from cell to cell which can allow for special properties such as antibacterial resistance.
- Contain a cell wall but no nucleus as in eukaryotes.
What is the difference between the cell wall of gram-positive and Gram-negative bacteria?
Some of the key differences are as follows:
- Peptidoglycan is present in high amounts in gram positive whereas gram negative contain only a few layers.
- the peptidoglycan in gram negative bacteria is between two layers of the cellular membrane
- The S-layer is directly attached to the outer membrane.
- Lipoprotiens are attached to the polysaccharide whereas have no lipoproteins present.
What are the 3 medically relevant Gram-negative cocci?
- cause a sexually transmitted disease (Neisseria gonorrhoeae),
- a meningitis (Neisseria meningitidis),
- respiratory symptoms (Moraxella catarrhalis).
what are the medically relevant bacilli that are gram negative?
Respiratory problems: Hemophilus influenzae, Klebsiella pneumoniae, Legionella pneumophila, Pseudomonas aeruginosa
Urinary problems: Escherichia coli, Proteus mirabilis, Enterobacter cloacae, Serratia marcescens
Gastrointestinal problems: Helicobacter pylori, Salmonella enteritidis, Salmonella typhi.
What does Chargaff’s Rule State?
The amounts of A = T, G = C, purines = pyrimidines
What are the four nucleotides that form the composition of DNA?
adenine, cytosine, thymine, or guanine
What is the key difference between ribose and deoxyribose?
Ribose; at the 2nd carbon there is a hydroxyl group attached
Deoxyribose; at the second carbon only a hydrogen is attached
What is the structure of DNA and how is it liked together?
- DNA is a double-stranded helix with antiparallel strands
- the nucleosides in each strand are held together by phosphodiester bonds
- while the bases are held tightly together busing hydrogen bonds
What is the central dogma of biology and how is it accomplished ?
-The central dogma of DNA states that the flow of genetic information flows from DNA-RNA-protiens. which can be divided or restated as DNA replication,Transcription,and Translation
What is the responsibility of DNA helicase?
DNA gyros relaxes the DNAby introducing positive supercoils, while helicase unwinds the double stranded helix by introducing negative supercoils into the strand and thus creating the replication fork.
What us the responsibility of the single stranded binding proteins during DNA replication?
The responsibility of the the single stranded binding proteins in DNA replication is to make the template available and thus keep the two strands from reforming the bond during DNA replication.
What does RNA primase do in DNA replication? Why is this step important and how does it accomplish this?
RNA primase catalyzes the synthesis of short RNA primers to which nucleotides are added and thus Thymine is replaced by Uricil in the fragment. This is important because without this short piece of RNA, DNA replication will not occur.
What is the difference in primary responsibilities of DNA polymerase I and DNA polymerase III?
The chief responsibility of DNA polymerase III is extend the DNA strand in the 5’-3’ direction creating the newly synthesized DNA strand. While DNA polymerase I degrades the RNA primer and fills in the gaps by replacing the strand and replacing uricil with thymine. Both have the ability to proofread.
What is the activity is caused by DNA ligase?
Joins the DNA fragments into a continuos daughter strands during DNA replication and DNA repair.
What are Nucleases and how do they function?
Nucleases are enzymes that degrade DNA strands by breaking the phosphodiester bonds holding the nucleotides together. They function as either 5’ or 3’ exonucleases.
