Module 10 - 3 Flashcards
(34 cards)
What are the weak forces that stabilize the double helix?
Hydrophobic effects, stacking interactions, hydrogen bonds, charge-charge interactions.
What are major and minor grooves?
Unequal width grooves in a double helix where base pairs are exposed and accessible to interactions with other molecules.
What is the function of restriction endonucleases?
Recognize and cleave specific DNA sequences as a bacterial defense mechanism against viral invasion.
How do host cells protect their own DNA from restriction endonucleases?
By covalent modification of bases at the restriction site (e.g. methylation).
What is the origin of the names of restriction enzymes?
Reflects the origins of the bacteria they were first characterized from.
What type of sequences do restriction enzymes cut at?
Palindrome sequences that are self-complementary.
What is the use of restriction enzymes?
As molecular scissors for manipulation of DNA.
What is DNA fingerprinting?
Breaking DNA into pieces with restriction enzymes to identify differences in genome sequences.
What is the purpose of hydrophobic effects in stabilizing the double helix?
Burying purine and pyrimidine rings in the interior of the helix.
What is the purpose of stacking interactions in stabilizing the double helix?
Forming van der Waals contacts between stacked base pairs.
What is the purpose of hydrogen bonds in stabilizing the double helix?
Hydrogen bonding between base pairs.
What is the purpose of charge-charge interactions in stabilizing the double helix?
Decreasing electrostatic repulsion of negatively charged phosphate groups by cations (e.g. Mg 2+) and cationic proteins.
What is the function of DNA-binding proteins?
To read a specific sequence by using interactions with base pairs in the major and minor grooves.
What is the difference between major and minor grooves?
Major grooves are deeper and have more exposed base pairs.
What is the function of treating DNA with restriction enzymes in DNA fingerprinting?
To break DNA into pieces for identification of differences in genome sequences.
What is the difference in DNA fragments between different individuals in DNA fingerprinting?
Different number of fragments and fragments of different sizes due to differences in genome sequences.
What is the purpose of methylation in protecting DNA from restriction endonucleases?
To covalently modify bases at the restriction site.
What is the mirrored sequence of a palindrome?
A sequence that is not a palindrome but is mirrored.
What is the example of a palindrome sequence?
TAGGAT and ATCCTA.
What are RFLPs?
Restriction Fragment Length Polymorphisms that can be used to identify individuals.
What is duplex DNA?
DNA containing two complimentary, anti-parallel strands.
What determines the sequence of one strand in duplex DNA?
The sequence of the other strand.
What is the direction of DNA sequences?
Always 5’ to 3’.
Why is the complementary nature of DNA strands important?
For replication and repair
