BIOCHEM Chp.6 NDA Flashcards
What is the diff b/w RNA and DNA composition?
RNA is made of ribose and single-stranded, whereas DNA is made of deoxyribose and double-stranded
What is the composition of purines?
2 ring structures found in adenine and guanine nucleic acids
What is the diff b/w purines and pyrimidines?
purines have 2 rings, whereas pyrimidine has 1 ring
Which pyrimidine is ONLY found in DNA?
Thymine
Which pyrimidine is ONLY found in RNA?
uracil
What is the structure of DNA?
2 strands that run antiparallel with the sugar-phosphate backbone on the outside of the helix and the nitrogenous base on the inside
What is the complementary base pairing of DNA?
Adenine always pairs with thymine via 2 hydrogen bonds, and guanine always pairs with cytosine with 3 hydrogen bonds
What does the chargeoffs rule state?
the amount of A equals the amount of T, and the amount of G equals the almond of C in DNA
What is the diff b/w B and Z-DNA?
B-DNA is a right-handed helix, and it turns every 3.4/10 bases, the Z-DNA is a zigzag appearance left-handed helix that turns every 4.6/12 base
What are common forms used to denature/anneal DNA?
Heat, alkaline pH, chemicals like formaldehyde and urean
What is recombinant endonuclease?
enzymes that recrognize palindromic sequences - the 5’ to 3’ sequence of one strand is identical to the 5’ to 3’ sequence of the other strand
How are nucleosomes formed?
DNA wound around histone proteins (H2A, H2B, H3, H1, and H4)
What is the diff b/w heterochromatin and euchromatin?
heterochromatin is dense, transcriptionally silent DNA that appears dark under light microscopy. euchromatins are less dense DNA, transcriptionally active, and appear light under light microscopy
What is the purpose of telomeres and centromeres?
Telomeres are at the end of chromosomes and contain high GC content to prevent the unraveling of the DNA. Centromeres are in the middle of chromosomes and contain high GC content to maintain a strong bond between the sister chromatids until they are separated during anaphase in mitosis
What is the role of single-stranded DNA-binding proteins?
they keep unwounded strands from reannealing or being degraded
What is the role of DNA topoisomerases?
releases torsional strain caused by supercoiling
What does it mean when DNA is semiconservative?
1 old parent strand and 1 new daughter strand is incorporated into each of the 2 new DNA molecules
What is the diff b/w prokaryotic and eukaryotic chromosomes?
prokaryotes have circular chromosomes that contain only 1 origin of replication. eukaryotes have linear chromosomes that contain many origins of replication
What is the diff b/w the leading and lagging strand?
the leading strand requires only 1 primer and can be continuously synthesized. the lagging strand requires many primers and is synthesized in discrete sections called Okazaki fragments
Which enzyme removes RNA primers?
DNA Polymerase I (in prokaryotes) or RNase H (in eukaryotes)
What is the role of DNA ligase?
fuses the DNA strands to create one complete molecule
How are oncogenes formed?
they are developed from mutations of proto-oncogenes and promote cell cycling
What is the role of tumor suppressor genes?
they code for proteins that reduce cell cycling or promote DNA repair; mutation of these genes can lead to cancer because mutated cells pass through the cell cycle unchecked
What is the role of MSH2 and MLH1?
they complete mismatch repair during G2 of the cell cycle
