Theme 1b Flashcards
What are the components of DNA
Pentose sugar, nitrogenous base and phosphate
What does the pentose sugar structure look like
Look at photos for reference lol
What is the difference between RNA and DNA sugars
Type of chemical group bound to the 2’ carbon
What are the nitrogenous bases for DNA and RNA
DNA: adenine (purine), guanine (purine), cytosine (pyrimidine) and thymine (pyrimidine)
RNA: adenine (purine), guanine (purine), cytosine (pyrimidine) and uracil (pyrimidine)
What is a nucleoside
Molecules of a sugar and base
What is a deoxyribosenucleoside
2-deoxyribose sugar and purine/pyrimidine base
Binds to Cl’ end of deoxyribose/ribose
What is the difference between a deoxyribonucleoside and a ribonucleoside
There would be an OH on the 2’ carbon
What is a nucleotide
A nucleoside and a phosphate with the phosphate group attached to the 5’ carbon of the ribose and deoxyribose sugars
What are some properties of DNA
A polymer of deoxyribonucleotides
-nucleotide monomers polymerize via phosphodiester bonds
-covalent bonds form between phosphate and the C3’ and C5’ of two pentose sugars (pentose phosphate backbone)
-has polarity with a 5’ PO4 end and a C3’ OH end
-charge is negative because of phosphate group
What is Chargaff’s rule
% purines (A + G) = % pyrimidine (C + T)
% A = % T and % C = % G
What did Watson and Crick do
Pieced together the clues to determine the structure of DNA
-antiparallel
-double helix
-purines are paired with pyrimidines
-exterior is hydrophilic (phosphate heads) and interior is hydrophobic (phosphate tails)
How does hydrogen bonding keep DNA intact
H-bonding between bases keeps the strands intact
3 h-bonds between G and C
2 h-bonds between A and T
What is nucleic acid hybridization
Annealing of single strands of DNA or RNA
Strands must be complementary in sequence and are highly specific
What is Watson and Cricks model of DNA replication
-complementary base pairing
-parental strands act as templates and can unwind by breaking the h-bonds between bases
-semi conservative replication
What are the differences between prokaryotic and eukaryotic chromosomes
Prokaryotic: have one circular chromosome sand other small independent circular DNA called plasmids in the cytoplasm
Eukaryotic: linear chromosomes and enclosed in the nucleus
What is a centromere
DNA sequences that are required for correct segregation of chromosomes by directing formation of the kinetochore
What are the origins of replication
DNA sequences that initiate DNA replication
What are telomeres
Sequences of DNA located at the ends of the chromosome that prevent degradation and allow proper replication of the chromosome ends
Because ends of DNA are very unstable
What are histones
Basic positively charged proteins that DNA wind around
Only in eukaryotic cells since bacterial cells are much smaller and need DNA to be more compacted
How can you tell the difference between a circular DNA and linear DNA
Cut the DNA in half, one fragment means circular DNA, two fragments means linear DNA
What is euchromatin
Regions have lower DNA compaction and genes are actively expressed
What is heterochromatin
Chromosomal regions of high DNA compaction where gene expression is silenced (no space for for enzymes to activate genes)
Constitutive vs facultative heterochromatin
Constitutive: DNA is always highly compacted (centromeres and sub-telomeric regions)
Facultative: can switch to euchromatin depending on cells type and environment
