DNA structure and function Flashcards
What does DNA consist of?
2 long polynucleotide chains
what is the predominant form of DNA?
right-handed B form
hydrogen bonds exist where within the strand?
between the bases
where do covalent bonds exist within the strand? more specifically, what are they called?
exist between the nucleotides along sugar-phosphate backbone; phosphodiester bonds
which bonds are considered weak?
hydrogen bonds
when do hydrogen bonds form?
when a hydrogen is bw 2 electron attractors
what contributes to overall stability of the double helix?
hydrogen bonds
how many hydrogen bonds bw a C and G?
3
how many hydrogen bonds bw an A and T?
2
what do nucleotides consist of?
nitrogenous base, 5 carbon sugar, and phosphate group
subunits of nucleic acids
nucleotides
“rungs” on DNA ladder
bases
strong chemical bond? how is it formed?
covalent bonds; sharing of electron pairs with a balance of attractive and repulsive forces
which bases are purines? how many rings?
adenine and guanine; 2
which bases are pyrimidines? how many rings?
cytosine and thymine; 1
what about the bases constitutes the genetic code?
variability of the bases on a DNA strand
where is the nitrogenous base attached to deoxyribose?
1’ carbon
where is the hydroxyl group located on deoxyribose?
3’ carbon
where does the phosphate group attach to deoxyribose?
5’ carbon
how/where are nucleotides joined? making what? what is the bond called?
joined by the phosphate group of one nucleotide attaching to 3’ carbon of next nucleotide; polynucleotide; phosphodiester bond
what does antiparallel mean? why does it occur? what principle is it called?
one strand compliments the other, necessary bc of base pairing requirements; “complementarity”
how is a nucleotide sequence read on a DNA strand?
5’ to 3’
why can’t a purine bond with a pyrimidine?
because of the chemical structure of the cyclic compound
_____ groups of one base bind with ________ groups of the other
keto; amino
what happens if wrong bases pair up?
DNA repair must be done
nitrogen-containing rings, either purines or pyrimidines
bases
what for the principle “complementarity”?
two strands of DNA are antiparallel; meaning one strand compliments the other
what does base pairing do?
holds monomers in place and thereby controls the selection of which base will be added to the strand.
how is the double helix formed?
each DNA strand is coiled around the same helical axis and intertwined
all proteins no matter how complex or simple are __________ by DNA.
templated(molded)
what is an exon?
portion of the code for the protein that is spliced together to form functional gene
what is an intron?
portion of the code from the protein that is unused.
