y5 bio: cluster 3 (nucleic acids)

what is a nucleic acid?

a polymer made of nucleotide monomers that stores and expresses genetic information (e.g. DNA and RNA)

what are the three components of a single nucleotide?

a pentose sugar (5C sugar), a phosphate group (inorganic phosphate), and a nitrogenous base (either 1 or 2 rings)

which pentose sugar is found in DNA and RNA respectively?

deoxyribose (DNA), ribose (RNA)

in a nucleic acid, what are the bonds in the sugar phosphate backbone and how are they formed?

covalent phosphodiester bonds between C3 of one pentose sugar and the phosphate group of the next. formed through condensation reaction and releases water per bond formed

nucleotides can only be added to the (____) of the chain

3’ end

what nitrogenous bases are found in DNA and RNA respectively?

adenine, thymine (uracil for RNA), cytosine, and guanine

what is the key structural difference between purines and pyrimidines?

purines are double-ring bases while pyrimidines are single-ring bases

which nitrogenous bases are purines?

adenine and guanine

which nitrogenous bases are pyrimidines?

cytosine, thymine, and uracil

how do you determine the directionality of a dna strand?

the 5' end has a free phosphate group and the 3' end has a free hydroxyl group.

how is a double-stranded DNA molecule structured?

two antiparallel (running in opposite directions) polynucleotide strands coiled into a right-handed double helix, with sugar phosphate backbone on the outside of the helix and base pairs in centre of helix

why is the DNA sugar phosphate backbone negatively charged?

due to the presence of ionised phosphate groups in the phosphodiester bonds

what holds complementary bases together in a DNA molecule?

hydrogen bonds between specific purines and pyrimidines, where there’s a constant width between them

how many hydrogen bonds form between A-T and C-G respectively and thymine?

A-T two hydrogen bonds, C-G three hydrogen bonds

what are 3 major structural differences between DNA and RNA?

DNA is double-stranded with deoxyribose and thymine, RNA is single-stranded with ribose and uracil

regarding their primary role, what is the difference between DNA and RNA

DNA store genetic info and RNA expresses genetic info

how to find number of possible DNA base sequences?

4^(number of bases on a single strand)

what feature of genetic code enables genes from one species to be expressed in the other (gene engineering)?

the genetic code being universal, where ALL organisms use the exact same four nitrogenous bases and codons to specify amino acids

what are the 4 traits that make the DNA stable?

1. hydrogen bonds between CBP throughout DNA molecule 2. CBP has constant width between purine and pyrimidine 3. strong covalent phosphodiester sugar-phosphate backbone 4. deoxyribose has no oxygen, makes DNA more chemically stable

what is the structural composition of a nucleosome?

an octamer core of eight histone proteins wrapped twice by DNA + bound by H1 linker histone + linker DNA to connect to adjacent nucleosomes

what is the main biological function of nucleosomes?

to package eukaryotic DNA for compact storage in the nucleus and to regulate replication and transcription

what was the purpose and conclusion from the Hershey-chase experiment

purpose: to find out if DNA or protein was genetic material? conclusion: DNA (and NOT protein) is the genetic material as when DNA is injected into bacteria, there was direct viral replication

what is chargaff's rule?

in double-stranded DNA, % of adenine equals thymine, and % of cytosine equals guanine. so A+G = T+C (purines = pyramidines)

what is inductive and deductive reasoning

inductive builds theory, deductive tests existing theory