Structure and Function of Nucleic Acids

nucleotides

monomer of nucleic acids

nucleotide

sugar + base + phosphate

nucleoside

sugar + base

ribose

A five-carbon sugar present in RNA

deoxyribose

A five-carbon sugar that is a component of DNA nucleotides

1'

carbon in DNA that forms the glycosidic bond with the base (purine or pyrimidine)

2'

carbon in DNA that differentiates it from RNA

3' and 5'

carbons in DNA that form phosphodiester bonds to link nucleotides, forming the backbone

adenine

guanine

thymine

cytosine

uracil

nucleotide triphosphate

starting material in polymerizing DNA - gets added onto polymer

dissociate

at intracellular pH, phosphates ______________ freeing hydrogen ions and leaving the phosphate group negatively charged on the backbone of DNA

positively

DNA is associated with ____________ charged proteins

Chargaff's Rule

[A]=[T] and [G]=[C]

antiparallel

DNA strands run _______________ of one another

3

number of hydrogen bonds between guanine and cytosine

2

number of hydrogen bonds between adenine and thymine

melting temperature

temperature at which 50% of the helical (ds) structure is lost

higher

the greater the GC%, the ________________ the Tm

semiconservative replication

Method of DNA replication in which parental strands separate, act as templates, and produce molecules of DNA with one parental DNA strand and one new DNA strand

20 mcm

diameter of a human cell

6 ft

human cells contain ______ of DNA

6 mcm

all DNA in a human cell fits into a ______ diameter nucleus; allowing for enzymes and proteins that act on the DNA to be concentrated where needed and ensures compartment-specific enzyme activity

negative

______ charges on the phosphates repel eachother, keeping DNA extended

4 billion

number of nucleotides in the haploid human genome

chromatin

nucleoprotein complex of DNA in eukaryotic cells not undergoing division; dynamic

50%

histones make up about ______ of chromatin by mass

chromosome 1

largest chromosome in human genome

chromosome 2

only way to differentiate human and primate chromosomes on a karyotype

euchromatin

gene-rich, transcriptionally active chromatin that is less compact and has less proteins

heterochromatin

gene-poor, inactive, compact, protein-rich chromatin that maintains chromosome structure, provides genome stability with repetitive DNA sequences, and regulates gene expression. Ex: telomeres and centromeres

histones

arginine and lysine-rich small basic proteins that form ionic bonds with the phosphorous on DNA backbone; amino acid sequence is highly conserved between species

core particle

146 bp of DNA wound around 8 histones (four types, two of each)

nucleosome

core particle + linker DNA of 20-80 base pairs

repetitive sequences

two main kinds: satellite DNA and short interspersed elements (SINES); used in DNA paternity and forensic testing (unique genetic fingerprints); allow for hyper-compact DNA to easily be distorted

satellite DNA

short sequences of repeated nucleotides (tandem)

SINEs (short interspersed nuclear elements)

are approximately 300 base pairs long, are present in over 1 million copies scattered throughout the human genome (not tandem)

mitochondrial genome

multiple copies of circular genome containing 16.5 Kbp in the mitochondria, allowing them to function independently of the human genomic DNA; transmitted maternally only

RNA

single stranded nucleic acid that contains a ribose sugar and uracil in place of thymine; is more reactive and less stable than DNA; produced as needed and acts as deletable memory

2' OH

makes RNA less stable than DNA because it allows for intramolecular nucleophilic attack resulting in the hydrolysis of the RNA

hairpin

secondary structure of RNA; forms when inverted palindrome sequences hybridize

RNA

two major classes of _________: protein coding and non-protein coding

mRNA

long molecule ranging from a few hundreds to many thousands of bases - length directly correlates with gene size

5' cap

The 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide; protects mRNA from degredation (increases stability), enhances translatability, transports mRNA out of the nucleus, and increases efficiency of splicing mRNA

poly-A tail

3' end of mRNA that is added post-transcriptionally; about 250 nucleotides long; the length correlates with half life of the mRNA

splicing

removal of introns from pre-mRNA to generate mature mRNA; five methods

normal

type of splicing that occurs 80% of the time

alternative

type of splicing that occurs 15% of the time

5

extended exon, skip exon, and intron retained methods of all together make up ___% of mRNA splicing methods

snRNA

small nuclear RNA; act as spliceosomes that cut mRNA in the splicing process; small sequences of RNA that can cut mRNA - multiple types exist in eukaryotes

rRNA

ribosomal RNA; provides platform for protein synthesis and is therefore very stable; consists of two subunits

tRNA

transfer RNA; short molecules of 25 KDa that translate message on mRNA into a polypeptide chain; have a specific amino acid attached to one end (first part of translation) and an anticodon on the other end (second part of translation) - can contain unusual nucleotides other than just the AUGC

61

number of different types of tRNA, each with a specific anticodon