Nucleic Acids: Structure & Function Flashcards
plasma membrane
single phospholipid bilayer
- contains proteins embedded into its bilayers
nuclear membrane
continuous double phospholipid bilayer (inner & outer)
- contains proteins embedded into its bilayers
nucleolus
responsible for ribosomal RNA processing and assembling ribosomal subunits
- site of ribosome assembly
gene
a sequence of DNA—located at a specific locus—with a specific job or function
- made up of proteins
metabolic pathway
a linked series of biochemical reactions that build up or break down a particular molecule
- product of one reaction is the substrate of the next reaction
locus
location on a chromosome
allele
gene sequence variability, which leads to variations in the gene function
nuclear localization signal (NLS)
a short amino acid sequence that marks a protein for delivery to nucleus
components of a nucleic acid
(1) phosphate group
(2) 5 carbon sugar
(3) nitrogenous base
antiparallel
opposing orientation of nucleic acid strands that are hydrogen bonded to one another
- one strand = 5’ -> 3’
- another strand = 3’ -> 5’
complementary base pairs
pair of bases that only bond to one another
- A + T or A + U = 2 H-bonds
- G + C = 3 H-bonds
ribozyme
RNA enzyme that act as a catalyst by speeding up a chemical reaction
- contains uracil instead of thymine
genotype
alleles of a gene
- determined by sequence of bases in its DNA
phenotype
physical traits expressed according to a genotype
- product of proteins it produces
central dogma
scheme for information flow in the cell: DNA S RNA S protein
types of transportation through nuclear pores
(1) nuclear export signal (mRNA)
2) nuclear localization signal (lamin
nucleotide structure
1’ - base
2’ - R (DNA or RNA) = OH or H
3’ - OH (polymer)
4’ - connect to 5’
5’ - phosphate
(1B 2R 3OH 45 5P)
purine
class of small, nitrogen-containing, double-ringed bases found in nucleotides - bases: adenine & guanine
*linked juntos by 9 atoms
pyrimidine
class of small, nitrogen-containing, single-ringed bases found in nucleotides - bases: cytosine, thymine OR uracil
*linked juntos by 6 atoms
polymer properties
(1) condensation reaction
(2) phosphodiester bond
(3) sugar-phosphate backbone
(4) 5’ & 3’ ends
(5) primary structure depends on order of nucleotides
primary structure
depends on order of nucleotides
- consists of sugar-phosphate backbone (phosphodiester linkages + sequence of 4 types of bases)
- RNA < stable than DNA
- supports catalytic activity in molecule
secondary structure
depends on H-bonds
- result of complementary base pairing btwn purine & pyrimidine bases
- section where fold occurs =unpaired bases + stem-&-loop configuration
nucleic acid functions in DNA
make up genetic material
nucleic acid functions in RNA
(1) gene expression (mRNA, tRNA, rRNA, siRNA)
(2) ribozymes
(3) ATP & GTP
(4) genetic material in some viruses
Watson & Crick
credited for discovery of DNA structure
- used Rosalind Franklin’s collected data but she was not credited
- basically trial & error
DNA structure
(1) double-stranded = secondary structure
(2) antiparallel
(3) self-perpetuating - can only be replicated/connected in 1 way
types of RNA
(1) messenger RNA, mRNA
(2) transfer RNA, tRNA
(3) siRNA
(4) rRNA
messenger RNA (mRNA)
complimentary to DNA
- carry info required to manufacture proteins
ribosomal RNA (rRNA)
forms part of ribosome
- manufactured in nucleolus
- bind to proteins -> ribosomes
- machinery
*most RNA
transfer RNA (tRNA)
interacts w/ amino acids & RNA
siRNA
gets rid of mRNA
- regulates translation
central dogma
scheme for info flow in cell
(1) DNA - info storage
TRANSCRIPTION
(2) mRNA - info carrier
TRANSLATION
(3) proteins - active cell machinery
[DNA -> RNA -> protein]
reverse transcription
RNA becomes DNA
translation
nonreversiable
types of proteins
(1) cytosolic proteins
(2) lumenal proteins
genetic code property
must be triplet code
- triplet code allows for more amino acids
reading frame
3 combo letters stand for specific amino acid
- always start w/ AUG (start codon)
- 3 stop codons
gene characteristics
(1) redundant
(2) unambiguous
(3) nearly universal
(4) conservative
redundant gene
more than 1 codon
all amino acids (except methionine & tryptophan) are coded by more than 1 codon
unambiguous gene
know codon, know amino acid
single codon never codes for more than 1 amino acid
nearly universal gene
all codons specify the same amino acids in all orgs
- few minor exceptions
conservative
several codons specify the same amino acid
1st 2 bases in those codons are almost always identical
mutations
(1) single base change
(2) few bases change
(3) part of chromosome change
(4) whole chromosome changes
karyotype
spread of all chromosome
RNA world hypothesis
chemical evolution produced RNAs that could catalyze key reactions involved in their own replication & basic metabolism
nucleic acid
macromolecule composed of nucleotide monomers
nucleic acid properties
(1) polymer
(2) made up of nucleotides
(3) stores & processes info
(4) examples: DNA & RNA
types of nucleotides in living cells
(1) ribonucleotide (RNA)
2) deoxribonucleotide (DNA
ribonucleotides (RNA)
monomers of ribonucleic acid
- sugar: ribose
*more stable than DNA
deoxyribonucleotide (DNA)
monomers of deoxyribonucleic acid
- sugar: deoxyribose
- carries info required for org’s growth & reproduction
phosphodiester linkage/bond
chemical linkage btwn adjacent nucleotide residues in DNA & RNA
- result of: condensation reaction
nucleic acid directionality
(1) 5’ end = phosphate
(2) 3’ end = hydroxyl
(3) base sequence always written in 5’-3’ direction
(4) bases only added at 3’ end of growing molecule
(5) primary
adenine triphosphate (ATP)
molecule consisting of adenine base, sugar & 3 phosphate groups that can be hydrolyzed to release energy
- universally used by cells to store & transfer energy
DNA points to prove (Watson/Crick)
(1) sugar phosphate backbone
(2) Erwin Chargaff empirical rules (# purines = # pyrimidines)
(3) DNA = helical (Rosalind Franklin)
complementary strand
new strand of RNA or DNA that has a base sequence complementary to template strand
5’-3’
template strand
original DNA strand
3’-5’
DNA double helix
(1) highly structured
(2) regular
(3) symmetric
(4) held together via H-bonds + hydrophobic interactions + phosphodiester bonds
hairpin
a stable loop formed by H-bonds btwn purine & pyrimidine bases on same strand
- reduces entropy of RNA molecules
- secondary structure in RNA
tertiary structure
3-D folding
- arises when secondary structures fold into more complex shapes
*not present in DNA
nucleus
info center of eukaryotic cells
- corporate headquarters
- design center
- library
- highly organized interior
nuclear lamina
lattice-like sheet of fibrous nuclear lamins
- type of intermediate filament
- lines inner membrane of nuclear envelope
- stiffens envelope
- organizes chromosomes
- defines organelle’s overall shape & structure
nuclear envelope
separates nucleus from rest of cell
nuclear pore
opening in nuclear envelope
- connects inside of nucleus w/ cytoplasm
- molecules (mRNA & some proteins) pass through here
nuclear pore complex
large complex of dozens of proteins lining a nuclear pore, defining its shape & regulating transport through pore
zip code
molecular address tag
- marks them for transport through nuclear pore complex
- allows nuclear pore complex to open in some way that permits larger proteins & RNA molecule to pass through
RNA polymerase
enzyme that catalyzes the synthesis RNA molecules from ribonucleotides according to info provided by sequence of bases using a DNA template
exceptions to central dogma
(1) many genes code for RNA molecules that ≠ fcn as mRNAs -> translated into proteins
(2) info flows from RNA back to DNA
(3) reverse transcriptase
reverse transcriptase
enzyme that can synthesize double-stranded DNA from a single-stranded RNA template
- RNA virus infecting cells use this mode of synthesis
genetic code
set of all codons & their meanings
- rules that specify relationship btwn nucleotide sequence in DNA or RNA & amino acid sequence in proteins
- triplet code
reading frame
series of non-overlapping, 3-base-long sequence (potential codons) in DNA or RNA
start codon
AUG triplet in mRNA @ which protein synthesis begins
- codes for amino acid, methionine
stop codon
any of 3 mRNA triplets (UAG, UGA, or UAA) that cause termination of protein synthesis
- signals protein = complete
- does not code for an amino acid
- ends translation
(aka) termination codon
mutation
any permanent change in an org’s DNA
- create new alleles
- modification in cell’s info archive
- alter DNA sequences that range in size from a single base pair in DNA to whole sets of chromosomes
point mutation
mutation result in change of single base pair in DNA
types of point mutation
(1) missense mutation
(2) silent mutation
(3) frameshift mutation
(4) nonsense mutation
missense mutation
point mutation that changes 1 amino acid for another w/in protein sequence
silent mutation
point mutation that changes codon sequence w/out changing amino acid that is specified
frameshift mutation
addition or deletion of nucleotide in a coding sequence that shifts the reading frame of mRNA
- alters meaning of all subsequent codons
nonsense mutation
point mutation that converts an amino-acid specifying codon into a stop codon
- large effect
- causes early termination of polypeptide chain
- often results in a non-fcnal protein
mutation categories
(1) beneficial
(2) neutral
(3) deleterious
beneficial mutation
mutation ↑ org fitness (ability to survive/reproduce) in certain environ
(ie) G-to-A mutation (beach habitats) camouflages mice
neutral mutation
mutation has no effect on fitness
(ie) silent mutation
deleterious mutation
mutation, allele, or trait that ↓ individual’s fitness
- harmful
(ie) cancerous cell chromosomes = aneuploidy + inversions + translocations + deletions + duplications
changes in chromosomes
(1) inversion
(2) translocation
(3) deletion
(4) duplication
inversion
mutation in which chromosome segment breaks from rest of chromosome, flips & rejoins in reversed orientation
translocation
attached to a different chromosome
deletion
chromosome segment is lost
duplication
additional copies of segment present
