Nucleic Acids Flashcards
central dogma of molecular biology
DNA transcription to RNA and its translation to protein
DNA
double-stranded chains of deoxyribonucleotides that reside in the nucleus
RNA
single-strande d chains of ribonucleotides that are transcribed in the nucleus and translated in cytosol
proteins
chains of amino cytosol but involved in all different areas of the cell
what are DNA and RNA the source of?
genetic info. in humans
DNA in eukaryotes
it is present in the nuclei of their cells (small amount contained in mitchondria)
DNA in prokaryotes
circular DNA that is not separate from the rest of the cell contents
what do viruses do?
utilize DNA or RNA for their genetic info. but require other host cells whose replication machinery they hijack in order to multiply; can infect eukaryotic organisms and prokaryotes as well
what are viruses that infect bacteria called?
bacteriophages
plasmids
circular DNA molecules that can enter bacterial cells and replicate independently of the genomic DNA; not infectious but are important since they can confer antibiotic resistance to bacteria
DNA bases
adenine, guanine, cytosine, thymine; they are nitrogenous
which bases are purines?
adenine and guanine
which bases are pyrimidines?
thymine and cytosine
what are the DNA base pairs?
A binds to T, G to C
DNA sugars
at the second carbon, will have an H instead of an OH hence “deoxy”
RNA sugars
ribose sugar; at the second carbon, will have an OH
what is a sugar bonded to a base called?
a nucleoside
once a phosphate is added to a nucleoside, it is called a…
nucleotide
at which end does one phosphate attach to another ?
at 5’
what does the DNA backbone consist of?
sugar and phosphate
at which carbon is the attachment point for the phosphate?
at the 3’ carbon
what type of bond links nucleotides?
phosphodiester bonds
how many hydrogen bonds are between A and T?
2 hydrogen bonds
how many hydrogen bonds are between C and G?
3 hydrogen bonds
what do the hydrogen bonds between the nitrogenous bases do?
stabilize DNA structure but are weak enough to allow separation of helices for replication + transcription
DNA replication
process in which DNA makes a duplicate copy of itself in semi-conservative manner; each strand provides the template for a new strand and attaches to that new strand to create helices
antiparallel nature of DNA
the strands run in opposite directions (5’ to 3’ and then 3’ to 5’); each strand can serve as a template for the strand
complementarity
a pyrimidine is always H-bonded to the same purine
sense strand
the strand of DNA that runs 5’ to 3’ and contains the genetic code for a protein
antisense strand
the strand of DNA that runs 3’ to 5’ and acts as a template strand during transcription
what charge does DNA carry?
negative; two oxygen molecules of the phosphate group form the phosphodiester bond, the free OH loses its L at physiological pH (allows binding/association of proteins or other molecules in major or minor grooves)
DNA packaging
eukaryotic DNA wraps around histones to form a solenoid structure (nucleosomes) that packs DNA tightly inside the nucleus
what do histones consist of?
many arginines and lysines (+vely charged)
chromosomes
threadlike structures made of DNA molecules that contain the genes
genome
total of all DNA in the cell
haploid
an organism or cell having only one complete set of chromosomes (23 in humans)
diploid cell
a cell containing two sets of chromosomes (2n), one set inherited from each parent (46 in humans)
gene
sequence of DNA (plus its regulatory regions) that code for a protein or RNA molecule
homologous chromosomes
chromosomes that have the same sequence of genes and the same structure
alleles
different versions of a gene
single nucleotide polymorphism
variation in a DNA sequence occurring when a single nucleotide in a genome is altered
what is the differing base in RNA? which base does it replace?
uracil (U) replaces thymine
Types of RNA
mRNA, tRNA, rRNA
messenger RNA
RNA molecule that carries copies of instructions for the assembly of amino acids into proteins from DNA; exported into cytoplasm to direct protein synthesis (transcribed from antisense strand)
Ribosomal RNA
type of RNA that associates with proteins to form ribosomes; subunits differ between prokaryotes and eukaryotes
transfer RNA
RNA in the cytoplasm that carries an amino acid to the ribosome and adds it to the growing protein chain
anticodon
a sequence of three nucleotides complementary to the mRNA sequence so it can be “read” and the correct a.a. can be added to the polypeptide chain
reverse transcriptase
a polymerase that catalyzes the formation of DNA using RNA as a template; some viruses insert this into a host’s chromosome and hijack its transcription and translation machinery (permanently incorporated into host DNA)
