When a solution of cesium chloride (cscl) is subjected to high-speed centrifugation, a stable density gradient is formed. meselson and stahl found that when cell contents were subjected to centrifugation with a cscl solution, a band of dna formed at the cscl density that matched the density of the dna. this technique is called density-gradient centrifugation. the test tubes below show the results of density-gradient centrifugation of five different dna samples. assign letters a-e to the pictures above. dna from e. coli cells grown in ^5n dna from e. coli cells grown in ^14 n a 1: 1 mixture of dna from cells grown in 14^n and cells grown in ^15 n a 1: 1 mixture of dna from cells grown in 14^n and 15^n, heated (to disrupt hydrogen bonds) and cooled (to allow reannealing) dna containing one strand of ^15 n-dna and one strand of ^14 n-dna

Proteins are the workhorses of the cell, controlling virtually every reaction within as well as providing structure and serving as signals to other cells. proteins are long chains of  amino acids  , and the exact sequence of the amino acids determines the final structure and function of the protein. instructions for that sequence are encoded in  genes  . to make a particular protein, a messenger ribonucleic acid (mrna) copy is made from the gene (in the process called  transcription  ), and the mrna is transported to the  ribosome  . protein synthesis, also called  translation  , begins when the two ribosomal subunits link onto the mrna. this step, called initiation, is followed by elongation, in which successive amino acids are added to the growing chain, brought in by transfer rnas (trnas). in this step, the ribosome reads the  nucleotides  of mrna three by three, in units called  codons  , and matches each to three nucleotides on the trna, called the anticodon. finally, during termination, the ribosome unbinds from the mrna, and the  amino acid  chain goes on to be processed and folded to make the final, functional protein

Breacking the law and lazy

This is s cute awee : (( . well if she's showing you signs that she may like you , then shoot your shot ! don't be afraid . & if you're unsure that she's giving you these signs , then wait out for a little bit . most girls are different . some may act really sweet , but only bc you're a good friend of hers . that , or she might like you . you just never know . but i think you should sit down with her & tell her how you feel . but don't be awkward & shy . just be straight up & tell her how you feel . if the feelings aren't mutual , then don't cry about it . you need to respect her decision & look for others in the world . feelings can be difficult & confusing , but don't be afraid to show them . i say you play it out & if you're still unsure about it , talk to her . - rach