Unit Five Study Guide

Chapter 16

  • Know that Watson and Crick discovered the double helix shape of DNA which also suggested the basic process of DNA replication
  • Know the structure of a single strand of DNA (ribose-phosphate backbone composed of phosphodiester bonds)
  • Know how DNA strands base pair and are connected by hydrogen-bonds
  • Know that DNA is antiparallel and nucleotides can only be added to the 3' end, MEANING DNA is synthesized in the 5' --> 3' direction
  • Know that DNA replication is semi-conservative, each strand serves as a template and becomes part of a new strand
  • Know the enzymes of DNA replication and their functions
  • Know the difference between the leading and lagging strand how each is built
  • Know how DNA is proofread by DNA polymerase and maintained by nucleases, DNA polymerase and ligase
  • Know how the ends of DNA are not replicated without the help of telomerase


Chapter 17

  • Know that the genetic code is near universal and that each triplet of RNA nucleotides codes for a single amino acid
  • Know that each gene codes for a single polypeptide
  • Recall that proteins are made from amino acids connected by peptide bonds
  • Know that transcription occurs in the nucleus of eukaryotes, when RNA polymerase binds to the promoter region of DNA and begins transcribing a pre-mRNA molecule
  • Know that transcription factors aid in the binding of RNA polymerase
  • Know that RNA is modified in eukaryotes, by the addition of a 5' cap and poly A tail and the splicing of introns
  • Know that splicing is accomplished by spliceosomes containing snRNPs which recognize the introns
  • Know that translation occurs in ribosomes in the cytoplasm
  • Know the structure of a ribosome and the binding sites
  • Know that AUG is the start codon and codes for Met (methionine) meaning every polypeptide begins with Met though it may be removed later
  • Know that tRNA molecules carry an amino acid to the ribosome, and that the anticodon of the tRNA complements the codon of the mRNA
  • Know how translation occurs, with each tRNA adding its amino acid then passing the polypeptide to the next tRNA
  • Know that the stop codons (UAA, UGA, UAG) do not code for amino acids, but instead cause the removal of the polypeptide from the ribosome
  • Know that multiple ribosomes can operate on a single mRNA molecule  

Chapter 18
  • Know the basic structure of a virus and how they reproduce in hosts (the lytic and lysogenic cycles)
  • Know that viruses may have evolved from mobile genetic elements and are more similar genetically to their hosts than to other viruses
  • Know the structures of bacterial chromosome (a single highly condensed circular DNA molecule) 
  • Know what plasmids are and their importance
  • Know how bacterial DNA is recombined without sexual reproduction (transformation, transduction, conjugation)
  • Know what transposons are
  • Know how operons control the expression of bacterial genes by bonding of a repressor molecule to the operator
  • Know the difference between a repressible operon (trp, binding of a molecule to the repressor turns off expression of the gene) and an inducible operon (lac, binding of a molecule to the repressor turns on expression of the genes)


 Chapter 19 

  • Know the levels of DNA packing, especially nucleosomes (DNA wrapped around histone proteins)
  • Know that much of eukaryotic DNA consists of repetitive sequences (which are important).
  • Satellite DNA consists of short repeated segments back to back and is important in the centromeres and telomeres of DNA
  • Interspersed repetitive DNA are larger segments found throughout the genome and are about 25-40% of mammalian DNA
  • Know that over the course of history genes have been copied and mutated in our genome, so that we have multiple copies of a gene (some slightly altered) which are called a gene family
  • This has been mostly accomplished by transposons (mobile genetic elements)
  • Genes can be temporarily copied (amplified) during certain developmental periods that require large amounts of proteins (i.e. growth of an egg)
  • Know how transposons work and why they are important
  • Know that each cell expresses only a small fraction of the genome
  • Know that the control of eukaryotic gene expression can occur at any step in the transcription/translation process
  • The most important regulatory methods are the packing of DNA (location of DNA and DNA methylation) and the control of transcription factors thus regulating transcription

Chapter 20 

  • Know what restriction enzymes are and why they are important in biotechnology
  • Know the basic process of gene cloning and why it is important (inserting genes into other organisms) 
  • Know what PCR is and its function
  • Know the basics of gel electrophoresis and Southern blotting and how they can be used to compare 2 DNA molecules
  • Know the basics of DNA sequencing and chromosome walking
  • Know what cDNA is and how microassays can tell us which genes are expressed in a tissue
  • Know some of the practical applications of biotechnology

Chapter 21

  • Know that cells differentiate into different tissues, mainly by transcribing different genes
  • Know that plants keep growing throughout their lifetime, while animals stop growing
  • Know that a single plant cell can be used to grow an entirely new plant
  • Know that this is much more difficult in animals, and that it gets increasingly more difficult the more developed/differentiated a cell is (thus the search for undifferentiated stem cells to grow new tissues)