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  

• 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)