BIOL 330 Study Guide - Spring 2018, Comprehensive Midterm Notes - Rna, Dna, Protein
BIOL 330
MIDTERM EXAM
STUDY GUIDE
Fall 2018
• Genes are DNA, encoded RNA and polypeptides.
o Chromosomes: discrete unit of the genome carrying many genes
▪ Chromosomes are usually very long unless they are in cell division, like mitosis,
in which they condense and DNA becomes visible
o Structural gene: A gene that codes for any RNA or polypeptide product other than a
regulator
▪ Ex. Structural protein, enzyme, or RNA molecule
o Allele: one of several alternative forms of a gene occupying a given locus on a
chromosome
o Locus: the position on a chromosome at which the gene for a particular trait resides;
it may be occupied by any one of the alleles for that gene
o Genetic recombination: process by which separate DNA molecules are joined into a
single molecule, due to such processes as crossing over and transposition
▪ Leads to different expressed traits
• DNA is the genetic material of bacteria and viruses:
o During bacterial transformation, genetic properties can be transferred from one
bacterial strain to another by extracting DNA from the first strain and adding it to
the second strain
o Transforming principle: DNA that is taken up by a bacterium and whose expression
then changes the properties of the recipient cell
o When DNA and protein components of bacteriophages are labeled with different
radioactive isotopes, only the DNA is transmitted to the progeny phages produced
by infecting bacteria
o How phages attack bacteria:
▪ Phage lands on bacteria
▪ It inserts its DNA
▪ DNA is synthesized and assembled into more phages
▪ It releases a chemical that disrupts the bacteria and releases the new phages
(the bacteria bursts and dies in the process)
• DNA is the genetic material of eukaryotic cells
o DNA can be used to introduce new genetic traits into animal cells or whole animals
o Transfection: acquisition of new genetic markers by incorporation of added DNA
o In some viruses, the genetic material is RNA
• Nucleoside (nucleotides without a phosphate group): consists of a purine or pyrimidines
base linked to the 1' carbon of a pentose sugar
o Purine: two carbon nitrogen base (adenine and guanine)
o Pyrimidines: one carbon nitrogen base (thymine and cytosine
▪ Both purine and pyrimidines serve the same functions; form of energy for cells
and is crucial for production of DNA, RNA, protein, starch, regulation of
enzymes, and cell signaling
o DNA contains four bases; adenine, guanine, cytosine, and thymine; RNA has uracil
instead of thymine
o Polynucleotides are many nucleosides linked together
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o Supercoiling: coiling of a closed duplex DNA in space so that it crosses over its own
axis--has a twisted and condensed form
• DNA is a double helix:
o Consists of two polynucleotide chains that run antiparallel
o Has a major (wide) and a minor (narrow) groove
o Overwound: has more than 10.5 bas pairs per turn of the helix
o Underwound: has fewer than 10.5 base pairs per turn of the helix
o Semiconservative replication: each of the new strand of DNA has 1 single strand of
the parent
• Polymerases act on separated DNA strands at the replication fork:
o Enzyme separates the parent strand and synthesizes the daughters
o Denature: separation of two strands due to the breakage of the hydrogen bond
o Renature: reassociation of two strands due to the reassembly of the hydrogen bond
o The replication fork is the point at which the parental strand are separated
▪ DNA polymerase: formation of DNA by assembling nucleotides
o Nucleases are enzymes that degrade nucleic acids
▪ Deoxyribonuclease (Dnase) and ribonuclease (Rnase) are endocleases
• Endocleases: cleave bonds within a nucleic acid
• Exonuclease: removes one base at a time
• Genetic information can be provided by DNA or RNA
o RNA polymerase: during transcription, creates RNA copy of DNA
o Central dogma: information cannot be transferred from protein to protein or protein
to nucleic acid, but can be transferred between nucleic acids and from nucleic acid
to protein
• Nucleic acids hybridize by base pairing
o Hybridization: single stranded RNA or DNA combines after cooling from
denaturation
o The melting point is the midpoint of the temperature range for denaturation
• Mutations change the sequence of DNA:
o All mutations are changes in the sequence of DNA
o Mutations may occur spontaneously or may be induced by mutagens
o A point mutation changes a single base pair
▪ Causes by the chemical conversion of one base into another or by errors
that occur during replication
o A transition replaces a G-C base pair with an A-T base pair
o A transversion replaces a purine with a pyrimidine, such as changing from A-T to
T-A
o Insertions and/or deletion can result from the movement of transposable
elements
o Forward mutations alter the function of a gene and back mutation reverse the
effects
▪ Insertions can revert by deletion of the inserted material, but deletions
cannot be reverted
o Mutations that can be reversed:
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