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AP BIOLOGY – DNA I
I. DNA Structure and Replication
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Genes were known to be on chromosomes in nucleus of cell in ________________.
Hereditary material was suspected to be either ________________component of chromosomes.
Hereditary material was proved to be DNA. Hershey-Chase (Frederick Griffith? Hint: Mice)
o a. _________were labeled with 35S in their protein outer coat; 32P-labeled DNA on inside.
o b. When viruses attached to new bacteria, scientists found only ________________
entered cells and produced more viral particles.
o c. Therefore only DNA was needed to reproduce these viruses -- DNA was the genetic
material.
DNA Structure
o a. Major discovery by American biologist ________________and English physicist
________________at University of Cambridge, England, 1951.
o b. Worked on puzzle made from pieces of data available from other researchers.
 i. DNA is composed of four ________________each nucleotide consists of a
phosphate group, sugar (deoxyribose), and a nitrogen base.
 ii. The four nitrogen bases are: ________________and ________________both
purines with double rings; and ________________and
________________pyrimidines with a single ring.
 iii. Chemist Erwin Chargaff discovered "________________" in late 1940s:
number of purines in DNA equals the number of pyrimidines, amount of T
equals the amount of A, and amount of G equals the amount of C.
 iv. ________________and Maurice Wilkins at King's College, London,
prepared ________________photograph suggesting DNA was double helix with
bases of constant diameter and stacked.
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c. Watson and Crick Model of DNA
 i. DNA consists of ________________of nucleotides, ________________
 ii. _______________ molecules make up sides of ladder, bases make up rungs.
 iii. The base pairs are ________________: A pairs with T; G pairs with C.
 iv. The hydrogen bonding of A=T and G=C provide rungs of _______________.
 v. Watson and Crick built DNA model of ________________
 vi. Their historic paper describing structure pointed out "possible copying
mechanism for the genetic material."
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Complimentary Base Pairing
o a. Purine is always bonded to a________________.
o b. Bases can be in any order, providing overwhelming variability; a chromosome can
have ________________base pairs with total number of possible nucleotide sequences in
the chromosome of 4140,000,000.
DNA Replication: Unzipping and Molding
o a. In double-stranded DNA, replication is possible because each strand serves as
t________________ for complementary strand.
o b. First step of replication involves DNA strands unwinding and unzipping; hydrogen
bonds between bases broken by enzyme called ________________.
o c. New complementary nucleotides move into place by
________________________________opposite each original template strand.
o d. Complementary nucleotides join together by enzyme ________________
o e. DNA again is double stranded with two DNA molecules identical to original molecule.
o f. ________________________________means each new double helix has one parental
strand conserved, and one new strand.
Cancer involves rapidly dividing cells; chemotherapeutic drugs stop replication by providing
analogs of the________________________________, thus stopping synthesis of effective DNA.
II. THE IMPORTANCE OF DNA
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DNA serves in nucleus as template for RNA ________________which in turn is used to
synthesize proteins ________________in ribosomes of cell cytoplasm.
Structure of RNA (ribonucleic acid)
o a. RNA is ______________ like DNA but has sugar_____________, not deoxyribose
o b. Pyrimidine thymine of DNA is replaced by pyrimidine ________________in RNA;
therefore in RNA, ________________ pairs with uracil.
o c. RNA is ________________unless it doubles back on itself.
Three types of RNA involved in protein synthesis:
o a. Messenger RNA (mRNA) carries ______________of bases from nucleus to ribosomes.
o b. Ribosomal RNA (rRNA) is found in ________________
o c. Transfer RNA (tRNA) ________________ amino acids to ribosomes.
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DNA Controls the Cell
o a. Occurrence of inherited metabolic disorders pointed to genes controlling cell metabolism.
 i. In phenylketonuria (PKU), mental retardation is due to inability to convert
________________ to tyrosine.
 ii. In albinism, tyrosine cannot be converted to melanin skin pigment.
o b. Evolution of gene -- product concepts:
 i. Early experiments with bread mold ________________ led to "one gene -________________" hypothesis.
 ii. This was broadened to one gene -- one protein since not all proteins are
enzymes; for example, ________________
 iii. When it was discovered some proteins have more than one polypeptide,
hypothesis became one gene -- one ________________
Overview of Protein Synthesis
o a. DNA both codes for its replication and is template for RNA formation.
o b________________ makes an RNA molecule complementary to a portion of DNA.
o c. ________________using labeled RNA show it moving through pores of nucleus to cytoplasm.
o d. Messenger RNA (mRNA) carries information for synthesis of ________________
o e. ________________uses this information to sequence amino acids of polypeptide.
DNA Base Sequence is Coded
o a. Order of bases in DNA codes for order of amino acids in polypeptides.
o b. A ________________of four bases would supply 64 different triplets, far more than
needed to code for the 20 essential and different amino acids; a doublet code would only
provide 16 combinations.
o c. A __________ is a "three letter" unit of three nucleotides in messenger RNA (mRNA).
o d. All 64 mRNA codons have been ________________
o e. ______________codons correspond to a particular amino acid; three are stop codons.
o f. One codon for methionine is also a start codon_______________ polypeptide formation.
Genetic code is essentially universal.
o a. Codons stand for same amino acids in most __________________________________.
o b. Uniformity suggests all living things have common ________________.
Transcription
o a. During transcription, portion of DNA helix ________________.
o b. Complementary ________________pair with DNA nucleotides of one strand.
o c. RNA nucleotides are joined together by ________________
o d. On RNA, uracil substitutes for thymine; where A, T, G, or C is present in DNA
template, U, A, C, or G is incorporated into mRNA.
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Processing Strips Introns from mRNA
o a. Exons are portions of DNA that are ultimately _____________ by producing proteins.
o b. Introns are segments of DNA between genes and are ________________ (intragene segments).
o c. Transcription produces mRNA complementary to both exons and introns.
o d. Nucleotides complementary to introns are processed or e________________ removed
before mRNA exits from nucleus.
o e. ___________ are enzymes that remove introns; therefore, not all enzymes are proteins.
o f. In eukaryotes, after processing occurs in nucleus, it passes into cytoplasm to ribosomes.
10. Translation
o a. During translation, sequence of codons in mRNA determines order of amino acids in polypeptide.
o b. Term translation is because sequence of DNA bases is finally________________ into
sequence of amino acids.
o c. Requires several enzymes, transfer RNA, and ribosomal RNA.
11. Transfer RNA (tRNA)
o a. Transfer RNA molecules bring ________________to ribosomes in cytoplasm.
o b. Single-stranded nuclei acid doubles back on itself with ________________across
complementary bases.
o c. An amino acid binds at one end of tRNA molecule; requires ___________.
o d. Research underway on how correct amino acid joins correct tRNA; tRNA synthetase
recognizes correct amino acid.
o e. Opposite end has specific ___________. which binds complementarily to mRNA codon.
o f. Example: Codon ACC has anticodon UGG to produce amino acid threonine.
12. Ribosomal RNA
o a. Called ___________ ; found in ribosome.
o b. Produced in nucleolus inside nucleus.
o c. Joins with ________migrated in from cytoplasm.
o d. Ribosomal subunits then migrate to ___________.
o e. Subunits join as protein synthesis begins; small subunit has one rRNA and proteins;
large subunit has two __________ plus proteins and subunits are joined by peptide bond.
13. Translation in Three Steps
o a. Initiation: mRNA binds to smaller, then larger of the two ribosomal subunits.
o b. Elongation:
 i. Polypeptide chain lengthens one __________ at a time.
 ii. Ribosome has sites to accommodate two tRNA molecules, an incoming
tRNA-amino acid complex and outgoing tRNA.
 iii. Ribosome moves __________. so that next mRNA codon is available to
receive incoming tRNA_amino acid complex.
o c. Termination:
 i. Occurs at ___________ on mRNA.
 ii. The two ribosome subunits dissociate from mRNA.
o d. ___________ ___________. are several ribosomes that move along one mRNA at a time.