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DNA AND GENETICS—STUDY GUIDE
Our chromosomes are made of DNA and proteins. The DNA contains the genetic
information, which codes for all the different proteins that a cell makes. The proteins
made by cells determine various attributes of an organism. For example, your eye color
results from specific proteins built in the cell. Someone with sickle cell disease has
slightly different DNA instructions compared to someone who does not have the
disease. Our goal is to understand this better by learning about DNA structure and by
learning about how DNA is passed from parents to their offspring.
I. The two scientists who discovered the structure of DNA in 1953 are
_________________ and __________________. (Mader pp. 186-188)
A. DNA structure
1. double helix
2. the purines (______ and ______) pair with the pyrimidines (_____ and
_____).
B. They used model-building (similar to the molecule kits we used in lab).
C. They used critical data from Rosalind Franklin.
II. DNA structure (Mader pp. 48–49; p. 189)
A. The monomers of DNA are called ______________. Each monomer is made
of three parts:
1. deoxyribose (a sugar)
2. phosphate group
3. nitrogenous base
B. The two sugar-phosphate backbones are connected by hydrogen bonds
between nitrogenous bases.
C. complementary base pairs
1. Adenine (A) pairs with ___________.
2. Guanine (G) pairs with ___________.
III. DNA replication (Mader p. 190)
A. When does it occur?
B. Why does it occur?
C. semiconservative model of DNA replication
1. The two strands of one DNA molecule separate.
2. A complementary strand is formed along each strand of the original
molecule.
3. The result is two identical DNA molecules, each with one strand from
the original molecule
D. very fast, very accurate (ca. 1 mutation per 100 million nucleotides copied)
E. involves many enzymes and other proteins
F. Is DNA replication an example of hydrolysis or dehydration synthesis?
IV. Some enzymes proofread DNA and repair errors that occur during replication
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The sequence of DNA nucleotides in a gene provides the instructions for making a
specific protein. These proteins allow our cells and our entire bodies to function. Life
evolves as changes in DNA (mutations) are passed to future generations. Humans
have found many practical uses for our knowledge about DNA, and biotechnology is
now important in agriculture, medicine, criminal investigations, and basic research.
I. A gene contains the instructions for producing either a protein, part of a protein, or a
molecule of RNA. (Mader p. 192)
II. Overview of Protein Synthesis (in eukaryotic cells) (Mader pp. 192–199)
A. The first step in protein synthesis is transcription.
1. During transcription, a gene's DNA instructions are copied onto a new
molecule of pre-mRNA.
2. Transcription occurs in a cell's _______________.
B. After transcription, RNA processing occurs.
1. pre-mRNA is modified to produce mature mRNA
2. RNA processing occurs in a cell's ________________.
3. Introns are removed from pre-mRNA and exons are spliced together.
a. What are introns?
b. What are exons?
C. After RNA processing, translation occurs.
1. During translation, the nucleotide sequence on the mRNA is used as
instructions for building a chain of amino acids. A chain of amino
acids is a ______________.
2. Translation occurs in a cell's ________________.
3. Know the roles of tRNA, mRNA, amino acids, and the ribosome during
translation.
4. Three consecutive nucleotides on mRNA make up a ______________.
5. Three consecutive nucleotides on tRNA make up an ______________.
6. What does complementary base pairing have to do with the mRNA and
tRNA during translation?
III. The structure of RNA is similar to that of DNA, but there are some key differences.
Be sure to know at least three differences between DNA and RNA. (Mader p.
48)
A. The monomers of RNA are nucleotides. Each RNA nucleotide consists of
three smaller molecules:
1. ribose
2. phosphate group
3. nitrogenous base
B. RNA has uracil (U) instead of thymine (T).
C. For RNA, complementary pairs are A-U and G-C
D. RNA can pair with a single strand of a DNA molecule.
E. RNA can pair with another RNA molecule.
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IV. The Genetic Code (Mader pp. 192-193)
A. DNA has only 4 different nucleotides.
B. Proteins are built from 20 different amino acids.
C. Each amino acid is specified by one or more nucleotide triplets (see table).
D. There are 64 different triplets (43 = 64).
E. 61 of the 64 different nucleotide triplets code for specific amino acids
F. The other 3 triplets are stop codes.
G. The genetic code is nearly universal among all species that have been
studied.
V. Mutations are accidental changes to the genome. (Mader pp. 200-201)
A. Are all mutations passed from parent to offspring?
B. How are mutations passed from parent to offspring?
C. How could a mutation in a gene (DNA) affect the process of translation and
ultimately the phenotype of an organism? See sickle cell disease as an
example.
D. Mutation is the source of all new alleles.
E. When do mutations occur? What can cause mutations?
VI. Biotechnology (Mader pp. 224-227, 230-231, 234-236)
A. What does PCR stand for? What is the main purpose of PCR?
B. Recombinant DNA Technology
1. Transgenic organisms contain their own DNA and DNA from another
species. Examples:
a. Transgenic bacteria make insulin; other bacteria clean up oil
spills.
b. Transgenic crops have been given pesticide and herbicide
resistance.
c. Transgenic animals produce medicine (e.g., in their milk).
C. What is cloning? How was Dolly created? What are some uses of cloning?
(Mader pp. 210-211)
D. Genomics and proteomics are the study of genomes and proteomes. What is
a genome? What is a proteome? How can we benefit from studying
them? Biologists have sequenced the entire genomes of some species.
E. Bioinformatics uses computer technology to study the huge volume of genetic
data that biologists have accumulated.
F. Gene therapy seeks to cure genetic disorders by introducing correctly
functioning genes into the cells of people with these disorders. What are
some diseases that could be treated with gene therapy?
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