Biology: Concepts and Investigations

Marielle Hoefnagels

Chapter 7

DNA Structure and Gene Function - all with Video Answers

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Chapter Questions

Problem 1

Explain how Griffith's experiment and Avery, MacLeod, and McCarty's experiment determined that DNA in bacteria transmits a trait that kills mice.

Scott Rhodes

Scott Rhodes

Numerade Educator

Problem 2

Describe the three-dimensional structure of DNA.

Aditya Sood

Numerade Educator

Problem 3

Explain Chargaff's observation that a DNA molecule contains equal amounts of A and T and equal amounts of G and C.

Megan Schrage

Numerade Educator

Problem 4

Write the complementary DNA sequence of each of the following base sequences:
a. $A G G C A T A C C T G A G T C$
b. GT T TAA TG C C C TA CA
c. $A A C A C T A C C G A T T C A$

Bryan Valdivia

Numerade Educator

Problem 5

Put the following in order from smallest to largest: nucleotide, genome, nitrogenous base, gene, nucleus, cell, codon, chromosome.

Bryan Valdivia

Numerade Educator

Problem 6

What is the function of DNA?

Aditya Sood

Numerade Educator

Problem 7

Use figure 7.9 to describe the structural and functional differences between RNA and DNA.

Bryan Valdivia

Numerade Educator

Problem 8

Explain how information in DNA is transcribed and translated into amino acids.

Bryan Valdivia

Numerade Educator

Problem 9

Some people compare DNA to a blueprint stored in the office of a construction company. Explain how this analogy would extend to transcription and translation.

Eric Tran

Numerade Educator

Problem 10

List the three major types of RNA and their functions.

Aditya Sood

Numerade Educator

Problem 11

List the sequences of the mRNA molecules transcribed from the following template DNA sequences:
a. $\mathrm{T}$ G $\mathrm{A}$ A $\mathrm{C}$ T $\mathrm{A}$ C $\mathrm{G}$ G $\mathrm{T}$ A $\mathrm{C}$ C $\mathrm{A}$ T $\mathrm{A}$ C
b. $G C A C$ TA $A A G A T C$

Bryan Valdivia

Numerade Educator

Problem 12

How many codons are in each of the mRNA molecules that you wrote for question $11 ?$

Bryan Valdivia

Numerade Educator

Problem 13

Refer to the figure to answer these questions: a. Add labels for mRNA (including the $5^{\prime}$ and $3^{\prime}$ ends) and tRNA. In addition, draw in the RNA polymerase enzyme and the ribosomes, including arrows indicating the direction of movement for each.
b. What are the next three amino acids to be added to polypeptide $b$ ?
c. Fill in the nucleotides in the mRNA complementary to the template DNA strand.
d. What is the sequence of the DNA complementary to the template strand (as much as can be determined from the figure)?
e. Does this figure show the entire polypeptide that this gene encodes? How can you tell?
f. What might happen to polypeptide $b$ after its release from the ribosome?
g. Does this figure depict a prokaryotic or a eukaryotic cell? How can you tell?

Scott Rhodes

Numerade Educator

Problem 14

Is changing the first nucleotide in a codon more likely or less likely to change the encoded amino acid than changing the third nucleotide in a codon?

Bryan Valdivia

Numerade Educator

Problem 15

Titin is a muscle protein whose gene has the largest known coding sequence: 80,781 DNA bases. How many amino acids long is titin?

Aditya Sood

Numerade Educator

Problem 16

If a protein is 1259 amino acids long, what is the minimum size of the gene that encodes the protein? Why might the gene be longer than the $\operatorname{minimum} ?$

Bryan Valdivia

Numerade Educator

Problem 17

How did researchers reason that a combination of at least three RNA bases must specify each amino acid?

Molly Crosswell

Molly Crosswell

Numerade Educator

Problem 18

The roundworm $C .$ elegans has 556 cells when it hatches. Each cell contains the entire genome but expresses only a subset of the genes. Therefore, the cells "specialize" in particular functions. List all of the ways that a roundworm cell might silence the unneeded genes.

Mark Tingey

Numerade Educator

Problem 19

The genome of the human immunodeficiency virus (HIV) includes nine genes. Two of the genes encode four different proteins each. How is this possible?

DJ

David Johnson

Numerade Educator

Problem 20

The shape of a finch's beak reflects the expression of a gene that encodes a protein called calmodulin. A cactus finch has a long, pointy beak; its cells express the gene more than a ground finch, which has a short, deep beak. When researchers boosted gene expression in a ground finch embryo, the bird's upper beak was longer than normal. Develop a hypothesis that explains this finding.

Mark Tingey

Numerade Educator

Problem 21

If a gene is like a cake recipe, then a mutation is like a cake recipe containing an error. List the major types of mutations, and describe an analogous error in a cake recipe.

Aditya Sood

Numerade Educator

Problem 22

A protein-encoding region of a gene has the following DNA sequence:
T T T CA T CA G G A T GA CA

Determine how each of the following mutations alters the amino acid sequence:
a. substitution of an A for the T in the first position
b. substitution of a G for the $C$ in the 17 th position
c. insertion of a T between the fourth and fifth DNA bases
d. insertion of a GTA between the 12 th and 13th DNA bases
e. deletion of the first DNA nucleotide

Scott Rhodes

Numerade Educator

Problem 23

Explain how a mutation in a protein-encoding gene, an enhancer, or a gene encoding a transcription factor can all have the same effect on an organism.

Mark Tingey

Numerade Educator

Problem 24

How can a mutation alter the sequence of DNA bases in a gene but not produce a noticeable change in the gene's polypeptide product? How can a mutation alter the amino acid sequence of a polypeptide yet not alter the organism?

Aditya Sood

Numerade Educator

Problem 25

Describe the mutation shown in figure 7.26 and explain how the mutation affects the amino acid sequence encoded by the gene.

Mark Tingey

Numerade Educator

Problem 26

Parkinson disease causes rigidity, tremors, and other motor symptoms. Only $2 \%$ of cases are inherited, and these tend to have an early onset of symptoms. Some inherited cases result from mutations in a gene that encodes the protein parkin, which has 12 exons. Indicate whether each of the following mutations in the parkin gene would result in a smaller protein, a larger protein, or no change in the size of the protein:
a. deletion of exon 3
b. deletion of six consecutive nucleotides in exon 1
c. duplication of exon 5
d. disruption of the splice site between exon 8 and intron 8
e. deletion of intron 2

Mark Tingey

Numerade Educator

Problem 27

Consult the genetic code to write codon changes that could account for the following changes in amino acid sequence:
a. tryptophan to arginine
b. glycine to valine
c. tyrosine to histidine

Bryan Valdivia

Numerade Educator

Problem 28

Researchers use computer algorithms that search DNA sequences for indications of specialized functions. Explain the significance of detecting the following sequences:
a. a promoter
b. a sequence of 75 to 80 nucleotides that folds into a shape resembling a backwards letter $L$
c. RNAs with poly A tails

Mark Tingey

Numerade Educator

Problem 29

In a disorder called gyrate atrophy, cells in the retina begin to degenerate in late adolescence, causing night blindness that progresses to total blindness. The cause is a mutation in the gene that encodes an enzyme, ornithine aminotransferase (OAT). Researchers sequenced the $O A T$ gene for five patients with the following results:
Patient A: A change in codon 209 of UAU to UAA
Patient B: A change in codon 299 of UAC to UAG
Patient C: A change in codon 426 of CGA to UGA
Patient D: A two-nucleotide deletion at codons 64 and 65 that results in a UGA codon at position 79
Patient E: Exon 6, including 1071 nucleotides, is entirely deleted.
a. Which patient(s) have a frameshift mutation?
b. How many amino acids is patient E missing?
c. Which patient(s) will produce a shortened protein?

Mark Tingey

Numerade Educator