4. Biomolecules

Nucleic Acids

Why is genetic drift aptly named? Select True or False for each statement.

T/F It causes allele frequencies to drift up or down randomly.
T/F It occurs when alleles from one population drift into another.
T/F It occurs when mutations drift into a genome.

In a population of 2500, how many babies would you expect to have cystic fibrosis, a homozygous recessive condition, if the frequency of the dominant allele is 0.9 and the population is at Hardy–Weinberg equilibrium?

a. 0.9×2500=2250
b. 2×0.9×0.1×2500=450
c. 0.9×0.1×2500=225
d. 0.1x0.1x2500=25

Determine what is incorrect in the following statement: Red deer mutated their genes so that they could have larger antlers to compete for mates.

Animation:  DNA Double Helix

Nucleic Acids Example 2

 RNA molecules generally consist of a single polynucleotide chain, whereas DNA molecules generally consist of two polynucleotide chains organized into a double helix. 

 No. This answer is true, but there is a better response. 

 Both molecules contain adenine, guanine, and cytosine, but DNA also contains thymine and RNA also contains uracil. 

 No. This statement is true, but there is a better response. 

 No. It is true that deoxyribose is the sugar in DNA and ribose is the sugar in RNA, but there is a better response. 

 The first and second listed responses correctly describe differences between DNA and RNA. 

 No. It is true that both the first two choices describe differences, but there is a better answer. 

 The first three listed responses correctly describe differences between DNA and RNA. 

Consider the components forming the nucleotides found in DNA and RNA.

Which of the following describes a difference between DNA and RNA?

Formation & Breakdown of Nucleic Acids

Sexual selection favors individuals with traits that increase their ability to obtain mates, such as mating calls in crickets. Using this example, propose a scenario where sexual selection could contribute to divergence in sympatric speciation.

Animation: Nucleic Acid Structure

DNA vs. RNA

 No. These examples are not pyrimidines; they are purines. 

 No. This answer is partially correct. Adenine is a purine. 

 No. Uracil is a pyrimidine found in RNA but not in DNA. Guanine is a purine. 

 No. This answer is partially correct. Guanine is a purine. 

Keep your nucleic acids straight. Do pyrimidines have a single- or double-ring structure?

Which of the following are pyrimidines found in the nucleic acid DNA?

When the ranges of two different species meet, a stable “hybrid zone” occupied by hybrid individuals may form. How is this possible?
a. Two diverged populations are capable of mating and producing viable and fertile offspring.
b. Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species.
c. Hybrid individuals may have reduced fitness and thus be strongly selected against.
d. One species has a selective advantage, so as hybridization continues, the other species will go extinct.

Major Elements in Biological Molecules: Nucleic acids

In the 1700s and 1800s, royalty in Europe often married their close relatives; furthermore, recessive genetic diseases such as hemophilia showed up much more often among royals than in the general population. Explain the likely connection.

 Although a DNA molecule demonstrates complementary base pairing between two DNA polynucleotides to form a double helix, an RNA molecule can base-pair only along stretches of nucleotides in the same RNA molecule, such as in transfer RNA molecules. 

 No. Base pairing can occur between two RNA molecules; for example, the base pairing between messenger RNA and transfer RNA in the process of protein synthesis on ribosomes. Base pairing can also occur between DNA and RNA&mdash;for example, the base pairing between a DNA strand and the messenger RNA that is synthesized during gene expression. 

 Complementary base pairing promotes an antiparallel orientation in the structure of DNA and RNA molecules. 

No. The term antiparallel refers to the manner in which the sugar-phosphate backbones of two polynucleotides run in opposite directions when in double-stranded form and is not directly related to the complementary base pairing that exists between the two strands.

 Complementary base pairing within single strands of DNA and RNA gives them particular three-dimensional structures that are necessary for their function. 

 No. DNA usually exists in a double-stranded form, whereas RNA is usually single-stranded, retaining the ability to base-pair with itself and with other RNA molecules along short stretches of nucleotides. 

 None of the listed responses is correct. 

 Although the base pairing between two strands of DNA in a DNA molecule can be thousands to millions of base pairs long, base pairing in an RNA molecule is limited to short stretches of nucleotides in the same molecule or between two RNA molecules. 

Think about the structures that DNA and RNA can demonstrate as they exist and function in cells.

Which of the following is true regarding complementary base pairing in DNA and RNA molecules?

 No. Adenine does not form a complementary base pair with guanine. 

 No. Thymine does not form a complementary base pair with guanine. 

 No. Adenine does not form a complementary base pair with cytosine. 

 No. Thymine does not form a complementary base pair with cytosine. 

A specific purine nitrogenous base will normally pair only with a specific pyrimidine nitrogenous base.

Based on complementary base pairing, you would expect the percentage of __________ to be equal to the percentage of __________.

Suppose you were studying several species of monkeys. In one, males never helped females raise offspring. In another, males provided just as much parental care as females except for actually carrying the fetus during pregnancy. How does the fundamental asymmetry of sex compare in the two species? How would you expect sexual dimorphism to compare between the two species?

The nucleic acid strands in a DNA molecule are oriented antiparallel to each other.

Nucleic acids are formed through phosphodiester bonds that link complementary nucleobases together.

Hydrogen bonds formed between the sugar-phosphate backbones of the two DNA chains stabilize the structure.

The pentose sugar in DNA is ribose (containing two hydroxyl groups).

Which of the following statements about DNA structure is true?a) The nucleic acid strands in a DNA molecule are oriented antiparallel to each other.b) Nucleic acids are formed through phosphodiester bonds that link complementary nucleobases together.c) Hydrogen bonds formed between the sugar-phosphate backbones of the two DNA chains stabilize the structure.d) The pentose sugar in DNA is ribose (containing two hydroxyl groups).

What are Nucleic Acids? Nucleic Acid Structure & Function

RNA and DNA are similar because                   .
a. both are double-stranded helices;
b. uracil is found in both of them;
c. both contain the sugar deoxyribose;
d. both are made up of nucleotides consisting of a sugar, a phosphate, and a base

 A nitrogenous base, an amino acid, and a pentose sugar 

 No. Nucleotides do not contain amino acids. 

 A nitrogenous base, an amino acid, and a phosphate group 

 A nitrogenous base, a fatty acid, and an amino acid 

 No. Nucleotides do not contain amino acids or fatty acids. 

 A series of nitrogenous bases, a nucleic acid backbone, and a hexose sugar 

 No. Nucleotides are the monomers of nucleic acids. Hexose sugars are not present in nucleotides; hence, they are not present in nucleic acids. 

 A nitrogenous base, a phosphate group, and a pentose sugar 

There are clues in the names DNA and RNA and in the type of covalent bond that links nucleotides together to form nucleic acids.

Which of the following lists represents the chemical components of a nucleotide?

Macromolecule Review

A nitrogenous base, phosphate group & a sugar.

A nitrogenous base, a carbohydrate, & a sugar.

Which of the following descriptions best fits the class of molecules known as nucleotides?a) A nitrogenous base &amp; a phosphate group.b) A nitrogenous base &amp; a sugar.c) A nitrogenous base, phosphate group &amp; a sugar.d) A nitrogenous base, a carbohydrate, &amp; a sugar.

Animation: DNA and RNA Structure

5 Nitrogenous Bases

Nucleic Acids Example 1

 No. None of the amino acids used by living organisms contains phosphorus. 

 No. Cellulose is a carbohydrate. It consists of carbon, oxygen, and hydrogen. 

 No. Fatty acids have long carbon skeletons with a carbonyl group at one end. They do not contain phosphorus. 

 No. Sucrose is a disaccharide sugar; it does not contain phosphorus. 

Consider which of the following substances contain phosphorus.

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture __________.

Introduction to nucleic acids and nucleotides | High school biology | Khan Academy

Nucleotides

 No. A steroid is a type of lipid, but it is not a monomer. 

 No. A protein is a polypeptide assembled from amino acid monomers. 

 No. Nucleic acids and polypeptides are two different types of macromolecules. 

 No. Amino acids are the monomers of polypeptides, and nucleotides are the monomers of nucleic acids. 

Think about which monomers form which polymers. and

A glucose molecule is to starch as __________.

Draw a small concept map showing how selection, genetic drift, gene flow, and mutation relate to genetic variation.

The four nitrogenous bases commonly found if DNA are: &nbsp;a) Adenine, thymine, cytosine, uracil&nbsp;b) Uracil, adenine, cytosine, guanine.c) Uracil, cytosine, guanine, thymine.d) Adenine, thymine, cytosine, guanine.e) None are correct.

Properties of Biological Macromolecules | AP Biology 1.4

Why isn’t inbreeding considered an evolutionary process?
a. It does not change genotype frequencies.
b. It does not change allele frequencies.
c. It does not occur often enough to be important in evolution.
d. It does not violate the assumptions of the Hardy–Weinberg principle.

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?
a. 5′-AGCT-3′ with 5′-TCGA-3′
b. 5′-GCGC-3′ with 5′-TATA-3′
c. 5′-ATGC-3′ with 5′-GCAT-3′
d. All of these pairs are correct.

Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?
a. The two strands of the double helix would separate.
b. The phosphodiester linkages of the polynucleotide backbone would be broken.
c. The pyrimidines would be separated from the deoxyribose sugars.
d. All bases would be separated from the deoxyribose sugars.

In what sense is the Hardy–Weinberg principle a null hypothesis?

HHMI BioInteractive: Chemical Structure of DNA

HHMI BioInteractive: Paired DNA Strands

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