AP Bio Ch 14 DNA Structure & Function

1. The amount of adenine is always equal to the amount of _______ in DNA.

Cytosine

Uracil

Guanine

Thymine

ATP

In DNA, adenine always pairs with thymine through hydrogen bonds. This means that the amount of adenine will always be equal to the amount of thymine in DNA. The other options, cytosine, uracil, guanine, and ATP, do not pair with adenine in DNA and are not equal in amount to adenine. Therefore, the correct answer is thymine.

Explanation

In DNA, adenine always pairs with thymine through hydrogen bonds. This means that the amount of adenine will always be equal to the amount of thymine in DNA. The other options, cytosine, uracil, guanine, and ATP, do not pair with adenine in DNA and are not equal in amount to adenine. Therefore, the correct answer is thymine.

2. Because one original strand of the double-stranded helix is found in each daughter cell, the replication process is called

Proofreading.

Semiconservative.

Redundant.

Freeing of DNA.

Mutation positive.

During DNA replication, each original strand of the double helix serves as a template for the synthesis of a new complementary strand. As a result, each daughter cell receives one original strand and one newly synthesized strand, conserving half of the original genetic information. This process is known as semiconservative replication. Proofreading refers to the mechanism that corrects errors during DNA replication. Redundant, freeing of DNA, and mutation positive are not accurate terms to describe the replication process.

Explanation

During DNA replication, each original strand of the double helix serves as a template for the synthesis of a new complementary strand. As a result, each daughter cell receives one original strand and one newly synthesized strand, conserving half of the original genetic information. This process is known as semiconservative replication. Proofreading refers to the mechanism that corrects errors during DNA replication. Redundant, freeing of DNA, and mutation positive are not accurate terms to describe the replication process.

3. Complementary base pairing always pairs a purine with a pyrimidine.

True

False

Complementary base pairing refers to the specific pairing of nitrogenous bases in DNA and RNA. Adenine (purine) always pairs with thymine (pyrimidine) in DNA, and cytosine (pyrimidine) always pairs with guanine (purine). This pairing is essential for maintaining the structure and function of DNA. Therefore, the statement that complementary base pairing always pairs a purine with a pyrimidine is true.

Explanation

Complementary base pairing refers to the specific pairing of nitrogenous bases in DNA and RNA. Adenine (purine) always pairs with thymine (pyrimidine) in DNA, and cytosine (pyrimidine) always pairs with guanine (purine). This pairing is essential for maintaining the structure and function of DNA. Therefore, the statement that complementary base pairing always pairs a purine with a pyrimidine is true.

4. Growth at two replication forks arising from a single origin of replication produce a "bubble" as daughter DNA molecules form.

True

False

The statement is true because during DNA replication, two replication forks are formed at a single origin of replication. These replication forks move in opposite directions, unwinding the DNA double helix and synthesizing new strands of DNA. As the replication forks progress, they create a "bubble" structure where the parental DNA strands separate and new daughter DNA molecules are synthesized. This bubble expands as replication continues, eventually leading to the formation of two complete daughter DNA molecules.

Explanation

The statement is true because during DNA replication, two replication forks are formed at a single origin of replication. These replication forks move in opposite directions, unwinding the DNA double helix and synthesizing new strands of DNA. As the replication forks progress, they create a "bubble" structure where the parental DNA strands separate and new daughter DNA molecules are synthesized. This bubble expands as replication continues, eventually leading to the formation of two complete daughter DNA molecules.

5. The X-ray diffraction photography of Rosalind Franklin and Maurice Wilkins was critical evidence of DNA.

Indicating that DNA has a double helix structure.

Showing equal numbers of purines and pyrimidines.

Showing the bases of DNA were held together by hydrogen bonds.

Revealing the structure of the deoxyribose sugar.

Of the location of each adenine, guanine, cytosine and thymine.

The X-ray diffraction photography of Rosalind Franklin and Maurice Wilkins provided evidence that DNA has a double helix structure. This means that DNA is shaped like a twisted ladder, with two strands that are connected by a series of base pairs. The X-ray diffraction pattern revealed the characteristic X-shape, which is indicative of a helical structure. This discovery was crucial in understanding the fundamental structure of DNA and its role in genetics and heredity.

Explanation

The X-ray diffraction photography of Rosalind Franklin and Maurice Wilkins provided evidence that DNA has a double helix structure. This means that DNA is shaped like a twisted ladder, with two strands that are connected by a series of base pairs. The X-ray diffraction pattern revealed the characteristic X-shape, which is indicative of a helical structure. This discovery was crucial in understanding the fundamental structure of DNA and its role in genetics and heredity.

6. The complementary bases of DNA are located on the outside of the helix, with the sugar-phosphate backbone on the inside.

True

False

The statement is false because the complementary bases of DNA are located on the inside of the helix, while the sugar-phosphate backbone is on the outside. The bases, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C), forming the rungs of the DNA ladder. The backbone, made up of sugar and phosphate molecules, forms the sides of the ladder.

Explanation

The statement is false because the complementary bases of DNA are located on the inside of the helix, while the sugar-phosphate backbone is on the outside. The bases, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C), forming the rungs of the DNA ladder. The backbone, made up of sugar and phosphate molecules, forms the sides of the ladder.

7. Which is NOT a major function of the genetic material?

Store information

Catalyze chemical reactions

Replicate itself

Undergo mutation

The genetic material is responsible for storing and transmitting information necessary for the functioning and development of an organism. It also undergoes replication to ensure the accurate transfer of genetic information to the next generation. Additionally, genetic material can undergo mutations, which contribute to genetic diversity. However, catalyzing chemical reactions is not a major function of genetic material. This function is primarily carried out by enzymes and other proteins.

Explanation

The genetic material is responsible for storing and transmitting information necessary for the functioning and development of an organism. It also undergoes replication to ensure the accurate transfer of genetic information to the next generation. Additionally, genetic material can undergo mutations, which contribute to genetic diversity. However, catalyzing chemical reactions is not a major function of genetic material. This function is primarily carried out by enzymes and other proteins.

8. Chargaff's rules showed that different species contain differing base compositions.

True

False

Chargaff's rules, discovered by Erwin Chargaff, state that in DNA, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal to the amount of cytosine (C). This means that the base composition of DNA varies between different species. Therefore, the statement that "Chargaff's rules showed that different species contain differing base compositions" is true.

Explanation

Chargaff's rules, discovered by Erwin Chargaff, state that in DNA, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal to the amount of cytosine (C). This means that the base composition of DNA varies between different species. Therefore, the statement that "Chargaff's rules showed that different species contain differing base compositions" is true.

9. Nucleic acid was first discovered in pus cells in

1824.

1869.

1912.

1931.

1953.

In 1869, Friedrich Miescher, a Swiss biochemist, discovered nucleic acids while studying the chemical composition of white blood cells. He isolated a substance from the nuclei of pus cells and named it "nuclein," which we now know as nucleic acid. This discovery laid the foundation for further research on nucleic acids and their role in genetics and heredity.

Explanation

In 1869, Friedrich Miescher, a Swiss biochemist, discovered nucleic acids while studying the chemical composition of white blood cells. He isolated a substance from the nuclei of pus cells and named it "nuclein," which we now know as nucleic acid. This discovery laid the foundation for further research on nucleic acids and their role in genetics and heredity.