Unit 3 Target 1: DNA Structure And Function

In eukaryotes, DNA is located in the nucleus. This is because the nucleus is the organelle that contains the genetic material of the cell, including the DNA. The nucleus provides a protected environment for the DNA, allowing it to be transcribed and translated into proteins. It also helps regulate the expression of genes and controls the replication and distribution of DNA during cell division. Therefore, the correct answer is that DNA is located in the nucleus.

DNA contains the sugar deoxyribose. Deoxyribose is a five-carbon sugar that is a component of DNA nucleotides. It is the sugar molecule that forms the backbone of the DNA double helix structure. The presence of deoxyribose in DNA is essential for the stability and function of the DNA molecule. The other options, ribose, glucose, and lactose, are not found in DNA. Ribose is the sugar found in RNA, glucose is a monosaccharide used for energy production, and lactose is a disaccharide found in milk.

In a DNA molecule, cytosine is always paired with guanine. This pairing is based on the complementary base pairing rule, where cytosine forms three hydrogen bonds with guanine. This pairing ensures the stability and integrity of the DNA molecule. Thymine is paired with adenine in DNA, while uracil is found in RNA instead of thymine.

Scientists concluded that A and T occur in equal percentages, and G and C occur in equal percentages based on the study's findings.

Cytosine and Thymine are both pyrimidines. Pyrimidines are one of the two types of nitrogenous bases found in DNA and RNA, the other being purines. They are characterized by a single-ring structure. Adenine and Guanine, on the other hand, are purines, which have a double-ring structure. Therefore, the correct answer is Cytosine and Thymine.

Adenine and Guanine are both purines. Purines are nitrogenous bases that consist of a double-ring structure. Adenine and Guanine are two of the four nitrogenous bases found in DNA and RNA, with the other two being cytosine and thymine (uracil in RNA). The presence of the double-ring structure in Adenine and Guanine makes them purines, while Cytosine and Thymine are pyrimidines, which have a single-ring structure.

The correct answer is deoxyribose + phosphate group + cytosine. This is because DNA is made up of nucleotides, which consist of a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base. Cytosine is one of the four nitrogenous bases found in DNA, along with adenine, guanine, and thymine. Uracil is found in RNA, not DNA, and ribose is the sugar molecule found in RNA, not DNA.

Genes are sections of DNA that contain instructions for assembling proteins. Proteins are essential molecules that perform various functions in the body, including building and repairing tissues, regulating chemical reactions, and carrying signals between cells. Genes provide the necessary information to produce specific proteins through a process called protein synthesis. Therefore, the correct answer is proteins.

Nitrogenous bases combine with sugar and a phosphate group to form a nucleotide. Nucleotides are the building blocks of nucleic acids, such as DNA and RNA. They consist of a nitrogenous base (adenine, thymine, cytosine, guanine, or uracil), a sugar (ribose in RNA or deoxyribose in DNA), and a phosphate group. The nitrogenous base provides the genetic information and determines the sequence of nucleotides in the nucleic acid molecule.

The 5' to 3' strand is called the lagging strand because during DNA replication, it is synthesized in short fragments called Okazaki fragments. These fragments are then joined together by an enzyme called DNA ligase. In contrast, the 3' to 5' strand, which is synthesized continuously, is called the leading strand. The terms "starting strand" and "replication strand" are not commonly used or recognized in the context of DNA replication.

The 3' to 5' strand is called the leading strand because it is oriented in the same direction as the replication fork and can be continuously synthesized by DNA polymerase. In contrast, the lagging strand is oriented in the opposite direction and requires the synthesis of short Okazaki fragments that are later joined together. The terms "ending strand" and "replication strand" are not commonly used in the context of DNA replication.

The correct answer is that the percentage of pyrimidines in DNA is about equal to the percentage of purines. This is because of base pairing in DNA. Adenine pairs with thymine (a pyrimidine), and guanine pairs with cytosine (a purine). The base pairing rule states that the amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine. Therefore, the percentage of pyrimidines (thymine and cytosine) is about equal to the percentage of purines (adenine and guanine) in DNA.