Biology test

What is the primary function of DNA?

The primary function of DNA is to store and transmit genetic information that guides the development, functioning, and reproduction of all living organisms.

Describe the shape and structure of DNA.

DNA has a double helix structure, consisting of two long strands of nucleotides twisted around each other, with bases pairing in the center.

Why is complementary base pairing essential in DNA?

Complementary base pairing is essential in DNA because it ensures accurate replication and transcription of genetic information, allowing for the proper synthesis of proteins and maintenance of genetic integrity.

Why is the antiparallel nature of DNA important?

The antiparallel nature of DNA is important because it allows for complementary base pairing and proper replication. This orientation ensures that the DNA strands run in opposite directions, facilitating the action of enzymes during DNA replication.

Compare the structural differences between DNA and RNA.

DNA is double-stranded with deoxyribose sugar, while RNA is single-stranded with ribose sugar. Additionally, RNA contains uracil instead of thymine.

What are the functional differences between DNA and RNA?

The functional differences between DNA and RNA include that DNA stores and transmits genetic information, while RNA plays a crucial role in protein synthesis and gene expression. DNA is stable and serves as a long-term repository of genetic data, whereas RNA is more versatile and involved in various cellular processes.

What are the main steps of DNA replication, and which enzymes are involved?

The main steps of DNA replication include initiation, elongation, and termination. Key enzymes involved are helicase, which unwinds the DNA strands; DNA polymerase, which synthesizes new strands; and ligase, which seals any gaps.

Why is DNA replication semiconservative?

DNA replication is semiconservative because each new DNA molecule consists of one original strand and one newly synthesized strand, ensuring that genetic information is accurately passed on to daughter cells.

What roles do DNA, mRNA, tRNA, and rRNA play in protein synthesis?

DNA serves as the template for transcription, mRNA carries the genetic code to ribosomes, tRNA brings amino acids to the ribosome during translation, and rRNA is a structural component of ribosomes.

Define transcription.

Transcription is the process by which the genetic information encoded in DNA is copied into messenger RNA (mRNA). This occurs in the nucleus and involves the enzyme RNA polymerase.

Define translation.

Translation is the process by which ribosomes synthesize proteins using the genetic information carried by mRNA, converting the sequence of nucleotides into a sequence of amino acids.

Explain RNA splicing and its significance.

RNA splicing is the process of removing introns from pre-mRNA and joining exons together to form a mature mRNA molecule. This process is significant because it allows for the production of multiple protein variants from a single gene, enhancing genetic diversity.

What is the genetic code, and why is it degenerate?

The genetic code is a set of rules that defines how the nucleotide sequences in DNA and RNA are translated into proteins. It is considered degenerate because multiple codons can specify the same amino acid, allowing for redundancy in the genetic code.

Describe the process of translation.

Translation is the process where ribosomes read mRNA sequences and assemble amino acids into proteins, crucial for gene expression.

What determines the primary, secondary, tertiary, and quaternary structures of proteins?

The primary structure of proteins is determined by the sequence of amino acids in the polypeptide chain, while secondary structure is influenced by hydrogen bonding between backbone atoms. Tertiary structure arises from interactions between side chains, and quaternary structure is formed by the assembly of multiple polypeptide chains into a functional protein.

How do enzymes lower activation energy?

Enzymes lower activation energy by providing an alternative reaction pathway, stabilizing the transition state, and facilitating the formation of products more efficiently than in the absence of the enzyme.

Explain the induced fit model of enzyme activity.

The induced fit model of enzyme activity describes how an enzyme changes shape upon substrate binding, enhancing its ability to catalyze the reaction. This dynamic interaction increases the specificity and efficiency of the enzyme's catalytic function.

What are the factors affecting enzyme activity?

Factors affecting enzyme activity include temperature, pH, substrate concentration, and the presence of inhibitors or activators.

What is DNA methylation, and which base is involved?

DNA methylation is a biochemical process that involves the addition of a methyl group to DNA, specifically affecting the cytosine base within cytosine-guanine (CpG) dinucleotides, which can regulate gene expression.

How do proto-oncogenes and tumor suppressor genes relate to cancer?

Proto-oncogenes promote cell growth and division, while tumor suppressor genes inhibit these processes. Mutations in these genes can lead to uncontrolled cell proliferation, contributing to cancer development.

What is the polymerase chain reaction (PCR), and what are its steps?

The polymerase chain reaction (PCR) is a technique used to amplify specific DNA sequences through cycles of denaturation, annealing, and extension.

What is gel electrophoresis, and what is its application?

Gel electrophoresis is a laboratory technique used to separate DNA, RNA, or proteins based on their size and charge, allowing for analysis and purification of these molecules.