Molecular Biology: Nitrogen Bases and DNA Structure

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Questions and Answers

What type of bonds hold the structure of DNA together?

Van der Waals forces

Covalent phosphodiester bonds (correct)

Ionic bonds

Hydrogen bonds

Which nitrogen bases are purines?

Adenine and Guanine (correct)

Cytosine and Thymine

Thymine and Guanine

Cytosine and Adenine

According to Chargaff's Rule, how do the amounts of adenine and thymine relate?

A = G

A + T = G + C

A = T (correct)

A = C

What is the role of histones in DNA structure?

To help with supercoiling of DNA Signup and view all the answers

How many hydrogen bonds form between adenine and thymine?

2 hydrogen bonds Signup and view all the answers

What does the tetranucleotide hypothesis propose about DNA?

DNA has a repeating sequence of four nucleotides Signup and view all the answers

What structure is formed when DNA wraps around histones?

Nucleosome Signup and view all the answers

Which of the following statements is correct regarding RNA and DNA?

RNA consists of a single chain while DNA is double-stranded Signup and view all the answers

What role does Reverse Transcriptase play in DNA technology?

It converts mRNA into cDNA. Signup and view all the answers

Which enzyme is crucial for splicing genes into the receiver DNA?

DNA Ligase Signup and view all the answers

Which process is NOT involved in DNA fingerprinting?

Reverse transcription of cDNA Signup and view all the answers

What is the purpose of Gel Electrophoresis in molecular genetics?

To separate DNA fragments by size. Signup and view all the answers

What do the 'sticky ends' created by restriction enzymes allow for in genetic engineering?

They facilitate the joining of different DNA fragments. Signup and view all the answers

What is the effect of mutations in gametic cells on the resulting organism?

All cells in the organism will be mutated. Signup and view all the answers

Which type of mutation causes a premature stop codon in protein synthesis?

Nonsense mutation Signup and view all the answers

What is the primary purpose of Polymerase Chain Reaction (PCR)?

To produce continuous copies of DNA Signup and view all the answers

How does a frameshift mutation affect protein coding?

It alters all subsequent amino acids. Signup and view all the answers

Which function do restriction endonucleases perform in molecular genetics?

They cut DNA at specific sequences. Signup and view all the answers

What is a result of a point mutation?

Only one specific triplet is affected. Signup and view all the answers

What occurs during the anneal step of PCR?

Primers attach to the DNA strand. Signup and view all the answers

Which type of mutation typically results in a nonfunctional protein due to a change in a single nucleotide?

Missense mutation Signup and view all the answers

What is the role of tRNA in the process of translation?

tRNA binds to mRNA codons and brings the corresponding amino acids. Signup and view all the answers

Which of the following correctly describes the process of elongation in translation?

A new tRNA displaces the old tRNA from the elongation site. Signup and view all the answers

What initiates the process of translation?

The binding of mRNA to the smaller ribosomal subunit. Signup and view all the answers

What type of mutation occurs due to internal errors in the DNA replication process?

Spontaneous mutations. Signup and view all the answers

What is the function of the ribosomal RNA (rRNA) in the ribosome?

To provide structural support to the ribosome. Signup and view all the answers

What does a stop codon signal during translation?

The end of the polypeptide chain. Signup and view all the answers

Which of the following is true about codon code?

It is universal among all living organisms. Signup and view all the answers

Which of the following types of mutations are beneficial?

Mutations that provide an advantage in a certain environment. Signup and view all the answers

Which enzyme is responsible for creating RNA primers during DNA replication?

RNA Primase Signup and view all the answers

What is the direction of synthesis for new nucleotides during DNA replication?

5’ to 3’ Signup and view all the answers

What role does DNA Ligase play in DNA replication?

Binds Okazaki Fragments together Signup and view all the answers

What is the first step of Transcription in protein synthesis?

DNA unwinds into Sense and Anti-Sense strands Signup and view all the answers

According to the 1 Gene: 1 Polypeptide Theory, how many proteins can a single gene code for?

Only one protein Signup and view all the answers

In the context of Transcription, what is the significance of the triplet TAC in DNA?

It serves as the start codon AUG in mRNA Signup and view all the answers

Which strand of DNA serves as the template for RNA Polymerase during transcription?

Anti-Sense Strand Signup and view all the answers

What are the segments produced on the Lagging Strand during DNA replication called?

Okazaki Fragments Signup and view all the answers

Study Notes

Nucleic Acids Structure

Pyrimidines: Single-ring nitrogen bases include Cytosine and Thymine.
Purines: Double-ring nitrogen bases include Adenine and Guanine.
DNA structure is maintained by covalent phosphodiester bonds that are stable and should remain intact.
Nitrogen bases connect via hydrogen bonds, which are weaker and can be broken to enable DNA reading.

Base Pairing and Chargaff’s Rule

Base Pairing Rule:
- Adenine (A) pairs with Thymine (T) through 2 hydrogen bonds.
- Guanine (G) pairs with Cytosine (C) through 3 hydrogen bonds.
Chargaff’s Rule establishes relationships among nucleotide amounts: A = T and G = C.
Tetranucleotide Hypothesis suggests an equal quantity of all four nitrogenous bases is present.

DNA Structure and Packing

DNA is organized into chromosomes during cell division, aided by proteins called histones.
Histones facilitate supercoiling, forming nucleosomes that consist of DNA wrapped around a core of eight histones.
Linking histones function as glue to bind nucleosomes together.

Types of Nucleic Acids

Deoxyribonucleic Acid (DNA): Double-stranded helical structure.
Ribonucleic Acid (RNA): Single-stranded structure composed of nucleotides.

DNA Replication Process

Begins at a replication origin, where helicase unwinds DNA strands.
DNA Primase creates RNA primers, crucial for the initiation of synthesis by DNA Polymerase.
Two strands are produced:
- Leading Strand: Continuously synthesized from 5’ to 3’.
- Lagging Strand: Synthesized in segments (Okazaki fragments) away from helicase, which are later joined by DNA Ligase.

Protein Synthesis

Consists of two main stages: Transcription and Translation.
Transcription transforms DNA into messenger RNA (mRNA) within the nucleus, utilizing RNA Polymerase.
Translation occurs in cytoplasm/rough ER, where mRNA interacts with tRNA and ribosomes to form polypeptides.
Ribosomes, made from rRNA, create a polypeptide chain by reading mRNA codons.

Mutation and Genetic Variation

DNA mutations alter genetic codes, providing the basis for evolution and genetic diversity.
Sources of mutations include spontaneous errors and external factors such as radiation and chemicals.
Mutations can be beneficial, neutral, or detrimental, affecting protein function.

DNA Technologies

Polymerase Chain Reaction (PCR): Amplifies DNA, involving three main stages: denaturation, annealing, and extension.
Restriction Endonucleases: Enzymes act like genetic scissors, cutting DNA at specific sequences and creating sticky ends for genetic splicing.
Recombinant DNA Technology: Involves combining DNA from different species, utilizing restriction enzymes and DNA ligase.
DNA Fingerprinting: Used in forensic analysis, identifies unique, non-coding sequences in individuals through PCR, restriction enzyme cutting, and gel electrophoresis.

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Description

This quiz covers the fundamental concepts of nitrogen bases in DNA, including pyrimidines and purines. It dives into their structures, bonding mechanisms, and the base pairing rules essential for understanding DNA functionality. Suitable for students studying molecular biology or genetics.