Molecular Biology Basics

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Questions and Answers

Which linkage connects the nitrogenous base to the ribose sugar?

Peptide bond

Phosphodiester linkage

Hydrogen bonding

Glycosidic linkage (correct)

What is the primary function of polymers of nucleotides like DNA and RNA?

Protein synthesis

Storing and transferring genetic information (correct)

Cell signaling

Energy transfer

What type of structure do two polynucleotide chains form in DNA?

Double helix (correct)

Circular structure

Triple helix

Linear arrangement

How do the two strands of DNA run in relation to each other?

anti-parallel Signup and view all the answers

Which group is bonded to C3’ or C5’ of the sugar in a nucleotide?

Phosphate group Signup and view all the answers

What type of bond forms the backbone of DNA?

Phosphodiester bond Signup and view all the answers

What structures are found on the surface of the DNA double helix?

Major and minor grooves Signup and view all the answers

Which of the following does NOT pertain to the Watson-Crick DNA structure?

Strands are oriented in the same direction. Signup and view all the answers

What base pair is complementary to Cytosine (C)?

Guanine (G) Signup and view all the answers

How many base pairs (bp) are present per turn in B-DNA?

10 Signup and view all the answers

Which type of DNA structure is left-handed?

Z-DNA Signup and view all the answers

What is the placement of base pairs in A-DNA?

Displaced away from the helical axis Signup and view all the answers

Which groove in B-DNA is described as wide?

Major groove Signup and view all the answers

What primary purpose does supercoiling serve in bacterial DNA?

To facilitate tighter packing and protection Signup and view all the answers

What nucleotide is used in RNA in place of Thymine (T)?

Uracil (U) Signup and view all the answers

In the context of DNA types, which of the following characteristics is true for Z-DNA?

It has a major groove that's not a real groove Signup and view all the answers

What is the central dogma of molecular biology?

Genes are transcribed into RNA, which is translated into proteins. Signup and view all the answers

Which type of nucleic acid contains thymine?

DNA Signup and view all the answers

What sugar is found in RNA?

Ribose Signup and view all the answers

Which statement is true regarding histone proteins?

They help organize DNA in chromosomes. Signup and view all the answers

What is the primary function of nucleotides?

To store and express genetic information. Signup and view all the answers

Which base is only present in RNA?

Uracil Signup and view all the answers

What is the composition of a nucleotide?

Base + Sugar + Phosphate Signup and view all the answers

Where does transcription occur in a cell?

In the nucleus Signup and view all the answers

What distinguishes purines from pyrimidines?

Purines are composed of nitrogenous bases with two rings, while pyrimidines have one ring. Signup and view all the answers

Which of the following statements about the human genome is accurate?

It contains about 35,000 genes. Signup and view all the answers

What is the primary factor that influences the melting temperature (MT) of DNA?

The nitrogenous base content of the DNA Signup and view all the answers

What is the role of tRNA in protein synthesis?

It recognizes codons for specific amino acids Signup and view all the answers

What percentage of the human genome is estimated to be non-coding or 'junk' DNA?

95% Signup and view all the answers

Which of the following describes the structure of nucleosomes?

Nucleosomes consist of a histone octamer and additional single-stranded DNA Signup and view all the answers

Histones play a crucial role in the organization of DNA. Which characteristic of histones assists in this function?

Histones have positively charged amino acids Signup and view all the answers

Which statement accurately reflects the central dogma of molecular biology?

It consists of the flow of information from DNA to RNA to protein Signup and view all the answers

How many hydrogen bonds are present between G-C base pairs compared to A-T base pairs?

G-C has 3 bonds; A-T has 2 bonds Signup and view all the answers

Which type of RNA serves as the site of protein synthesis?

rRNA (Ribosomal RNA) Signup and view all the answers

At which carbon position of the sugar molecule is the nitrogenous base attached?

C1’ Signup and view all the answers

How many base pairs are present per turn in A-DNA?

10 Signup and view all the answers

What is the orientation of the two strands in the DNA double helix?

Both strands are anti-parallel Signup and view all the answers

Which type of bond holds the two strands of the DNA double helix together?

Hydrogen bonds Signup and view all the answers

Which type of DNA is characterized by the absence of a real groove?

Z-DNA Signup and view all the answers

What is the primary function of nucleic acids like DNA and RNA?

Genetic information coding Signup and view all the answers

In a DNA double helix, where are the nitrogenous bases positioned?

On the inside of the helix Signup and view all the answers

Which of the following statements about DNA structure is incorrect?

The strands are composed of ribose sugar Signup and view all the answers

Study Notes

Objectives of Molecular Biology

Central dogma: DNA is transcribed to RNA, which is then translated to proteins.
Human genome comprises approximately 35,000 genes.
Replication and transcription occur in the nucleus; translation occurs in the cytoplasm.

Nucleic Acids Overview

Nucleic acids are essential for genetic information storage and expression.
Building blocks are nucleoside triphosphates, or nucleotides.

Types of Nucleic Acids

DNA (Deoxyribonucleic Acid): Contains thymine (T).
RNA (Ribonucleic Acid): Contains uracil (U) instead of thymine.

Nucleotide Components

Nucleotides are composed of a nitrogenous base, sugar, and phosphate group.
Purines (Adenine and Guanine) have a two-ring structure; Pyrimidines (Cytosine, Thymine, Uracil) have a one-ring structure.

Nucleotide Structure

Nucleotide structure consists of a base + sugar (nucleosides) + phosphate (nucleotides).
Sugar carbons are primed (1’, 2’, 3’, etc.).

Chemical Structure of DNA and RNA

Backbone of DNA is formed by phosphodiester bonds between nucleotides.
Nitrogenous bases bond to C1’ of sugar; the phosphate group is linked to C3’ or C5’ of the sugar.

DNA Double Helix

DNA structure was established by Watson and Crick in 1953.
Composed of two anti-parallel polynucleotide chains forming a right-handed double helix.
The two strands are linked by hydrogen bonds between complementary base pairs (A=T, G≡C).

Base Pairing

In DNA: Adenine pairs with Thymine, Guanine pairs with Cytosine.
In RNA: Uracil replaces Thymine.

Types of DNA Structures

A-DNA: Right-handed, short, 11 base pairs per turn, deep and narrow major groove.
B-DNA: Right-handed, elongated, 10 base pairs per turn, wide major groove.
Z-DNA: Left-handed, more elongated, 12 base pairs per turn, narrow grooves.

DNA Supercoiling

Bacterial and viral chromosomes contain supercoiled circular DNA to save space and enhance protection.

RNA Types and Functions

mRNA (Messenger RNA): Transfers genetic information from DNA for protein synthesis.
tRNA (Transfer RNA): Recognizes codons and transfers amino acids during protein assembly.
rRNA (Ribosomal RNA): Forms the structural and functional core of ribosomes.

Organization of DNA in Chromosomes

Human genome has 3.5 billion base pairs, with over 95% considered non-coding (junk DNA).
Each chromosome consists of a single linear DNA molecule and protein, forming chromatin.
Histones, comprising five types (H1, H2A, H2B, H3, H4), stabilize chromatin by binding to negatively charged DNA.

Nucleosomes

Nucleosomes are complexes of DNA and histones, organized like beads on a string, facilitating DNA packaging.

Key Takeaways

Central dogma features vital interactions between DNA, RNA, and protein.
Nucleic acids are chemically distinct but crucial for genetic functions.
DNA organization into chromosomes allows effective genomic packaging.

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Description

This quiz covers the fundamental concepts of molecular biology, including the central dogma and the structure of nucleic acids. It explores the components of nucleotides and the differences between DNA and RNA. Test your knowledge on these essential building blocks of life!