DNA Structure Overview

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Questions and Answers

What is the primary function of DNA in living organisms?

To produce energy for cellular functions

To facilitate cellular communication

To hold the instructions for development, survival, and reproduction (correct)

To serve as a structural component of cells

Which of the following correctly describes the monomers that make up DNA?

Nucleotides (correct)

Amino acids

Fatty acids

Carbohydrates

Which of these components is NOT part of a nucleotide?

Phosphate group

Base

Sugar

Amino group (correct)

How does Chargaff's Rule describe the relationship between purines and pyrimidines in DNA?

Total number of purines is equal to total number of pyrimidines Signup and view all the answers

What are the two types of nitrogenous bases found in DNA?

Purines and pyrimidines Signup and view all the answers

Which sugar is found in the nucleotides of DNA?

2'-deoxyribose Signup and view all the answers

What structural feature of DNA allows it to store information over the long term?

Double helix structure Signup and view all the answers

What role do genes play in a cell?

Biological information and inheritance Signup and view all the answers

What is the term used for the bonding that holds the two strands of DNA together?

Hydrogen bonding Signup and view all the answers

What pairs with adenine in DNA structure?

Thymine Signup and view all the answers

Which nucleotide is not included in the DNA structure?

dUTP Signup and view all the answers

Which feature describes the orientation of the two strands in a DNA double helix?

Antiparallel Signup and view all the answers

In which form of DNA is hydration essential for its stability?

B-DNA Signup and view all the answers

Which base-pair combination follows Chargaff's Rule?

A-T Signup and view all the answers

What does GC content refer to in DNA?

The amount of guanine and cytosine nucleotides Signup and view all the answers

Which statement about the DNA double helix is incorrect?

It is a single-stranded structure. Signup and view all the answers

Which two organisms have the highest and lowest GC content for their DNA?

Human DNA vs. Streptomyces griseolus Signup and view all the answers

Which of the following is true about Z-DNA?

It is found only in specific regions of DNA. Signup and view all the answers

What describes a gene in the context of molecular biology?

A segment of a DNA molecule Signup and view all the answers

Which of the following is NOT typically a component of a gene's structure?

Histones Signup and view all the answers

What is the approximate average length of human genes in terms of introns and exons?

8 introns and 9 exons Signup and view all the answers

Which term refers to the segments of a gene that contain the information needed to make a protein?

Exons Signup and view all the answers

What is the function of introns in genes?

They are non-coding sequences within a gene. Signup and view all the answers

What is the longest recorded length of a human gene?

2,400,000 bp Signup and view all the answers

How do gene families arise?

Through duplications and mutations over evolutionary time. Signup and view all the answers

What unit is commonly used to describe the length of DNA molecules?

Base pairs (bp) Signup and view all the answers

What are the functional end products of gene expression?

Proteins and RNAs Signup and view all the answers

Which statement best describes a pseudogene?

A non-functional gene with altered nucleotide sequence Signup and view all the answers

The molecular clock is used to measure what aspect of genes?

The rate at which a gene's sequence changes Signup and view all the answers

What is a common characteristic of complex multigene families?

Genes have similar but not identical DNA sequences Signup and view all the answers

Which genes are involved in binding and transporting oxygen in humans?

Globin genes Signup and view all the answers

What is the role of noncoding RNAs in a cell?

They have various important cellular functions Signup and view all the answers

The alpha-globin genes are located on which chromosome in humans?

Chromosome 16 Signup and view all the answers

What is the expected outcome as time passes since gene duplication?

Greater differences appear between the sequences Signup and view all the answers

What happens to genes that are duplicated and subsequently lose their function?

They become pseudogenes Signup and view all the answers

Study Notes

DNA Structure

DNA is a polymer, composed of monomers called nucleotides.
Each nucleotide consists of three parts: a sugar (2'-deoxyribose), phosphate groups, and a base.
The sugar is 2' deoxyribose.
Four bases exist in DNA: adenine (A), guanine (G), cytosine (C), and thymine (T).
A and G are purines; C and T are pyrimidines.
Bases are attached to the sugar via a β-N-glycosidic bond.
Chargaff's rule states the total number of purines equals the total number of pyrimidines in a DNA molecule.
The names of the four nucleotides are: 2'-deoxyadenosine 5'-triphosphate (dATP), 2'-deoxyguanosine 5'-triphosphate (dGTP), 2'-deoxycytidine 5'-triphosphate (dCTP), and 2'-deoxythymidine 5'-triphosphate (dTTP).
Nucleotides are joined together via phosphodiester bonds.
DNA has a 5' to 3' direction.
DNA in living cells is a double helix composed of two polynucleotide strands.
The double helix structure was discovered by James Watson and Francis Crick in 1953, based on data from Rosalind Franklin and others.

DNA Double Helix

DNA has an antiparallel structure, meaning the strands run in opposite directions.
It possesses a major and minor groove.
The two strands are held together by complementary base pairing (A with T, G with C), via hydrogen bonds.
DNA can exist in different forms: A-DNA, B-DNA, and Z-DNA.

Important Features of DNA Types

B-DNA is the most common and predominant form.
A-DNA is rare, found during dehydrating conditions.
Z-DNA is found naturally with B-DNA in specific regions, its biological activity isn't fully understood.

Additional Features

The amount of G+C nucleotides in an organism's DNA is referred to as GC content. Human DNA has a GC content of 40.3%. Examples of other organisms GC content are provided, such as Plasmodium falciparum (19.0%) and Streptomyces griseolus (72.4%).

Resources for Further Study

Introduction to Genetics, a Molecular Approach by Brown.
- Chapter 2, pages 11 to 19.
Essential Cell Biology by Alberts.
- Chapter 5, pages 173 to 178.
Supplementary material is available on Blackboard. This includes PDFs containing reading materials, learning objectives, keywords, and exercises.

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Description

This quiz covers the structure of DNA, including its composition of nucleotides and the double helix model discovered by Watson and Crick. You'll learn about the components of nucleotides, Chargaff's rule, and the significance of the 5' to 3' direction. Test your knowledge on the fundamental building blocks of life!