DNA and Genes Structure of DNA Genes and chromosomes Genome organization

All life on Earth, from the simplest life forms to the most complex humans, carries an amazing biological instruction system which dictates how life develops, how it functions and how it reproduces. The information is encoded within molecules called DNA (Deoxyribonucleic Acid). DNA is referred to as the “blueprint of life” because it carries the instructions for the creation and upkeep of an organism.

Genetics is the study of the DNA and genes and how they are passed down from one generation to the next. It is a branch of biology that explores heredity, variation and passing down of biological information. Genetics accounts for why children look like their parents, why people have different characteristics to one another and how they have adapted and changed over time.

DNA and Genes: The Blueprint of Life

To become familiar with the structure of DNA, Genes, Chromosomes and Genome Organization

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Introduction: The Language of Life

All living things on Earth, from the smallest bacterium to the most complex human being, possess an amazing biological instruction system that helps life develop, function and reproduce. The instructions are contained within molecules known as DNA (deoxyribonucleic acid). DNA is one of the most crucial molecules as it carries the information essential to the construction and maintenance of an organism.

DNA and genes are the subject of study and research and is called genetics; it is a branch of biology that deals with the study of heredity, variation and passing down of traits through generations. Genetics is the cause of the characteristics children share with their parents, the differences between people, and the way alterations in the genetic material affect health, evolution and adaptation.

DNA is not the only worker that functions. It is in the form of functional units called genes which are arranged on structures called chromosomes. DNA, genes and chromosomes are the building blocks of an organism's genome—the total genetic information.

The complexity of life can be understood by knowing the structure of DNA, the role of genes, the organization of chromosomes and the arrangement of genomes

The Discovery of DNA: A Journey into the Genetic Code

Scientists for centuries have been wondering how traits are passed from the parents to the offspring. There were preliminary studies indicating that some biological material contained hereditary information, but the nature of it was not known.

Scientists in the 19th century started to study the chemical constituents of cells. Subsequent experiments showed that the molecule storing genetic information was DNA and not proteins

A big step forward was the discovery of the double-helical structure of DNA in the 1950s. James Watson and Francis Crick, and others such as Rosalind Franklin carried out research that led to the understanding of the unique structures of DNA and how the information is stored.

When they discovered the structure of DNA, it revolutionized biology and paved the way for today's genetics, biotechnology and medical research.

Structure of DNA: Double Helix of Life

Every molecule of DNA consists of many smaller molecules called nucleotides. Nucleotides have three components:

A phosphate group

The sugar that constitutes a molecule (e.g. deoxyribose)

A nitrogen-containing base

The four bases which are present in DNA are:

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

These bases form particular pairs:

Adenine is a base that is complementary to Thymine (A-T).

Cytosine is paired with Guanine (C–G)

This complementary pairing is called complementary base pairing. It enables the DNA to replicate itself precisely during cell division.

The structure of the DNA molecule is called the double helix.

DNA is two long chains of molecules twisted into a double helix. The sides of the DNA molecule are formed by alternating sugar and phosphate, and the paired nitrogen bases are the steps in the middle.

The double helix has some benefits:

It safeguards the genetic information.

It enables correct duplication of DNA.

It allows gene instructions to be read by cells.

The sequence of bases in DNA molecules works like an alphabetic code. Just as letters make words and sentences, sequences of the bases of DNA code for proteins.

3. DNA is an information storage molecule

DNA can be called the blueprint of life since it provides instructions for the construction and maintenance of organisms.

Proteins are made according to a sequence of bases on the DNA which carry out very important functions within cells. Proteins can act as:

Enzymes that control chemical reactions

Cell components (structure)

Signalling molecules and hormones

Antimicrobial compounds like antibodies

There are two important processes by which the information in DNA is transformed into proteins.The information contained in DNA is transferred to proteins by two major processes.

Transcription

A piece of the DNA has been copied into a molecule called messenger RNA (or mRNA). It enables genetic information to be transferred out of the DNA storage area to the cellular machinery that synthesizes proteins.

Translation

In translation, the mRNA message is used to direct the synthesis of protein, with the ribosome serving as the mechanism for the synthesis.

The two processes of transcription and translation enable genes to regulate biological functions.

Determine the function of a gene.

A gene is a particular stretch of DNA which codes for the formation of a functional product, typically a protein or a functional RNA molecule.

The basic units of heredity are genes. They affect the following qualities:

Eye color

Blood type

Height

Metabolism

Disease susceptibility

But genes don't work alone. Many traits are polygenetic, meaning that they are the product of interactions between multiple genes and the environment.

Human height is an example as it is determined by numerous genes, nutrition, health and the environment.

Gene Structure

A typical gene consists of a number of regions:

Promoter Region

A promoter is a region of DNA which determines when a gene is turned on. It is similar to a switch that enables the cell to start reading the gene.

Coding Region

The coding region includes the directions for creating a protein.

Regulatory Regions

These regions regulate the expression of a gene, that is, their strength and timing.

This is because the cells in the body have the same DNA, but different functions, which require different regulation. For example

Brain cells

Muscle cells

Liver cells

all contain the same genetic information, but different genes are activated in each cell type.

the genetics, chromosomes and genome organisation.

5.50 Genes and Chromosomes: The Organized Structure of Genetic Information

DNA molecules are very big. The DNA in one human cell would stretch to about 2 metres long. But the cell nucleus of a human cell is just a few micrometers in diameter. The DNA is compacted and organised into a very small space.

This packaging system makes structures known as chromosomes.

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A chromosome is a strand of DNA that is tightly coiled around proteins called histones. Histones function to package DNA and keep it from tangling. DNA and histone proteins combine to make a substance called chromatin.

The chromosomes are particularly prominent when the DNA is highly condensed, as in cell division. The purpose of this organization is to allow accurate replication and transmission of genetic information to new cells.

The Packaging System of DNA – Chromatin

There are several steps to the packaging of DNA.

This is the DNA Double Helix.This is the DNA Double Helix (Level 1).

The first is the DNA molecule itself, in which the nucleotides are in a particular sequence.The second level of DNA has wrapped around histones.DNA has wrapped around histones at level 2.

Groups of histone proteins bundle DNA to create nucleosomes. The basic unit of DNA packaging is a nucleosome.

Level 3: Chromatin Formation

Chromatin is made up of several nucleosomes. Chromatin can exist in two major forms:

Euchromatin

Euchromatin is less condensed DNA that is typically more active. Cells are able to read genes more easily in euchromatin.

Heterochromatin

Heterochromatin are densely packed DNA that is typically inactive. Is involved in the maintenance of chromosome structure and the regulation of gene activity.

The tightness and looseness of packing the DNA lets cells turn on and off the genes that are required at certain times and not others.

How genes are packaged into humans.The Genetic Packages: Human Chromosomes.

There are 46 chromosomes in the majority of human body cells. These chromosomes are paired into 23 pairs.

Each pair contains:

The gene from one of the mother's chromosomes

A single chromosome from the father

There are 22 pairs of chromosomes known as autosomes. They carry instructions in the form of genes for most of the functions of the body.

The last two are sex chromosomes that play a role in the development of biological sex:

The number 100 is usually associated with females.

XY would generally be the male sex.

There are thousands of genes in chromosomes. For instance, there are many hundreds of genes needed for important biological processes on the largest human chromosome, chromosome #1.

8. Genes on chromosomes

The positions on a chromosome where genes occur are known as loci.

Genes are located at specific positions and scientists are able to map the genes and study their function.

For example:

One gene for a particular protein will always be on a particular location.

Variants of a single gene are known as alleles.

Alleles can lead to variations in traits. The variation of which alleles contributes to: For example:

Blood groups

Hair characteristics

Eye color

Certain inherited conditions

An individual's set of alleles is called their genotype and the characteristics that are displayed are called the phenotype.

9. Inheritance: How Genes are passed down through generations

Gametes are reproductive cells that pass on genes from parent to offspring.

During reproduction:

The mother passes down one set of chromosomes.

One set of chromosomes comes from the father.

The offspring inherits the full genetic make-up.

This process of inheritance makes family members similar and also results in genetic variation.

Dominant and Recessive Trait

It is sometimes the case that some alleles are dominant, which means that just one copy of the gene is enough to have an effect on a characteristic.

Other Alleles are recessive and normally need to be paired to cause a trait to be expressed.

Some genetic disorders are caused by a person inheriting two recessive alleles that cause the disease, for instance.

But, some human characteristics are more complicated and are controlled by several genes.

10. Genome Organization: The Complete Genetic Collection

The entire genome of a particular organism is the genome.

There are about: __________ genes in the human genome.

The DNA in a cell contains 3 billion base pairs.

Around 20,000 protein-coding genes

Thousands of regulatory DNA sequences are involved in the process of gene regulation.

Genome organization refers to the arrangement, regulation and utilization of this genetic information by cells

A genome includes:

Coding DNA

Non-coding DNA

Regulatory sequences

Repetitive DNA regions

All parts work and develop organisms.

11. Coding and Non Coding DNA

For many years, scientists referred to large portions of DNA as “junk DNA” because their functions were not understood. Recent research has indicated that much of the non-coding DNA has functional roles.

Coding DNA

Genes are found in coding regions, which give instructions for proteins.

These genes influence:

Cellular structure

Metabolism

Growth

Development

Biological functions

Non-Coding DNA

Non-coding DNA is not responsible for the production of proteins and can control the activity of genes.

The functions of non coding DNA are:

Gene regulation and switching on/off of genes.

Maintaining chromosome structure

Producing regulatory RNA molecules

Supporting genome stability

The organization of coding and non-coding DNA helps regulate the many complicated processes of living organisms.

The Function of Regulatory DNA

There does not need to be a need for all genes to be active simultaneously. It is essential that cells have control systems that are able to tell which genes to turn on and which to turn off.

Regulatory DNA sequences are like control switches.

They help determine:

In the presence of a gene activator

The site of a gene's expression

How many grams of protein are formed

Genes that build muscle, for instance, are very active in muscle cells, and largely inactive in nerve cells.

This ability to turn genes on and off makes it possible for cells that have the same DNA to turn into different tissues.

Genome Variation and Human Diversity

There are only 0.1% differences in the DNA sequence that give rise to differences in humans.

Such differences are known as genetic variations.

Common form of genetic variation is:

This is called Single Nucleotide Polymorphisms (SNPs).

SNPs are simply small variations at one base in the DNA. They can impact on attributes like:

Drug response

Disease risk

Physical traits

Insertions and Deletion

These are caused when portions of DNA are inserted or deleted.

Structural Variations

Big changes in the DNA can alter areas of the chromosome and create variations in traits.

Genenic variation is absolutely necessary for evolution because it provides the difference on which natural selection operates.

14. Genome Research: It's importantance

On the whole, the research of genomes has revolutionized modern science and medicine.

Research on human genomes helps scientists to understand:

Explain why some diseases are inherited.

How cancers develop

How organisms evolve

How medicines can be personalised

The Human Genome Project is a major scientific endeavor that finished and gave a reference map of human DNA.

Genome sequencing technology is currently available to researchers to sequence DNA more quickly and accurately than ever before.

Applications include:

Genetic diagnosis

Personalized medicine

Disease prevention

Biotechnology development

Each DNA mutation and its impact.Every DNA mutation and its implications.

A relationship between genes and proteins.

Machinery for the regulation of genes and epigenetics.

Genome evolution

The genetic sciences have many potential applications in the future.

DNA and genes: The blueprint of life.

The third part is devoted to Mutations, Gene Regulation, Genome Evolution and the future of Genetics.The third part is dedicated to Mutations, Gene Regulation, Genome Evolution and the future of Genetics.

DNA Mutations: Changes in the Geneic Code

DNA is replicated very precisely but sometimes errors occur which result in changes in the DNA sequence. Such changes are known as mutations.

Mutations are changes to the sequence of bases that are permanent. Mutations may occur in the normal DNA copying process, or be induced by environmental agents like radiation, some chemicals or biological processes.

Not all mutations are bad mutations. Their effects are variable depending upon their location and their impact on the functioning of the gene.

DNA Mutations are of four types:

1. Substitution Mutation

A substitution is when one base in DNA is changed for another.

Example:

Original DNA

A–T–G–C

Changed DNA:

A–T–A–C

A slight change can have a negligible effect, or it could cause a change in the protein coded for by a gene.

2. Insertion Mutation

Insertion of additional DNA bases into a sequence.

Insertions can alter the normal reading of genetic information and can throw off the entire protein sequence.

3. Deletion Mutation

Deletion occurs when DNA bases are deleted.

Deletions, similar to insertions, can disrupt the production of protein and can cause genetic disorders.

Identify the effects of mutations on organisms.Describe how mutations can affect organisms.

There are different outcomes of mutations:

Beneficial Mutations

Certain mutations are beneficial and aid in survival and reproduction.

For instance, organisms can change their genetic makeup in response to environmental stresses.

Neutral Mutations

There are numerous mutations that have no effect on an organism. They can be found in areas of DNA that have no biological significance.

Harmful Mutations

Some mutations interfere with the normal functioning of the gene and may be a contributing factor in diseases.

These include mutations linked to:

Cystic fibrosis

Sickle cell disease

Certain inherited cancers

The effect of a mutation will vary depending on the location, the gene and environmental conditions.

DNA Repair: Protecting Genetic Information.17. DNA Repair: Protecting Genetic Information

There are many complex repair systems in the cell that prevent damage to DNA.

Repair mechanisms correct a lot of errors in DNA before they turn into mutations.

Important DNA repair processes are:

Mismatch Repair

Uses a system to correct errors during DNA replication.

Nucleotide Excision Repair

This is to remove damaged parts of DNA due to environmental factors.

Double-Strand Break Repair

This repairs double stranded breaks of DNA.

If DNA repair systems were not present then mutations would build up very quickly and would pose a threat to the survival of the cell.

The relationship between genes and proteins.

Genes are important because they contain instructions for the production of proteins.

Proteins are necessary molecules that have various functions in living organisms

Examples include:

Enzymes that are concerned with accelerating chemical reactions.

The structural proteins which assist tissues.

Carry substances from one place to another

These are hormones which control body functions.

The relationship of genes to proteins has been summarized as the central dogma of molecular biology:

DNA → RNA → Protein

This process is the mechanism in which genetic information is translated into biological activity.

20. The Bicycle Factory: Blood Clots and the Brain.21. The Apollo Program: Apnea, altitude and weightlessness.

Not all genes are turned on in all cells. Gene expression is the utilization of a gene to create a functional product.

There are several ways in which cells regulate the expression of their genes:

Regulatory DNA sequences

Transcription factors

Chemical modifications

Chromatin structure changes

For example:

The cells in the liver and brain have the same DNA but activate different sets of genes. This difference enables them to carry out specific tasks.

The process of gene expression is important for:

Growth

Development

Adaptation

Keeping the body functions normal.

20. Epigenetics: Regulation Without Changing DNA Sequence

Epigenetics is the field of study that examines changes in how the DNA is used, but not in its sequence.

Epigenetic mechanisms can affect the activity of genes.

The following are some of the key epigenetic processes:

DNA Methylation

Chemical group can bind to DNA and decrease gene expression.

Histone Modification

Modifications to histone proteins may alter the tightness of DNA compaction and its accessibility to genes.

Non-Coding RNA Regulation

Some RNA molecules can control the activity of genes.

Epigenetics can account for the differences among identical twins, whose genes are almost identical, as to what changes can be influenced by:

Nutrition

Stress

Environment

Age

Epigenetics also offers an explanation as to how identical twins can differ despite their virtually identical DNA.

21st. Genome Evolution: Evolution of the Genome over time

Genomes are not immutable. They get modified over generations by evolution.

Populations are different genetically from each other over time and this is what causes evolution.

The most important factors affecting genome evolution are:

Mutation

New genetic variations occur due to mutations.

Natural Selection

Those genes that are beneficial are passed on more often, leading to an increase in their prevalence.

Genetic Drift

Random fluctuation of gene frequencies can be observed, particularly in small populations.

Gene Flow

Transfer of genes between populations can bring new variation.

These processes work together to create the diversity of life on Earth.

22. Comparative Genomics: Study of Different Organisms

Comparative genomics is a comparison of different organisms' genomes to understand similarities and differences.

Genome comparisons are used by scientists to:

Evolutionary relationships

Shared biological functions

Disease-related genes

Species adaptations

Humans have many of the same genes as other organisms, for instance, thus showing the common origin of life.

Comparative genomics has shown that many basic cellular processes are shared by different species.

23. Modern Genetic Technologies

Technological advances in genetics have developed highly effective ways to study and alter DNA.

DNA Sequencing

Sequencing of DNA is used to know the exact order of bases in a DNA molecule.

It helps researchers:

Identify genetic variation

Diagnose diseases

Study evolution

Polymerase Chain Reaction (PCR).

PCR is a technique that can be used in the lab to make millions of copies of a particular piece of DNA.

Applications include:

Medical testing

Research

Forensic analysis

Genome Editing

Scientists can make targeted changes to DNA by using technologies like CRISPR.

Potential applications include:

Treating genetic disorders

Improving agricultural crops

Understanding gene function

24. The Future of Genetics

Genetics is still playing a major role in changing medicine, agriculture, and biotechnology.

The following are possible future developments:

Personalized Medicine

A person's genetic information can be used to determine the best treatment for a person.

Disease Prevention

Genetic information can be used to help identify risk for specific conditions and for early interventions.

Advanced Biotechnology

genetic technologies can help in the following areas:

New medicines

Improved food production

Environmental solutions

But there are also ethical issues that arise with genetic research, such as:

Ensuring the privacy of genetic information.

Far access genes are among the most important discoveries in the history of biology. DNA has a structure which enables it to store, copy and pass on genetic information over generations. Genes are viewed as functional to genetic technologies.

Properly engineered use of genome editing.

With the ongoing development of genetic science, careful considerations are required.

In this section, students will present their findings about DNA and explain how it serves as the foundation of life.

One of the biggest discoveries in the history of biology is DNA and genes. The DNA molecule is designed to carry, store and transmit genetic information from one generation to the next. The genes are the functional instructions and the chromosomes are organized units for storing information.

The genome is the full genetic content of an organism including coding and regulatory sequences that regulate life processes. DNA is pivotal in all living organisms, from determining physical characteristics to affecting health and evolution.

Today's genetics is more than just about inheritance. Now it can be used to help scientists in the study of disease, the development of personalized treatments, the study of evolution, and the creation of new biological technologies

As the research continues, knowledge of DNA and genes will increase and so will knowledge of the complexity, diversity and remarkable organisation of life.