THE SHOCKING REVELATION OF GENES STRUCTURE AND FUNCTION

Introduction

Genes are the basic units of heredity in living organisms. They are segments of DNA molecules that contain the instructions for building and maintaining an organism. Genes determine the traits or characteristics of an organism, such as eye color, hair color, height, and susceptibility to certain diseases.

Genes are located on chromosomes, which are long, coiled-up strands of DNA found in the nucleus of a cell. Each chromosome contains many genes, and humans have 46 chromosomes in total, arranged in 23 pairs. One chromosome in each pair is inherited from the mother and the other from the father.

The expression of genes is regulated by a complex network of interactions between the genes themselves and the environment in which an organism lives. Mutations or changes in genes can occur spontaneously or as a result of exposure to environmental factors, such as radiation or chemicals, and can lead to changes in an organism’s traits or the development of diseases.

 

DNA (deoxyribonucleic acid) is a long, double-stranded helical molecule that contains the genetic instructions used in the development and functioning of all known living organisms. The structure of DNA was first described by James Watson and Francis Crick in 1953, and is often depicted as a double helix.

Each strand of DNA is composed of a repeating unit called a nucleotide, which consists of a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base. There are four types of nitrogenous bases in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C). The nitrogenous bases pair up in a specific way, with A always pairing with T and G always pairing with C, through hydrogen bonds.

The double helix structure of DNA consists of two strands of nucleotides that are twisted around each other. The sugar and phosphate groups form the backbone of the molecule, while the nitrogenous bases project inward from each strand and form the base pairs. The two strands are held together by hydrogen bonds between the base pairs.

The specific sequence of the nucleotides along a DNA strand is what carries the genetic information that is used to determine an organism’s traits and characteristics. The DNA molecule is able to replicate itself, allowing the genetic information to be passed on from one generation to the next.

 

Nucleic acids are the building blocks of genetic information, and they are composed of nucleotides, which are made up of three components: a nitrogenous base, a sugar molecule, and a phosphate group.

The nitrogenous bases are classified into two types: purines and pyrimidines. Purines are adenine (A) and guanine (G), and pyrimidines are cytosine (C), thymine (T) (in DNA), and uracil (U) (in RNA).

A nucleoside is composed of a nitrogenous base and a sugar molecule, but it lacks a phosphate group. When a phosphate group is added to a nucleoside, it becomes a nucleotide. Therefore, nucleotides are composed of a nitrogenous base, a sugar molecule, and a phosphate group.

In DNA, the sugar molecule is deoxyribose, while in RNA, the sugar molecule is ribose. The nitrogenous bases of DNA are A, T, C, and G, while in RNA, they are A, U, C, and G.

Nucleotides play crucial roles in the storage and transfer of genetic information, as well as in the regulation of metabolic pathways in cells.

 

In vitro transfer of genetic information involves the transfer of genetic material, such as DNA or RNA, from one cell to another in a laboratory setting outside of a living organism. This process is important in genetic research and biotechnology, as it allows scientists to study and manipulate genetic information in a controlled environment.

One common method of in vitro transfer of genetic information is transfection, which involves introducing foreign genetic material into cells using chemical or physical methods. This allows researchers to study the effects of introducing specific genes or mutations into cells, and can help to identify the function of particular genes or their role in disease.

Once genetic material has been extracted from cells, it can be identified through a variety of chemical and analytical techniques, such as DNA sequencing or PCR amplification. These methods allow researchers to identify specific genetic sequences and analyze their structure and function. Overall, in vitro transfer of genetic information has revolutionized the field of genetics and has opened up many new avenues for research and discovery.

 

The 5′-3′ polarity of DNA strands refers to the orientation of the two strands of DNA. The two strands of DNA are antiparallel, meaning that they run in opposite directions. One strand runs in the 5′ to 3′ direction, while the other runs in the 3′ to 5′ direction.

The base pairing rules dictate how the two strands of DNA are held together. Adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). These base pairs are held together by hydrogen bonds. A and T form two hydrogen bonds, while G and C form three hydrogen bonds. These base pairs are complementary, meaning that they fit together perfectly like puzzle pieces.

The base pairing rules and the 5′-3′ polarity of DNA strands are important for DNA replication, where the two strands of DNA are separated and new strands are synthesized using each strand as a template. Additionally, the base pairing rules are important for DNA transcription, where RNA is synthesized from a DNA template using complementary base pairing, with uracil (U) pairing with adenine (A) instead of thymine (T).

 

The DNA double helix consists of two strands of nucleotides that wind around each other. The two strands run in opposite directions, which is referred to as being anti-parallel. This means that the 5′ end of one strand is aligned with the 3′ end of the other strand, and vice versa.

The orientation of the DNA strands is important because it determines how the nucleotides are linked together to form the backbone of the DNA molecule. The backbone of DNA is made up of sugar and phosphate molecules, which are linked together by phosphodiester bonds. The orientation of the sugar molecules is such that the 5′ carbon of one sugar is linked to the 3′ carbon of the next sugar.

The anti-parallel nature of the DNA double helix means that the two strands of DNA are oriented in opposite directions, with one strand running from the 5′ end to the 3′ end, and the other strand running from the 3′ end to the 5′ end. This allows the nucleotides on each strand to be linked together in the correct order, with the sugar-phosphate backbone running in the same direction on both strands.

The anti-parallel nature of the DNA double helix also has implications for DNA replication and transcription. During DNA replication, the two strands of the double helix are separated and each strand serves as a template for the synthesis of a new complementary strand. The anti-parallel orientation of the two strands means that the new strands must be synthesized in opposite directions. During transcription, RNA is synthesized from a DNA template. The RNA strand is synthesized in the same direction as the 3′ to 5′ strand of the DNA template, which is the opposite direction to the direction of the RNA polymerase enzyme that synthesizes it.

 

Genetic information is carried by nucleic acids, which include DNA and RNA, but not by proteins. Proteins are molecules made up of amino acids and have various roles in the body, such as catalyzing chemical reactions and serving as structural components of cells. However, they do not carry genetic information.

DNA, or deoxyribonucleic acid, is a double-stranded nucleic acid that carries genetic information in the form of a sequence of nucleotide bases (adenine, thymine, cytosine, and guanine). RNA, or ribonucleic acid, is a single-stranded nucleic acid that plays a key role in protein synthesis by carrying genetic information from DNA to the ribosome. Both DNA and RNA are involved in the transfer of genetic information from one generation to the next.

 

Semi-conservative DNA replication

Semi-conservative DNA replication is the process by which DNA is replicated in cells. It was first proposed by James Watson and Francis Crick in 1953, and it is now widely accepted as the most accurate model of DNA replication.

During semi-conservative DNA replication, the double-stranded DNA molecule is unwound by an enzyme called DNA helicase. This creates a replication fork, which is the point at which the two strands of DNA are separated.

Each of the separated strands then acts as a template for the synthesis of a new complementary strand, with the help of an enzyme called DNA polymerase. The new strands are synthesized in the 5′ to 3′ direction, which means that nucleotides are added to the 3′ end of the growing strand.

The two resulting DNA molecules each contain one of the original strands and one newly synthesized strand, hence the name “semi-conservative” replication. This process ensures that each new cell receives a complete and accurate copy of the genetic information contained in the original DNA molecule.

 

There are several types of physical evidence for the structure of DNA:

1. X-ray crystallography: In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Physiology or Medicine for their discovery of the structure of DNA. They used X-ray crystallography to analyze the structure of DNA, which allowed them to deduce the double helix structure of the DNA molecule.
2. Electron microscopy: This technique has also been used to image DNA. In electron microscopy, a beam of electrons is focused on a sample, and the resulting image can reveal the three-dimensional structure of the sample. Electron microscopy has been used to study the structure of DNA in different forms, such as double-stranded, single-stranded, and circular DNA.
3. Gel electrophoresis: This technique separates DNA fragments based on their size and charge. A gel is used to create a matrix that slows down the movement of the DNA fragments as they pass through an electric field. The smaller fragments move faster and travel farther through the gel, while the larger fragments move more slowly and do not travel as far. Gel electrophoresis can be used to analyze the size and shape of DNA fragments, which can provide evidence for the double helix structure of DNA.
4. Chemical analysis: The chemical composition of DNA, including the four nucleotide bases (adenine, thymine, guanine, and cytosine), also provides evidence for the structure of DNA. The base pairs in DNA are arranged in a specific way, with adenine always pairing with thymine and guanine always pairing with cytosine. This specific arrangement allows the DNA to form a double helix structure.

Overall, these physical evidence provide strong support for the double helix structure of DNA.

 

X-ray diffraction is a technique used to study the crystal structure of materials. It works by shining a beam of X-rays onto a sample, which causes the X-rays to scatter in different directions. By analyzing the pattern of scattered X-rays, it is possible to determine the arrangement of atoms within the crystal.

Here are the basic steps involved in X-ray diffraction:

1. Prepare the sample: The sample to be analyzed must be in the form of a crystal, and it should be free of impurities that could interfere with the diffraction pattern.
2. Set up the experiment: The X-ray diffraction experiment is typically performed using a specialized device called a diffractometer. The sample is mounted on the diffractometer, and an X-ray beam is directed onto it.
3. Collect the data: As the X-rays scatter off the crystal, they form a diffraction pattern on a detector located on the other side of the sample. The detector records the intensity of the scattered X-rays at different angles.
4. Analyze the data: The diffraction pattern is then analyzed to determine the crystal structure of the sample. This is typically done using software that compares the pattern to a database of known crystal structures.

 

DNA polymerases are enzymes that are responsible for replicating DNA during cell division. There are several different types of DNA polymerases, each with unique properties and functions. However, some common properties and requirements of DNA polymerases are:

1. DNA polymerases require a template strand of DNA: DNA polymerases cannot initiate the formation of a new DNA strand, but they can only add nucleotides to an existing DNA strand. Thus, a template strand is required for DNA polymerases to begin replication.
2. DNA polymerases require a primer: DNA polymerases require a short RNA or DNA strand called a primer to begin DNA synthesis. The primer provides a free 3’-OH group, which is necessary for the polymerase to add nucleotides to the growing DNA strand.
3. DNA polymerases require deoxynucleoside triphosphates (dNTPs): DNA polymerases add nucleotides to the growing DNA strand by catalyzing the formation of a phosphodiester bond between the 3’-OH group of the last nucleotide and the 5’-phosphate group of the incoming nucleotide. For this reaction to occur, DNA polymerases require dNTPs, which are the building blocks of DNA.
4. Proofreading function: DNA polymerases have a proofreading function, which allows them to correct errors that occur during DNA synthesis. This function involves the ability of the polymerase to recognize and remove incorrectly incorporated nucleotides from the growing DNA strand. DNA polymerases that lack this function are more error-prone and are associated with diseases such as cancer.

In summary, DNA polymerases require a template strand, a primer, dNTPs, and have a proofreading function to accurately replicate DNA during cell division.

 

DNA replication is a complex process that requires several enzymes to ensure the accurate duplication of genetic material. Some of the key enzymes involved in DNA replication are:

1. DNA helicase: This enzyme unwinds the double-stranded DNA molecule at the replication fork, separating the two strands and creating a replication bubble.
2. DNA polymerase: This enzyme adds nucleotides to the growing DNA strand, using the complementary base pairing rules (A with T, and C with G) to ensure the correct sequence.
3. Primase: This enzyme synthesizes a short RNA primer on each DNA strand, which provides a starting point for DNA polymerase to begin adding nucleotides.
4. DNA ligase: This enzyme seals the gaps between the Okazaki fragments on the lagging strand, joining the individual nucleotides into a continuous strand.
5. Topoisomerase: This enzyme relieves the tension that builds up as DNA unwinds and is replicated by cutting and rejoining the DNA strands.

These enzymes work together to ensure the accurate and efficient replication of DNA during cell division.

 

The genetic code refers to the set of rules by which information encoded in DNA or RNA sequences is translated into proteins. The nature of the genetic code has been extensively studied and there is strong evidence that it is both universal and redundant.

1. Universal: The genetic code is universal, meaning that it is used by all living organisms on Earth. This suggests that the genetic code is fundamental to life itself and has been conserved throughout evolutionary history. The universality of the genetic code is supported by the fact that the same codons (triplet nucleotide sequences) code for the same amino acids in all organisms, from bacteria to humans.
2. Redundant: The genetic code is also redundant, meaning that more than one codon can code for the same amino acid. For example, the amino acid leucine can be coded for by six different codons (CUA, CUC, CUG, CUU, UUA, and UUG). This redundancy provides a buffer against mutations and errors in the genetic code, as a change in one nucleotide may not necessarily affect the amino acid that is ultimately produced.
3. Experimentally verified: The nature of the genetic code has been experimentally verified through a number of techniques, including in vitro translation experiments using cell-free systems, mutagenesis studies, and genome sequencing. These experiments have confirmed the universality and redundancy of the genetic code.

Overall, the evidence strongly supports the view that the genetic code is a fundamental aspect of biology that is conserved across all living organisms, and that its redundancy provides a robustness that allows for variation and adaptation.

 

Role of tRNAs and aminoacyl-tRNA synthase

tRNAs (transfer RNAs) are small RNA molecules that play a critical role in protein synthesis. They act as the molecular link between the genetic information in DNA and the amino acid sequence of proteins. Each tRNA molecule carries a specific amino acid at one end and has a three-nucleotide sequence called an anticodon at the other end. The anticodon base-pairs with a complementary codon on messenger RNA (mRNA) during translation, allowing the correct amino acid to be added to the growing protein chain.

Aminoacyl-tRNA synthase enzymes (aaRS) are responsible for attaching the appropriate amino acid to its corresponding tRNA molecule. There are 20 different types of aaRS, one for each of the 20 standard amino acids. Each aaRS recognizes a specific amino acid and a specific set of tRNAs that can carry that amino acid. This process of attaching an amino acid to a tRNA is called aminoacylation or charging.

The accuracy and efficiency of aminoacylation are critical for protein synthesis. Mistakes can lead to errors in the amino acid sequence of proteins, which can affect their function and potentially cause disease. Therefore, the tight specificity and fidelity of the aaRS enzymes are essential for accurate protein synthesis.

 

Identification of individual codons, stop and start signals

In genetics, a codon is a sequence of three nucleotides that encodes for a specific amino acid during protein synthesis. The start codon, AUG, signals the beginning of protein synthesis and the incorporation of the amino acid methionine. The stop codons, UAA, UAG, and UGA, signal the end of protein synthesis and do not code for any amino acid.

Here is a list of all the individual codons, start and stop signals:

Start codon:

• AUG

 

Stop codons:

• UAA
• UAG
• UGA

 

Individual codons:

UUC UUU UUA UUG CUU

CUC CUA CUG AUU AUC AUA AUG GUU GUC GUA GUG UCU UCC UCA UCG CCU CCC CCA CCG ACU ACC ACA ACG GCU GCC GCA GCG UAU UAC CAU CAC AAU AAC AAA AAG GAU GAC GAA GAG UGU UGC UGG CGU CGC CGA CGG AGU AGC AGA AGG GGU GGC GGA GGG

 

Note that each codon represents a specific amino acid, as well as a start or stop signal in some cases.