1.1. Describe the structure and function of genes in relation to DNA

This guide will help you answer 1.1. Describe the structure and function of genes in relation to DNA.

Genes and DNA are fundamental elements of the human body. They play a key role in determining inherited traits, guiding the body’s growth, and ensuring it functions correctly. In this guide, we’ll cover the relationship between genes and DNA.

What is DNA?

DNA, or deoxyribonucleic acid, is a molecule found in almost every cell of the body. It carries the information needed to build and maintain an organism. DNA is like a set of instructions that tells the body how to develop and operate.

DNA molecules are incredibly long and are tightly packed into structures called chromosomes. Humans have 23 pairs of chromosomes in each cell, making a total of 46 chromosomes. These chromosomes are stored in the cell’s nucleus, which acts as the control centre of the cell.

DNA is made up of smaller units called nucleotides. Each nucleotide has three components:

• A sugar molecule (deoxyribose)
• A phosphate group
• A nitrogen base

The nitrogen bases are divided into four types:

1. Adenine (A)
2. Thymine (T)
3. Cytosine (C)
4. Guanine (G)

These bases pair in a specific way: A always pairs with T, and C always pairs with G. This pairing forms the famous double helix structure, resembling a twisted ladder.

What Are Genes?

Genes are segments of DNA. Each gene contains a set of instructions for making specific proteins. Proteins are complex molecules that perform most of the body’s functions, including building tissues, transporting materials, and acting as enzymes to trigger chemical reactions.

The human genome, which is the complete set of DNA, contains about 20,000-25,000 genes. These genes are located across the 23 pairs of chromosomes.

Structure of Genes

The structure of a gene can be divided into several key parts:

1. Promoter Region: This is the “on/off switch” for a gene. It tells the cell when to start or stop reading a gene.
2. Coding Region: This is the part of the gene that contains the actual instructions for making a protein. It consists of sequences called exons, which are the portions that code for protein, and introns, which are non-coding segments.
3. Terminator Region: This marks the end of the gene and signals the cell to stop reading it.

Genes are arranged in a linear order along the DNA strand. Their location and sequence determine which proteins will be produced by the body.

How Do Genes Work?

Genes work by providing the instructions for protein synthesis. This process happens in two key stages:

1. Transcription: In this stage, the DNA sequence of a gene is copied into a molecule called messenger RNA (mRNA). RNA is similar to DNA but has some differences, such as using the base uracil (U) instead of thymine (T).
2. Translation: In this stage, the mRNA is read by a structure called a ribosome to assemble the protein. The ribosome reads the mRNA in groups of three bases at a time, called codons. Each codon corresponds to a specific amino acid, the building blocks of proteins.

The sequence of bases in the DNA determines the order of amino acids in the protein. This order is crucial because it affects the protein’s shape and function.

Functions of Genes

Genes contribute to many vital functions within the body. Here are some of the most important ones:

• Inheritance: Genes carry instructions that are passed down from parents to their children. This is why children inherit traits like eye colour, hair texture, and height from their parents.
• Growth and Development: Genes control how the body grows, from the formation of an embryo to adulthood. They influence processes like the development of organs, bones, and muscles.
• Disease Resistance: Some genes help protect the body against diseases by supporting the immune system. However, mutations in certain genes can result in genetic disorders.
• Cell Repair: Genes instruct cells on how to repair damaged DNA. This is essential for maintaining the body’s overall health.

DNA, Genes, and Genetic Variation

Every person’s DNA is about 99.9% identical. The small percentage that differs accounts for the variation in physical characteristics such as eye colour, hair type, and skin tone. This variability is due to differences in genes, known as alleles.

An allele is a variant of a gene. For example, a gene that determines eye colour might have alleles for blue, brown, or green eyes. The combination of alleles someone inherits will influence their traits.

Some genetic variations are harmless or even beneficial. Others, however, may increase the risk of developing certain diseases or conditions, such as cancer, diabetes, or Alzheimer’s disease.

Chromosomes and Gene Organisation

Chromosomes are like storage units for DNA. Each chromosome contains many genes arranged in a specific sequence. For example, the first chromosome contains about 2,800 genes, while the Y chromosome (found only in males) contains just over 70 genes.

The number and structure of chromosomes are the same in almost every cell of the body. Exceptions include reproductive cells, such as sperm and egg cells, which only have 23 chromosomes each.

Mutations in Genes

Sometimes, changes occur in genes. These changes are called mutations. Mutations can happen naturally, or they may be caused by environmental factors like radiation, chemicals, or viruses.

Not all mutations are harmful. Some may have no effect, while others might improve a gene’s function. However, harmful mutations can disrupt the function of a gene and contribute to diseases such as cystic fibrosis, sickle cell anaemia, or certain forms of cancer.

Key Facts About DNA and Genes

For simplicity, here is a quick summary of the structure and function of DNA and genes:

• DNA is a double helix made of nucleotides.
• Genes are sections of DNA that provide instructions for building proteins.
• DNA is organised into chromosomes, which are stored in the cell’s nucleus.
• The sequence of bases in a gene determines the type of protein produced.
• Proteins are essential for the structure, function, and regulation of the body’s tissues and organs.
• Mutations can affect how a gene works, potentially leading to health problems.

DNA and Genes in Health and Social Care

Knowing about DNA and genes is important for health and social care workers. This knowledge helps in recognising genetic conditions, supporting patients with inherited disorders, and providing accurate information to service users.

For example, a health care worker may need to explain how a genetic condition like Huntington’s disease is inherited. Or they might help families understand the risks of passing on genetic conditions.

In addition, advances in genetics have led to new treatments, such as gene therapy, which could potentially correct faulty genes. Health and social care workers play a key role in helping individuals access these treatments and navigate their options.

Final Thoughts

The structure and function of genes in relation to DNA is a fascinating area of biology. DNA serves as the master blueprint for all living organisms, while genes are the specific instructions that guide protein production and influence traits. This knowledge doesn’t just apply to science but is crucial for understanding health and well-being. By appreciating how DNA and genes work, health and social care professionals can better support the people they care for and promote positive outcomes in their health journeys.