Question

Which hormone directly affect transcription by acting on gene? (a) FSH (b) GH (c) Oestrogen (d) \(\mathrm{CCK}\)

Short answer

The hormone that directly affects transcription by acting on genes is oestrogen.

Step-by-step solution

Understanding hormone actions

Different types of hormones have different methods of action. Some hormones bind to receptors on the cell surface and use a second messenger to deliver their message, this is the case for FSH, GH and CCK. The other type of hormones pass through the cell membrane and interact directly with the DNA in the cell nucleus

Identify hormones that influence transcription by interaction with the DNA

Only hormones that are not impeded by the cell membrane and that can reach the DNA in the nucleus can directly influence transcription. In this case, oestrogen is known to do that.

Affirm the correct answer

From the options given, only oestrogen has the capacity to directly influence transcription by acting on the gene. FSH, GH and CCK affect cellular functions usually by triggering a cascade of responses after binding with cell surface receptors, but do not directly impact transcription.

Key concepts

Oestrogen and Gene Regulation

Oestrogen plays a crucial role in regulating genes within the human body. This hormone directly affects transcription, which is the process of making an RNA copy from a DNA sequence. Oestrogen can pass through cellular membranes without hindrance. Once it enters the cell, it finds its way to the cell nucleus where our DNA reside. Upon reaching the DNA, oestrogen influences the expression of specific genes. This regulation is important in various processes such as growth, development, and reproductive functions. By binding directly to DNA-associated receptors, oestrogen initiates gene transcription, ultimately contributing to various cellular functions.

Hormone-Receptor Interactions

Hormones exert their effects by interacting with specific receptors. These receptors act like 'locks' that only certain 'keys' — in this case, hormones — can activate. This activation is necessary for the hormone to produce its physiological effects. Oestrogen, for example, binds to intracellular receptors present in the nucleus. Once attached, this hormone-receptor complex functions as a transcription factor, which directly influences specific segments of DNA, resulting in the production of messenger RNA (mRNA). This mRNA is then utilized to synthesize proteins necessary for biological functions. The hormone-receptor interaction is essential in translating hormonal signals into cellular responses, thereby regulating various biological processes.

Transcription Mechanisms

Transcription refers to the process of copying a gene's DNA sequence to mRNA, which is later used to synthesize proteins. This process is fundamental to gene expression. Transcription occurs in several steps: initiation, elongation, and termination. During initiation, RNA polymerase binds to a specific region on DNA called the promoter. Hormones like oestrogen can influence transcription by enhancing the recruitment of RNA polymerase to these promoter sites. Through elongation, RNA polymerase moves along the DNA, extending the mRNA transcript. Finally, in termination, the RNA polymerase detaches, and the mRNA transcript is released for further processing. The entire transcription process is tightly regulated by various factors, including hormonal signals like those carried by oestrogen.

Cell Membrane Permeability

Not all hormones can pass through the cell membrane freely. The cell membrane selectively regulates the movement of substances based on their size, charge, and solubility. Oestrogen is a lipid-soluble hormone, giving it the ability to diffuse directly through the lipid bilayer of the cell membrane. This permeability is crucial for hormones that act within the cell, such as oestrogen, as it needs to reach the nucleus to exert its influence on gene transcription. In contrast, water-soluble hormones like FSH and GH cannot pass as easily and interact with surface receptors to transmit their signals via second messengers. Understanding membrane permeability aids in comprehending how different hormones achieve their respective biological effects.

Types of Hormone Actions

Hormones can affect cellular activities in a variety of ways. Broadly, these actions are categorized based on how hormones interact with cells. Lipid-soluble hormones, such as oestrogen, exert their effects by diffusing through the cell membrane and directly influencing genes in the nucleus. Meanwhile, water-soluble hormones like FSH, GH, and CCK act indirectly. Unable to cross the membrane directly, they bind to receptors on the cell surface. This binding triggers a cascade of intracellular signals, often involving molecules known as second messengers. These second messenger systems amplify the signal, leading to various cellular responses. Each type of hormone action plays a distinct role in regulating complex physiological processes.