Problem 34 - Anatomy and Physiology of Animals

Question

Which of the following terms means "many genes"? a. polymorphism b. polygeny c. polypeptide d. multiple alleles

Step-by-Step Solution

Answer

The correct term is polygeny (option b).

Step 1: Understand the Meanings

First, we need to understand the definitions of each term provided in the choices: - **Polymorphism**: Variation in DNA sequence among individuals. - **Polygeny**: The phenomenon where multiple genes determine a particular trait. - **Polypeptide**: A chain of amino acids forming a protein or part of a protein. - **Multiple alleles**: Presence of more than two allele forms of a gene within a population.

Step 2: Identify the Correct Term

Next, we need to identify which term corresponds to 'many genes'. Since 'polygeny' refers to a situation where multiple genes influence a single trait, it matches the description of 'many genes'.

Step 3: Choose the Correct Option

Based on the definitions, polygeny is the term that means 'many genes'. Therefore, the correct answer is option b: polygeny.

Key Concepts

Polygeny

Polygeny refers to the concept where multiple genes are involved in determining a specific trait. This is a key aspect of genetics, as it explains why certain traits do not follow simple Mendelian inheritance patterns. Instead of a single gene influencing a trait, multiple genes work together to produce a phenotypic outcome. For example, human skin color is determined by at least three to six different genes, making it a polygenic trait. This complexity allows for a wide range of possible phenotypes, contributing to the diversity we see in humans and other organisms. Understanding polygeny can help in predicting and studying complex traits, particularly those that involve environmental interactions.

Polymorphism

Polymorphism in genetics refers to the occurrence of two or more different sequences or forms of a particular DNA segment within a population. It's not limited to just physical or visible traits but can also include variations that occur at a molecular level, such as in enzymes or hormones. - **Importance of Polymorphism:** - Provides genetic variation within a population which can lead to increased survival and adaptation. - Helps in studying disease susceptibility as some polymorphisms are linked to certain health conditions. - **Examples:** - Blood groups in humans (e.g., ABO blood types). Polymorphisms are considered crucial for evolution, as they can provide the raw material for selection to act upon. Moreover, they're used in genetic mapping and studying inheritance patterns to identify genes associated with specific traits.

Multiple Alleles

Multiple alleles refer to the existence of more than two allele versions of a gene within a population. This genetic principle explains that at any given locus within a genome, there could be more than two alleles, although an individual will inherit only two alleles (one from each parent). - **Characteristics of Multiple Alleles:** - They add to genetic diversity by providing a variety of possible genetic combinations. - Traits governed by multiple alleles include variations such as fur color in rabbits and eye color in humans. - The ABO blood group system in humans is a classic example, where alleles A, B, and O result in different blood types. Multiple alleles therefore contribute significantly to the genetic variability within a species, impacting traits at both the individual and population levels.

Polypeptides

Polypeptides are chains of amino acids linked together by peptide bonds, and they form the building blocks of proteins. Each polypeptide can contain hundreds or thousands of amino acids, with its structure determined by the sequence of these amino acids. - **Function and Importance:** - Polypeptides fold into specific three-dimensional structures to form proteins, crucial for virtually all cellular processes. - They are responsible for a diverse array of functions, including enzyme activity, cell signaling, and structural support. - **Relation to Genes:** - The genetic code defined by DNA ultimately directs the synthesis of polypeptides, linking genes to physical traits and functions. Understanding the role of polypeptides is fundamental in biochemistry and genetics, as disruptions in their formation can lead to diseases. They serve as a critical bridge between genetic information and cellular function, highlighting their essential role in both molecular biology and genetics.