Question

An individual that has two different alleles of a particular gene is said to be a. dihybrid. b. recessive. c. homozygous. d. heterozygous. e. hemizygous.

Short answer

The correct term for an individual that has two different alleles of a particular gene is heterozygous.

Step-by-step solution

Understanding alleles

An allele is one of two or more versions of a gene that are found at the same place on a chromosome. For any gene, a person may have the same two alleles, also known as homozygosity, or two different ones, known as heterozygosity.

Understanding terms

The terms provided in the options break down as follows: a. Dihybrid is an individual that is heterozygous for two traits; b. A recessive trait or gene is expressed only when two recessive alleles are present; c. Homozygous individuals have two copies of the same allele; d. Heterozygous individuals have two different alleles at a locus; and e. Hemizygous indicates presence of single allele at a locus instead of two.

Choosing the correct term

Based on definitions, an individual that has two different alleles of a particular gene is heterozygous. This is because the term heterozygous specifically refers to the state where there are two different alleles at a locus.

Key concepts

Understanding Alleles

Alleles are different versions of the same gene. Genes are the basic units of heredity, and they dictate various traits and characteristics that make each individual unique. For any given gene, alleles reside on corresponding locations, or loci, on pairs of chromosomes.
Although we often talk about genes, alleles are the specific forms of genes that we inherit from our parents. In a more simplified way, what makes our eye color brown or blue, or our hair curly or straight, are the various alleles we possess.

• Two identical alleles make someone homozygous for that gene.
• Two different alleles make someone heterozygous for that gene.

This mix of alleles creates the potential for diverse traits in living organisms, influencing their appearance, behavior, and even responses to environmental factors. The mixing of alleles from both parents is a fundamental factor in genetic diversity.

Homozygous vs. Heterozygous

The terms homozygous and heterozygous get thrown around quite a bit in genetics, and understanding them is key to grasping how traits are passed down from generation to generation. Individuals can be either homozygous or heterozygous for a particular gene.

• Homozygous: This means having two identical alleles for a specific gene. If both alleles are dominant, the individual is homozygous dominant; if both are recessive, then the individual is homozygous recessive.
• Heterozygous: This means having two different alleles for a gene. In this case, often one dominant allele can mask the effect of a recessive allele.

Understanding these terms is essential when predicting how genetic traits may manifest within families. The combination of alleles determines whether certain traits will be expressed, spread through generations, or remain hidden.

Gene Expression

Gene expression is the process by which the information encoded in a gene is used to direct the production of proteins, which are crucial for the development and functioning of all living cells.
In a simple sense, gene expression is how instructions in our DNA are converted into the functional products that help form our bodies and keep them running.
This intricate process involves two main stages: transcription and translation.

• Transcription: The first step where a specific segment of DNA is copied into RNA.
• Translation: The RNA copy is then used to build proteins by assembling amino acids in the correct order.

The combination of different alleles impacts which genes are expressed. Therefore, understanding gene expression helps explain why a heterozygous individual may exhibit traits associated with the dominant allele. Environmental and epigenetic factors can also influence this important biological process, leading to varied phenotypes within a species.