Question

then answer these questions: 1. what is an allele? 2. what is the difference between homozygous and heterozygous? 3. how can a recessive gene show back up after several generations?

Explanation:

1. What is an allele?

An allele is a variant form of a gene. Genes are segments of DNA that code for a particular trait, and alleles are different versions of that gene that can exist at a specific locus (position) on a chromosome. For example, in the gene that determines flower color in pea plants, there might be an allele for purple flowers and an allele for white flowers. These different alleles can lead to different expressions of the trait (phenotype) depending on how they interact with other alleles (e.g., dominant - recessive relationships).

• Homozygous: An organism is homozygous for a particular gene when it has two identical alleles at a given genetic locus. For example, if the gene for eye color has an allele for brown eyes (let's represent it as \( B \)), a homozygous individual would have \( BB \) (homozygous dominant) or if the allele is for blue eyes (\( b \)), it would have \( bb \) (homozygous recessive). In the case of homozygous dominant (\( BB \)), the dominant trait (brown eyes) will be expressed. In homozygous recessive (\( bb \)), the recessive trait (blue eyes) will be expressed.
• Heterozygous: An organism is heterozygous for a gene when it has two different alleles at a given genetic locus. Using the eye - color example, a heterozygous individual would have \( Bb \). In most cases of simple dominant - recessive inheritance, the dominant allele (\( B \) for brown eyes) will be expressed in the phenotype, and the recessive allele (\( b \) for blue eyes) will be masked but can be passed on to offspring.

1. Carrier Mechanism: Recessive alleles can be carried in heterozygous individuals (\( Aa \)) without being expressed in the phenotype. These heterozygous individuals are called carriers. Over generations, carriers can pass on the recessive allele to their offspring.
2. Independent Assortment and Inheritance: When two carriers (\( Aa\times Aa \)) have offspring, there is a \( \frac{1}{4} \) chance (using Mendelian genetics for a single - gene trait) that their offspring will inherit two recessive alleles (\( aa \)). If carriers continue to reproduce over several generations, eventually, two carriers may have a child who inherits the two recessive alleles, causing the recessive trait (associated with the recessive gene) to be expressed. Also, in cases of more complex inheritance patterns (e.g., polygenic inheritance or when multiple genes interact), the frequency of the recessive allele in the population can remain stable, and through random mating, the chance of two recessive alleles coming together in an individual increases over time.

Answer:

An allele is a variant form of a gene, differing in DNA sequence, that occupies the same locus on a chromosome and can influence the expression of a particular trait.

2. What is the difference between homozygous and heterozygous?