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Ch. 14 - Mendel and the Gene
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Non è quello che usi tu?Cambia libro di testo
Capitolo 14, Problema 12a

Suppose you are heterozygous for two genes that are located on different chromosomes. You carry alleles A and a for one gene and alleles B and b for the other. Draw a diagram illustrating what happens to these genes and alleles when meiosis occurs in your reproductive tissues.

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Start with a diploid cell containing homologous chromosomes for Gene 1 (A and a) and Gene 2 (B and b).
During Meiosis I, homologous chromosomes are separated into two different cells. Each cell will have one chromosome from each pair (e.g., one cell will have A and B, the other will have a and b).
In Meiosis II, the sister chromatids of each chromosome are separated into different cells.
This results in four haploid cells, each with one allele from each gene (e.g., AB, Ab, aB, ab).
These haploid cells can then participate in fertilization, combining with another haploid cell to form a diploid organism.

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Meiosis

Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in four haploid gametes. It consists of two sequential divisions: meiosis I and meiosis II. During meiosis I, homologous chromosomes are separated, while meiosis II separates sister chromatids. This process is crucial for sexual reproduction, ensuring genetic diversity through recombination and independent assortment.
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Meiosis I & Meiosis II

Independent Assortment

Independent assortment is a principle of genetics that states that alleles for different genes segregate independently of one another during gamete formation. This occurs during metaphase I of meiosis when homologous chromosome pairs align randomly at the cell's equator. As a result, the combination of alleles that end up in gametes is a mix of maternal and paternal genes, contributing to genetic variation in offspring.
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Independent Assortment

Heterozygosity

Heterozygosity refers to the presence of two different alleles at a specific gene locus on homologous chromosomes. In the context of the question, being heterozygous for genes A/a and B/b means that the individual carries one dominant and one recessive allele for each gene. This genetic variation is important for the expression of traits and can influence the phenotype of the organism, especially when considering dominant and recessive interactions.
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Balancing Selection
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