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Difficulty: Very hardBasic Genetics Terminology and Concepts

In a diploid cell analyzed during interphase, a specific sequence of nucleotides that governs seed coat structure is situated at a precise, fixed position along a pair of morphologically matching chromosomes. An individual organism carries two different functional variants of this sequence at that position, resulting in different protein products. Which of the following correctly identifies the genetic terms for the matching chromosomes, the specific position, and the alternative sequence variants?

  1. The matching chromosomes are homologous chromosomes, the fixed position is the locus, and the alternative sequence variants are alleles.Answer
  2. B
    The matching chromosomes are sister chromatids, the fixed position is the locus, and the alternative sequence variants are genotypes.
  3. C
    The matching chromosomes are homologous chromosomes, the fixed position is the allele, and the alternative sequence variants are continuous phenotypes.
  4. D
    The matching chromosomes are homologous chromosomes, the fixed position is the locus, and the alternative sequence variants are codominant traits regardless of their expression.

Answer

The matching chromosomes are homologous chromosomes, the fixed position is the locus, and the alternative sequence variants are alleles.
In diploid genetics terminology, matching maternal and paternal chromosome pairs are termed homologous chromosomes. The physical coordinate or position of a gene along the chromosome is called the locus, and the alternative versions of the DNA sequence at that locus are called alleles.

Step-by-Step Solution

1
Identify the relationship between morphologically matching chromosome pairs in a diploid organism.
Morphologically matching pairs carrying genes for identical traits (one inherited from each parent) are defined as homologous chromosomes.
Diploid organisms inherit one chromosome set from each parent, forming homologous pairs.
2
Determine the term for the fixed physical location of a gene on a chromosome.
The specific physical position occupied by a gene on a chromosome is its locus (plural: loci).
Locus specifically designates physical mapping location on chromosomal DNA.
3
Determine the term for non-identical nucleotide variants of the gene situated at that location.
Alternative forms or variants of a gene occupying the same locus are defined as alleles.
Alleles account for genetic variations in traits.

Key Concept

Basic Genetics Terminology: Homologous Chromosomes, Locus, and Alleles
Estimated Time:1m 30s
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Topics

Basic Genetics Terminology and Concepts

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