Problem 9 - Biology Concepts and Applications

Question

Match each term with its description. ________chromosome number ________alleles ________metaphase I ________interphase a. different molecular forms of the same gene b. none between meiosis I, II c. all chromosomes aligned at spindle equator d. all chromosomes in a given type of cell

Step-by-Step Solution

Answer

chromosome number - d; alleles - a; metaphase I - c; interphase - b.

Step 1: Identify Terms and Descriptions

First, let's look at the terms we need to match: 'chromosome number', 'alleles', 'metaphase I', and 'interphase'. The descriptions are: a. different molecular forms of the same gene, b. none between meiosis I, II, c. all chromosomes aligned at the spindle equator, d. all chromosomes in a given type of cell.

Step 2: Match 'chromosome number'

The term 'chromosome number' refers to the total number of chromosomes in a given type of cell. This matches description d: 'all chromosomes in a given type of cell'.

Step 3: Match 'alleles'

The term 'alleles' refers to different versions of the same gene, which can lead to genetic variation. Therefore, it matches with description a: 'different molecular forms of the same gene'.

Step 4: Match 'metaphase I'

During metaphase I in meiosis, the primary feature is that all homologous chromosomes align at the spindle equator. This corresponds to description c: 'all chromosomes aligned at spindle equator'.

Step 5: Match 'interphase'

Interphase is a phase of the cell cycle where the cell prepares for division. However, in the context of meiosis, and considering the given options, the correct match is b: 'none between meiosis I, II', indicating there is no interphase between these meiosis stages.

Key Concepts

Chromosome number

The term "chromosome number" is essential for understanding the genetic identity of a cell. Chromosomes are structures made of DNA that contain the instructions needed for an organism to grow, develop, and function.

The chromosome number refers to the total number of chromosomes in a cell of an organism.

• This number is constant for all cells of a particular organism. For example, humans have 46 chromosomes in each body cell.
• In sexually reproducing organisms, the chromosome number is halved in gametes compared to somatic cells, ensuring genetic diversity when sperm and egg unite.

Mistakes in chromosome number can lead to genetic disorders. Understanding chromosome number helps in genetic studies and medical diagnostics.

Alleles

Alleles are different versions of the same gene. They arise from mutations and contribute to the diversity of organisms, which is crucial for evolution.

Each individual inherits two alleles for each gene, one from each parent.

• If the alleles are identical, the organism is homozygous for that gene.
• If the alleles are different, the organism is heterozygous, leading to variations in traits.

Alleles can affect visible traits, like flower color, or invisible traits, like resistance to a disease. The study of alleles is fundamental in genetics to comprehend inheritance patterns.

Metaphase I

Metaphase I is a critical stage in meiosis, the process by which germ cells divide to produce sperm and egg cells. During this phase:

• Homologous chromosomes, which are pairs of chromosomes containing the same genes from each parent, line up along the spindle equator in the center of the cell.
• This alignment is crucial for the equal distribution of genetic material.

This stage sets the stage for genetic variation, as it determines how alleles are assorted into gametes. Understanding Metaphase I is vital in studying genetic inheritance and variation.

Interphase

Interphase is a part of the cell cycle that precedes both mitosis and meiosis. However, its role differs in these processes. In the context of meiosis:

• Interphase occurs before meiosis I and involves the duplication of DNA.
• However, there is no interphase between meiosis I and meiosis II. This lack of a second interphase prevents the doubling of genetic material again, a key distinction from mitosis.

Skipping interphase means meiosis II can begin without further DNA replication, maintaining the reduced chromosome number necessary for sexual reproduction.