Problem 6 - Biology Concepts and Applications

Question

Chromosome number______. a. refers to a particular chromosome in a cell b. is an identifiable feature of a species c. is the number of autosomes in cells of a given type

Step-by-Step Solution

Answer

Chromosome number is an identifiable feature of a species (Option B).

Step 1: Understand the Question

The question is asking about what the term "chromosome number" refers to. We need to choose the correct definition from the given options.

Step 2: Evaluate Option A

Option A states that chromosome number refers to a particular chromosome in a cell. This is incorrect because chromosome number refers to the overall number of chromosomes, not identifying a single chromosome.

Step 3: Evaluate Option B

Option B states that chromosome number is an identifiable feature of a species. This is often true because different species have characteristic numbers of chromosomes, making this a common feature used to identify species.

Step 4: Evaluate Option C

Option C states that chromosome number is the number of autosomes in cells of a given type. This is incorrect because chromosome number includes both autosomes and sex chromosomes in a species, not just autosomes.

Step 5: Conclusion

Among the options, B is the most accurate as chromosome number is indeed an identifiable feature of a species, commonly used to describe and differentiate species.

Key Concepts

Species Identification

Species identification is the process of distinguishing one species from another based on certain characteristics. One of these characteristics is the chromosome number.

Each species has a unique chromosome count. This serves as a genetic fingerprint of sorts. For example:

• Humans typically have 46 chromosomes.
• Fruit flies, known for their simple genetic makeup, have only 8 chromosomes.
• Some plants, like the fern Ophioglossum reticulatum, have over 1,000 chromosomes.

Chromosome number alone is not the sole method for identifying species, but it certainly helps researchers in classifying and studying them. It's a part of a larger toolkit along with traits like morphological characteristics, DNA sequences, and more.

Autosomes

Autosomes are chromosomes that are not directly involved in determining the sex of an organism. In humans, out of the 46 total chromosomes, 44 are autosomes, arranged in 22 pairs.

These chromosome pairs are referred to as homologous pairs, each obtained from one parent. Autosomes are responsible for the vast array of genetic instructions beyond gender determination. They play a key role in the inheritance and expression of numerous traits.

Examples of traits controlled by autosomes include:

• Blood type
• Hair color
• Eye color

Understanding autosomes is crucial in studying genetics as they carry the bulk of our genetic blueprint.

Sex Chromosomes

Sex chromosomes are a particular type of chromosome responsible for determining the sex of an organism. In humans, these are the X and Y chromosomes.

Females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The presence of the Y chromosome usually determines maleness.

However, sex determination can vary among species:

• Birds have a ZW system, where males are ZZ and females are ZW.
• Some reptiles' sex is influenced by environmental factors like temperature.

These chromosomes also carry genes that affect various biological processes. In humans, for instance, the X chromosome carries genes that can influence brain development. Understanding sex chromosomes is vital because abnormalities can lead to disorders such as Turner syndrome (XO) and Klinefelter syndrome (XXY).