Problem 6 - Biology Concepts and Applications

Question

Dogs have a diploid chromosome number of \(78 .\) How many chromosomes do their gametes have? a. 39 b. 78 c. 156 d. 234

Step-by-Step Solution

Answer

The number of chromosomes in dog gametes is 39.

Step 1: Understanding Diploid and Haploid Numbers

Dogs have a diploid chromosome number of 78, meaning that this is the total number of chromosomes found in somatic (body) cells, where chromosomes are organized in pairs.

Step 2: Identifying the Chromosome Number in Gametes

Gametes, such as sperm and egg cells, have half the chromosome number of somatic cells. This is known as the haploid number, which represents one complete set of chromosomes.

Step 3: Calculating the Haploid Number

Since the diploid number is 78, to find the haploid number, we divide the diploid number by 2. So, the haploid number is \( \frac{78}{2} = 39 \).

Step 4: Selecting the Correct Answer

Based on the calculation, the number of chromosomes in dog gametes is 39, which corresponds to answer choice 'a'. Therefore, the correct answer is 'a. 39'.

Key Concepts

Understanding Diploid

Diploid is a term used to describe the number of chromosomes present in most animal and plant cells. These cells contain two complete sets of chromosomes, one set inherited from each parent. In dogs, the diploid chromosome number is 78. This means that their somatic cells (like skin, liver, and muscle cells) contain 78 chromosomes, organized in pairs.

The term "diploid" is denoted as 2n, where "n" represents the number of distinct chromosomes. Hence, in the case of dogs, 2n equals 78, indicating 39 pairs of chromosomes. This pairing is crucial since it ensures the proper distribution and genetic variation of chromosomes during cellular division and reproduction.

Exploring Haploid

Haploid refers to cells that contain only one complete set of unpaired chromosomes. These are typically the reproductive cells, or gametes, such as sperm and egg cells. In animals, gametes are responsible for transmitting genetic information from one generation to the next.

For instance, since dogs have a diploid number of 78 (2n = 78), their haploid number, represented as "n," is half of that. This is because, during the process of meiosis, the chromosome number becomes halved to ensure genetic diversity without doubling the chromosome count in offspring. Therefore, for dogs, the haploid number is calculated as \( \frac{78}{2} = 39 \).

• Haploid cells are crucial for sexual reproduction.
• Each gamete carries a unique chromosome set, ready to combine with another during fertilization.
• This helps maintain a stable chromosome count across generations.

Role of Gametes

Gametes play a pivotal role in sexual reproduction, representing the cells used for fertilization. In many organisms, there are two types of gametes: sperm cells from males and egg cells from females. These special cells are formed through a process called meiosis, which reduces the diploid chromosome number to a haploid number.

Gametes are unique because they carry only half of the chromosome set needed to form a new organism. This reduction is vital, ensuring that when a sperm cell meets an egg cell during fertilization, the resulting zygote will have the species-specific diploid number of chromosomes. In dogs, as established, this number is 78.

• Gametes ensure genetic diversity through their haploid nature.
• They are fundamental to passing genetic material to future generations.
• Without the careful chromosome reduction in gametes, species could experience genetic disparities.