Problem 1 - Campbell Biology

Question

A human cell containing 22 autosomes and a \(Y\) chromosome is (A) a sperm. (B) an egg. (C) a zygote. (D) a somatic cell of a male.

Step-by-Step Solution

Answer

The cell is a sperm (A).

Step 1: Understand the Definitions

Different types of cells in human reproduction should be identified. Sperm cells and egg cells are gametes with half the chromosome number. A zygote is a fertilized egg containing the full set of chromosomes. Somatic cells are body cells other than gametes.

Step 2: Identify the Chromosomes in the Problem

The problem specifies a human cell with 22 autosomes and a Y chromosome. Remember, humans normally have 22 pairs of autosomes and 1 pair of sex chromosomes (XX for females and XY for males).

Step 3: Determine the Type of Cell

A cell with 22 autosomes and a Y chromosome is a male gamete because it has half the number of autosomes and one sex chromosome (Y). It must be a sperm cell, as sperm cells determine sex and carry either an X or a Y chromosome.

Step 4: Cross-Check with Other Options

Eggs have 22 autosomes and an X chromosome, not a Y. A zygote would have 46 chromosomes (22 pairs of autosomes and two sex chromosomes, either XX or XY). A male somatic cell would have 46 chromosomes (22 pairs of autosomes and XY sex chromosomes).

Step 5: Select the Correct Answer

Given the characteristics, the correct answer is a sperm cell (A).

Key Concepts

sperm cell

A sperm cell is a male gamete responsible for fertilizing the female egg during reproduction. Each sperm cell carries half the genetic information needed to form a new organism.
This is known as haploid, meaning it contains 23 chromosomes, including either an X or a Y sex chromosome.
In normal cases, a man's sperm will determine the sex of the baby:

• Sperm carrying an X chromosome -> female offspring (XX)
• Sperm carrying a Y chromosome -> male offspring (XY)

Sperm cells are specially adapted to travel long distances within the female reproductive system to reach the egg.
They have a tail, called a flagellum, which propels them forward and helps in navigation.

Understanding the role and structure of sperm cells helps in grasping how genetic information is transferred from one generation to the next.

chromosomes

Chromosomes are long strands of DNA wrapped around proteins, carrying genetic information essential for the development and functioning of living organisms.
Humans have a total of 46 chromosomes in each somatic cell, organized into 23 pairs. Out of these, 22 pairs are autosomes (chromosomes that do not determine sex) and one pair is the sex chromosomes (XX for females, XY for males).

A single set of genetic information is halved in gametes (i.e., sperm and egg cells), comprising 23 individual chromosomes.
Each gamete thus contains one chromosome from each pair, ensuring that upon fertilization, the resulting zygote regains the full set of 46 chromosomes.Chromosomes are crucial because:

• They carry genes that determine inherited characteristics.
• Alterations in chromosome number or structure can lead to genetic disorders.

Understanding chromosomes provides a basis for learning how genetic traits are passed down and can explain various biological phenomena, including genetic disorders and traits.

gametes

Gametes are reproductive cells that are crucial for sexual reproduction.
There are two types of gametes: sperm cells (male gametes) and egg cells (female gametes). Each gamete has half the number of chromosomes compared to most other cells in the body.
This haploid number (23 chromosomes) ensures that when a sperm and egg combine during fertilization, the resulting zygote has a diploid number (46 chromosomes).

Key features of gametes include:

• Haploid nature: contains 23 chromosomes.
• Ability to merge: can fuse with the opposite gamete.
• Carry genetic diversity: mixtures of parental genes allow for genetic variation.

This incredible merging process not only ensures that the offspring have the full set of chromosomes but also introduces genetic diversity, which is vital for the adaptation and evolution of species.

zygote

A zygote is the first cell formed when a sperm cell fertilizes an egg cell.
This cell contains the full set of chromosomes (46), combining genetic material from both parents.
From here, the zygote undergoes multiple divisions and eventually forms all different types of cells needed to build a complete organism.

Key aspects of a zygote include:

• Diploid nature: contains 46 chromosomes.
• Genetic mixture: represents a mix of both parents’ genes.
• Initiation: marks the beginning of a new organism.

Understanding the formation and early development of a zygote provides insight into the complex process of human development and the role genetics play from the very first cell stage.

somatic cells

Somatic cells are any cells forming the body of an organism, excluding the reproductive cells or gametes.
These cells contain the full set of chromosomes (46), divided into 23 pairs.

Key features of somatic cells include:

• Diploid nature: they have two sets of chromosomes (46 in total).
• Diversity in function: different types of somatic cells perform various functions, from skin cells to muscle cells.
• Role in growth and repair: essential for the organism's development, maintenance, and tissue repair.

Different from germ cells (gametes), somatic cells undergo mitosis for growth and repair, ensuring genetic continuity across the body.
Understanding somatic cells helps in understanding the structure and functioning of the human body, as well as the process of cellular replication and differentiation.