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Chapter 11: Problem 25

One of the ways that sexual reproduction enhances the diversity of offspring from the same parents is through a process called crossing over. What entities does this occur between during prophase I? a. sister chromatids b. tetrads c. non-homologous chromosomes d. non-sister chromatids of homologous chromosomes

Short Answer

Expert verified
d. non-sister chromatids of homologous chromosomes

Step by step solution

01

Understand the Question

The question asks about the entities involved in crossing over during prophase I of meiosis, a process that enhances genetic diversity.
02

Review Cross Over

Crossing over is the exchange of genetic material between two homologous chromosomes that occurs during prophase I of meiosis.
03

Define Key Terms

Understand the options provided: sister chromatids (identical copies of a single chromosome), tetrads (paired homologous chromosomes), non-homologous chromosomes (chromosomes that do not pair during meiosis), non-sister chromatids of homologous chromosomes (chromatids from different homologous chromosomes).
04

Determine Correct Entity

Crossing over occurs between non-sister chromatids of homologous chromosomes, as this type of exchange diversifies the genetic material passed to offspring.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Prophase I
Prophase I is the first stage of meiosis I wherein homologous chromosomes pair up and exchange genetic material through a process called crossing over. During this stage, the chromosomes condense, becoming visible under a microscope.
The nuclear envelope disintegrates, and spindle fibers begin to form.
This stage is essential for ensuring genetic diversity in the resulting gametes.
Notably, the chromosomes align closely, forming structures called tetrads.
At this point, crossing over occurs between non-sister chromatids of homologous chromosomes.
Non-sister Chromatids
Non-sister chromatids are chromatids from different homologous chromosomes. Each chromosome in a homologous pair consists of two chromatids after DNA replication.
During prophase I, these chromatids can exchange segments of genetic material in a process called crossing over.
This swapping of segments is what increases genetic diversity.
Unlike sister chromatids, which are identical copies, non-sister chromatids may carry different genetic information.
Genetic Diversity
Genetic diversity refers to the variety of genetic characteristics found within a population. Crossing over during prophase I of meiosis significantly contributes to this diversity.
By exchanging segments of DNA between non-sister chromatids, new combinations of genes are created.
This leads to offspring with unique genetic makeup, even from the same parents.
Genetic diversity is crucial for the adaptation and survival of species over time.
Homologous Chromosomes
Homologous chromosomes are pairs of chromosomes that have the same size, shape, and carry genes controlling the same traits. One chromosome of each pair is inherited from each parent.
During prophase I of meiosis, homologous chromosomes pair up closely in structures known as tetrads.
These homologous chromosomes align in such a way that their non-sister chromatids are close enough to exchange genetic material through crossing over.
This pairing and subsequent crossing over ensures variation and is key to the genetic differences seen in gametes.
Meiosis
Meiosis is a special type of cell division that reduces the chromosome number by half, resulting in four haploid cells from one diploid cell. This process is essential for sexual reproduction.
Meiosis consists of two main stages: meiosis I and meiosis II.
Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I.
Prophase I is particularly important because this is where crossing over between non-sister chromatids occurs.
Meiosis II resembles a typical mitotic division, separating the chromatids into different cells.
The final result is four genetically unique haploid cells, each contributing to genetic diversity in reproduction.

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Most popular questions from this chapter

What is a disadvantage of sexual reproduction over asexual forms of reproduction? a. Half the population is capable of carrying offspring. b. Identical offspring are not produced. c. Adaptation to rapidly changing environments is more difficult. d. Mutation rates are slower.

Though the stages of meiosis have the same names as the stages of mitosis, they exhibit fundamental differences. What are the main differences between the two processes? a. Meiosis differs from mitosis in that the number of chromosomes is halved and genetic variation is introduced in meiosis, but not in mitosis. b. Meiosis differs from mitosis in that the number of chromosomes is halved and genetic variation is reduced in meiosis, but not in mitosis. c. Metaphase and telophase portions of meiosis and mitosis are the same. Meiosis and mitosis are also the same, except for the number of chromosomes. Anaphase I and anaphase are different. d. Prophase and telophase portions of meiosis and mitosis are the same. Meiosis II and mitosis are also the same and have the same number of chromosomes. Anaphase I and anaphase are different.

Reproductive cells in most species are different from the cells that make up the rest of the organism. What are the 鈥渂ody鈥� cells called and how are they different from the reproductive cells? a. Body cells are called gametes and they have half the number of chromosomes found in reproductive cells. b. Body cells are called somatic cells and have the same number of chromosomes as reproductive cells. c. Body cells are called somatic cells and have double the number of chromosomes found in reproductive cells. d. Body cells are called gametes and have double the number of chromosomes found in reproductive cells.

During which phase does the second round of genetic variation occur during meiosis? a. anaphase I b. metaphase I c. prophase II d. Genetic variation only occurs during prophase I.

Explain how the orientation of homologous chromosomes during metaphase I of meiosis contributes to greater variation in gametes. a. The random alignment of homologous chromosomes at the metaphase plate ensures the random destination of the chromosomes in the daughter cells. b. Because homologous chromosomes dissociate from the spindle fibers during metaphase I, they move randomly to the daughter cells. c. The homologous chromosomes are paired tightly during metaphase I and undergo crossover as the synaptonemal complex forms a lattice around them. d. Recombination of maternal and paternal chromosomes occurs in metaphase I because the homologous chromosomes are not connected at their centromeres.
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