Meiosis and Sexual Life Cycles Quiz

Questions and Answers

What is meiosis?

The cell division process that gives rise to gametes.

What types of cells undergo meiosis?

Only those that produce gametes, e.g., eggs in females and sperm in males.

What type of reproduction results in two daughter cells that are identical to the parent cell?

Asexual or mitosis.

What type of reproduction takes half genetic material from each parent?

Sexual or meiosis. Signup and view all the answers

How can genetic variation arise in cells that reproduce asexually?

DNA mutations. Signup and view all the answers

How many chromosomes are in a normal somatic cell?

<ol start="46"> <li></li> </ol> Signup and view all the answers

How many chromosomes are in a typical gamete?

<ol start="23"> <li></li> </ol> Signup and view all the answers

How many sex chromosomes does a haploid cell contain?

<ol> <li></li> </ol> Signup and view all the answers

How many autosomes are in a haploid cell?

<ol start="22"> <li></li> </ol> Signup and view all the answers

When are karyotypes always done?

In metaphase of mitosis. Signup and view all the answers

What sex chromosomes exist in males?

X and Y. Signup and view all the answers

What sex chromosomes exist in females?

Two X chromosomes. Signup and view all the answers

How are genes passed down from generation to generation?

They are passed via gametes. Signup and view all the answers

Homologous chromosomes carry the same genes at similar loci, but what can vary?

Alleles, except for the X and Y chromosomes. Signup and view all the answers

In meiosis, when are the chromosomes replicated?

During the S phase. Signup and view all the answers

What is the result of meiosis?

Four daughter cells, each with only half the chromosomes as the parent cell. Signup and view all the answers

What phase typically occupies 90% of the time required for meiosis?

Prophase I. Signup and view all the answers

What happens in synapsis?

Homologous chromosomes loosely pair up, aligned gene by gene. Signup and view all the answers

What occurs in crossing-over?

Non-sister chromatids exchange DNA segments. Signup and view all the answers

A group of four chromatids is called what?

A tetrad. Signup and view all the answers

What is a chiasmata?

The x-shaped region where crossing-over of chromosomes occurred. Signup and view all the answers

What occurs in metaphase I?

Tetrads line up at the metaphase plate, with one chromosome facing each pole. Signup and view all the answers

What occurs in anaphase I?

Pairs of homologous chromosomes separate. Signup and view all the answers

What occurs during telophase I and cytokinesis?

The cell begins to form two daughter cells, each with a haploid set of chromosomes. Signup and view all the answers

What occurs in prophase II?

A spindle apparatus forms. Signup and view all the answers

What occurs in metaphase II?

The sister chromatids are arranged at the metaphase plate. Signup and view all the answers

What occurs in anaphase II?

The sister chromatids separate and move toward opposite poles. Signup and view all the answers

What occurs in telophase II?

The chromosomes arrive at opposite poles, nuclei form, and chromosomes begin decondensing. Signup and view all the answers

What occurs in meiosis that makes it different from mitosis?

Synapsis and crossing over in prophase I. Signup and view all the answers

What allows sister chromatids to stay together through meiosis I?

Sister chromatid cohesion. Signup and view all the answers

What is responsible for sister chromatid cohesion?

Protein complexes called cohesins. Signup and view all the answers

When are cohesins cleaved in mitosis?

At the end of metaphase. Signup and view all the answers

When are cohesins cleaved in meiosis?

Along the chromosome arms in anaphase I, and at the centromeres in anaphase II. Signup and view all the answers

What is the original source of genetic diversity?

Mutations, or changes in an organism's DNA. Signup and view all the answers

What results from mutations?

Different versions of genes, also called alleles. Signup and view all the answers

What produces genetic variation during sexual reproduction?

The reshuffling of alleles. Signup and view all the answers

What are the three mechanisms that contribute to genetic variation?

Independent assortment, crossing over, and random fertilization. Signup and view all the answers

What happens in independent assortment?

Homologous pairs of chromosomes orient randomly at metaphase I. Signup and view all the answers

For humans, there are over ____ possible chromosome combinations.

8 million. Signup and view all the answers

What happens in crossing-over?

Homologous portions of two non-sister chromatids switch places. Signup and view all the answers

What happens in random fertilization?

The fusion of two gametes produces a zygote with over 70 trillion possible diploid combinations. Signup and view all the answers

How does random fertilization contribute to genetic variation?

Any male gamete can fuse with any female gamete. Signup and view all the answers

Why is it important to have genetic variation in a population?

There needs to be many different options for natural selection to 'choose' as being the most fit. Signup and view all the answers

Study Notes

Meiosis Overview

Meiosis is the cell division process essential for producing gametes (egg and sperm).
In meiosis, genetic material is halved, unlike asexual reproduction (mitosis) where daughter cells are identical to the parent.

Chromosome Counts

Normal somatic cells contain 46 chromosomes; typical gametes have 23.
In haploid cells, there is one sex chromosome (X or Y) and 22 autosomes.

Genetic Transmission

Genes are inherited through gametes, carrying alleles that can vary between homologous chromosomes.
Exception: X and Y chromosomes differ in genetic content.

Meiosis Stages

Chromosome replication occurs during the S phase before meiosis.
Meiosis results in four daughter cells, each with half the chromosomes of the parent.

Meiosis I Key Phases

Prophase I occupies 90% of meiosis duration and involves synapsis, where homologous chromosomes pair gene by gene.
Crossing-over occurs in prophase I, allowing non-sister chromatids to exchange DNA segments, enhancing genetic diversity.
Metaphase I sees tetrads aligning at the metaphase plate, each chromosome connected to spindle fibers from opposing poles.
Anaphase I involves separation of homologous chromosomes, with sister chromatids remaining attached.
Telophase I and cytokinesis result in two haploid cells, each with chromosomes made of two sister chromatids.

Meiosis II Overview

Prophase II involves the formation of the spindle apparatus and movement of chromosomes toward the metaphase plate.
In metaphase II, sister chromatids, now genetically unique, align at the plate.
Anaphase II sees sister chromatids separating and moving toward opposite poles.
Telophase II results in nuclei formation and chromosomal decondensation.

Differences from Mitosis

Meiosis includes unique events like synapsis and crossing-over in prophase I.
Tetrads form in meiosis I, contrasting with individual chromosomes in mitosis.
Homologous chromosomes separate in anaphase I, while sister chromatids separate in mitosis.

Genetic Diversity Mechanisms

Genetic variation arises from mutations, which create different alleles.
Three main processes contributing to variation in sexual reproduction are independent assortment, crossing-over, and random fertilization.
Independent assortment allows for random orientation of homologous pairs at metaphase I, generating over 8 million combinations in humans.

Importance of Genetic Variation

Random fertilization can lead to more than 70 trillion unique diploid combinations by fusing any male and female gametes.
Genetic diversity is crucial for evolution, allowing natural selection to operate on various traits within a population.

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Description

Test your knowledge on meiosis and the fundamental processes of sexual life cycles. This quiz includes definitions and concepts related to gametes and cell division. Perfect for biology students looking to review essential topics in reproduction.