Cellular Reproduction Chapter 16

Questions and Answers

What occurs during Prophase II of meiosis?

Chromosomes form tetrads and exchange genetic material.

Sister chromatids align at the equator.

The nucleolus disappears and chromatin condenses.

Centrioles move to opposite poles and spindle fibers start to appear. (correct)

What characterizes Anaphase II in meiosis?

Chromosomes align at the center of the cell.

Cytokinesis occurs, forming two haploid cells.

Homologous chromosomes separate and move to opposite poles.

Sister chromatids separate at the centromeres. (correct)

How many chromosomes are present at each pole after Anaphase II is complete?

46 single chromosomes.

23 homologous pairs.

23 single chromosomes. (correct)

46 paired chromosomes.

What process contributes to genetic variation during meiosis?

Independent assortment. Signup and view all the answers

What happens during Telophase II?

Chromosomes uncondense to form chromatin and the nuclear envelope reappears. Signup and view all the answers

What is the primary function of the sperm produced during spermatogenesis?

To facilitate movement Signup and view all the answers

Which statement about oogenesis is correct?

Only one ovum is produced per oocyte after meiosis. Signup and view all the answers

When does meiosis I in females typically resume after being suspended?

At puberty Signup and view all the answers

What is the result of the division of an oogonium in the female fetus?

It forms one primary oocyte and one polar body. Signup and view all the answers

Which of the following correctly describes spermatogenesis?

Occurs continuously after puberty Signup and view all the answers

What type of cells are described as having two sets of similar chromosomes?

Somatic cells Signup and view all the answers

What term describes the process through which genetic material from two parental cells is combined?

Sexual reproduction Signup and view all the answers

What is the haploid number of chromosomes in human gametes?

23 Signup and view all the answers

Which of the following is NOT a characteristic of asexual cell reproduction?

Produces genetic variation Signup and view all the answers

What happens to the chromosome number when a sperm fertilizes an egg?

It returns to the diploid number of 46 chromosomes Signup and view all the answers

What is the purpose of reducing the chromosome number in gametes during sexual reproduction?

To return to the original chromosome number after fertilization Signup and view all the answers

What is the diploid number of chromosomes in humans?

46 Signup and view all the answers

Which type of cells give rise to gametes such as eggs and sperm?

Germ cells Signup and view all the answers

What is the result of nondisjunction during cell division?

One daughter cell is missing chromosomes while the other has extra. Signup and view all the answers

What defines the male zygote in terms of sex chromosomes?

A zygote with a Y chromosome. Signup and view all the answers

What is the outcome of crossbreeding a water-melon with 8n ploidy and one with 6n ploidy?

The offspring will have ploidy of 7n and will be sterile. Signup and view all the answers

What characteristic do mules possess that makes them sterile?

They cannot undergo meiosis due to unequal chromosome pairs. Signup and view all the answers

What does the presence of the TDF gene signify in a zygote?

The zygote is likely to develop male characteristics. Signup and view all the answers

What type of chromosomal mutation occurs if an individual has three copies of a chromosome?

Trisomy. Signup and view all the answers

What causes seedless fruits to be produced?

Meiosis is manipulated to prevent gamete formation. Signup and view all the answers

Which statement correctly describes the behavior of primary oocytes?

They are inactive until they are stimulated post-puberty. Signup and view all the answers

What is the ploidy of the spores produced through meiosis?

Haploid Signup and view all the answers

What process occurs to produce sperm and egg cells in the life cycle of moss?

Mitosis Signup and view all the answers

What is the process noted as B in the development of a multicellular gametophyte from a single spore?

Mitosis Signup and view all the answers

What type of twins form when two eggs are fertilized simultaneously?

Fraternal twins Signup and view all the answers

Which type of stem cell can develop into any tissue and forms all parts of the embryo?

Totipotent Signup and view all the answers

What advantage does asexual reproduction provide to simple organisms like bacteria?

Faster population growth Signup and view all the answers

What is a common misconception about identical twins?

They come from two fertilized eggs. Signup and view all the answers

What significant applications can emerge from stem cell research?

Cloning organs to address transplant rejection Signup and view all the answers

Study Notes

Cellular Reproduction Overview

Two main cell types in the human body: somatic (body) cells and germ (gamete) cells.
Somatic cells are diploid (2n), containing two sets of chromosomes.
Germ cells are haploid (n), with a single set of chromosomes, producing gametes (eggs and sperm).

Asexual Reproduction

Asexual reproduction involves no genetic variation; new cells are genetically identical to the original cell.
Common in organisms and somatic cells for growth, repair, and replacing old cells.

Sexual Reproduction

Introduces genetic variation through the fusion of genetic material from two parental cells.
Gametes have half the chromosome number; fertilization restores the diploid number (2n).
In humans, gametes contain 23 single chromosomes, leading to a total of 46 chromosomes upon fertilization.

Chromosome Count in Organisms

Various species have distinct diploid chromosome numbers (e.g., cats 38, dogs 78, horses 64).
Human diploid number is 46 (23 pairs).

Meiosis Process

Meiosis II resembles mitosis but occurs in haploid cells.
Stages in Meiosis II:
- Prophase II: Centrioles separate and spindle fibers form.
- Metaphase II: Chromosomes align at cell center.
- Anaphase II: Sister chromatids separate, moving to opposite poles.
- Telophase II: Chromosomes uncoil, nuclear envelope reappears, followed by cytokinesis.

Genetic Variation Sources

Crossing over during Prophase I and independent assortment during Meiosis I contribute to genetic diversity.
In humans, with 23 chromosome pairs, over 8 million different gametes can be produced.

Gametogenesis

Spermatogenesis: Production of sperm in males, occurring continuously post-puberty; results in four small, motile sperm cells.
Oogenesis: Formation of mature egg cells in females, typically producing one ovum and three polar bodies; begins before birth and is arrested until puberty.

Genetic Sex Determination

A zygote's sex is determined by sex chromosomes: XX for female and XY for male.
The Y chromosome carries the Testes Determining Factor (TDF).

Nondisjunction and Chromosomal Mutations

Nondisjunction occurs when chromosomes fail to separate during cell division, leading to aneuploidy (trisomy or monosomy).
Seedless fruits are often a result of induced nondisjunction.

Ploidy Levels

Crossbreeding different ploidy plants can result in sterile offspring when the resulting hybrid has an odd ploidy number.

Asexual Reproductive Strategies

Simple organisms, fungi, and some plants often reproduce asexually, which can be advantageous for rapid population increase.

Stem Cells

Types of stem cells:
- Pluripotent: Can develop into multiple specialized cells.
- Totipotent: Can develop into all cell types in an organism, significant for research.

Potential of Stem Cell Research

Organ cloning from adult stem cells could reduce rejection issues and wait times for organ transplants.

Twins

Identical twins originate from one fertilized egg that splits, sharing identical DNA.
Fraternal twins result from two separate eggs fertilized simultaneously, leading to genetic diversity between the siblings.

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Description

Explore the fundamental concepts of cellular reproduction, focusing on the differences between somatic and germ cells. This chapter provides insights into diploid and haploid cell types and their roles in human biology. Test your knowledge on asexual and sexual reproduction processes.