Chromosome Transmission During Cell Division and Sexual Reproduction

Flashcards for Genetics: Analysis & Principles EIGHTH EDITION, Chapter 2: Chromosome Transmission During Cell Division and Sexual Reproduction

What is the ultimate result of mitosis?

Two equal cells with the same genetic material

What is the outcome of mitotic cell division?

Mitosis and cytokinesis ultimately produce two daughter cells having the same number and complement of chromosomes as the mother cell.

What is the main purpose of Mitosis

To replicate cells

What is the main purpose of Meiosis?

To produce gametes.

What is sexual reproduction?

A common way for eukaryotic organisms to produce offspring that leads to genomic diversity.

How does sexual reproduction occur at the chromosomal level?

Parents (diploid) make gametes with half the amount of genetic material (haploid), which fuse during fertilization.

Are gametes typically haploid or diploid?

Haploid

What do haploid chromosomes contain?

They contain a single set of chromosomes

How many chromosomes does a diploid human cell contain?

46 chromosomes

How many chromosomes does a human gamete contain?

23 chromosomes

How many cell divisions are there in meiosis?

Two successive divisions to reduce the chromosome content.

What are the stages of Meiosis?

Prophase, Prometaphase, Metaphase, Anaphase, Telophase

What happens during Prophase I of Meiosis?

Homologous chromosomes pair together in a process called synapsis to form a bivalent (or tetrad).

What is 'crossing over' and when does it occur during Meiosis I?

DNA is exchanged between homologous pairs at chiasmata in a process called crossing over.

What occurs during Prometaphase of Meiosis I?

The nuclear envelope breaks apart, and spindle fiber microtubules attach to kinetochore proteins at the centromeres.

What occurs during Metaphase of Meiosis I?

Bivalents align along the metaphase plate, allowing for independent assortment and promoting genetic diversity.

What happens during Anaphase of Meiosis I?

Pairs of sister chromatids within a bivalent separate and move to opposite poles.

What happens during Telophase of Meiosis I?

Sister chromatids reach respective poles, DNA decondenses, and the nuclear envelope reforms, forming two non-identical daughter cells.

Meiosis I is followed by what event?

Meiosis II.

What process are the steps of meiosis II similar to?

Mitosis, but starts with half the genetic content.

What is the end result of Meiosis II?

Four haploid daughter cells.

What is the key difference in the products of mitosis versus meiosis?

Mitosis produces two diploid daughter cells, while meiosis yields four haploid daughter cells.

What is the key difference in the genetic outcomes of mitosis versus meiosis?

Mitosis produces genetically identical daughter cells; meiosis produces genetically different daughter cells.

Does synapsis occur in Meiosis I ?

Yes

Does synapsis occur in Mitosis and Meiosis II ?

No

Does crossing over occur in Meiosis I ?

Commonly

Does crossing over occur in Mitosis and Meiosis II ?

Rarely

During Prometaphase, where does the attachment to the poles in Mitosis occur ?

A pair of sister chromatids to both poles.

During Prometaphase, where does the attachment to the poles in Meiosis I occur ?

A pair of sister chromatids to one pole.

What separates during anaphase in Mitosis?

Sister Chromatids

What separates during anaphase in Meiosis I?

Bivalents

What separates during anaphase in Meiosis II?

Sister Chromatids

What is the end result of Mitosis?

Two diploid cells

What is the end result of Meiosis I?

Four haploid cells

How does sexual reproduction start the life of a new diploid organism?

Parents (diploid) make gametes through gametogenesis with half the amount of genetic material (haploid) and these gametes fuse during fertilization.

What is isogamy?

Isogamous species produce gametes that are morphologically similar.

What is heterogamy?

Heterogamous species produce gametes that are morphologically different, such as sperm and egg cells.

What are the differences between sperm and egg cells?

Sperm cells are relatively small and mobile, while egg cells are large and nonmotile.

What are oogenesis and spermatogenesis?

Oogenesis is the production of egg cells, while spermatogenesis is the production of sperm.

Where does oogenesis occur in female animals?

In the ovaries

What is the first step of Oogenesis?

Diploid oogonia produce diploid primary oocytes, which initiate meiosis 1 but are arrested in prophase 1.

When are the primary oocytes activated in Oogenesis?

At puberty, primary oocytes are activated to progress through meiosis 1.

How many cells per meiosis becomes an egg?

One cell.

What does the division in meiosis 1 result in for Oogenesis?

A large secondary oocyte and a small polar body.

What happens to the secondary oocyte in Oogenesis?

The secondary oocyte is released into the oviduct at ovulation.

What happens if the secondary oocyte is fertilized?

Meiosis 2 is completed, producing a haploid egg and a second polar body.

What does asymmetric division in Oogenesis produce?

The divisions produce polar bodies that contain very little cytoplasm

Where does spermatogenesis occur in male animals?

In the testes.

How does spermatogenesis begin?

A diploid spermatogonial cell divides mitotically to produce a spermatogonial cell and a primary spermatocyte.

How does the primary spermatocyte advance in spermatogenesis?

Through meiosis 1 and meiosis 2.

What are the components of sperm?

A long flagellum and a head containing a haploid nucleus.

What is the function of the acrosome?

The acrosome contains digestive enzymes that enable the sperm to penetrate the egg's protective layers.

How many sperm do human males produce each day?

A mature human male produces several hundred million sperm per day.

What characterizes the generations for plant species?

The life cycles of plant species alternate between the haploid gametophyte and diploid sporophyte generations.

What is formed through the mitosis of spores?

Spores divide by mitosis to produce the gametophyte.

What do spores develop into in simpler plants?

Spores develop into gametophytes that have large numbers of cells.

What do spores develop into in flowering plants?

Spores develop into gametophytes that have only a few cells.

Where does meiosis occur within the sporophyte?

Anthers and ovaries.

What is the purpose of Anthers in the sporophyte?

To produce the male gametophyte.

What is the purpose of Ovaries in the sporophyte?

To produce the female gametophyte.

What occurs within the ovaries of the sporophyte?

Meiosis produces four megaspores, three of which degenerate. The remaining megaspore undergoes mitosis, yielding a seven-celled structure called the embryo sac.

What occurs within the anthers of the sporophyte?

Meiosis produces four microspores, which undergo mitosis to produce a tube cell and a generative cell. The microspore differentiates into a pollen grain.

What is double fertilization in flowering plants?

One sperm fertilizes the egg, and a second sperm unites with the central cell to produce the endosperm.

What develops from the ovule and ovary after fertilization?

The ovule develops into a seed, and the surrounding ovary develops into a fruit.

What are sex chromosomes?

Chromosomes that differ between males and females.

What is sex determination?

A process that determines the development of sexual characteristics that give rise to males and females.

What chromosomes do humans have?

Humans have 44 autosomes and 2 sex chromosomes.

What is the chromosomal makeup of males and females in mammals?

Males are XY and termed heterogametic; females are XX and termed homogametic.

What determines maleness in mammals?

The Y chromosome

What is the chromosomal makeup of insects within the X-0 System?

In some insects, males are X0 and females are XX.

What determines sex in fruit flies?

The ratio between the X chromosomes and the number of sets of autosomes (X/A).

What is the chromosomal makeup of males and females in birds and some fish?

Males are ZZ and homogametic; females are ZW and heterogametic.

What is the chromosomal makeup of males and females in bees?

Males are haploid and produced from unfertilized eggs; females are diploid and produced from fertilized eggs.

What determines sex in some reptiles, fish, and clownfish?

Environmental temperatures and behavior.

How is gender determined in alligators?

In alligators, environmental temperatures determine sex.

How is gender determined in clownfish?

Clownfish are protandrous hermaphrodites, where males can change into females due to behavioral changes.

What does it mean for plant species to be dioecious?

Producing only either male or female gametophytes.

What factors determine sex?

Chromosomes, genes, temperature, and social conditions.

How many cells are produced at the end of Mitosis?

Two diploid cells

How many cells are produced at the end of Meiosis II?

Four haploid cells

Where do bivalents align during Metaphase I?

Metaphase plate

During which phase of Meiosis I does DNA decondense back into chromatin?

Telophase I

What is released into the oviduct during ovulation?

Secondary Oocyte

What creates the diploid nucleus of a new individual?

A haploid egg and sperm nuclei fuse to create the diploid nucleus of a new individual

How do parents make gametes?

Through the process of gametogenesis

What happens to the new gametes to produce a new diploid organism?

Gametes fuse with each other during fertilization to begin the life of a new diploid organism

What do isogamous species produce as gametes?

Morphologically similar

What do heterogamous species produce as gametes?

They are morphologically different, such as sperm and egg cells

What is oogenesis?

Production of egg cells

What is spermatogenesis?

Production of sperm

What do asymmetric divisions in oogenesis produce?

Polar bodies that contain very little cytoplasm

What does the Acrosome contain in Spermatogenesis?

The acrosome contains digestive enzymes that enable the sperm to penetrate the protective layers of the egg.

What are some Dioecious Plant Species?

Hollies, willows and ginkgo trees

What are life cycles of plant species characterized by?

Alternating between the haploid gametophyte and diploid sporophyte generations.

How are spores formed in plant life cycles?

Spores divide by mitosis to produce the gametophyte.

What controls the sex of some reptiles and fish?

Environmental temperature.

What controls the sex of some clownfish?

Behavior.

Where does Oogenesis occur in female animals?

In the ovaries.

When are primary oocytes activated to progress through meiosis 1?

At Puberty

What are the resulting products of meiosis 1 in oogenesis?

A large secondary oocyte and a small polar body