Chapter 14.3 Meiosis and Sexual Reproduction

The Simple 3 Steps of Meiosis:

1.) Chromosomes replicate during S phase and then condense at the start of meiosis 2.) Homologous chromosomes separate 3.) Sister chromatids separate

When are each pair of sister chromatids (within a bivalent) attached to a single pole?

During meiosis 1

When are pairs of sister chromatids attached to both poles?

During prometaphase of mitosis and Meiosis 2

During __________, chromosomes condense and the nuclear envelope breaks down, if needed.

During prophase II, chromosomes condense and the nuclear envelope breaks down, if needed.

What is an example of a diploid?

For example a diploid human cell contains 46 chromosomes

What is an example of a haploid?

For example, a human gamete-sperm or egg cell- contains only 23 chromosomes

For human gametes to be produced, what must chromosomes do?

For gamete cells to be produced: 1.) Each gamete must receive 1 chromosome from each of the 23 pairs 2.) 2 rounds of division are necessary

What is a bivalent?

Homologous pairs of sister chromatids associated with each other, lying side by side

Like mitosis, meiosis has each continuous process of stages called...

Like mitosis, meiosis has each continuous process of stages called: 1.) Prophase 2.) Prometaphase 3.) Metaphase 4.) Anaphase 5.) Telophase

___________ is the process by which haploid cells are produced from a cell that was originally diploid.

Meiosis is the process by which haploid cells are produced from a cell that was originally diploid.

Meiosis 1 is followed by cytokinesis and then ________.

Meiosis 1 is followed by cytokinesis and then meiosis 2.

What process is known has "mitosis for haploid cells"?

Meiosis II is known as "mitosis for haploid cells."

What produces haploid spores?

Meiosis in certain cells within the sporophyte

The alignment of bivalents occurs during when?

Metaphase 1

Most species of animals are diploid (2n), and their haploid gametes (1n) are considered to be specialized type of cell. For this reason, as...

Most species of animals are diploid (2n), and their haploid gametes (1n) are considered to be specialized type of cell. For this reason, as Diploid-dominant species

Does meiosis always produce 4 gametes?

Nope. In some cases, meiosis does produce four functional gametes: for instance, meiosis during spermatogenesis, or sperm production, in human males yields four sperm cells. At the end of meiosis I, only one of the two daughter cells continues down the egg cell pathway, while the other becomes a non-egg cell called a polar body. The polar bodies are not normally fertilized by sperm cells, and they typically undergo programmed cell death, or apoptosis, within 24 hours of being produced

Telophase 1: Do all organisms have their nuclear membrane's reformed and chromosomes decondensed?

Not all organisms In some organisms, the nuclear membrane re-forms and the chromosomes decondense, although in others, this step is skipped—since cells will soon go through another round of division, meiosis 2

Plants and fungi produce ___________ _____ by _________.

Plants and fungi produce reproductive cells by mitosis

What happens in Metaphase 1?

1.) Bivalents randomly align along the metaphase plate 2.) Each pair of sister chromatids is attached to one pole

What happens in Telophase 2 and Cytokinesis?

1.) Chromosomes decondense, and the nuclear envelope re-forms 2.) Cleavage Furrows separate the 2 cells into 4 cells

What happens in Prophase 1?

1.) Homologous chromosomes bind to each other to form bivalents, and crossing over occurs. 2.) Chromosomes condense, and the nuclear envelope begins to dissociate into vesicles

What happens in Anaphase 1?

1.) Homologous chromosomes separate and move toward opposite poles as kinetic microtubules shorten 2.) Polar microtubules lengthen and push the poles apart

What happens in Metaphase 2?

1.) Sister chromatids align along the metaphase plate 2.) Each pair of sister chromatids is attached to both poles

What happens in Prophase 2?

1.) Sister chromatids condense, and the spindle starts to form 2.) The nuclear envelope begins to dissociate into vesicles

What happens in Anaphase 2?

1.) Sister chromatids separate, and individual chromosomes move toward the poles as kinetochore microtubules shorten 2.) Polar microtubules lengthen and push the poles apart

What happens in Telophase 1 and Cytokinesis?

1.) The chromosomes decondense, and the nuclear envelope reforms 2.) The 2 daughter cells are separated by a cleavage furrow

What happens in Prometaphase 2?

1.) The nuclear envelope completely dissociates into vesicles 2.) Sister chromatids attach to the spindle via kinetochore microtubules

What is a zygote?

A diploid formed by the fusion of 2 gametes

Prophase 1: What happens after synapsis?

A process in which segments of chromosomes are exchanged with each other, at a Crossover Site

Alternation of generations are the species between diploid multicellular organisms called _________ and happily multicellular organisms called _________

Alternation of generations are the species between diploid multicellular organisms called sporophyte and happily multicellular organisms called gametophytes

Animals produce _________ by _______.

Animals produce gametes by meiosis.

Meiosis 1: During Prophase 1, what is the difference between mitosis and meiosis 1?

As in mitosis, the chromosomes begin to condense, but in meiosis I, they also pair up

____________ _______________, which produces offspring genetically identical to the parent

Asexual Reproduction, which produces offspring genetically identical to the parent

At _________, the bivalents are organized along the metaphase plate.

At Metaphase 1, the bivalents are organized along the metaphase plate.

At ____________, the sister chromatids have reached their respective poles and then decondense

At Telophase 1, the sister chromatids have reached their respective poles and then decondense

What is the difference between sister chromatids during anaphase in meiosis, mitosis, and meiosis 2?

At anaphase of meiosis 1, the homologous chromosomes separate, but the sister chromatids remain together Sister chromatid separation occurs during anaphase of mitosis and meiosis 2

Mitosis, Meiosis 1, or Meiosis 2: Bivalents align along the metaphase plate during...

Bivalents align along the metaphase plate during Meiosis 1

What is the difference between metaphase in Meiosis 1, Mitosis, and Meiosis 2?

Bivalents align along the metaphase plate during metaphase of meiosis 1, whereas sister chromatids align along the metaphase plate during metaphase of mitosis and meiosis 2

Meiosis 1: What is separated during Anaphase 1?

Bivalents are separated during Anaphase 1

What structures keep the homologues connected to each other after the synaptonemal complex breaks down?

Chiasmata: cross-shaped structures where homologues are linked together

Mitosis, Meiosis 1, or Meiosis 2: Crossing over during prophase happens commonly in...

Crossing over during prophase happens commonly in Meiosis 1

Mitosis, Meiosis 1, or Meiosis 2: Crossing over during prophase happens rarely in...

Crossing over during prophase happens rarely in Mitosis and Meiosis 2

Prophase 1: What is the importance of crossing over?

Crossing over increases the genetic variation of sexually reproducing species

Crossing over is helped along by a protein structure called the ___________ ________ that holds the homologues together.

Crossing over is helped along by a protein structure called the synaptonemal complex that holds the homologues together.

Meiosis 1: What phase does crossing over occur?

Crossing over occurs in Prophase 1

_________ splits the chromosome sets into new cells, forming the final products of meiosis

Cytokinesis splits the chromosome sets into new cells, forming the final products of meiosis

__________ usually occurs at the same time as telophase I, forming two haploid daughter cells.

Cytokinesis usually occurs at the same time as telophase I, forming two haploid daughter cells.

Mitosis, Meiosis 1, or Meiosis 2: DNA does not occur between...

DNA does not occur between meiosis 1 and 2

Mitosis, Meiosis 1, or Meiosis 2: DNA replication occurs prior to...

DNA replication occurs prior to Mitosis and Meiosis 1

DNA replication occurs prior to mitosis and Meiosis 1 but...

DNA replication occurs prior to mitosis and Meiosis 1 but not between meiosis 1 and 2

What cell contains 2 homologous sets of chromosomes?

Diploid

During ___________, the nuclear envelope is completely broken down into vesicles, and the spindle apparatus is entirely formed

During Prometaphase 1, the nuclear envelope is completely broken down into vesicles, and the spindle apparatus is entirely formed

During __________, the nuclear envelope starts to fragment into small vesicles

During Prophase 1, the nuclear envelope starts to fragment into small vesicles

How is a diploid multicellular organism produced?

During fertilization, sperm and egg unite to form a diploid zygote, which undergoes repeated mitotic cell division

What explains why crossing over occurs commonly during meiosis but early during mitosis?

During prophase of meiosis 1, the homologs bind to each other to form bivalents

How are spores produced in Haploid-Dominant Species?

During sexual reproduction, haploid cells unite to form a diploid zygote, which then immediately proceeds through meiosis to produce 4 haploid cells called spores

Prophase 1: Each chromosome carefully aligns with its __________ __________ so that the two match up at corresponding positions along their full length.

Each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length.

Anaphase 1: Each joined pair of chromatids migrates to one pole, and the homologous pair of chromatids moves to the opposite pole, both pulled by __________ __________.

Each joined pair of chromatids migrates to one pole, and the homologous pair of chromatids moves to the opposite pole, both pulled by Kinetochore Microtubules.

How do haploids become a multicellular organism?

Each spore goes through mitotic cellular division to produce a haploid multicellular organism

True or False DNA replication occurs between Meiosis 1 + Meiosis 2

False DNA replication does not occur between meiosis 1 and meiosis 2

True or False Meiosis 1 is a shorter and simpler process than meiosis 2

False Meiosis 2 is a shorter and simpler process than meiosis 1

What is the main purpose of mitosis in animals?

Following fertilization, the purpose of mitosis is to produce a multicellular organism

For haploid cells to be produced, what must chromosomes do?

For haploid cells to be produced: 1.) chromosomes must be correctly sorted 2.) chromosomes must be correctly distributed in a way that reduces the chromosome number to half its original diploid value

What cell contains 1 single set of chromosomes or half of the complete set of chromosomes?

Haploid

What produces the gametophyte?

Haploid spores, which divide by mitosis

Mitosis, Meiosis 1, or Meiosis 2: Homologous chromosomes separate during anaphase and a pair of sister chromatids move to each pole in...

Homologous chromosomes separate during anaphase and a pair of sister chromatids move to each pole in Meiosis 1

Homologue pairs separate during a first round of cell division, called _________

Homologue pairs separate during a first round of cell division, called meiosis I.

Prometaphase 1: What is the key difference between mitosis and meiosis 1?

In Mitosis: a pair of sister chromatids is attached to both poles via kinetochore microtubules In Meiosis 1: a pair of sister chromatids is attached to just one pole

In __________ ___________, sex cells (gametes) from two parents combine in the process of fertilization, leading to the formation of a new, genetically distinct individual.

In Sexual Reproduction, sex cells (gametes) from two parents combine in the process of fertilization, leading to the formation of a new, genetically distinct individual.

In _________, the homologues are pulled apart and move apart to opposite ends of the cell.

In anaphase I, the homologues are pulled apart and move apart to opposite ends of the cell.

In ________, the sister chromatids separate and are pulled towards opposite poles of the cell.

In anaphase II, the sister chromatids separate and are pulled towards opposite poles of the cell.

In humans, the products of meiosis are...

In humans, the products of meiosis are sperm or egg cells

In __________, the chromosomes line up individually along the metaphase plate.

In metaphase II, the chromosomes line up individually along the metaphase plate.

What is a gametophyte?

In plants and many multicellular protists, that haploid stage that produces by mitosis

When did the centrosomes duplicate?

In some organisms, the centrosomes duplicate between meiosis I and II, even though DNA is not copied during this period. For instance, the centrosomes duplicate between meiosis I and II during spermatogenesis, sperm production, in humans. In other organisms, however, the centrosomes do not duplicate at all between meiosis I and II. Instead, the two centrioles that make up a single centrosome separate, and each acts as a separate spindle pole during meiosis II. This pattern of centriole separation is seen in insect spermatogenesis

In ____________, the chromosomes arrive at opposite poles of the cell.

In telophase I, the chromosomes arrive at opposite poles of the cell.

In _________, nuclear membranes form around each set of chromosomes, and the chromosomes decondense

In telophase II, nuclear membranes form around each set of chromosomes, and the chromosomes decondense

What is a synapsis?

The process of forming a bivalent

______ _________, a process in which 2 haploid gametes unite to form a diploid cell called a _______.

Sexual Reproduction, a process in which 2 haploid gametes unite to form a diploid cell called a Zygote.

Mitosis, Meiosis 1, or Meiosis 2: Sister chromatids align along the metaphase plate during...

Sister chromatids align along the metaphase plate during Mitosis and Meiosis 2

Meiosis 2: What is separated during Anaphase 2?

Sister chromatids are separated during Anaphase 2

Sister chromatids separate during a second round, called __________.

Sister chromatids separate during a second round, called meiosis II.

Mitosis, Meiosis 1, or Meiosis 2: Sister chromatids separate during anaphase, and a single chromatid, now called a chromosome, moves to each pole in....

Sister chromatids separate during anaphase, and a single chromatid, now called a chromosome, moves to each pole in Mitosis and Meiosis 2

After crossing over, the spindle begins to capture chromosomes and move them towards the center of the cell (metaphase plate). What is the difference between Metaphase 1 and Mitosis?

So, during metaphase I, homologue pairs—not individual chromosomes—line up at the metaphase plate for separation.

What are diploid-dominant species?

Species in which the diploid organism is the prevalent organism in the life cycle. Animals are an example

What are haploid-dominant species?

Species in which the haploid organism is the prevalent organism in the life cycle. example include fungi and some protists

What generation produces haploid spores by the process of meiosis?

Sporophyte

Mitosis, Meiosis 1, or Meiosis 2: Synapsis does occur during prophase in...

Synapsis does occur during prophase in Meiosis and bivalents are formed

Mitosis, Meiosis 1, or Meiosis 2: Synapsis doesn't occur during prophase in...

Synapsis doesn't occur during prophase in Mitosis and Meiosis 2

What protein structure helps the crossing over of homologous chromosomes by holding the homologues together?

The Synaptonemal Complex

Mitosis, Meiosis 1, or Meiosis 2: The attachment of sister chromatid pairs to kinetochore microtubules on one pole during prometaphase occurs during...

The attachment of sister chromatid pairs to kinetochore microtubules on one pole during prometaphase occurs during Meiosis 1

Mitosis, Meiosis 1, or Meiosis 2: The attachment of sister chromatid pairs to kinetochore microtubules on both poles during prometaphase occurs during...

The attachment of sister chromatid pairs to kinetochore microtubules to both poles during prometaphase occurs during Mitosis and Meiosis 2

The cells that enter meiosis II are the ones made in _________.

The cells that enter meiosis II are the ones made in meiosis I.

Anaphase 1: What happens to the connections between bivalents and sister chromatids?

The connections between bivalents break, but not the connections that hold sister chromatids together

What is a sporophyte?

The diploid generation of plants or multicellular protists that have a sporic life cycle

How does Telophase 1 contain "reduction division"?

The end result of meiosis 1, we see that two nuclei are produced, each with half the number of sister chromatids as the starting cell in Prophase

Mitosis, Meiosis 1, or Meiosis 2: The end result when the mother cell is diploid creates four daughter cells that are haploid occurs in...

The end result when the mother cell is diploid creates four daughter cells that are haploid occurs in Meiosis 2

Mitosis, Meiosis 1, or Meiosis 2: The end result when the mother cell is diploid creates two daughter cells that are diploids occurs in...

The end result when the mother cell is diploid creates two daughter cells that are diploids occurs in Mitosis

What is meiosis 1?

The first division of meiosis in which the homologs are separated into different cells

The gametophyte of plants is a __________ multicellular organism that is created by _____________ cellular divisions of a ________ _______

The gametophyte of plants is a haploid multicellular organism that is created by mitotic cellular divisions of a haploid spore

What happens in Prometaphase 1?

The nuclear envelope completely dissociates into vesicles, and bivalents become attached to kinetochore microtubules

What are the products of telophase 1?

The nuclear envelope now reforms to produce two separate nuclei

Relative to the original cell, what is the end result, the products, of meiosis?

The original cell is diploid with two sets of chromosomes, whereas the four resulting are haploid with one set of chromosomes

What is the alternation of generations?

The phenomenon that occurs in plants and come protists in which the life cycle alternates between multicellular diploid organisms, called sporophytes, and multicellular haploid organisms, called gametophytes

What is d?

The process by which haploid cells are produced from a cell that was originally diploid

The process of forming a bivalent is termed _______.

The process of forming a bivalent is termed synapsis.

What is the main purpose of meiosis in animals?

The purpose of meiosis in animals is to produce gametes. these gametes combine during fertilization to produce a diploid organism

What is Meiosis 2?

The second division of meiosis in which sister chromatids are separated into different cells

The segregation homologs occur during __________

The segregation homologs occur during Anaphase 1

Metaphase 1: Why is the pattern of alignment strikingly different from that observed during mitosis?

The sister chromatids are aligned in a double row rather than a single row (as in mitosis)

Anaphase 1: What happens to the sister chromatids of each chromosome when the homologues are pulled apart and moved to opposite ends?

The sister chromatids of each chromosome, however, remain attached to one another and don't come apart.

What is the difference between Meiosis 2 and Mitosis in their sorting events?

The sorting events of Meiosis 2 and Mitosis are similar, but the starting point is different

The sorting that occurs during _______ separates homologous chromosomes from each other

The sorting that occurs during meiosis 1 separates homologous chromosomes from each other

What are the products from Meiosis 1 moving into Meiosis 2 as their reactants?

These cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids.

This process, in which homologous chromosomes trade parts, is called _________ ________

This process, in which homologous chromosomes trade parts, is called Crossing Over

True or False The steps that occur during prophase, prometaphase, metaphase, anaphase, and telophase of meiosis 2 are analogous (similar) to those in a mitotic division

True The steps of meiosis 2 are analogous (similar) to those in a mitotic division

When a cell begins meiosis, how many chromosomes are found?

When a cell begins meiosis, it has chromosomes that are found in homologous pairs

When meiosis is completed, what are the reactants and products?

When meiosis is completed, a single diploid cell with homologous pairs of chromosomes has produced 4 haploid cells

Metaphase 1 What allows for the formation of gametes with different sets of homologues?

When the homologous pairs line up at the metaphase plate, the orientation of each pair is random.

A type of organism that exhibits alternation of generations is what?

a plant

What is sexual reproduction?

a process that requires a fertilization event in which two gametes unite to produce a cell called a zygote

In meisois 1, crossing over occurs during when?

prophase