lab 17, Mitosis and meiosis

Literally means “colored material.” This is the term for the uncoiled DNA in the nucleus when the cell is undergoing its normal activity. The chromatin coils during prophase to form the chromosomes.

• uncoiled DNA

• in nucleus

• normal cell activity

chromatin

Literally means “colored bodies.” These are the rod-shaped structures of DNA present in the cell during a cell division process, either mitosis or meiosis. They form from chromatin condensing during prophase. “Chromosome” can be used as a general term for DNA during any part of the cell cycle.

• rod shaped DNA

• condense during Prophase

chromosomes

The two identical strands of DNA that form a chromosome after DNA replication, during S-phase. The sister chromatids are held together by the centromere. The sister chromatids are separated into two different cells during mitosis and meiosis II.

• indentical strands of DNA

• form after replication

• held together by centromere

• separate during mitosis and meiosis II

• two long identical strands

chromatid

What is sister chromatid?

• held together by the centromere

• are separated into two different cells during mitosis and meiosis II.

____ cells only have one complete set of chromosomes. This is the number of chromosomes found in eggs or sperm. The ____ number of chromosomes in humans is 23.

• 1 complete set of chromosomes (23)

haploid

____ cells have two complete sets of chromosomes. Humans have a ____ number of 46 chromosomes. Occurs when a haploid egg combines with a haploid sperm. This is the normal number of chromosomes in regular body cells. 

• 2 complete sets of chromosomes (46)

Diploid

Humans have 23 pairs of ____ chromosomes. Each pair consists of a chromosome inherited from each parent. ______ chromosomes are identical in size and shape, and possess the same genes. The exception is chromosome pair #23, the sex chromosomes. Females contain two copies of the X chromosome and males contain an X and Y chromosome.

• 23 pairs of chromosomes. One of each is inherited from each parent. Each pair is the same size and shape, except for the sex chromosomes.

homologus chromosomes

The period of time between nuclear divisions is called?

interphase

The cell undegoes normal activity for the majority of its life cycle while in?

while in interphase

During interphase, the chromosomes are unwound into the form of?

chromatin

Interphase is is subdivided into three phases. What are they?

• gap 1 (G1) phase

• S (synthesis) phase

• gap 2 (G2) phase

What happens during the Gap 1 (G1) phase?

• the cell grows by creating cytoplasm and organelles. It also engages in other normal activities for that particular kind of cell, like the synthesis of particular proteins

• cell growth and normal activities, like protein synthesis

What happens during the S (synthesis) phase?

• the DNA is replicated so that each chromosome consists of two chromatids

• DNA replicaiton

What happens during the gap 2 (G2) phase?

• the cell prepares for division by continuing to grow, synthesis of organelles and proteins, and the replication of the centrioles

• cell growth, organelle and protein synthesis, centriole replication

What are the processes by which cells reproduce?

mitosis and cytokinesis

What reproduces the nucleus?

Mitosis

What subdivides the cytoplasm?

cytokinesis

Process produces two identical daughter cells with same number of chromosomes as parent cell

mitosis

The result of these two processes is the production of two identical daughter cells which contain the same number of chromosomes as the parent cell. The function of _____ and ____ is general body growth as well as the replacement of old and worn out cells, and damaged tissues.

the process of mitosis and cytokinesis

What is the purpose of the cell division, mitosis

general body growth as well as the replacement of old and worn out cells and damaged tissues

Mitosis is a continuous process subdivided into four phases, name them.

prophase, metaphase, anaphase, and telophase

• Chromosomes condense from chromatin and the nuclear membrane disappears. Centrioles produce spindle fibers

• chromatin condenses to chromosomes

• nucleus membrane disappears

• centrioles produce spindle fibers

prophase, which is a phase of mitosis

Spindle fibers attach to the centromere connecting sister chromatids. This attachment causes chromosomes to line up along the equatorial plane of the cell. 

• spindle fibers attach to centromeres

• chromosomes line up along the equatorial plane (the middle)

metaphase, which is a phase of mitosis

The spindle fibers shorten, separating the sister chromatids on each chromosome, and moving the daughter chromosomes toward opposite poles of the cells.

• spindle fibers shorten

• sister chromatids separate

• daughter chromosomes move toward opposite poles

anaphase, which is a phase of mitosis

A nuclear membrane forms around each group of daughter chromosomes, at the poles of the cell. Chromosomes begin to unwind, and assume the form of chromatin. 

• daughter chromosomes reach poles of the cell

• nuclear membrane forms around each group

• chromosomes unwind into chromatin

telophase, which is a phase of mitosis

Division of the cytoplasm is not part of mitosis, but it usually occurs at the same time. Here, the cytoplasm of the cells divide in half. Each half receives approximately half of the cytoplasm. ____ typically begins during anaphase and continues through telophase.  

• can begin during anaphase, but mainly during telophase

• produces two equal daughter cells

cytokinesis

Identify the phases of mitosis under the microscope

I will Identify the phases of mitosis under the microscope

For sexual reproduction to occur the number of chromosomes in a cell must be reduced by?

half

the process that reduces the diploid number chromosomes from 46 to the haploid number of 23 to produce the gametes, eggs and sperm.

meiosis

Meiosis consists of two cycles called?

meiosis I

meiosis II

What is the 1st step of producing gametes by reducing the number of chromosomes from diploid to haploid?

Meiosis I

What separates the homologous chromosomes into two different cells.

Meiosis I

What separates the sister chromatids of the chromosome into different cells? These cells then differentiate into haploid eggs and sperm. Fertilization of the egg by the sperm results in the restoration of the diploid number of chromosomes, and thereby maintains the normal chromosome complement of 46,

Meiosis II

Chromatin condenses to form the chromosomes. The homologous chromosomes form pairs in an event called “synapsis.”  Chromosomes can crossover during synapsis. During crossing-over, the chromatids of homologous chromosomes can exchange segments of the chromatids. The result of crossover is that sister chromatids of one chromosome are no longer genetically identical. Crossover is one of the mechanisms that generates genetic variability. The nuclear envelope disappears and the spindle apparatus forms during late ______ _

• chromatin condenses to chromosomes

• holologus chromosomes pair and crossing over occurs

• nuclear membrane disappers

• centrioles produce spindle fibers

prophase I

Spindle fibers connect to each homologous chromosome. The homologous chromosomes pair along the equatorial plane of the cell so each homolog is on the opposite side of the plane. 

• spindle fibers attach

• homologus chromosomes line up along equitorial plane

metaphase I

The spindle fibers shorten, separating the homologous chromosomes and bringing them to the poles of the cell. 

• spindle fibers shorten

• homologous chromosomes separate to poles

anaphase I

The homologous chromosomes reach the poles of the cell, and cytokinesis occurs. Nuclear membranes form around each haploid group of chromosomes. Each chromosome consists of two chromatids. The chromosomes relax into chromatin.  

• daughter chromosomes reach poles of the cell

• nuclear membrane forms around each group

• chromosomes unwind into chromatin

telophase I

What are the phases of Meiosis I

• Prophase I

• Metaphase I

• Anaphase I

• Telophase I

Is meiosis I haploid or diploid?

starts with diploid but it goes to haploid

______ consists of prophase II, metaphase II, anaphase II, and telophase II. During _____ the two sister chromatids of each chromosome are separated. The result is four haploid cells, each containing 23 different chromosomes.  

meiosis II

Is meiosis II haploid or diploid?

haploid

What is the 2nd step of producing gamates by separating the sister chromatids to form 4 truly haploid cells?

Meiosis II

What are the phases of Meiosis II

• Prophase II

• Metaphase II

• Anaphase II

• Telophase II

• Chromatin condenses to chromosomes

• nuclear membrane disappears

• centrioles produce spindle fibers

Prophase II, a phase of meiosis II

• spindle fibers attach

• chromosomes line up along the equitorial plane

metaphase II, a phase of meiosis II

• Spindle fibers shorten

• sister chromatids separate

anaphase II, a phase of meiosis II

• daughter chromosomes reach poles of the cell

• nuclear membrane forms around each group

• chromosomes unwind intro chromatin

telophase II, a phase of meiosis II

the term for gametogenesis (the formation of gametes) in males. It is the formation of sperm by the processes of meiosis and differentiation. meiosis reduces the chromosomes from their diploid to their haploid number. You begin with a diploid spermatogonium, which goes through S-phase replication to develop into the primary spermatocyte

• produced 4 equally sized haploid sperm from a single spermatogonium

Spermatogenesis

1. The primary spermatocyte undergoes meiosis I to yield,

2. The secondary spermatocytes then go through meiosis II to form the,

1. haploid secondary spermatocytes

2. four haploid spermatids

During differentiation, the spermatids acquire an enzyme head and flagellum to become

functional spermatozoa

the term for gametogenesis in females. It is the formation of a haploid secondary oocyte and two or three polar bodies by the process of meiosis. It begins with a diploid oogonia, which goes through S-phase replication to develop into a primary oocyte.

• produces a single, large, haploid oocyte

• because of production of polar bodies which are incapable of fertilization

oogenesis

The primary oocyte undergoes meiosis I to produce a, _____The polar body is produced due to uneven cytokinesis during telophase I.

The secondary oocyte receives most of the cytoplasm and cellular contents, while the polar body receives very little. The polar body may or may not go through meiosis II and will eventually disintegrate. The secondary oocyte will begin meiosis II, and if fertilization occurs, will produce a _____

1. haploid secondary oocyte and a polar body.

2. mature ovum and another polar body

How many functional spermatozoa are produced from one spermatogonium during spermatogenesis?

4

How many mature ovums are produced from one oogonia during oogenesis?

1

What is the term for the number of chromosomes found in eggs or sperm?

haploid

What are two things that occur in the G1 phase of mitosis?

cell growth

protein synthesis

In which phase of meiosis do homologous chromosomes separate, and are drawn to the opposite sides of the cell (be sure to give Roman numeral)?

Anaphase I