Biology 30 - Mitosis and Meiosis

What are the stages of the cell cycle of mitosis?

Interphase, Mitosis, and Cytokinesis.

What processes are in interphase of mitosis?

Growth phase one (G1), Synthesis (S), and Growth phase 2 (G2).

What happens in growth phase one of mitosis?

1) Cell grows.

2) Carries out metabolic functions.

What happens in synthesis of mitosis?

DNA replication (synthesis of DNA). Sister chromatids come together.

What happens in growth phase two of mitosis?

1) Cell grows.

2) prepares for mitosis.

3) Making of proteins.

What happens in mitosis?

The division of genetic material and the contents of the nucleus into two complete sets. Prophase, Metaphase, Anaphase, Telophase (cytokinesis).

What happens in cytokinesis in mitosis?

The division of the cytoplasm and the organelles into two separate cells. Occurs during telophase.

What is the definition of mitosis?

Process of cell division in somatic cells (any cell other than sperm or ovum).

What does mitosis result in ?

Conservation of diploid chromosome number.

What is a diploid cell ?

Cell containing two sets of chromosomes, one set is inherited from each parent (46 total).

What is a haploid cell?

Cell containing one set of chromosomes (23 total).

What is chromatin?

Un-coiled/ condensed chromosomes.

When are chromosomes considered chromatin?

Interphase.

What is a centromere?

Centralized region that joins the sister chromatids together.

What is a gene?

The single unit of inheritance, found at particular loci (address) on chromosome.

What is a chromatid?

Either of the two cells daughter stands of a replicated chromosome that are joined by a single centromere and separate during cell division to become individual chromosomes.

What happens in prophase of mitosis?

Chromosomes condense and become visible. Nuclear membrane disappears. Nucleolus disappears.

What happens in metaphase of mitosis?

Chromosomes line up single file at the equatorial plate.

What happens in Anaphase of mitosis?

Sister chromatids separate and move to opposite poles.

What happens in Telophase of mitosis?

Nuclear membrane reforms.

What happens in Cytokinesis of mitosis?

Division of the cytoplasm into 2 cells. Occurs during telophase.

What is cancer?

Rapid, uncontrolled growth and division of cells (by mitosis). These excessively dividing cells can invade other tissues (metastasize).

What is meiosis?

The process of cell division in sex cells (gametes); reduction division.

What happens in the production of gametes?

Chromosomes number is reduced by half. Four non-identical haploid cells are produced. 2 division events (meiosis I and meiosis II). Crossing over (prophase I) and independent assortment (metaphase I) are two events that lead to increase genetic variability.

What happens in interphase of meiosis?

The chromosomes replicate. It is similar to chromosome replication of mitosis. Two identical sister chromatid are held together by a centromere.

What happens in prophase 1?

Contents of the nucleus visible - DNA strands shorten and thicken chromatin -> chromosomes.

Centrioles separate and move to opposite poles.

Spindle fibres start to appear.

Chromosomes pair with corresponding homologue (SYNAPSIS).

Crossing over occurs.

What happens in metaphase 1?

TETRADS line up at the cell centromeres on the equator.

Spindle fibres attach to centromeres.

What happens in anaphase 1?

Homologous pairs separate and move to opposite sides of the cell (SEGREGATION).

Sister chromatids remain attached at their centromeres.

Should be 23 doubled chromosomes at each pole - chromosomes remain double stranded.

What stage does crossing over happen in?

Prophase 1.

What happens in crossing over.

During prophase 1, each pair of chromatids line up next to its homologue - pairing of homologous chromosomes forms tetrads - (4 chromatids).

What is crossing over?

Crossing over is the exchange of genetic information between segments of homologous chromosomes during meiosis - This is the source of genetic information.

What is synapsis?

Homologous chromosomes pair up side by side so the corresponding genes are lined up side by side. The homologous chromosomes will criss-cross over each other, occasionally breaking and exchanging segments.

What happens in telophase I?

Chromosomes at opposite ends of the cell.

Chromosomes do not condense to form chromatin.

Nuclear envelope occasionally reappears in some cells.

What happens in prophase II?

The cell moves directly to metaphase since there is no DNA replication and no formal organization of the nucleus.

What happens in metaphase II?

Pairs of sister chromatids line up at the center.

Spindle fibres attach to the centromeres.

What happens in anaphase II?

Chromatids separate at the centromeres and move to opposite poles of the cell.

Should be 23 single stranded chromosomes at each pole.

What happens in telophase II and cytokinesis?

Chromosomes are at opposite ends of the cell.

They condense to form chromatin.

Nuclear envelope reappears.

What is gametogenesis?

The formation of ova and sperm follow the process of meiosis.

Specialized according to their function.

What is spermatogenesis?

Process of sperm production.

Sperm are designed for movement.

Little cytoplasm, Lots of cell division, 4 small sperm produced.

What is oogenesis?

Process of egg production.

Eggs are designed to nourish the zygote.

Only one ovum is produced per oocyte. The other 3 polar bodies sacrifice their cytoplasm to produce on large egg.

What is non-disjunction?

Inappropriate meiosis.

Where chromosomes do not properly separate during anaphase I or anaphase II.

Where chromosomes do not properly separate anaphase I or anaphase II.

Results in one daughter cell with an extra chromosome (trisomy), and one lacking a chromosome (monosomy).

Has serious effects since cells with too little or too much information do not function properly.

Can be detected prenatally with CVS, amniocentesis and karyotype (when cells are in metaphase).

What are examples of non-disjunction disorders?

Down's syndrome, Turner's syndrome, Klinefelter's syndrome.

What is Down's Syndrome?

Trisomy 21. Characteristic facial features, short stature, heart defects, sexually underdeveloped, and mentally retarded. Older mothers at a higher risk of having a child with down's syndrome.

What is Turner's Syndrome?

Monosomy 23 XO. Abnormal female phenotype, sterile.

What is Klinefelter's syndrome

Trisomy 23 - XXY. Having male sex organs but testes are abnormally small.

Sterile.

Produces female sex hormones in higher concentrations resulting in breast enlargement and other feminine characteristics.

Low to normal intelligence.

What are autosomes?

1-22.

What is cloning?

The process of making identical offspring.

Used in some plants and animals for reproduction.

What is budding?

Nucleus of an organism cell divides equally but the cytoplasm divides unequally.

The new cells formed may live as individuals or as clones.

What is binary fission?

Bacteria. Equal division of the cytoplasm and nucleus of an organism resulting in two new organisms. Bacteria and other prokaryotes don't have a nucleus. A bacterial cell does not undergo mitosis, but instead it reproduces in cell division. Cells in binary fission are all genetically the same. Binary fission results in 2 daughter cells. The cell elongate and become 2 new cells.

What is sporulation?

The production of spores.

Ex. molds spores. Single, specialized cells which are released from the parent. They are enclosed in a protective case and develop when environmental conditions are favourable.

What is regeneration?

The development of an entire new organism from part of an original organism.

May also involve the restoration of lost body parts.

What is vegetative production?

Regeneration in plants. Complete new plants develop from part of the original plant.

Reproduction ability of cells decreases as?

Specialization increases.

Only spermatocytes & cancerous cells appear to have _________________________ (although mature sperm do not have an infinite life span)

No defined life span.

Why might cells die or for aging process?

Maybe spontaneous mutations cause the cells to be declared incompetent & shuts them down (no)

maybe aging genes shut the cells down (ex. graying of hair - but at different ages)

maybe cell lineages die no longer able to divide, so worn-out cells are not replaced

What is cancer?

Defined as the rapid, uncontrolled growth of cells too much life.

What is abnormal growth?

Without the signals of the body directing growth (unlike normal controlled growth - replacing dying & dead cells.

What are tumours?

Are believed to be monoclonal - the result of one transformed cell dividing rapidly.

What is metastasis?

The spreading of cancer cells through the body - caused by the fact that cancerous cells have lost the attraction to each other that other cells have.

What are cancer cells?

Lost the ability to differentiate & carry out cell processes.

What is synapsis?

Homologous chromosomes pair up, forming a tetrad in meiosis I (prophase I).

What are chromosome pairs 1-22 called?

Autosomes.

What is segregation?

Homologous pairs separate and move to opposite sides of the cell.

What is conjugation?

Bacteria. Conjugation involves the transfer of genetic material from one cell to another by cell- to - cell contact through bridging structure called a pilus. Conjugation creates cells with new genetic combinations and thereby provides a chance that some cells may be better adapted to changing conditions.

When can conjugation only take place?

Conjugation can only take place between non identical bacteria cells and only creates one daughter cell which then undergoes binary fission to create a whole bunch of cells.

What is budding?

Budding is a form of asexual reproduction in which a complete but miniature version of the parent grows out from the parent's body and then separates to become an individual organism.

What is vegetative reproduction?

Takes place in many plants. Extend themselves (creeping stem). A new plant develops at the end of each stem. Once the new plant has taken root, the stem disintegrates, separating the new plant from its parent.

What is fragmentation?

A creation of new plants from a fragment (portion) of a parent plant.

What is parthenogenesis?

In animals. Some animals can reproduce by fragmentation (starfish). An unfertilized egg develops into an adult.

What are spores?

A spore is a structure that contains genetic material and cytoplasm surrounded by a protective sheath or wall. The wall protects the contents until conditions are favourable, at which point the spore wall opens and the organisms begin to develop. Spores may be haploid or diploid.

What is a diploid generation called?

Sporophyte.

What is a sporophyte?

Diploid generation of a plant that produces haploid spores through the process of meiosis that develop without fertilization into a gametophyte.

What does each haploid spore grow into?

A plant called a gametophyte.

What is a gametophyte?

Gamete making body. Gametophytes produce male and female gametes by mitosis, which fuse at fertilization and develop into another sporophyte. The cell then repeats.

What is hermaphroditic?

Both male and female organs in an organism to reproduce.