Chapter 12 Biology 3201 - End of Term 1st Term Assessment - Review

Cell Cycle

Cell Cycle

The life cycle of a cell. Is defined as the sequence of events from one cell division to the next.

Somatic Cell

Are body cells, they divide through Mitosis, are diploids (2n), have 46 chromosomes and 23 pairs of chromosomes.

Gamete Cell

Are sex cells, they divide through Meiosis, are Haploids (n), have 23 individual chromosomes.

Parent Cell

Genetic material is replicated and passed from the original cell.

Daughter Cell

When a parent cell divides and creates a new cell.

Chromosomes

Made of a long strand of condensed DNA and are held within the cell's nucleus.

Chromatin

DNA that exists in the cell in its non-condensed form.

DNA (Deoxyribonucleic Acid)

The molecule that carries genetic information for the development and functioning of an organism.

Diploid (2n)

Full chromosome number.

Haploid (n)

Half a chromosome number.

Autosomes

Chromosomes that do not determine the sex.

Sex Chromosomes

A chromosome that determines the sex.

G1 Phase

One of the three main phases in interphase where rapid growth and metabolic activity happen.

S Phase

One of the three main phases in interphase where DNA synthesis and replication occurs.

G2 Phase

One of the three main phases in interphase where the cell prepares for division.

Mitosis

Division of genetic material and the cell’s nucleus. There are 4 main stages to this process: Prophase, Metaphase, Anaphase, and Telophase.

Cytokinesis

Is the final stage of cell division. It is the division of cytoplasm which completes the creation of two daughter cells (two daughter cells begin their cell cycle).

Interphase

The longest part of the cell cycle. This is when the cell grows and copies its DNA before moving into mitosis. There are three phases within it: G1, S, and the G2 Phase.

Prophase

Chromatin condenses to form visible chromosomes. Nuclear membrane breaks down. Centrioles move to opposite poles of the cell and begin to form spindle fibers.

Metaphase

Chromosomes line up at the equator of the cell. Spindle fibers attach to the centromere of each chromosome. Each sister chromatid has its own spindle fiber.

Anaphase

Centromeres split apart and the sister chromatids separate from each other. Sister chromatids are pulled to opposite poles. Cell begins to change shape

Telophase

Chromatids have reached the opposite poles of the cell. Chromatids begin to unwind into less visible chromatin. Spindle fibers break down. Nuclear membrane forms around each new set of chromosomes.

Sister Chromatids

Two homologous but non-identical chromatids.

Cancer

The result of a genetic mutation (change in DNA) in genes which control cell division. It is uncontrolled cell division.

Oncogenes

Mutated genes.

Meiosis

The process that produces haploid gametes from diploid germ cells in the ovaries and testes.

Reduction Division

Reducing chromosome number by half (diploid to haploid).

Recombination

Producing genetically unique gametes.

Meiosis I

There are 4 main phases to the first meiotic division: Prophase I, Metaphase I, Anaphase I, and Telophase I.

Meiosis II

There are four main stages to the second division: Prophase II, Metaphase II, Anaphase II, and Telophase II. At the end of this process four haploid daughter cells are produced, containing single unreplicated chromosomes.

Prophase I

Each pair of homologous chromosomes (23 pairs) align side by side. The process by which homologous chromosomes pair up is called synapsis. This alignment plays an important role in genetic recombination

Metaphase I

Homologous chromosomes line up at the equator of the cell. They line up independently and randomly to each other. Spindle fibers from each pole attach to each chromosome in every homologous pair.

Anaphase I

Homologous chromosomes are pulled apart and move to opposite ends of the cell. The result is that a single chromosome (made up of two sister chromatids) from each homologous pair moves to each pole of the cell.

Telophase I

Spindle fibers disappear, cytoplasm divides, the nuclear membrane forms around each group of chromosomes. Two cells are formed. Each new cell contains one set of chromosomes that are haploid in number.

Prophase II

The nuclear membrane dissolves and spindle fibers form.

Metaphase II

Spindle fibers attach to the centromere of each chromosome. Chromosomes line up at the equator of each cell.

Anaphase II

Centromeres split. Sister chromatids from each chromosome move to the opposite poles of each cell.

Telophase II

Nuclear membrane reforms around each set of 23 unreplicated chromosomes. Spindle fibers disappear. Cytoplasm divides to form 4 haploid (n) daughter cells.

Homologous Chromosomes

Are chromosomes that share the same structural features.

Synapsis

The process by which homologous chromosomes pair up.

Tetrad

A homologous pair.

Independent Assortment

During Metaphase I, homologous chromosomes line up at the equator of the cell independently and randomly to each other. The resulting gametes have different combinations of parental chromosomes.

Crossing Over

During Prophase I synapsis occurs -- homologous chromosomes pair up and  may exchange pieces of their chromosomes. As a result, individual chromosomes during meiosis contain some genes of maternal and paternal origin. 

Spermatogenesis

Aka. meiosis in males Occurs in the male testes Process begins with a diploid germ cell called a spermatogonium. Following two stages of meiotic division, of which there is an equal division of cytoplasm between cells, four haploid spermatid cells are produced.  Spermatids migrate to the male epididymis for maturation - to become sperm.

Spermatogonium

A diploid germ cell that takes place at the beginning of spermatogenesis.

Spermatid

Adolescent sperm cells that are produced. They migrate to the male epididymis for maturation

Sperm

Male reproductive cell, or gamete that originates in the testicles.

Oogenesis

Aka. meiosis in females. Occurs in the female ovaries. Process begins with a diploid germ cell called a oogonium. Each oogonium divides to produce two primary oocytes. Each of these primary oocytes are then suspended in Prophase I of meiosis until puberty. Every month after puberty, one primary oocyte completes meiosis I However, there is an unequal division of cytoplasm. This produces one secondary oocyte and one polar body. Secondary oocyte begins meiosis II, it too unequally divides to produce a second polar body and one ova. Meiosis II of the secondary oocyte doesn’t complete until fertilization occurs. 

Oogonium

A diploid germ cell that takes place at the beginning of oogenesis.

Polar body

A small haploid cell that is formed at the same time as an egg cell during oogenesis, but generally does not have the ability to be fertilized.

Ova (Egg)

The female reproductive cell, or gamete that is formed in the female ovary.

Acrosome

Produces enzymes used to penetrate the egg during fertilization In the sperm cell.

Nucleus

Carries the genetic material of 23 chromosomes.

Head

A piece of the sperm cell which contains the nucleus and the acrosome.

Midpiece

A section of a sperm cell which contains mitochondria.

Mitochondria

In a sperm cell. Produces energy for the movement of the sperm.

Flagella

A tail on a sperm cell used for movement.

Asexual Reproduction

Reproduction that requires only one parent. Parent organism produces genetically identical offspring.

Sexual Reproduction

Reproduction that requires two parents. Involves the fertilization of gametes. Offspring are genetically unique.

Binary Fission

Bacteria reproduce through this process. When a bacterial cell reproduces, it copies its DNA and then distributes one complete copy of that DNA into each of two identical daughter cells.

Budding

A form of asexual reproduction in which a new organism develops from an outgrowth of the parent body. The new organism then separates to become an independent organism.

Vegetative Reproduction

A form of asexual reproduction in plants, where a new plant grows from the growth of a modified stem, for example: stolons (runners).

Fragmentation

A form of asexual reproduction that involves the development of a new species from a fragment (portion) of the parent species.

Parthenogenesis

A form of asexual reproduction in which an unfertilized egg develops into an adult.

Spores

A Reproductive cell able to develop into a new organism. Are small and readily dispersed by the wind. Are released by the parent body.

Virus

An infectious microbe that are not classified as a living organism. They possess DNA. They cannot replicate on their own, they require a host. There are two main reproductive strategies used: Lytic Cycle and Lysogenic Cycle.

Lytic Cycle

A five-step process, where a virus actively invades and destroys a host cell.

Step 1: Attachment - Virus attaches itself to the host cell.

Step 2: Entry -Injects its DNA and breaks down host cell DNA.

Step 3: Replication - Viral DNA is replicated.

Step 4: Assembly- New viruses are constructed.

Step 5: Lysis - Host cell breaks open to release newly assembled viruses.

Lysogenic Cycle

A viral life cycle where a virus can use a host to replicate its DNA but the virus itself isn’t immediately destroying the host. Viral DNA enters as a provirus, combining itself with the host DNA. Host cell divides as normal. Environmental factors will ultimately activate the viral DNA and at such time the viral DNA will enter the lytic cycle.

Alternation of Generations

 Is the concept that plants (and some animals) alternate between two generations:

1. A haploid (n) generation -  also called  a gametophyte generation . which produces gametes which fertilize and develop into another sporophyte.

The cycle repeats. 

2. A diploid (2n) generation - is called the sporophyte generation. The sporophyte produces haploid spores capable of growing into a plant body called the gametophyte. 

Stamen

Male reproductive parts in plants.

Anther

Where pollen is stored and produced in plants.

Pollen

Sacs that contain male gametes in plants.

Filament

Part of a plant that supports the anther.

Pistil

Female reproductive parts in plants.

Stigma

A sticky structure that captures pollen in plants.

Style

A sack that supports the stigma in plants.

Ovary

The base of the pistil that contains ovules in plants.

Ovules

Sacs that contain female gametes in plants.

Sepals

Leaves that surround the bud in plants.

Petals

Attract pollinators in plants.

Double Fertilization

One sperm fertilizes the egg forming the diploid zygote (2n). The second sperm fertilizes the polar nuclei forming a triploid (3n) cell called endosperm - a starch food reserve for the embryo.

Pollination

When pollen lands on the stigma of a plant.

Tube Nucleus

The vegetative nucleus that guides the growth of the pollen tube when it enters the pistil in plants.

Pollen Tube

A specialized structure in plants. Its sole purpose is to deliver sperm cells to the female gametophyte for double fertilization.

Generative Nucleus

The one of the two nuclei resulting from the first division in the pollen grain of a seed plant that gives rise to sperm nuclei.

Endosperm

Tissue that surrounds and nourishes the embryo in the seeds of flowering plants.