Zoology (Cell Division & Inheritance & Perspective)

Reproduction

Essential for Life

Single Cell Reproducing Itself

Most basic level of reproduction

Unicellular Organisms

Cellular reproduction also reproduces the organism.

Multicellular Organisms

Cellular reproduction is involved in growth, repair, and the formation of sperm and egg cells that enable the organism to reproduce

Genetics

Is the study of how biological information is transmitted from one generation to the next.

Modern Molecular Genetics

provides biochemical explanations of how this information is expressed in an organism.

Proteins

Contribute to observable traits, such as eye color and hair color, and they function as enzymes that regulate the rates of chemical reactions in organisms.

Environmental Limits

Animals are what they are by the proteins they synthesize

Gregor Mendel (1882 - 1884)

Genetics proponent

DNA

Genetic Material

Chromosomes

Protein Form of DNA

Chromatin

Highly Dispersed State of Chromosomes

Genes

Unites of inheritance that may actively participate in the formation of protein

Heterochromatic Regions

Inactive portions of chromosomes produce dark banding patterns with certain staining procedures and thus

Euchromatic Regions

Active portions of the chromosomes

James D. Watson and Francis Crick, 1986

· DNA molecule exists in the form of a three-dimensional double helix.

Histones

Proteins that are wrapped in chromosomes consisting of long DNA molecules

Nucleosomes

DNA and histone complex

Solenoid

Coiled chain of nucleosomes.

Rosettes

Solenoid that loops around a scaffold protein

Sex chromosomes

Chromosomes that are represented differently in females than in males and function in sex determination.

Autosomes

Chromosomes that are alike and not involved in determining sex.

X-O system

System of Sex Determination

X-O system

It is the simplest system for determining sex because it involves only one kind of chromosome.

X-Y system

Sex determination of other animals such as fruit flies and humans

Male XY, Female XX

In the X-Y system, males and females have an equal number of chromosomes, but the male is usually ______, and the female is _____.

Sex Chromosomes

They also helpp in determining non-sex related traits

Z-W system

System in Birds

10 - 50

Usual chromosome numbers of animals

Chromosomes

present in sets, with the number in a set being characteristic of each kind of animal

N

Chromosomes are expressed in ____. It identifies the number of different kinds of chromosomes

Diploid

Most animals have two sets, or 2N chromosomes.

Haploid

Some animals have only one set, or N chromosomes (like gametes)(e.g., male honeybees and some rotifers).

Polyploidy

Have more than the diploid number of chromosomes

Asexual Reproduction

· often accompanies polyploidy.

Cell Cycle

The life of a cell, from its beginning until it divides to produce the new generation of cells

G1 Phase

Cell components are synthesized and metabolism occurs, often resulting in cell growth.

S phase

The chromosomes replicate resulting in two identical copies called sister chromatids.

G2 Phase

Metabolism and growth continues until the mitotic phase is reached.

Mitosis

· The distribution of chromosomes between two daughter cells=

Cytokinesis

Partitioning of the cytoplasm between two daughter cells

Interphase

the time between the end of cytokinesis and the beginning of the next mitotic division.

Interphase

It is a time of cell growth, DNA synthesis, and preparation for the next mitotic division

G1 phase

Represents the early growth phase of the cell

S phase

Growth Continues, but this phase also involves DNA replication

G2 phase

Prepares cell for division.

G2 phase

It includes replication of the mitochondria and other organelles, synthesis of microtubules and protein that will make up the mitotic spindle fibers, and chromosome condensation.

G1, S, G2

Phases of Interphase

Mitotic Phase

Includes events associated with partitioning chromosomes between two daughter cells and the division of the cytoplasm (cytokinesis).

First Growth/ Gap Phase, Synthesis Phase, Second Growth/ Gap Phase

G1, S, G2

Interphase

Typically occupies about 90% of the total cell cycle.

Replication

Before a cell divides, an exact copy of the DNA is made during the S (synthesis) phase

Replication

Essential to ensure that each daughter cell receives identical genetic material to that present in the parent cell.

Chromatid

Copy of a chromosome produced by replication.

Centromere

Sister Chromatids attach to each other then at this point of constriction

220 Nucleotides

Centromere is a specific DNA sequence of about ______________and has a specific location on any given chromosome

Kinetochore

Disk of protein bound to each centromere. The attachment site for the microtubules of the mitotic spindle.

Early Prophase, Late Prophase, Metaphase, Anaphase, Telophase

Five Phases of Mitosis

Prophase

Begins when chromosomes become visible with the light microscope as threadlike structures

Prophase

The nucleoli and nuclear envelope begin to break up, and the two centriole pairs move apart

Prophase

By the end, the centriole pairs are at opposite poles of the cell

Asters

· The centrioles radiate an array of microtubules, which brace each centriole against the plasma membrane.

Prometaphase

A second group of microtubules attach at one end to the kinetochore of each chromatid and to one of the poles of the cell at the other end of the microtubule

Prometaphase

This bipolar attachment of spindle fibers to chromatids is critical to the movement of the chromatids of each chromosome to opposite poles of the cell in subsequent phases of mitosis

Metaphase

The chromatids (replicated chromosomes) begin to align in the center of the cell, along the spindle equator.

Metaphase

The centromeres divide and detach the two sister chromatids from each other. After the centromeres divide, the sister chromatids are considered full-fledged daughter chromosomes.

Anaphase

Shortening of the microtubules in the mitotic spindle, and perhaps the activity of motor proteins of the kinetochore

Anaphase

Pulls each daughter chromosome apart from its copy and moves it toward its respective pole.

Anaphase

Ends when all daughter chromosomes have moved to the poles of the cell.

Telophase

Begins once the daughter chromosomes arrive at the opposite poles of the cell.

Telophase

The mitotic spindle disassembles. A nuclear envelope re-forms around each set of chromosomes, which begin to uncoil for gene expression, and the nucleolus is resynthesized. The cell also begins to pinch in the middle.

Cytokinesis

The final phase of cell division, in which the cytoplasm divides.

Cytokinesis

Usually starts sometime during late anaphase or early telophase.

Contractile Ring

A contracting belt of microfilaments. Pinches the plasma membrane to form the cleavage furrow

Sexual Reproduction

Requires a genetic contribution from two different sex cells.

Gametes

Egg and Sperm Cells

Zygote

First Cell of an Animal

Meiosis

Occurs in germ-line cells of the ovaries and testes and reduces the number of chromosomes to the haploid (1N) number.

Spermatogenesis, Oogenesis

The result of meiosis in most animals is the formation of gametes.

Spermatogenesis

Produces mature sperm cells and follows the sequence previously described.

Spermatogenesis

All four products of meiosis often acquire a flagellum for locomotion and a cap-like structure that aids in the penetration of the egg.

Oogenesis

Produces a mature ovum or egg.