The Hierarchical Organization of Life

DNA

Deoxyribonucleic acid - the material that contains the genetic information necessary for the development and functioning of an organism.

Purines and their identifying factor

Adenine and Guanine, two-ringed structures

Pyrimidines and their identifying factor

Thymine and Cytosine, single-ringed structures

Why does a pyrimidine have to bond with a purine?

To maintain equidistance between the backbones, by having 3 rings per pair.

What does n represent?

The number of different cells in an organism

Haploid

Cells that contain one set of chromosomes

Diploid

Cells that contain two sets of chromosomes

A gene

A segment of DNA that codes for a particular characteristic

Mitosis

Cell divison that produces two daughter cells, identical to the parent cell.

What is the importance of Mitosis in multicellular organisms?

Growth, repair and developpment

What is the importance of Mitosis in unicellular organisms?

Population growth (asexual reproduction)

What are the milestones in zygote development?

Day 5: Blastocyst forms, considered an embryo - cells begin to become specialized

Week 9: All major structures are present - called a fetus

Genome

All the genetic information in an organism; all of an organism's chromosomes.

Gene

A segment of DNA on a chromosome that codes for a specific trait

Allele

An alternative form of a gene.

Fraternal Twins

Non-identical, dizygotic (two zygotes), two eggs were released. Have separate placentas and amniotic sacks.

Identical Twins

Monozygotic (one zygote), 1 egg is fertilized and splits. Embryos share amniotic sack and placenta.

Why is genetic diversity important?

It strengthens the ability of a species to resist to diseases, pests, changes in climate and other adaptations.

Protects a species from extinction.

Contributing factors to genetic diversity (5)

Independant assortment, genetic recombination, random fertilization, genetic mutation, population mixing

Homozygous

When an organism inherits two identical alleles for a trait

Heterozygous

When an organism ingerits two different alleles for a trait

Genotype

The Genetic makeup of an individual, determines by the alleles present

Phenotype

The physical appearance of a trait. The expression of a genotype

Asexual reproduction pros (3) and cons (2)

PROS: No need for a partner, mass production of offspring, possible positive mutations.

CONS: Possible negative mutations, no genetic diversity.

Sexual reproduction pros (2) and cons (3)

PROS: Genetic diversity, encourages mixing behavior

CONS: Takes energy and time to find a partner, takes time for the offspring to develop, and there are less offspring.

Meiosis

For of cell divison that produces Gametes, with half the number of chromosomes. - sexual reproduction

Where does meiosis occur?

The gonads - testes or ovaries

Why do gametes have half the number of chromosomes?

So that when the fusion of the sperm and the egg occurs, the resulting zygote contains 46 chromosomes, typical for the species.

Meiosis I

Homologous pairs of chromosomes are separated

Prophase I

Chromosomes condense

Synapsis occurs - homologous chromosomes form a tetrad

Nucleoli and nuclear membrane disappear

Portions of chromatids break off and attach to homologous pair, which causes genetic recombination.

Spindle fibers begin to attach.

Metaphase I

Spindle fibers pull tetrads to align on the equator.

Independent assortment means the orientation of tetrads can differ, which causes genetic recombination.

Anaphase I

Tetrads separate and chromosomes move towards the poles as the spindle fibres condense. Sister chromatids remain attached.

Telophase I (+cytokinesis)

Chromosomes arrive at the poles.

Nuclear envelopes and nucleoluses reform, cytokinesis begins

Cytokinesis: Divison of cytoplasm to complete the process of creating two separate daughter cells, forming a cleavage furrow. 2 haploid, genetically different daughter cells now exist.

Prophase II

Nucleolus and nuclear membranes disappear, centrosomes move towards the poles and spindle fibres begin approaching the chromosomes.

Metaphase II

Chromosomes line up along the metaphase plate, pushed by the spindle fibers.

Anaphase II

Sister chromatids are separated by spindle fibers and are pulled to opposite sides of the cell as the fibres condense.

Telophase II (=Cytokinesis II)

Nucleolus and nuvlear membranes reform, with now four nuclei. Cytoplasm begins to divide with the presence of a cleavage furrow, which is complete during cytokinesis II. There are now 4 Haploid, genetically different daughter cells.

What are cells that cannot reproduce called?

Amniotic cells

Name some amniotic cells

Neurons in the nerves, as well as nerve cells in the brain and spinal cord.

Apoptosis

Planned cell death

Necrosis

Unplanned cell death

Quiescence

Dormant cell, with the possibility to become alive again

Senescence

Deterioration

4 types of Tissue

Epithelial, connective, muscle and nerve tissues.

Organ

A structure that contains two or more types of tissue working together towards a common function.

Organ system

A structure that contains two or more organs working together towards a common function.