AllImagestakenform: Audeirk, D. Audesirk, J & Byers, B. (2008) Biology with Physiology: Life on Earth. New Jersey. : Pearson.
ASEXUAL REPRODUCTION. Paramecium sp. Is a protists, a microorganism. Yeast, a unicellular fungus reproduces asexually. Hydra a sea animal, reproduces a sexually. It starts growing a bud until it grows big enough to be an independent organism.
PROKARYOTIC CELL CYCLE. Prokaryotic Cell Cycle consist of DNA growth and former cell division. Cell Division in Prokaryotic cells is called BINARY FISSION.
EUCARYOTIC CELL CYCLE. This cycle consist of the following main phases: Interphase(Yellow). Cell Division (Light Blue). Interphase has 4 phases: G1,G0, S and G2. Cell Division could be either: Mitosis or Meiosis
CHROMOSOME. A human chromosome consist of a single DNA double helix and some proteins called Histones and scaffolds. Chromosomes are a compact DNA container.
CHROMOSOME. These are the main features of chromosomes: Genes: sequences of DNA that have an specific function. Centromere: it joins two parts of the chromosome, it does NOT have to be at the center. Telomeres: the “end” of the chromosome, they maintain the equilibrium and seal the chromosome’s material.
DUPLICATED CHROMOSOME. A duplicated chromosome consist of two identical chromosomes.
KARYOTYPE. A karyotype is the full set of chromosomes located at each cell of an organisms. All this chromosomes are located at the nucleus. They consist of homologues pairs. For example, chromosome 1 consists of two identical chromosomes. They share the same genes at the same order and the same length. Exception: sexual chromosomes. This photo is from a male, since it has XY, if it were from a women’s it would be XX.
Spindle Microtubules align the chromosomes along the cells’ “Equator”.
MITOTIC CELL DIVISION. Anaphase:
Sister chromatids are separated and moved to opposite sides of the cell. Microtubules push each pole apart.
Microtubules start extending, nuclear envelop reforms and spindle microtubules disappear.
CYTOKINESIS: ANIMAL CELLS. Microfilaments attached to the plasmas membrane start contracting the cell’s Equator, until it divides in two.
CYTOKINESIS: PLANT CELL. During Cytokinesis in plan cells, once the cell is divided , the Golgi Apparatus starts sending vesicles with carbohydrates (cellulose) to start creating a cell wall in-between both daughter nuclei.
CELL CYCLE CHECKPOINTS. Checkpoints throughout the cell cycle:
After G1 : Is your DNA suitable and intact for it to synthesize?
After G2: Has DNA replication successfully occurred?
After Metaphase: Are all the chromosomes aligned at the Equator?
FIRST CHECKPOINT. Cycling-dependent kinases are proteins that are assigned to control the progress of the cell cycle.
ALLELES. Homologues have same of different Alleles. Alleles are variations of the same gene, that determine different characteristics.
MEIOTIC CELL DIVISION. Both members of a pair of homologues chromosomes are replicated before Meiosis. One chromosome is parental and the other is maternal.
MEIOSIS I. After MEIOSIS I, each daughter cell receives one of each pair of homologues chromosomes.
MEIOSIS II. After MEIOSIS II, sister chromatids separate into independent chromosomes and each daughter cell receives one of these chromosomes.
CROSSING OVER. Crossing Over occurs at Prophase I and it adds genetic diversity to the chromosomes.
METAPHASE I. Homologues chromosomes are paired up taking as a reference the Equator. Each PAIR of chromatids gas a single functional kenitochore. In MITOSIS, each sister chromatids have one kenitochore.