Mitosis and Meiosis Flashcards
Growth and Preparation of chromosomes for replication
Gap 1 (G1)
Stage when DNA replication occurs
Synthesis (S)
Preparation of mitosis
Gap 2 (G2)
Chromosome separates
Nuclear division
Cytokinesis
Cytoplasmic division
Two basic types of cells
Somatic cells
Gametes
General body cells
Somatic cells
Sex cells
Gametes
number of chromosomes in a human somatic cell
46 chromosomes
the chromosomes are arranged in how many pairs
23
how many individual chromosomes in sex cells
23 individual chromosomes
Stages of Mitosis
Interphase Prophase Metaphase Anaphase Telophase
Cells are not dividing
Interphase
chromatin begins to coil and condense to form chromosomes
Prophase
Spindle grows and forms attachments to the chromosomes at the centromeres
Metaphase
Centromeres divide to create two chromosomes instead of a pair of attached chromatids
Anaphase
Nuclear envelopes reassemble and surround each set of daughter chromosomes
Telophase
Chromosomes are decondensed (called chromatin) and their information is available to the cell for synthesizing products
Interphase
The nuclear envelope and nucleolus disappears
Prophase
Chromosomes move to an equatorial plate (metaphase plate) which is formed along the midline of the cell between poles
Metaphase
poles of the spindle apparatus are pushed apart as the cell elongates
Anaphase
Nucleoli reappear inside the newly formed nuclei
Telophase
Takes place only in the ovaries and testes
Meiosis
Involves one duplication of the DNA and two cell divisions (Meiosis I and Meiosis II)
Meiosis
A single cell divides into two
Meiosis I
The two cells from meiosis I divides again
Meiosis II
2 important processes that occur in Prophase I
Synapsis
Crossing over
The coming together of two homologous chromosomes
Synapsis
Segments of DNA from one chromatid in the tetrad pass to another chromatid in the tetrad
Crossing over
subdivisions of Prophase I
Leptotene Zygotene Pachytene Diplotene Diakinesis
Once ____ takes place, the cell is committed to meiosis
Leptotene
Chromosomes appear threadlike
Zygotene
Synapsis is complete during this stage
Pachytene
Chromosomes continue to shorten and thicken
Diplotene
Point at which crossing-over took place
Chiasmata
Chromosomes reach their greatest contraction during this last stage of prophase
Diakinesis
Characterized by disappearance of the nuclear membrane and formation of the meiotic spindle
Metaphase I
Centromeres of each tetrad separate and migrate to opposite poles
Anaphase I
The two haploid sets of chromosomes reach opposite poles and the cytoplasm divides
Telophase I
Stages of Meiosis II
Interphase II Prophase II Metaphase II Anaphase II Telophase II
No duplication of DNA
Interphase II
The chromatin material condenses, and each chromosome contains two chromatids attached by the centromere
Prophase II
The 23 chromosome pairs gather at the center of the cell prior to separation
Metaphase II
The centromeres divide, and the 23 chromosome pairs (46 chromatids) divides
Anaphase II
The chromosomes gather at the poles of the cells and become indistinct
Telophase II
__1. homologous chromosomes independent
__2. homologous chromosome pair forming bivalents until anaphase I
Mitosis
Meiosis
__1. Daughter cell haploids
__2. identical daughter cells
Meiosis
Mitosis
__1. chromatids not identical, crossing over
__2. identical daughter cells
__3. daughter cells have new assortment of parental chromosomes
Meiosis
Mitosis
Meiosis
