bio quiz Flashcards
what is meiosis
reduction division 2n to n or diploid (2n 46) to haploid (n 23)
Homologus
Chromosomes that have corresponding chromosomes from opposite parents and are similar but not identical. Code for same trait but may not have same code. They are found in diploid cells. One from each parent and they can have different allels
Tetrad
structure containing 4 homologous chromatids that forms during meiosis. (Prophase 1)
crossing-over
process in which homologous chromosomes exchange portions of their chromatids during meiosis
when does formation of a tetrad happen
When crossing over in prophase 1
What does meiosis produce
4 genetically different haploid cells
Prophase 1
chromatin condenses into visible chromosomes. Crossing over begins to happen. Chromosomes pair to form a tetrad
Interphase 1
Prepares for Meiosis, Dna is replicated resulting in two sister chromatids so double the dna
Metaphase 1
Spindle fibers attach to the chromosomes. Homologus chromosomes align along the metaphase plate
Anaphase 1
Homologues chromosomes come apart.
telophase and cytokinesis 1
Nuclear membranes form and the cell separates into two cells
Prophase 2
Chromosomes condense, nuclear envelope breaks down and spindle fibers form
Metaphase 2
chromosomes align on the metaphase plate
Anaphase 2
Sister chromatids finally separate
Telophase and cytokenisis 2
Halved again and 4 haploid cells are made
gametes
sperm and egg cell
nondisjunction
Paired homologus chromosomes refuse to separate
polar bodies
Small haploid cells that are byproducts
alleles
Variants of genes
