Chapter 10 Meiosis Flashcards
sexual reproduction;
offspring are produced through the union of gametes (sperm and egg),
locus
a specific place on a DNA double helix of which a gene is located.
alleles
are slightly different nucleotide sequences of a gene in a certain species. as per a result of a mutation or error in replicating DNA.
Mutation
a cell makes a mistake copying its DNA prior to cell division (see Chapter 12) or when a ray of ultraviolet light from the sun or certain chemicals in the environment cause changes in a cell’s DNA.
karyotype
The complete set of chromosomes from a single cell.
homologous chromosomes
Humans have 23 pairs of chromosomes, for a total of 46 per cell. The two chromosomes that make up a pair are called Homologous, they contain the genes that control the same inherited characteristics.
diploid cells are? and contain DNA from where ?
Cells with pairs of homologous chromosomes are called diploid, meaning “double.” One homologue of each pair, which we will call the maternal homologue, is inherited from the mother, and the other, called the paternal homologue, is inherited from the father.
autosomes
Pairs of chromosomes with nearly identical DNA sequences and that are found in diploid cells of both sexes are called autosomes. people have 22 pairs of autosomes and 1 pair of sex chromosomes (total of 23 chromosomes)
Haploid
Not all cells are diploid: If a cell contains only one member of each pair of homologues, it is haploid. the 4 gametes produced from meiosis are haploid cells.
polyploid
organisms that have more than two copies of each homologous chromosome in each cell.
step 1. of 2 (sexual reproduction);
During meiotic cell division, a diploid cell gives rise to haploid daughter cells containing a single member of each pair of homologues. The haploid cells, or their descendants produced by mitotic cell division, become gametes. In animals, the haploid cells produced by meiotic cell division differentiate into sperm or eggs.
Step 2. of 2 (sexual reproduction);
Fertilization of an egg by a sperm restores the diploid number of chromosomes in the offspring.
meiosis
a specialized type of nuclear division in which a diploid nucleus di- vides twice, producing four haploid nuclei, and cytokinesis, which packages the four nuclei into separate cells.
The first division of meiosis (called meiosis I)
separates the pairs of homologous chromosomes and sends one homologue from each pair into each of two daughter nuclei, which are therefore hap- loid. Each chromosome, however, still consists of two chromatids
The second division (called meiosis II)
separates the chromatids into independent chromosomes and parcels one chromosome into each of two daughter
Duplicated chromosomes condense. Homologous chromosomes pair up and chiasmata occur as chromatids of homologues exchange parts (DNA) by crossing over. The nuclear envelope disintegrates, and spindle microtubules form. what phase of Meiosis?
Prophase I
Paired homologous chromosomes line up along the equator of the cell. One homologue of each pair faces each pole of the cell and attaches to the spindle microtubules via the kinetochore (blue). what phase of meiosis?
Metaphase I
Homologues separate, one member of each pair going to each pole of the cell. Sister chromatids do not separate. what phase of meiosis?
Anaphase I
Spindle microtubules disappear. Two clusters of chromosomes have formed, each containing one member of each pair of homologues. The daughter nuclei are therefore haploid. Cytokinesis commonly occurs at this stage. what phase of meiosis?
Telophase I
interphase between meiosis I and II?
There is little or no interphase between meiosis I and meiosis II
Spindle microtubules re-form and attach to the sister chromatids in each haploid cell. what phase of meiosis?
Prophase II
Metaphase II
The chromosomes line up along the equator, with sister chromatids of each chromosome attached to kinetochore microtubules that lead to opposite pole
Anaphase II
The chromatids separate into independent daughter chromosomes, one former chromatid moving toward each pole.
Telophase II
Cytokinesis results in four haploid cells, each containing one member of each pair of homologous chromosomes.
chiasmata
where chromatids of the maternal and paternal chromosomes have exchanged parts.
recombination:
the formation of chromosomes with combinations of alleles that differ from those of either parent
