Meiosis Flashcards
Tetrad
Paired set of homologous chromosomes that can exchange pieces of genetic information with one another or “cross over”
Karyotype
A display of all the chromosomes within a cell at the time of metaphase, arranged by matching pairs
Recombinant
A chromosome that has gene combinations different from those carried by the parental chromosomes
Describe diploid cells.
Diploid cells have two sets of chromosomes present (homologous pairs), and thus have 23 pairs of chromosomes (for a total of 46 chromosomes).
Describe haploid cells.
Haploid cells have a single set of chromosomes present, and so have 23 chromosomes in the cell.
Gametes
Sex cells - egg or sperm. They are haploid cells.
Zygote
A zygote is what is created when haploid gametes merge during the process called fertilization. It is a diploid cell.
Fertilization
The process through which haploid gametes merge into a zygote (a type of diploid cell).
Meiosis
Meiosis is a type of cell division that produces four haploid daughter cells (gametes) each time it occurs in diploid organisms.
What occurs in the interphase stage of meiosis?
In the interphase stage of meiosis, chromosomes duplicate, yielding sister chromatids, and centrosomes emerge.
What occurs, broadly, in the meiosis I stage of meiosis?
Broadly, homologous chromosomes separate.
What occurs, broadly, during the meiosis II stage of meiosis?
Broadly, sister chromatids separate during the meiosis II stage of meiosis.
What occurs in the prophase I stage of meiosis?
During the prophase I stage of meiosis, homologous chromosomes pair up and exchange segments (mixing up the DNA).
What occurs during the metaphase I stage of meiosis?
During the metaphase I stage of meiosis, the tetrads line up in the center of the cell.
What occurs in the anaphase I stage of meiosis?
In the anaphase I stage of meiosis, the pairs of homologous chromosomes split up, but the sister chromatids remain attached.
What occurs during the Telophase I and cytokinesis stages of meiosis?
During the telophase I and cytokinesis stages of meiosis, two haploid cells form, but the chromosomes are still double.
How does genetic mixing-up occur in prophase I of meiosis?
In prophase I, genetics get mixed up because homologous chromosomes pair up and some crossing-over occurs between non-sister chromatids, resulting in recombinant chromatids.
How does genetic mixing-up occur during the metaphase I stage of meiosis?
During the metaphase I stage of meiosis, genetic mixing-up occurs when the homologous pairs of chromosomes align independently.
What occurs differently in the anaphase II stage of meiosis?
In the anaphase II stage of meiosis, sister chromatids separate.
What occurs in the telophase II and cytokinesis stage of meiosis?
In the telophase II and cytokinesis stage of meiosis, the four haploid daughter cells form, containing single chromosomes.
Nondisjunction
Nondisjunction is an error in meiosis when members of a chromosome pair fail to separate. It normally results in a non-viable offspring.
Down Syndrome
A disability resulting from an error in meiosis, when a person has an extra #21 chromosome.
