Chapter 2 - Mitosis and Meiosis

Flashcards covering key concepts from Chapter 2, 'Mitosis and Meiosis,' focusing on cell structure, chromosome organization, and the processes and outcomes of mitosis and meiosis, including gamete formation.

Before 1940, what limited the knowledge of cell structure?

Knowledge of cell structure was limited to what could be seen with a light microscope.

What major development in microscopy occurred between 1940 and 1960?

The development of transmission electron microscopy.

What are the four classifications of chromosomes based on centromere location?

Metacentric (middle), Submetacentric (between middle and end), Acrocentric (close to end), and Telocentric (at end).

What is the primary role of mitosis?

It is the basis for asexual reproduction, development of a zygote into an adult, wound healing, and blood/skin cell production.

What are the main phases of the cell cycle?

Interphase (G1, S, G2) and Mitosis (Prophase, Prometaphase, Metaphase, Anaphase, Telophase).

What occurs during the S phase of interphase?

DNA synthesis (replication) occurs.

What is the G0 phase of the cell cycle?

A phase where cells withdraw from the active cell cycle and do not divide.

What is a characteristic of cancer cells regarding the cell cycle?

Cancer cells are characterized by uncontrolled cell division and either never enter G0 or pass through it very quickly.

What key events characterize prophase in mitosis?

Migration of centrioles, breakdown of nuclear envelope and nucleolus, and chromatin condensation.

When do centromeres align on the metaphase plate during mitosis?

During Metaphase.

What critical event occurs during anaphase in mitosis?

Sister chromatids disjoin and migrate to opposite ends of the cell.

What is cytokinesis and when does it commence?

Cytokinesis is the partitioning of the cytoplasm, and it commences during telophase.

Why are chromosomes typically invisible during interphase but visible during mitosis?

During interphase, chromosomes are extended and uncoiled (chromatin); during mitosis, they coil up and condense, becoming visible.

What is the main difference in daughter cells produced by mitosis versus meiosis?

Mitosis produces two genetically identical diploid daughter cells, while meiosis produces four haploid gametes or spores with genetic variation.

What two features of meiosis generate genetic variation?

In meiosis, genetic variation is generated by segregation and independent assortment of parental chromosomes and by crossing over (genetic exchange).

What happens during Prophase I of meiosis that does not happen in mitotic prophase?

Homologous chromosomes pair up (synapsis) to form tetrads, and crossing over occurs.

What is a tetrad in meiosis?

A structure formed during Prophase I by the synapsis of homologous chromosomes, consisting of two pairs of sister chromatids.

What is the significance of random alignment of chromosomes at the metaphase plate during Metaphase I?

It contributes to genetic variation through independent assortment of homologous chromosomes.

What is the ploidy level of cells at the end of Meiosis I?

Each cell is haploid (n), but chromosomes still consist of sister chromatids.

What is the result of Telophase II and cytokinesis in meiosis?

Four haploid gametes with equal cytoplasm (in spermatogenesis) or one functional ootid and polar bodies (in oogenesis), containing a combination of maternal and paternal genes.

Where does spermatogenesis take place?

In the testes.

What is the initial undifferentiated germ cell in spermatogenesis?

A spermatogonium.

What is the final product of spermatogenesis?

Four highly specialized, motile spermatozoa (sperm).

Where does oogenesis take place?

In the ovaries.

What is the initial undifferentiated germ cell in oogenesis?

An oogonium.

Why does oogenesis produce only one functional ovum instead of four?

Meiosis I and Meiosis II result in unequal cytoplasm division, forming one large oocyte/ootid and smaller polar bodies that disintegrate.

When is Meiosis II completed in oogenesis?

Meiosis II is completed only after fertilization.