Bio 111 Ch. 9 & 10 Mitosis and Meiosis

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.

16

Normal human gametes carry ______ chromosomes

23

What number and types of chromosomes are found in a human somatic cell?

44 autosomes and 2 sex chromosomes (22 pairs of autosomes and either two X chromosomes (in females) or an X and a Y chromosome (in males).)

Homologous chromosomes migrate to opposite poles during _____.

Anaphase I

During _____ sister chromatids separate.

Anaphase II; Anaphase II is essentially the same as mitotic anaphase except that the cell is haploid

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.

At the end of telophase I and cytokinesis, there are two haploid cells with chromosomes that consist of two sister chromatids each.

At the end of _____ and cytokinesis there are four haploid cells.

At the end of telophase II and cytokinesis there are four haploid cells.

How do cancer cells differ from normal cells?

Cancer cells may be immortal. Cancer cells can go on dividing indefinitely in culture if they are given a continual supply of nutrients; in essence, they are "immortal." Read about HeLa cells.

the point of attachment between two sister chromatids of a duplicated chromosome is called

Centromere

What occurs during prophase I?

Chromosomes condense, homologous pairs line up gene by gene, crossing over occurs

Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?

Cleavage. In animal cells, the cleavage furrow forms when a ring of microfilaments contracts, causing the parent cell to be pinched in two

What is the G0 section of interphase?

G0 occurs if the outside conditions do not support cell division; the cycle pauses until conditions change or the cell just leaves the cell cycle completely (becomes post-mitotic).

What occurs during anaphase I?

In anaphase I, pairs of homologous chromosomes separate One chromosome moves toward each pole, guided by the spindle apparatus Sister chromatids remain attached at the centromere and move as one unit toward the pole

What occurs during anaphase II?

In anaphase II, the sister chromatids separate The sister chromatids of each chromosome now move as two newly individual chromosomes toward opposite poles

What occurs during metaphase I?

In metaphase I, homologous pairs line up at the metaphase plate, with one chromosome facing each pole Microtubules from one pole are attached to the kinetochore of one chromosome of each tetrad Microtubules from the other pole are attached to the kinetochore of the other chromosome

What occurs during prophase II?

In prophase II, a spindle apparatus forms In late prophase II, chromosomes (each still composed of two chromatids) move toward the metaphase plate

What occurs during telophase I?

In the beginning of telophase I, each half of the cell has a haploid set of chromosomes Each chromosome still consists of two sister chromatids Cytokinesis usually occurs simultaneously, forming two haploid daughter cells

During _____ the cell grows and replicates both its organelles and its chromosomes.

Interphase

For what purpose(s) might a karyotype be prepared?

Karyotypes can show if all of the chromosomes are present and whether an individual is male (XY) or female (XX). In addition, by staining the chromosomes and examining the resulting banding patterns, it is possible to detect defects such as deletions, translocations, and inversions.

When is the only time that chromosomes line up by homologous pairs?

Meiosis I

Meiosis I produces _____ cells, each of which is _____.

Meiosis I produces two cells, each of which is haploid.

Meiosis II typically produces _____ cells, each of which is _____.

Meiosis II typically produces four cells, each of which is haploid

During _____ chromosomes align single file along the equator of a haploid cell.

Metaphase II

Compared to most prokaryotic cells, eukaryotic cells typically have

More DNA molecules and a larger genome

Why is there no chromosome replication between meiosis I and meiosis II?

No chromosome duplication occurs between the end of meiosis I and the beginning of meiosis II because the chromosomes are already replicated!

What occurs during telophase II?

Nuclei form, and the chromosomes begin decondensing At the end of meiosis, there are four daughter cells, each with a haploid set of unduplicated chromosomes Each daughter cell is genetically distinct from the others and from the parent cell

Synapsis, the pairing of homologous chromosomes, occurs during what phase?

Prophase I

During _____ a spindle forms in a haploid cell.

Prophase II; Prophase II is essentially the same as mitotic prophase except that the cells are haploid.

The pairing of homologous chromosomes that only occurs during prophase I of meiosis is called ______?

Synapsis

What occurs during meiosis but not during mitosis?

Synapsis

What happens during the G2 section of interphase?

The cell continues to grow and make the proteins it needs, manufactures microtubules, makes sure no DNA is damaged after replication

What happens during the G1 section of interphase?

The cell grows, begins protein synthesis and organelle duplication, checks to make sure no DNA is damaged

What happens during the S section of interphase?

The duplication of DNA so that each chromosome contains two identical copies

What occurs during metaphase II?

The sister chromatids are arranged at the metaphase plate Because of crossing over in meiosis I, the two sister chromatids of each chromosome are no longer genetically identical The kinetochores of sister chromatids attach to microtubules extending from opposite poles

What are kinetichores?

The sites at which microtubules attach to chromosomes

In alternation of generations, what is the diploid stage of a plant that follows fertilization called?

The sporophyte is the diploid, multicellular stage of the plant that produces haploid spores by meiosis.

Why is it difficult to observe individual chromosomes with a light microscope during interphase?

They have uncoiled into long, thin strands

The result of the exchange of homologous portions of nonsister chromatids is new combinations of _____?

genetic material (genetic recombination)

Once meiosis 1 is completed, cells are haploid or diploid?

haploid; Gametes or germ cells are haploid cells (example: sperm and ova) containing only one set (or n) number of chromosomes and autosomal or somatic cells are diploid cells containing 2n number of chromosomes. The number of chromosomes (n) differs in different organisms.

Variation

is demonstrated by the differences in appearance that offspring show from parents and siblings

In some organisms, such as certain fungi and algae, cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this?

large cells containing many nuclei

What is crossing over?

the exchange of homologous portions of nonsister chromatids

Genetics

the scientific study of heredity and variation

Heredity

the transmission of traits from one generation to the next

Humans produce skin cells by mitosis and gametes by meiosis. The nuclei of skin cells produced by mitosis will have

twice as much DNA as the nuclei of gametes produced by meiosis.

Mitosis results in the formation of how many cells; meiosis results in the formation of how many cells?

two diploid cells ... four haploid cells In mitosis, a cell that has doubled its genetic material divides to produce two diploid daughter cells. In meiosis, a cell that has doubled its genetic material undergoes two rounds of division, producing four haploid cells.

What events are unique to meiosis?

-Synapsis and crossing over in prophase I: Homologous chromosomes physically connect and exchange genetic information -Alignment of homologous pairs at the metaphase plate: Homologous pairs of chromosomes are positioned there in metaphase I -Separation of homologs during anaphase I