Chapter 11 Flashcards

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1
Q

Diploid cells

A

2n Somatic cells. 2 sets of chromosomes

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2
Q

Haploid cells

A

n. Gametes have 1 set of chromosomes
Inheritance - 1 set of chromosomes from each parent

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3
Q

Zygote

A

undergoes mitosis to produce diploid cells. zygote into fetus into child into adult

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4
Q

Meiosis

A

Two rounds of cells division. Start with one cell and end with 4 cells with genetic variation.
Meiosis I (reduction division, separate chromosomes) and Meiosis II (separate chromatids) NO S phase
PMAT - Prophase I, Metaphase I, Anaphase I, Telophase I. Prophase II, Metaphase II, Telophase II.

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5
Q

Synapsis

A

(crossing over) during early prophase I homologous chromosomes become closely associated and eventually swap DNA.
Tetrads

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6
Q

Prophase I

A

Chromosomes condense, nuclear envelope disappears, spindle fibers form from centrosomes. Each chromosome composed of 2 sister chromatids. Homologous chromosomes become paired (synapse tetrads). Genetic variation from crossing over, random exchange of DNA between non-sister chromatids of homologous pairs of chromosomes.

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7
Q

Crossing Over

A

Occurs between non-sister chromatids to allow maternal and paternal homologues to exchange chromosomal material. Alleles form on separate homologues.

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8
Q

Chiasmata

A

Site of crossing over. Contact maintained until anaphase I

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9
Q

Metaphase I

A

Not single file line, homologous pairs of chromosomes are aligned at metaphase plate side by side. Orientation random (independent assortment). Microtubules attach from opposite poles to each homologue, not each sister chromatid

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10
Q

Anaphase I

A

Separate homologous pairs. Chiasmata break, sister or non-sister chromatids remain attached to each other at their centromeres. Each pole has complete haploid set of chromosomes consisting of one member of each homologous pair.

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11
Q

Telophase I

A

Nuclear envelope re-forms around each daughter nucleus. Cytokinesis may or may not occur after telophase I depending on species.

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12
Q

Prophase II

A

Follows a brief or no interphase, no S phase. Chromosomes move toward metaphase plate.

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13
Q

Metaphase II

A

Chromosomes align on metaphase plate, kinetochore microtubules from opposite poles attach to kinetochores.

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14
Q

Anaphase II

A

Microtubules shorten and sister chromatids break and are pulled to opposite poles

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15
Q

Telophase II

A

Nuclear membrane reforms around four different clusters of chromosomes. After cytokinesis 4 haploid cells

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16
Q

Final result of meiosis

A

Four haploid cells that are unique. Animals 4 spermtogenesis and 4 oogenesis (1 egg, usable and 3 polar bodies, unusable).
Some plants, fungi and protists divide haploid by mitosis

17
Q

Errors in meiosis

A

Nondisjunction-failure of chromosomes to move to opposite poles during either meiotic divisions
Aneuploid gametes-Gametes with missing or extra chromosomes