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BIO207 > Chromosomes and Inheritance > Flashcards

Chromosomes and Inheritance Flashcards

1
Q

What is mitosis?

A

Nuclear division that generates two daughter cells containing the same number and type of chromosomes as parent cell.

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2
Q

What is meiosis?

A

Nuclear division that generates gametes containing half the number of chromosomes found in other cells.

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3
Q

What is fertilization?

A

The union of haploid gametes to produce diploid zygotes.

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4
Q

What is a centromere?

A

A specific location at which chromatids are attached.

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5
Q

What is a metacentric chromosome?

A

A chromosome whose centromere is in the middle.

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6
Q

What is an acrocentric chromosome?

A

A chromosome whose centromere is near one end.

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7
Q

What are sister chromatids?

A

Identical copies of a replicated chromosome.

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8
Q

What are homologs?

A

Chromosomes that contain the same set o genes but may have different alleles for some genes.

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9
Q

What are nonhomologs?

A

Chromosomes that carry completely unrelated sets of genes.

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10
Q

What is a karyotype?

A

A micrograph of stained chromosomes arranged in homologous pairs.

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11
Q

How do homologous chromosomes appear in karyotypes?

A

Same size, shape, and banding.

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12
Q

What are autosomes?

A

All chromosomes except the sex chromosomes.

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13
Q

How do chromosomes usually exist in the nucleus?

A

As chromatin

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14
Q

What is chromatin?

A

A long thread primarily made of DNA with some protein scaffolding.

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15
Q

When does chromatin duplicate and condense into the visible chromosomes of a karyotype?

A

Only in preparation for cellular division.

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16
Q

What are the three phases of interphase?

A

Gap 1 (G1) phase, synthesis (S) phase, gap 2 (G2) phase

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17
Q

What is interphase?

A

The period of cell growth and chromosome duplication between divisions

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18
Q

Where does microtubule formation occur?

A

In the cytoplasm

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19
Q

What is a centrosome?

A

Microtubule organizing center near the nuclear envelope

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20
Q

What are centrioles?

A

Core of the centrosome (not found in plant cells)

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21
Q

Where does the majority of cell growth occur?

A

During G1 and G2

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22
Q

When do chromosomes replicate to form sister chromatids?

A

During S phase

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23
Q

Do all cells divide indefinitely?

A

No, some terminally differentiated cells stop dividing and arrest in G0 phase (ex. mature neurons)

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24
Q

What occurs during G1 phase?

A

Cell growth, chromosomes are not duplicating or dividing

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25
What occurs during S phase?
Duplication of chromosome into sister chromatids
26
What occurs during G2 phase?
Cell growth, synthesis of proteins required for mitosis
27
What happens during prophase?
Chromosomes condense and become visible Centrosomes move apart toward opposite poles Nucleoli begin to disappear
28
What occurs during prometaphase?
Nuclear envelope breaks down Microtubules from centrosomes invade the nucleus and kinetochores in the centromere of each chromatid -> sister chromatids attach to microtubules from opposite poles
29
What are the three kinds of microtubules that form mitotic spindles?
Astral, kinetochore, polar
30
What occurs during metaphase?
Chromosomes align on the metaphase plate with sister chromatids facing opposite poles
31
How do chromosomes stay in place along the metaphase plate during metaphase?
Forces pushing and pulling chromosomes to or from each other are in balanced equilbrium
32
What occurs during anaphase
Centromeres of all chromosomes split simultaneously Kinetochore microtubules shorten and pull separated sister chromatids to opposite poles
33
What occurs during telophase?
Nuclear envelop forms around each group of chromatids Nucleoli re-form Spindle fibers disappear Chromosomes uncoil and reform as chromatin
34
What is cytokinesis?
Cytoplasm of parent cells split into two daughter cells with identical nuclei
35
Differentiate between animal cytokinesis and plant cytokinesis.
Animals - contractile ring that contracts to form cleavage furrow Plants - cell plate forms near equator of cell Both - organelles distributed to each daughter cell
36
What is the result of cytokinesis not occurring after mitosis
Syncytium, cell with multiple nuclei
37
How does the cell cycle prevent errors?
Checkpoints that will not enable the cycle to move forward unless prior events have been completed.
38
What needs to happen at the checkpoint before chromosome duplication can begin?
Cell is of sufficient size and proper signals have been received.
39
What needs to happen before the checkpoint enables mitosis to begin?
Chromosomes completely duplicated
40
What needs to happen before the checkpoint enables anaphase
All chromosomes arrived and aligned at metaphase plate
41
What are somatic cells?
Vast majority of cells in an organism
42
What are germ cells?
Precursors to gametes
43
Generally describe the two rounds of cell division in meiosis
Chromosomes duplicate once, nuclei divide twice
44
What happens in meiosis I?
Reduces chromosomes from 2n to n
45
What happens in meiosis II?
Produces four haploid nuclei
46
What are the three main events of meiosis I?
Homologs pair, cross over and then segregate
47
What are the first three substages of prophase I?
Leptotene, zygotene, pachytene
48
In meiosis, what holds homologous chromosome pairs together?
Synaptonemal complex
49
What happens during leptotene?
Chromosomes begin condensing Centrosomes start moving toward opposite poles
50
What happens during zygotene?
Homologous chromosomes enter synapsis The synaptonemal complex forms
51
What happens during pachytene?
Synapsis is complete Crossing over occurs
52
What is crossing over?
Genetic exchange between non-sister chromatids of a homologous pair
53
What are the last two substages of prophase I?
Diplotene and diakinesis
54
What happens during diplotene?
Synaptonemal complex dissolves Tetrad of four chromatids is visible Crossover points appear as chiasmata, holding nonsister chromatids together Meiotic arrest occurs in many species
55
What happens during diakinesis?
Chromatids thicken and shorten Nuclear membrane breaks down and spindle begins to form
56
Describe the state of chromosomes in leptotene
Threadlike chromosomes begin to condense, becoming visible as discrete structures. Sister chromatids can't be distinguished yet.
57
Describe the state of chromosomes during zygotene
Chromosomes are clearly visible and begin pairing with homologous chromosomes along the synaptonemal complex to form a bivalent/tetrad
58
Describe the state of chromosomes during pachytene.
The homologs synapse fully. Recombination nodules appear along synaptonemal complex
59
Describe the state of chromosomes during diplotene.
Bivalent pulls apart slightly, homologs remain connected through chiasmata
60
Describe the state of chromosomes during diakinesis
The bivalent condenses further
61
What happens during metaphase I?
Tetrads line up along metaphase plate Each chromosome of a homologous pair attaches to fibers from opposite poles Sister chromatids attach to fibers from the same pole
62
What happens during anaphase I?
Sister centromeres remain connected Chiasmata dissolve Homologous chromosomes move to opposite poles
63
What happens during telophase I?
Nuclear envelope reforms Resultant cells have half the number of chromosomes, each consisting of two sister chromatids Cytokinesis separates daughter cells
64
What happens during interkinesis?
No chromosomal duplication Chromosomes decondense in some species
65
What happens in prophase II?
Chromosomes condense Centrioles move toward poles Nuclear envelope breaks down
66
What happens during metaphase II?
Chromosomes align at metaphase plate Sister chromatids attach to spindle fibers from opposite poles
67
What happens during anaphase II?
Sister centromeres detach from each other, allowing movement to opposite poles
68
What happens during telophase II?
Chromosomes begin to uncoil Nuclear envelopes and nucleoli reform
69
What is nondisjunction?
Homologs of a chromosome pair do not segregate during meiosis I
70
What may nondisjunction result in?
Inviable gametes or embryos OR Abnormal chromosome numbers in viable individuals
71
What are the two ways in which meiosis contributes to genetic diversity?
Independent assortment of nonhomologs creats different combinations of alleles across gametes Crossing over between homologs creates different combinations of alleles within each chromosome
72
What is the chromosome theory of inheritance?
Chromosomes carry Mendel's units of heredity
73
Who came up with the chromosome theory of inheritance?
Walter Sutton

BIO207 (9 decks)

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