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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
Q

What occurs during S phase?

A

Duplication of chromosome into sister chromatids

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26
Q

What occurs during G2 phase?

A

Cell growth, synthesis of proteins required for mitosis

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27
Q

What happens during prophase?

A

Chromosomes condense and become visible
Centrosomes move apart toward opposite poles
Nucleoli begin to disappear

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28
Q

What occurs during prometaphase?

A

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

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29
Q

What are the three kinds of microtubules that form mitotic spindles?

A

Astral, kinetochore, polar

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30
Q

What occurs during metaphase?

A

Chromosomes align on the metaphase plate with sister chromatids facing opposite poles

31
Q

How do chromosomes stay in place along the metaphase plate during metaphase?

A

Forces pushing and pulling chromosomes to or from each other are in balanced equilbrium

32
Q

What occurs during anaphase

A

Centromeres of all chromosomes split simultaneously
Kinetochore microtubules shorten and pull separated sister chromatids to opposite poles

33
Q

What occurs during telophase?

A

Nuclear envelop forms around each group of chromatids
Nucleoli re-form
Spindle fibers disappear
Chromosomes uncoil and reform as chromatin

34
Q

What is cytokinesis?

A

Cytoplasm of parent cells split into two daughter cells with identical nuclei

35
Q

Differentiate between animal cytokinesis and plant cytokinesis.

A

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
Q

What is the result of cytokinesis not occurring after mitosis

A

Syncytium, cell with multiple nuclei

37
Q

How does the cell cycle prevent errors?

A

Checkpoints that will not enable the cycle to move forward unless prior events have been completed.

38
Q

What needs to happen at the checkpoint before chromosome duplication can begin?

A

Cell is of sufficient size and proper signals have been received.

39
Q

What needs to happen before the checkpoint enables mitosis to begin?

A

Chromosomes completely duplicated

40
Q

What needs to happen before the checkpoint enables anaphase

A

All chromosomes arrived and aligned at metaphase plate

41
Q

What are somatic cells?

A

Vast majority of cells in an organism

42
Q

What are germ cells?

A

Precursors to gametes

43
Q

Generally describe the two rounds of cell division in meiosis

A

Chromosomes duplicate once, nuclei divide twice

44
Q

What happens in meiosis I?

A

Reduces chromosomes from 2n to n

45
Q

What happens in meiosis II?

A

Produces four haploid nuclei

46
Q

What are the three main events of meiosis I?

A

Homologs pair, cross over and then segregate

47
Q

What are the first three substages of prophase I?

A

Leptotene, zygotene, pachytene

48
Q

In meiosis, what holds homologous chromosome pairs together?

A

Synaptonemal complex

49
Q

What happens during leptotene?

A

Chromosomes begin condensing
Centrosomes start moving toward opposite poles

50
Q

What happens during zygotene?

A

Homologous chromosomes enter synapsis
The synaptonemal complex forms

51
Q

What happens during pachytene?

A

Synapsis is complete
Crossing over occurs

52
Q

What is crossing over?

A

Genetic exchange between non-sister chromatids of a homologous pair

53
Q

What are the last two substages of prophase I?

A

Diplotene and diakinesis

54
Q

What happens during diplotene?

A

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
Q

What happens during diakinesis?

A

Chromatids thicken and shorten
Nuclear membrane breaks down and spindle begins to form

56
Q

Describe the state of chromosomes in leptotene

A

Threadlike chromosomes begin to condense, becoming visible as discrete structures. Sister chromatids can’t be distinguished yet.

57
Q

Describe the state of chromosomes during zygotene

A

Chromosomes are clearly visible and begin pairing with homologous chromosomes along the synaptonemal complex to form a bivalent/tetrad

58
Q

Describe the state of chromosomes during pachytene.

A

The homologs synapse fully. Recombination nodules appear along synaptonemal complex

59
Q

Describe the state of chromosomes during diplotene.

A

Bivalent pulls apart slightly, homologs remain connected through chiasmata

60
Q

Describe the state of chromosomes during diakinesis

A

The bivalent condenses further

61
Q

What happens during metaphase I?

A

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
Q

What happens during anaphase I?

A

Sister centromeres remain connected
Chiasmata dissolve
Homologous chromosomes move to opposite poles

63
Q

What happens during telophase I?

A

Nuclear envelope reforms
Resultant cells have half the number of chromosomes, each consisting of two sister chromatids
Cytokinesis separates daughter cells

64
Q

What happens during interkinesis?

A

No chromosomal duplication
Chromosomes decondense in some species

65
Q

What happens in prophase II?

A

Chromosomes condense
Centrioles move toward poles
Nuclear envelope breaks down

66
Q

What happens during metaphase II?

A

Chromosomes align at metaphase plate
Sister chromatids attach to spindle fibers from opposite poles

67
Q

What happens during anaphase II?

A

Sister centromeres detach from each other, allowing movement to opposite poles

68
Q

What happens during telophase II?

A

Chromosomes begin to uncoil
Nuclear envelopes and nucleoli reform

69
Q

What is nondisjunction?

A

Homologs of a chromosome pair do not segregate during meiosis I

70
Q

What may nondisjunction result in?

A

Inviable gametes or embryos
OR
Abnormal chromosome numbers in viable individuals

71
Q

What are the two ways in which meiosis contributes to genetic diversity?

A

Independent assortment of nonhomologs creats different combinations of alleles across gametes
Crossing over between homologs creates different combinations of alleles within each chromosome

72
Q

What is the chromosome theory of inheritance?

A

Chromosomes carry Mendel’s units of heredity

73
Q

Who came up with the chromosome theory of inheritance?

A

Walter Sutton

BIO207 (9 decks)

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