MICROSCOPIC EXAMINATIONS OF THE DIVIDING CELLS Flashcards

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1
Q

The chromosomes shorten, thicken and become visible as thick rods. They are longitudinally double, with each half called a chromatid. The chromatids are closely pressed against each other throughout their length. Nucleoli and the nuclear membrane completely disappear by late prophase. Spindle fibers would then radiate from microtubule organizing centers.

A

Prophase

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2
Q

The chromosomes, which are maximally condensed, align at the equatorial plane. The chromatids in each chromosome separate from each other except at the centromere. The spindle fibers attach to the kinetochore proteins on opposite sides of the centromere.

A

Metaphase

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3
Q

Each chromatid of a chromosome possesses its own centromere. Prior to anaphase, the centromeres of sister chromatids function as one. At anaphase, the centromeres become functionally double. Each member of the doubled chromosome begins to move toward opposite poles. The poleward movement of the chromosomes is due to depolymerization of the spindle fibers attached to the kinetochores at the centromere.

A

Anaphase

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4
Q

Upon reaching the opposite poles, the chromosomes regroup into two nuclear regions. They begin to uncoil and lengthen, and finally lose their visible identity. Cytokinesis usually follows. In plant cells, the cytoplasm is divided via cell wall plate formation where separation starts from the inside towards the periphery. In animal cells, cytokinesis occurs via cleavage furrow formation that starts from the periphery going inwards.

A

Telophase

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5
Q

Objectives of Lab Act 3

A
  1. Illustrate the chromosomal behavior which occur in somatic and sex cells during mitosis and meiosis;
  2. Identify the specific events in mitosis and meiosis that allow the inheritance of traits and generation of genetic variation.
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6
Q

Mitosis in multicellular organisms and unicellular organisms

A

multicellular organisms = increasing the number of cells and of replacing worn out tissues

unicellular organisms = mode of reproduction

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7
Q

Why is there a need to change the water daily?

A

Oxygen Supply
Nutrient and Waste Balance
Preventing Microbial Growth

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8
Q

What time is the mitotic activity optimal

A

between 11 am to 2 pm

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9
Q

Why do we need to put the root tip in Farmer’s fluid?

A

Fixing
Prevention of decay
Soften tissue

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10
Q

Why do we need to put the onion root tip in 1 N HCL for 10 minutes?

A

To hydrolyze to soften the tissues and make them transparent

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11
Q

Why use acetocarmine stain on the root tip?

A

Contrast = DNA-specific stain

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12
Q

Chromosome number of onion

A

2n=16

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13
Q

Chromosome number of whitefish (coregonus sp.)

A

2n = 80

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14
Q

At what stage of mitosis is it easiest to determine the kind and number of chromosomes? Why?

A

Metaphase = chromosomes are fully condensed and line up in the middle

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15
Q

which of the stage of mitosis appears to be the most numerous? Why do you think so?

A

Prophase = prophase lasts longer, as it involves the condensation of chromosomes, formation of spindle fibers, and disintegration of the nuclear envelope

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16
Q

What is the significance of mitosis?

A

ensures that daughter cells retain the same number of chromosomes after division.

growth and development of multicellular organisms and is also essential for the repair of damaged tissues

17
Q

meiosis consists of two nuclear divisions

A

Meiosis I (reduction division)
Meiosis II (equation division)

18
Q

Prophase I: sub-stages

A

leptotene stage
zygotene stage
pachytene stage
diplotene stage
diakinesis

19
Q

Chromosome number of Grasshopper (Gesonula punctifrons)

A

2n = 23

20
Q

What happens during Leptotene

A

Chromosomes start to condense and become visible

21
Q

What happens during zygotene?

A

Homologous chromosomes pair
Synapsis

22
Q

What happens during pachytene

A

Crossing over

23
Q

What happens during Diplotene?

A

Chromosomes separate except at the chiasmata

24
Q

What happens during diakinesis?

A

Paired chromosomes condense further and become attached to spindle fibers

25
Q

Chromosome number of Wheat (Triticum aestivum)

A

2n = 42

26
Q

Where does crossing over occur? From an evolutionary perspective, why is this
advantageous?

A

prophase I of meiosis (Pachytene)

produces genetic variation which enhances a species’ diversity, which in turn boosts its ability to adapt to changing environments over time and thus facilitates evolution

27
Q

Why is meiosis I called reduction division?

A

chromosome number decreases from diploid to haploid

28
Q

Type of cell that undergoes mitosis

A

Somatic cells

29
Q

Type of cell that undergoes meiosis

A

Germ cells

30
Q

Genetic consequences of mitosis and meiosis

A

Mitosis = Genetically identical
Meiosis = Genetically unidentical