Biology Lab || Mitosis

Summary

This lab explores the stages of chicken embryo development through mitosis, where a single cell becomes a multicellular organism. The process involves five phases: prophase, prometaphase, metaphase, anaphase, and telophase. The video demonstrates preparing a microscope slide with onion root tip cells to observe these stages. Techniques include soaking in hydrochloric acid and car noise solution, staining with toluidine blue, and examining under a microscope to witness cells in various phases, illustrating the fundamental process of growth and development in both plants and animals.

Takeaways

• 🐣 The process of mitosis is how a single fertilized cell becomes a multicellular organism, such as a chicken, through cell division.
• 🔬 Mitosis involves five phases: prophase, prometaphase, metaphase, anaphase, and telophase, each with distinct cellular changes.
• 🧬 During mitosis, each daughter cell receives an identical set of chromosomes to the parent cell, maintaining genetic consistency.
• 🧅 The lab focuses on examining onion root tip cells, which are actively dividing and can display all stages of mitosis.
• 🌱 The onion's apical meristem is the region of active growth and cell division, ideal for observing mitosis.
• 🧪 The preparation of the sample involves soaking in hydrochloric acid to break down cell walls and then in Carnoy's solution to fix the cells.
• 🔍 A thin section of the root tip is prepared for microscopic examination to observe cells in various stages of mitosis.
• 📏 Toluidine blue dye is used to stain DNA, enhancing visibility of chromosomes during microscopic examination.
• 🔬 The microscope is used to first observe the sample under low power to identify the terminal end and then under high power to see cells in detail.
• 🌌 During interphase, the nucleus appears cloudy blue due to DNA staining, but chromosomes are not yet condensed and visible.
• 🧬 Prophase is marked by chromosome condensation, making them visible as X-shaped structures under the microscope.
• 🌐 Prometaphase involves the dissolution of the nuclear membrane and the formation of the spindle apparatus by microtubules.
• 🌈 Metaphase lines up the chromosomes along the cell's equator, preparing for separation in anaphase.
• 🔄 Anaphase sees the separation of sister chromatids and their movement toward opposite poles of the cell.
• 🛡️ Telophase involves the formation of new nuclear membranes around the separated chromosomes, leading to cell division.
• 🌿 Mitosis is crucial for the growth and development of organisms, including plants like onions and humans.

Q & A

What is the main focus of the lab described in the script?

The main focus of the lab is to examine the stages of mitosis in the development of a chicken embryo and to prepare and observe a microscope slide containing a sample of onion cells in various phases of mitosis.

How does a single fertilized cell become a multicellular organism through mitosis?

A single fertilized cell becomes a multicellular organism through mitosis by dividing to form two daughter cells, each with the same number of chromosomes as the parent cell, ensuring genetic continuity.

What are the five phases of mitosis mentioned in the script?

The five phases of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase.

Why is the onion root tip used for observing cells in mitosis?

The onion root tip is used because the cells in the apical meristem are actively growing and dividing, providing a rich sample to observe various phases of mitosis.

What is the purpose of soaking the sample in hydrochloric acid during the preparation process?

The purpose of soaking the sample in hydrochloric acid is to break down the plant's hard cell walls, making it easier to observe the cells under a microscope.

What is a tissue fixative and why is it used in the lab?

A tissue fixative is a solution that stops any chemical or biological reactions, preserving the sample for longer use. It is used to maintain the cells' state for examination.

What is the role of the toluidine blue dye in the lab?

Toluidine blue is a dye that stains the DNA, making it more visible under a microscope by enhancing the contrast of the cell's nucleus and chromosomes.

How is the sample prepared for examination under a microscope?

The sample is prepared by placing it on a microscope slide, adding toluidine blue dye, allowing it to soak for two minutes, blotting excess dye, adding water, and covering it with a glass coverslip to prevent air bubbles.

What is the significance of ensuring the cells are in a single layer under the coverslip?

Ensuring the cells are in a single layer allows light to pass through for clear observation under the microscope, and it prevents the cells from being destroyed or the coverslip from cracking.

What happens during prophase of mitosis as described in the script?

During prophase, each replicated chromosome undergoes condensation, becoming shorter and thicker, and is visible under a microscope as it resembles a letter X.

Can you describe the process of replication mentioned in the script?

Replication is the process by which a chromosome produces a duplicate of itself, preparing the cell for the first phase of mitosis, prophase.

Outlines

00:00

🔬 Mitosis in Chicken Embryo Development

This paragraph introduces the process of mitosis, which is fundamental to the development of a chicken embryo from a single fertilized cell into a multicellular organism. It explains the five phases of mitosis: prophase, prometaphase, metaphase, anaphase, and telophase. The lab activity involves preparing a microscope slide with onion cells to observe these phases. The onion's apical meristem, where cells are actively dividing, is the source of the sample. The preparation process includes soaking in hydrochloric acid to break down cell walls, followed by treatment with Carnoy's fixative to halt reactions. A thin section of the root tip is stained with toluidine blue to visualize DNA and then mounted on a microscope slide for examination.

05:02

🌿 Observing Mitosis Phases in Onion Root Cells

The second paragraph delves into the observation of mitosis stages in onion root tip cells under a microscope. It starts with an overview of cells in interphase, where the nucleus appears cloudy blue due to DNA staining. As cells progress to prophase, chromosomes condense and become visible. Prometaphase sees the dissolution of the nuclear membrane and the formation of the spindle by microtubules. In metaphase, chromosomes align at the cell's equator, and anaphase involves the separation and movement of chromosomes toward cell poles. Finally, telophase is characterized by the formation of new nuclear membranes and the emergence of two daughter cells. The paragraph concludes by emphasizing the importance of mitosis in growth and development, both in plants and humans, and hints at the next lab's focus on plant genetics.

Keywords

💡Mitosis

Mitosis is a type of cell division that results in two daughter cells, each having the same number and kind of chromosomes as the parent cell. It is fundamental to the growth and repair of multicellular organisms. In the video, mitosis is the central process by which a fertilized chicken egg develops into a multicellular organism, and the script describes the various phases of mitosis observed in onion root tip cells.

💡Prophase

Prophase is the first phase of mitosis where the chromatin condenses into visible chromosomes, and the nuclear envelope breaks down. This is the stage where the replicated chromosomes become distinguishable under a microscope, as mentioned in the script when discussing the changes observed in the cell's nucleus during mitosis.

💡Prometaphase

Prometaphase is the phase following prophase, during which the nuclear membrane dissolves completely, and microtubules begin to attach to the chromosomes. The script describes this phase as a time when the microtubules start to form a spindle, which is essential for the separation of chromosomes in the subsequent phases of mitosis.

💡Metaphase

Metaphase is the phase of mitosis where the chromosomes align at the cell's equator, forming the metaphase plate. This alignment is crucial for the equal distribution of genetic material to the daughter cells. The script refers to this phase when explaining the process by which the microtubules position the replicated chromosomes for separation.

💡Anaphase

Anaphase is the phase of mitosis during which the sister chromatids separate and move towards opposite poles of the cell. This phase ensures that each daughter cell will receive a complete set of chromosomes. The script describes anaphase as the moment when the replicated chromosomes split apart and begin their journey to the cell's poles.

💡Telophase

Telophase is the final phase of mitosis where the chromosomes decondense, and the nuclear envelope reforms around each set of chromosomes. The script explains that during telophase, new nuclear membranes form around the chromosomes at the cell's poles, marking the end of mitosis and the beginning of the formation of two daughter cells.

💡Apical Meristem

The apical meristem is a region of actively dividing cells found in the tips of roots and shoots in plants. It is responsible for the growth of the plant. In the script, the cells in the apical meristem of the onion root are highlighted as an ideal sample for observing mitosis due to their active growth and division.

💡Toluidine Blue

Toluidine blue is a dye used in microscopy to stain cellular structures, particularly DNA, making it visible under a microscope. The script describes the use of toluidine blue to stain the onion root tip sample, allowing for the clear visualization of the chromosomes during the various phases of mitosis.

💡Interphase

Interphase is the phase of the cell cycle during which the cell is not dividing but is preparing for the next division by carrying out metabolic activities and DNA replication. The script mentions interphase as the stage before mitosis begins and describes the appearance of the cell's nucleus during this phase.

💡Chromosome Replication

Chromosome replication is the process by which a chromosome duplicates itself, resulting in two identical copies, or sister chromatids, before cell division. The script discusses this process as a necessary step before the cell enters prophase of mitosis, ensuring that each daughter cell will receive a complete set of genetic material.

💡Microtubules

Microtubules are protein structures that form part of the cytoskeleton and play a crucial role in cell division, particularly in the formation of the spindle during mitosis. The script describes microtubules as they extend across the cell and attach to the replicated chromosomes, facilitating their movement to the cell's poles.

Highlights

The process of mitosis allows a single fertilized cell to develop into a multicellular organism, such as a chicken.

Mitosis involves five phases: prophase, prometaphase, metaphase, anaphase, and telophase.

The apical meristem of an onion root tip is an area of active cell growth and division.

Samples from the onion root tip are preserved in an alcohol solution for lab examination.

Hydrochloric acid is used to break down plant cell walls in preparation for microscopy.

A tissue fixative, such as Carnoy solution, is used to stop chemical and biological reactions for sample preservation.

Identifying the terminal end of the onion root tip is crucial for selecting the appropriate sample for examination.

A section of the root tip is sliced off for examination, using a magnifying glass to assist in identification.

Toluidine blue dye is applied to stain DNA, enhancing visibility under the microscope.

Proper preparation of the microscope slide is essential to avoid air bubbles and ensure a single layer of cells.

Low-power microscopy reveals cells in interphase, before mitosis begins.

High-power microscopy allows for the observation of cells in various stages of mitosis.

During interphase, the nucleus appears cloudy blue due to DNA staining, but chromosomes are not yet visible.

Chromosome replication occurs near the end of interphase, preparing the cell for mitosis.

Prophase is characterized by chromosome condensation, making them visible under the microscope.

Prometaphase involves the dissolution of the nuclear membrane and the formation of the mitotic spindle.

Metaphase is when chromosomes line up at the cell's equator, facilitated by microtubules.

Anaphase is marked by the separation of replicated chromosomes moving toward cell poles.

In telophase, new nuclear membranes form around the chromosomes at the cell poles.

The final stage of mitosis is the separation of the two daughter cells, each entering a new interphase.

Mitosis is fundamental to the growth and development of organisms, including plants and humans.

Transcripts

[Music]

in an earlier lab we examine the stages

in the development of a chicken embryo

how did one fertilized cell become a

multicellular chicken the answer is

through the process of mitosis during

mitosis a parent cell divides to form

two daughter cells each daughter cell is

a smaller copy of the parent cell with

the same number of chromosomes as the

parent cell during mitosis a cell goes

through five phases prophase

prometaphase metaphase anaphase and

telophase in this lab we will prepare a

microscope slide containing a sample of

onion cells and examine the cells in

each phase of mitosis the bulb of the

onion is a type of stem that grows

underground the bulb produces shoots

which sprout from the top of the bulb

and roots which descend from the bottom

of the bulb the region near the tip of

an onion root is called the apical

meristem the cells in the apical

meristem were actively growing and

dividing when the plant was alive so we

should be able to see cells in the

various phases of mitosis when the root

tip is examined under a microscope tiny

samples have been cut from the tips of

onion roots and preserved in an alcohol

solution we will use one of the samples

in this lab several steps are needed to

prepare the sample for viewing under the

microscope to break down the plants hard

cell walls the sample must be soaked in

hydrochloric acid for four minutes after

four minutes we remove the sample from

the hydrochloric acid and transfer it to

a container with a tissue fixative a

tissue fixative is a solution that will

stop any chemical or biological

reactions that might be occurring so

that a bile

sample can be preserved for longer use

the fixative we are using is car noise

solution the onion root tip must soak in

car noise solution for four minutes

after the sample soaks for four minutes

we transfer it to a clean microscope

slide we need to examine the onion root

tip to determine which end is the

terminal end the terminal end of this

sample is the rounded end since the root

is so thin a magnifying glass will help

us identify the terminal end once we

have identified the terminal end of the

root tip we hold it down with the

forceps and use a scalpel to slice off a

section about two millimeters from the

terminal end this is the sample we will

examine the rest of the root tip can be

discarded we place the sample on the

microscope slide and add two drops of

toluidine blue toluidine blue is a dye

that stains the DNA in order to see it

more clearly the toluidine blue needs to

remain undisturbed for two minutes

once the toluidine blue has had time to

soak into the cells of the onion root

tip we blot the excess dye with a paper

towel taking care not to touch the

sample with the paper towel we've lot as

much of the dye as possible from the

edge of the drop using a pipette we add

two drops of water to the sample and

cover it with a glass coverslip to keep

from trapping air bubbles under the

coverslip we place one edge of the

coverslip against the slide and gently

lower the cover slip into place the

cells of the sample must be in a single

layer to allow light to pass through to

make certain the cells are in a single

layer we place a paper towel over the

coverslip and then slowly butt

firmly press down on the coverslip

we must not twist or turn the sample

while pressing down on the coverslip

or the cells may be destroyed and we

must not press too hard or we could

crack the coverslip or the microscope

slide now we are ready to examine our

sample under the microscope to see a

large portion of the sample we examine

it under the low-power objective most of

the cells will be an interface which is

the stage of development before mitosis

begins to see details of individual

cells we will switch to the highest

power objective in this view cells in

several phases are visible during

interphase the nucleus of the cell

appears to be a cloudy blue the

toluidine blue has stained the DNA but

the individual chromosomes are not yet

visible because the chromosomes are

spread out in long intertwined strands

near the end of interphase each

chromosome in the cell's nucleus

undergoes replication replication is the

process by which a chromosome produces a

duplicate of itself

now that the chromosomes have replicated

the cell is ready to begin the first

phase of mitosis called prophase during

prophase each replicated chromosome

undergoes condensation condensation is

the process in which a replicated

chromosome twists around itself to

become shorter and thicker at this point

the replicated chromosomes are thick

enough to be visible under a microscope

each chromosome looks like a letter X

but since the chromosomes are tangled

together within the nucleus it is

difficult to see their shapes the next

phase of mitosis is prometaphase during

prometaphase the cell's nuclear membrane

dissolves notice that the shapes of the

rep

kated chromosomes are becoming easier to

distinguish after the nuclear membrane

dissolves hollow protein tubes called

microtubules extend across the cell and

attach to the replicated chromosomes the

microtubules begin to form an

oval-shaped grid or spindle which

stretches across the cell from pole to

pole the next phase of mitosis is called

metaphase during metaphase the

microtubules cause the replicated

chromosomes to line up along the cell's

equator after metaphase a cell enters

the next phase of mitosis called

anaphase during anaphase the replicated

chromosomes split apart again into

individual chromosomes and the

chromosomes begin to move toward the

poles of the cell once all the

chromosomes cluster together near the

poles of the cell the cell begins the

last phase of mitosis which is called

telophase during telophase the cell

forms a separate nuclear membrane around

each cluster of chromosomes near the

poles as soon as the new nuclear

membranes form during telophase the cell

separates into two separate daughter

cells after the two daughter cells have

been formed each cell enters interphase

and prepares to continue the process of

mitosis through the process of mitosis

an onion is able to grow and develop

into a mature plant the same process of

mitosis enables our bodies to grow and

develop into mature adults in our next

lab we will explore genetics in plants

at this time proceed with the

corresponding activities

you