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Review Questions

What is the main difference between prokaryotes and eukaryotes?

What cell structure (organelle) contains the genetic material?

What macromolecule is your genetic material classified as?

What are segments of DNA that encode for amino acids called?

Prokaryotes = No Nucleus

Eukaryotes = Nucleus

Nucleus

Nucleic Acid

Genes

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What is the difference between DNA, Chromatin, and Chromosomes?

1. DNA- deoxyribonucleic acid

Structure: double helix

Sugar phosphate backbone and nitrogen bases paired in the middle.

2. Chromatin- long strands of DNA wrapped around histones (proteins) that condense the DNA.

3. Chromosomes- tightly coiled chromatin that condense the DNA even further.

Structure: 2 sister chromatids attached at the centromere.

Sister chromatids are identical.

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Parts of a Chromosome

DNA

Histones

Chromatin

Chromosome

Sister Chromatid

Centromere

Telomeres

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Recall- In your body…

You have 2 main types of cells…

Body cells called somatic cells, which are described as diploid (2n), human somatic cells have 46 chromosomes.

Sex cells called gametes, which are described as haploid (n), humans gametes have 23 chromosomes.

All cells have a cell cycle, which consists of a period of growth and a period of division.

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Chromosome Numbers

In the body cells (somatic) of animals and most plants, chromosomes occur in pairs.

One chromosome from each pair comes from the male parent and the other one comes from the female parent.

A cell with 2 of each chromosome (1 pair of chromosomes) is called a diploid cell (2n).

A cell with only 1 of each chromosome (or half a pair) is called a haploid cell (n).

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How many chromosomes?

If a frog has 26 chromosomes in a body cell…

How many are in a diploid cell?
How many are in a haploid cell?
How many are in a gamete?
How many are in a somatic cell?

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How many chromosomes?

If an elephant has 56 chromosomes in a skin cell…

How many are in a diploid cell?
How many are in a haploid cell?
How many are in a sperm cell?
How many are in a nerve cell?

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Why do cells divide?

Cell size is limited…

Remember as a cell grows, its volume increases faster than its surface area.

Diffusion/transport cannot happen fast enough.
Cannot take in enough nutrients to make enough ATP to run the cell.
Not enough DNA to make proteins to run the various functions in the cell.

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The Cell Cycle

The life of a cell consists of a cell cycle which is made up of of the following parts:

1. Interphase- Cell Growth and DNA Replication
2. Mitosis- Division of the Nucleus
3. Cytokinesis- Division of the Cytoplasm

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The Cell Cycle

The life of a cell consists of a cell cycle which is made up of of the following parts:

1. Interphase- Cell Growth and DNA Replication
2. Mitosis- Division of the Nucleus
3. Cytokinesis- Division of the Cytoplasm

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Depending on the type of cell…

It will go through one of two processes

Mitosis OR Meiosis

Somatic cells go through mitosis
Gametes go through meiosis

Mitosis

Meiosis

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Mitosis (nuclear division)

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Mitosis (nuclear division)

Interphase- cell growth

Cell spends MOST of its lifespan in this stage.
Chromosomes are replicated (duplicated).

Phases of Mitosis

Prophase
Metaphase
Anaphase
Telophase

I-PMAT

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Prophase

First and longest phase of mitosis.

Chromatin coils (condenses) to form visible chromosomes.

Nuclear membrane (envelope) and nucleolus disappear.

Centrioles appear and move to the opposite sides of the cell.

Spindle fibers begin to form between the centrioles.

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Metaphase

Second phase of mitosis, very short!!!

The replicated chromosomes become attached to the spindle fibers by their centromeres.

The chromosomes are pulled by the spindle fibers and line up in the center of the cell (along the equator).

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Anaphase

Begins by the separation of sister chromatids.

The chromatids are pulled to the opposite sides of the cell by the spindle fibers. (Centromere breaks)

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Telophase

Final phase of mitosis.

Chromosomes unwind.

Spindle fibers break down.

Nucleolus reappears.

Nuclear membrane (envelope) reforms around the chromatin and nucleolus.

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Cytokinesis

Division of the cell’s cytoplasm.

Differs between plants and animals.

Animals: the cytoplasm pinches off.

Plants: a cell plate is laid down across the cell’s equator.

Eventually a cell membrane grows around the cell plate and true cell wall grows from the cell plate.

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Cytokinesis

Division of the cell’s cytoplasm.

Differs between plants and animals.

Animals: the cytoplasm pinches inward and eventually severs and separates.

Plants: a cell plate is laid down across the cell’s equator.

Eventually a cell membrane grows around the cell plate and true cell wall grows from the cell plate.

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Write down the name of each phase in the diagram below.

Keep in mind that some diagrams can be in either early or late stages of the phase.

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Please check your answers:

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis