Cellular Reproduction

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Cellular Reproduction

Important Structures

Chromosomes-

Coiled up DNA that looks like an X. If pulled straight it could be up to 5centimeters long.

Humans have 23 pairs of chromosomes Each half of a chromosome has a copy of genetic information (DNA) = Chromosomes are diploid

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Chromatid- half of a chromosome

They are haploid = having only one copy of the genetic information / DNA

• A human sperm is haploid. So is a human

egg.

= when they fuse

together they form a whole chromosome

Centromere- a round structure that holds two chromatids together =

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Binary Fission

 the division of prokaryotic cells.

1. DNA is copied. Each copy moves to opposite

sides of the cell.

The Steps ===

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The Process in a

picture

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Other Types of

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• Involves the transfer of plasmid DNA between two bacteria cells via direct contact or a bridge-like

connection. (technically not sexual reproduction, since it laterally transfers genes)

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

division of eukaryotic cells

The Steps ===

1. prophase- DNA coils up and the chromosomes become visible, the nuclear membrane dissolves, and spindle fibers form

spindle fibers- fibers that connect to the centrioles and

centromeres. These fibers move the

chromosomes around

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2. metaphase- the spindle fibers line the

chromosomes up in the middle of the cell.

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4. telophase- the nuclear membranes reappear and cytokinesis occurs. The cell completely splits into 2 identical daughter cells.

5. interphase- the time of a cells life

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CELL CYCLE

G1 phase- first growth phase the cell grows rapidly and performs routine functions

S phase- synthesis phase DNA copies itself.

Remember at the end of mitosis you only have

one copy (chromatids)

G2 phase- second growth phase the nucleus prepares for

mitosis and other organelles make copies of themselves

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• If a cell receives a go-ahead signal at the G₁

checkpoint, it will usually complete the S, G₂, and M phases and divide

• If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G₀ phase

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• Cyclin-dependent kinasis (CDKs) turn on and off the processes that take place in cell division by partnering with proteins called cyclins.

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External Signals For Cell Division

• Some external signals are growth factors, proteins released by certain cells that stimulate other cells to divide

• Another example of external signals is density-dependent inhibition, in which crowded cells stop dividing.

• Most animal cells also exhibit anchorage dependence, in

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Cancer…….Mitosis gone wrong

_{There are over 200 types of cancer}

_{Normal cells grow, divide, and die in an orderly}

way. Abnormal cells develop when DNA is

damaged from chemicals, radiation, or viruses.

Breast Cancer cell

Brain Cancer cells

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 _{Malignant tumors may be dangerous}

because they can invade nearby parts of the body and stop them functioning properly. Cells from malignant tumors can also break

away and travel to other parts of the body, where they can form new

groups of abnormal cells, called secondary growths or metastases.

_{Abnormal cells, instead of dying, continue to}

grow and produce more abnormal cells

_{This cluster of abnormal cells is called a tumor.}

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Genes Linked To Cancer

• Proto-oncogenes normally control what kind of cell it is and how often it divides. When a proto-oncogene mutates (into an oncogene, it can

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Genes Linked To Cancer

• Tumor suppressor genes are genes that slow down cell division, repair DNA mistakes, or apoptosis. When tumor suppressor genes don't work properly, cells can grow out of control.

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- The production of haploid sperm and egg cells

Spermatogenesis- process of forming 4 haploid sperm

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Cross over- parts of the chromosomes overlap and swap genetic information. This creates

unlimited combinations of genetic traits.

ANOTHER BIG DIFFERENCE

It goes through division twice and 4

non-identical haploid cells are produced

The Steps === Same as mitosis except…

1. Prophase 1- Same as mitosis except the

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Nondisjunction

• The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis.

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Polyploidy

• Polyploids arise when a rare mitotic or meiotic catastrophe, such as nondisjunction, causes the formation of gametes that have a complete set of duplicate chromosomes.