1. Involves cell specialization in structure and function 2. Is controlled by turning specific sets of genes on or off

Biology ch 11 Flashcards by Ye Eun Kim

Differentiation

Involves cell specialization in structure and function

2. Is controlled by turning specific sets of genes on or off

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Almost all of the cells in the organism contain…..

An identical genome

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The differences between cell types are

Not due to the presence of different genes but instead due to selective gene expression

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Eukaryotic chromosomes undergo multiple levels of folding and coiling called…

DNA Packing

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Nucleosomes are formed….

When DNA is wrapped around histone proteins.

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The histone protein packing gives a…

“Beads on a string” appearance

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Each nucleosome bead includes…

DNA and 8 histones

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Linkers

Stretches of DNA that join consecutive nucleosomes

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At the next level of packing, the beaded string is….

wrapped into a tight helical fiber

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The tight helical fiber coils further into..

a thick supercoil

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What can further compact the DNA?

Looping and folding

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DNA packing tends to prevent….

Gene expression by preventing RNA polymerase and other transcription proteins from contacting the DNA

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Higher levels of packing can….

Inactivate genes for the long term

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Where is highly compacted chromatin usually found in?

In varying regions of interphase chromosomes.

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Highly compacted chromatin is….

generally not expressed at all

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Chemical modification of DNA bases or histone proteins can result in what?

Epigenetic inheritance

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X chromosome inactivation

one of the 2 X chromosomes is chemically modified and highly compacted
Either the maternal or paternal chromosome is randomly inactivated
Inactivation only during early embryonic development and all cellular descendants have the same inactivated chromosome

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Barr body

An inactivated X chromosome

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Tortoiseshell fur coloration is due to…

Inactivation of X chromosomes in heterozygous female cats

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Most cells express only a..

small percentage of their genes

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One way to approach questions, “If all genes are still present but some are turned off, have the unexpressed genes become permanently disabled?” and “Or do all genes (even the unexpressed ones) retain the potential to be expressed?” is to…

determine if a differentiated cell can be stimulated to generate a whole new organism

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A differentiated plant cells can undergo…

cell division and give rise to all the tissues of an adult plant

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Clone

An organism, produced through asexual reproduction from a single parent

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In animals, a good indication that differentiation need not impair a cell’s genetic potential is the natural process of

Regeneration

The regrowth of lost body parts

When a salamander loses a leg...

Certain cells in the leg stump differentiate, divide, and then redifferentiate, giving rise to a new leg

Animal cloning can be achieved using

Nuclear Transplantation

Nuclear Transplantation steps

1. The nucleus is removed from an egg cell 2. A somatic cell from an adult donor is added 3. The cell grows in culture to produce a blastocyst (early embryo) 4. The blastocyst is implanted in a surrogate mother

Nuclear transplantation was first performed in

1950s using cells from frog embryos

First mammals produced in 1996 by using nuclear transplantation is called

Dolly

Dolly demonstrated...

that the differentiation of animal cells is achieved by changes in gene expression, rather than by permanent changes in the genes themselves

Researchers have cloned many other mammals such as

Mice, cats, horses, cows, mules, pigs, rabbits, ferrets, and dogs

Conservation biologists hope that..

reproductive cloning can be used to restock the populations of endangered animals

However, an increasing body of evidence suggests that

Cloned animals may be less healthy than those arising from a fertilized egg

What did recent research suggests that may be responsible for health problems in cloned animals?

Methylation of chromatin

A blastocyst can provide

Embryonic Stem cells (ES cells)

Embryonic Stem Cells (ES Cells)

- Can differentiate in an embryo to give rise to all the specialized cell types of the body - Can divide indefinitely when grown in laboratory culture

When the goal is to produce embryonic stem cells to use in therapeutic treatments, this process is called

Therapeutic cloning

The adult body also has stem cells, which serve to...

Replace non-reproducing specialized cells as needed

Because adult stem cells are farther along the road to differentiation than ES cells..

They can give rise to only a few related types of cells

Cancer

a set of disease in which the control mechanisms that normally limit cellular growth have malfunctioned

The malfunction of cancer is due to

Changes in gene expression

Oncogene

The genes that a cancer-causing virus inserts into a host cell can make the cell cancerous

One example of viruses that harbor cancer-causing genes is

Human Papillomavirus (HPV)

- Can be transmitted through sexual contact | - Is associated with several types of cancer, most with cervical cancer

2 types of genes in mutations that can cause cancer

1. Oncogenes | 2. Tumor-suppressor Genes

Proto-Oncogenes

Normal genes that promote cell division - Mutation to this create cancer-causing oncogenes that often stimulate cell division

Tumor-Suppressor genes

- Normally inhibit cell division or function in the repair of DNA damage - Mutation to this inactivate the genes and allow uncontrolled division to occur

What cancer is one of the best-understood types of human cancer and illustrates an important principle about how cancer develops?

Colon Cancer

Colon cancer illustrates

The gradual progression from somatic mutation to cancer

Cancer progression

1. An oncogene arises or is activated, resulting in increased cell division in apparently normal cells in the colon lining 2. Additional DNA mutations cause the growth of a small benign tumor (polyp) in the colon wall 3. Additional mutations lead to a malignant tumor with the potential to metastasize

What is the second-leading cause of death in most industrialized nations?

Cancer

Cancer can run in families if

An individual inherits an oncogene or a mutant allele of a tumor-suppressor gene that makes cancer one step closer

Carcinogens

Cancer-causing agents that alter DNA

Most mutagens are

Carcinogens

2 of the most potent carcinogens are

1. X-Rays | 2. Ultraviolet radiation in sunlight

What substance is known to cause more cases and types of cancer than any other single agent?

Tobacco - Lung Cancer

Healthy lifestyle that reduce the risks of cancer include:

1. Avoiding carcinogens, including the sun and tobacco products 2. Exercising adequately 3. Regular medical checks for common types of cancer 4. A healthy high-fiber, low-fat diet including plenty of fruits and vegetables