Introns

Topics: DNA, Gene, Messenger RNA Pages: 7 (1196 words) Published: June 4, 2013
transcription

translation

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Fig. 9.17 Processing eukaryotic mRNA

Protect from degradation and facilitate translation

Different combinations of exons can generate different polypeptides via alternative splicing Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

6. The polypeptide chain grows until the protetin is completed.

Amino acid

Completed polypeptide

tRNA

5’ Ribosome moves toward 3’ end

Fig. 9.18 How protein synthesis works in eukaryotes

Cytoplasm

5. tRNAs bring their amino acids in at the A site of the ribosome. Peptide bonds form between amino acids at the P site, and tRNAs exit the ribosome from the E site.

Ribosome

DNA Nuclear membrane 3’ 5’ 5’ 5’ 3’ Primary RNA transcript 5’ Cap mRNA Poly-A tail mRNA 3’ 2. Introns are excised from the RNA transcript, and the remaining exons are spliced together, producing mRNA Small ribosomal subunit Nuclear pore

4. tRNA molecules become attached to specific amino acids with the help of activating enzymes. Amino acids are brought to the ribosome in the order dictated by the mRNA.

3’ RNA polymerase 1. In the cell nucleus, RNA polymerase transcribes RNA from DNA

Cap

3’ Poly-A tail Introns

Exons

Large ribosomal subunit

3. mRNA is transported out of the nucleus. In the cytoplasm, ribosomal subunits bind to the mRNA

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Fig. 9.23

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9.9 Mutation
Mutation and recombination provide the raw material for evolution Evolution can be viewed as the selection of particular combinations of alleles from a pool of alternatives Mutations in germ-line tissues can be inherited Mutations in somatic tissues are not inherited Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Mutation, Smoking and Lung Cancer Agents that cause cancer are called carcinogens These are typically mutagens

Many investigations have determined that chemicals can cause cancer in both animals and humans For example, tars and other chemicals in cigarette smoke can cause cancer of the lung Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

10.1 A scientific Revolution
Genetic engineering is the process of moving genes from one organism to another A major impact on agriculture & medicine Fig. 10.1

Producing insulin

Curing disease

Increasing yields

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Making “Magic Bullets”
In diabetes, the body is unable to control levels of sugar in the blood because of lack of insulin Diabetes can be cured if the body is supplied with insulin The gene encoding insulin has been introduced into bacteria Fig. 10.1

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10.7 Genetic Engineering of Crop Plants
Pest resistance Leads to a reduction in the use of pesticides Herbicide resistance Crop plants have been created that are resistant to Fig. 10.14 glyphosate Glyphosateresistant plants

Glyphosatesensitive plants

Petunias

Herbicide resistance offers two main advantages 1. Lowers the cost of producing crops 2. Reduces plowing and conserves the top soil Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

10.7 Genetic Engineering of Crop Plants
More Nutritious Crops Worldwide, two major deficiencies are iron and vitamin A Deficiencies are especially severe in developing countries where the major staple food is rice Ingo Potrykus, a Swiss bioengineer, developed transgenic “golden” rice to solve this problem Fig. 10.15

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