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Eli Minkoff • Pam Baker
Biology Today
Third Edition
Chapter 3
Human Genetics
Copyright © 2004 by Garland Science
What Do Genes Do?
•
Direct the production of a protein
– Two steps:
1. transcription of DNA to RNA
2. translation of RNA to protein
• together, are called gene expression
•
Just because you have a gene for a
trait doesn’t mean it will be expressed
(show up)
RNA: the other nucleic acid
• Ribonucleic Acid
• How is it similar to DNA?
– Made of nucleotides
• A sugar
• A phosphate
• Nitrogenous bases
RNA: the other nucleic acid
• Ribonucleic Acid
• How is it different from DNA?
– Made of nucleotides
• A sugar: ribose instead of deoxyribose
• A phosphate: the same PO4
• Nitrogenous bases: Adenine, Cytosine,
Guanine, and URACIL (no Thymine)
– Single stranded
RNA: the other nucleic acid
• Three types….three different jobs
– mRNA = messenger RNA
– tRNA = transfer RNA
– rRNA = ribosomal RNA
Figure 3.2
Figure 3.2a
Figure 3.2b
Figure 3.3 (1)
Figure 3.3 (2)
Figure 3.3 (3)
Figure 3.3 (4)
Figure 3.4
Figure 3.5
Figure 3.5 (1)
Figure 3.5 (2)
Figure 3.5 (3)
Figure 3.6
Figure 3.6a
Figure 3.6b
Figure 3.7a
Figure 3.7b
Figure 3.7c
Identifying genetic causes for
traits/diseases
• Is the trait/disease environmental or
genetic?
– Lifestyle-can still be influenced by family
– Studies of twins
• Pp. 72 to 75-discuss how a particular
trait/disease might be linked to a
particular gene; not testworthy
Figure 3.8
Figure 3.9a
Figure 3.9b
Linkages found 1980-1990
•
•
•
•
•
Huntington’s-chromosome 4
Cystic fibrosis-chromosome 7
Alzheimerj’s disease-chromosome 21
One colon cancer-chromosome 2
Two forms of manic depressionchromosome 11 and X
Figure 3.10
Only a few follow simple
Mendelian genetic processes:
•
•
•
•
•
Alkaptonuria
Phenylketonuria
Duchenne’s muscular dystrophy
Cystic fibrosis-chromosome 7
Huntington’s disease/choreachromosome 4
Some genes increase risk or
susceptibility
• Alcoholism
• Obesity
Some traits are governed by
several to many genes
• Height
• Skin color
How can this info be used?
• Gather/share info through genetic
testing and counseling
• Change individual genotype (gene
therapy)
• Change gene pool at populational level
• Change balance between
environmental and genetic factors
Figure 3.11a
Figure 3.11b
Polymerase Chain Reaction (PCR)-Nobel-worthy discovery
Figure 3.12
Figure 3.13
Figure 3.13a
Figure 3.13b