3.1 genes every living organism inherits a blueprint for life from its parents
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3.1 Genes
Every living organism inherits a blueprint for life from its parents.
A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic.
Q: Are humans “more complex” than other species? A gene occupies a specific position on a chromosome.Q: What is the location of a gene called?
The various specific forms of a gene are alleles.
Alleles differ from each other by one or only a few bases.
Q: How many alleles make up human blood type?Q: What do alleles have in common?
Most animals and plants have two copies of each gene.
What combinations of alleles could be present?
New alleles are formed by mutation.• Mutations are not likely to:– Allow you to control weather– Read minds– Sprout claws from between your knuckles– Fly– Shoot fire or lasers from your eyes– Freeze things– Heal fatal wounds– Bend the will of others– Absorb other mutants powers
New alleles are formed by mutation.
• The cumulative effects of millions of mutations and natural selection have allowed all organisms to evolve from simpler ancestors
• Not all mutations cause diseases, but some do.• Even though DNA replication is protected by base-pairing, mistakes can occur.
• This is more likely after exposure to radiation or some chemicals.• The mutation may cause a gene to be wrongly expressed – a genetic disease
Application: The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin. Recall one specific base substitution that causes glutamic acid to be substituted by valine as the sixth amino acid in the hemoglobin polypeptide.
The genome is the whole of the genetic information of an organism.
The entire base sequence of human genes was sequenced in the Human Genome Project.
Q: Explain two discoveries that resulted from the Human Genome Project.
Ethics of genome research
• Is it ethical to take a DNA sample from ethnic groups around the world and sequence it without their permission?
• Is it ethical for a biotech company to patent the base sequence of a gene to prevent other companies from using it to conduct research freely?
• Who should have access to genetic information? Should employers, insurance companies, and law enforcement agencies know our genetic makeup?
Application: Comparison of the number of genes in humans with other species. The Genbank® database can be used to search for DNA base sequences. The cytochrome C gene sequence is available for many different organisms and is of particular interest because of its use in reclassifying organisms into three domains. At least one plant and one bacterium should be included in the comparison and at least one species with more genes and one with fewer genes than a human.
Skill: Use of a database to determine differences in the base sequence of a gene in two species.
Nature of science: Developments in scientific research follow improvements in technology—gene sequencers are used for the sequencing of genes.