Genes 3.1

Essential Idea: Every living organism inherits a blueprint for life from its parents. 3.1 Genes Understandings: A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic   A gene occupies a specific position on a chromosome The various specific forms of a gene are alleles Alleles differ from each other by one or only a few bases New alleles are formed by mutation 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 Applications: The cause 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 Compare the number of genes in humans with other species Skill: Use a database to determine differences in the base sequence of a gene in two species

Found at a particular locus on a chromosome. Gene – a heritable factor that consists of a length on DNA and influences a specific characteristic Found at a particular locus on a chromosome.

Number of genes in various species

Alleles – versions of a gene (variation in one – a few bases) that code for different expressions of genes

Mutations Change in the DNA Responsible for creating different alleles Where is the mutation? What would be the resulting mRNA if these sequences are transcribed?

What effect does this have on the amino acid sequence?

What effect would this change have on the functioning of this polypeptide and why?

Types of Mutations Base substitutions – one base in substituted for another Frameshift mutations – additions or deletions Changes the reading frame for the rest of the polypeptide

Cystic Fibrosis

HIV and the LRP5 gene Original allele produces receptor that HIV uses to infect cells Mutation = no receptor = HIV cannot infect cells

Lactose intolerance Originally humans did not produce lactase much past infancy As cultures became more agriculture dependent, more people continued to produce lactase into adulthood

Sickle cell disease 6th triplpet in hemoglobin protein DNA changed from GAG to GTG Results in 6th amino acid changing from glutamic acid to valine

Advantages of sickle cell allele Malaria resistance – Plasmodium parasites cannot infect sickle red blood cells

Genome All of the DNA in a cell of an organism Human Genome Project – base sequencing of all human genes Started in 1990, finished in 2003