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 (trait) Found at a particular locus on a chromosome Traits may also be influenced by multiple genes

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

Mutations Change in the DNA Responsible for creating different alleles Discuss as a table: 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?

Gene mutations can be beneficial, detrimental or neutral. Beneficial mutations change the gene sequence to create new variations of a trait that are advantageous Detrimental mutations change the gene sequence in a way that stops the normal function of a trait Neutral mutations have no effect on the functioning of the specific feature

Discuss as a table: Discuss the impact of beneficial, detrimental, and neutral mutations on natural selection an evolution.

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

Types of point mutations

Cystic Fibrosis https://www.youtube.com/watch?v=DySt5tLi4G8

HIV and the LRP5 gene Original LRP5 allele produces receptor on any types of cells 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 triplet 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 Genome is the total genetic information of a cell, organism or organelle This includes all genes all well as non-coding DNA sequences The human genome consists of: 46 chromosomes 3 billion base pairs 21,000 genes

Human Genome Project – base sequencing of all human genes Started in 1990, finished in 2003 Approximately 23,000 genes Led to the discovery of “junk DNA” – not really junk, just doesn’t code for proteins https://unlockinglifescode.org/timeline?tid=4

Number of genes in various species