Agents Of Micro Evolution

Agents of Microevolution

Mutation

hemoglobin tetramer

sickle cell Hb (forms long tubular rods)

Mutation(ex.,CFTR gene) ► ► ► ► ►

Found on chromosome 7 Codes for a protein that is 1,480 amino acids long Deletion of 3 nucleotides at positions 507-508 in the CFTR protein Results to the genetic disorder “cystic fibrosis” Common among Caucasian-Americans, one in every 2,000 births

CFTR gene mutation    

 

 

A  T ISOLEUCINE 506  C   A  T      ISOLEUCINE 507  C                               -->    ISOLEUCINE  507         T                                                T      PHENYLALANINE 508    --> NO 508  T  

G  G      GLYCINE 509   T

 

G  T      VALINE 510  T

 

Protein coded for by CFTR gene

Migration

Genetic Drift: effect

Bottleneck

Geneticall y diverse

Genetic diversit y lost

Genetic drift: Bottleneck effect

► Caused

by intense competition, adverse environmental conditions, or parasitism ► Increases the rate of random genetic drift ► Inbreeding is also increased due to reduced genetic pool ► Reduces resistance to parasites and diseases, & the ability to respond to environmental changes ► Genetic variation is reduced

Population bottleneck

Northern elephant seal

► By

1910, it is estimated that there were less than 100 elephant seals, all found on Guadalupe island, in Mexico. ► Present population is estimated to be more than 150,000.

Population bottleneck ► Exhibits

almost no allelic variation ► Assumed to have survived a great, persistent population bottleneck some 10,000 years ago

Cheetah

Genetic drift: Founder effect exemplified by the Dunkers of Pennsylvania ► Result of blood type survey: Nearly 60 % of the Dunkers had blood type A; the West German population was 45 % A and the US neighbor population was only 40 %. ► Little dispersal; new allele predominates ►

Nonrandom mating ► Inbreeding

lessens heterozygosity ► Increases the chance of producing offsprings with defective genes

Ellis van Creveld syndrome

Royal family afflicted with hemophilia

Selection: Natural selection ► Stabilizing

selection limits extremes of population ► Examples: human birth weight, gallmaking fly Eurosta ► Operates in stable habitats

Stabilizing selection

Eurytoma gigantea (wasp)

Eurosta solidaginis (fly), laying its eggs on goldenrod (Solidago altissima) stem

Downy woodpecker

► Directional

selection- a single allele is favored; allele frequency continuously shifts to one direction ► The population is faced with a new environmental condition

Disruptive selection- intermediate forms are selected against