ANP 120 (Lectures 6-9, Hereditary Genetics, Theories of Evolution, and Species)

Structural genes

Genes which contain information to make proteins.

Regulatory genes

Genes which determine the physical form of an organism (or a species).

Genotype

The set of specific genes (or alleles, one from mom and one from dad) an organism carries; it is the genetic constitution of that organism.

Phenotype

The observable physical feature of an organism that is under some form of genetic control or influence.

The ABO system

Refers to a protein found on the surface of red blood cells. This gene has three possible alleles: A, B, and O. Blood types need to be matched for safe blood transfusions.

Blending Inheritance

Idea embraced in the nineteenth and early twentieth centuries that each parent contributes equally to the offspring, and these contributions are halved at each successive generation.

Gregor Mendel

He was interested in hybridization or cross breeding, and carefully recorded the transmission of several phenotypic traits from one generation to the next.

His work was able to show that Blending Inheritance was too simplistic of an explanation.

A true-breeding plant

A plant that reliably produces the same phenotype generation after generation.

Mendel’s law of segregation

During the formation of gametes, the paired unit factors separate, or segregate, randomly so that each sex cell receives one or the other with equal likelihood.

Mendel’s law of independent assortment

During gamete formation, segregating pairs of unit factors assort independently of each other.

Mutation

An error that occurs in the replication of DNA (mitosis and/or meiosis).

It is any change in a DNA sequence during cellular replication (think somatic cells), resulting in daughter cells that are not genetic duplicates of the mother cell.

Point mutation

This occurs when a single base (A, C, G and T) in a gene is changed.

Sickle cell anemia

A point mutation which is caused by an abnormal form of hemoglobin.

Hemoglobin (Hb)

The protein contained in red blood cells that is responsible for delivery of oxygen to the tissues.

It consists of four polypeptide chains (two alpha chains and two beta chains).

Insertion mutation

A type of mutation that occurs when one or more nucleotides are added to a DNA sequence.

Huntington's disease

An example of an insertion mutation. It is a degenerative neurological disorder that is caused by a dominant allele on Chromosome 4.

In normal individuals, the codon CAG (codes for the amino acid glutamine) usually is repeated 10 to 35 times. In contrast, people who have this disorder have 40 to 180 CAG repeats.

Deletion mutation

A type of mutation that involves the loss of one or more nucleotides from a segment of DNA.

Williams Syndrome

An example of a deletion mutation. It is a dominant allele disease which results from the deletion of, most commonly, 28 genes from one region of chromosome 7.

Also sometimes called “Happy Syndrome”.

Neutral mutations

Mutations which make no contribution to the phenotype. They occur in noncoding regions. Mutations that occur in a gene but do not alter the amino acid in a protein also fall into this category.

Habsburg face

Example of a neutral mutation: A face with a very characteristic jaw shape passed down in an inbred family.

Good mutations

Mutations that increase an organism’s chance of surviving and reproducing.

X-linked disorders

Genetic conditions that result from mutations to genes on the X chromosome. They are almost always expressed in males, who have only one copy of the X chro­mosome; in females, the second X chromosome containing the nor­mally functioning allele protects them from developing x-linked disorders.

Hemophilia

Example of an x-linked disorder. It is a rare genetic disorder that prevents blood from clotting properly. It was passed down in the Romanoff family.

Evolutionary forces

In natural populations, forces that cause changes in gene frequencies over multiple generations.

Directional selection

Natural selection that drives evolutionary change by selecting for greater or lesser frequency of a given trait in a population.

Stabilizing selection

Selection that maintains a certain phenotype by selecting against deviations from it. Basically, forces that maintain the average trait.

Gene flow

Movement of genes between populations.

Genetic drift

Random changes in gene frequency in a population.

The Founder Effect

A type of genetic drift. When new populations become isolated from the parent population, their genepool only consists of genotypes from the new, small subpopulation.

It is only through a slow accumulation of mutations can the genetic diversity of the subset increase.

Genetic bottleneck

A type of genetic drift. When a large, genetically diverse population undergoes a rapid reduction in population size but later rebounds and increases again.

Sexual dimorphism

Sexes of the same species exhibit different morphological (physical) characteristics, including characteristics NOT directly involved in reproduction.

This can be seen as size difference of either sex (black widows), or colorful feathers (pheasants).

Homology

Similarity of traits resulting from shared ancestry.

Analogous

Having similar traits due to similar use, not due to shared ancestry.

Convergent evolution (or parallel evolution)

Similar form or function brought about by natural selection under similar environments rather than shared ancestry.

Systematics

This approach for organizing organisms, understands that all organisms are composed of many ancestral characteristics that have been inherited.

The goal is to show the evolutionary relationships of species.

Phylogeny

Family tree which groups related organisms based on their evolutionary history in a way that shows the level of relationship and the time scale of splitting between ancestors and descendants.

Cladistics

System which classifies organisms according to the order in time that branches arise along a phylogenetic tree.

Speciation

Formation of one or more new species via reproductive isolation.

Mayr’s biological species concept (His definition of a species)

Defines species as interbreeding populations reproductively isolated from other such populations.

Anagenesis

The process of one species evolving into another over time.

Allopatric speciation

Speciation due to isolation.

Parapatric speciation

Speciation in a case of less extreme isolation meaning that there is a bit of gene flow, but there is a build up of traits which leads to speciation.

RIM (reproductive isolating mechanisms)

Any factor—behavioral, ecological, or anatomical—that prevents a male and female of two different species from hybridizing.

Gradualism

Darwinian view of slow, incremental evolutionary change.

Macroevolution

Large-scale evolutionary change over a long time period or evolution of major phenotypic changes over relatively short time periods.

Punctuated equilibrium

Model of evolution characterized by rapid bursts of change, followed by long periods of stasis.

Adaptation

An evolved trait that increases an organism’s reproductive success (natural selection).

Archaeopteryx

A dinosaur with feathered wings (~150 million years ago) whose feathered wings were for some purpose other than flight.

Flight was likely to be have developed in evolutionary stages as these dinosaurs evolved into birds.

Adaptationism

The idea that all aspects of an organism are the product of natural selection or sexual selection.

Scientists who believe this try to understand the function of each component of an organism, assuming each component is an adaptation, to understand the whole organism.

Holism

Idea that adaptations are the by-product of natural selection + ALL the other evolutionary forces