Chapter 16: Variation and Evolution

Species

Specific group of organisms that are capable of mating and producing fertile offspring.

Gene

Section of chromosome that controls a specific trait.

Allele

Different form of the same gene.

Locus

Location of a gene on a chromosome.

Genotype

Set of genes an individual possesses.

Genome

All the genes in an organism.

Heterozygous

One dominant and one recessive gene.

Homozygous

Two dominant or two recessive genes.

Phenotype

The physical expression of the genotype.

Dominant Genes

Always expressed when present.

Recessive Genes

Genes that are only expressed in the absence of dominant genes.

Mutation

Any permanent change in the structure of the gene.

Homologous Chromosomes

Pairs of chromosomes with identical genes and loci.

F1 Cross

Cross between two pure breeding parents.

Haploid

Single set of chromosomes.

Diploid

Paired set of chromosomes.

Mendel’s First Law

Inherited characteristics are controlled by pairs of genes.

Mendel’s Second Law

Separation of one pair of alleles is independent from the separation of other alleles.

Monohybrid Crosses

Cross between heterozygous parents that results in a 3:1 ratio.

Dihybrid Crosses

Cross between heterozygous parents that results in a 9:3:3:1 ratio.

Incomplete Dominance

No allele is dominant, resulting in traits that are intermediate.

Meiosis

Process that results in gametes with half the number of chromosomes.

SRY gene

Sex determining region of Y chromosome.

X linked traits

Traits associated with genes found on the X chromosome.

Point Mutation

Change in one base pair of DNA.

Chromosome Mutation

Large change in the structure of a chromosome.

Linkage

Genes that are on the same chromosome and inherited together.

Sex Linkage

When a characteristic is controlled by a gene on an X chromosome.

Variation

Differences between members of the same species.

Acquired Variation

Not genetically controlled but learned throughout life.

Inherited Variation

Genetically controlled variation.

Causes of Inherited Variation

Independent assortment, crossing over, fertilization, mutations.

Evolution

Inheritable change in a population producing new forms of life over time.

Natural Selection

Mechanism proposed by Darwin for evolution.

Survival of The Fittest

Only organisms with advantageous traits will survive and reproduce.

Speciation

Formation of a new species through the process of evolution.

Paleontology

The study of fossils.

Radioactive Carbon Dating

Method to date fossils using carbon-14.