Bio 30 Unit 3 Ch. 17 _ Genetics

Genes

Genes

Segments of DNA that determine specific traits in an organism.

Alleles

Different variations of genes that can exist for a specific trait.

Genotype

The combination of alleles an organism has for a given trait, which determines its genetic makeup.

Phenotype

The physical expression of a trait, which is influenced by the organism's genotype.

Monohybrid Crosses

Crosses between individuals that differ in only one trait.

Punnett squares

A tool used to predict the possible genotypes and phenotypes of offspring in a genetic cross.

Selective breeding

The intentional breeding of organisms with desirable traits to produce offspring with those traits.

Dominant allele

An allele that is expressed in the phenotype when present.

Recessive allele

An allele that is only expressed in the phenotype when two copies are present.

Law of Segregation

The principle that during gamete formation, the two alleles for a trait segregate randomly and each gamete receives one allele.

Homozygous dominant

Having two copies of the dominant allele for a trait.

Heterozygous

Having one copy of the dominant allele and one copy of the recessive allele for a trait.

Homozygous recessive

Having two copies of the recessive allele for a trait.

Blending theory

An incorrect theory of inheritance that suggested traits blend together from both parents.

Monohybrid Crosses

Crosses where only one trait is considered.

Phenotype

the physical expression of a trait

Genotype

The genetic makeup of an individual, represented by the combination of alleles.

Independent assortment

The principle that states that alleles for different traits segregate independently of each other during gamete formation.

Incomplete dominance

A mode of inheritance where neither allele is completely dominant over the other, resulting in a blending of traits in heterozygotes.

Co-dominance

A mode of inheritance where both alleles are fully expressed in heterozygotes, resulting in the simultaneous expression of both traits.

Sex-linked traits

Traits that are located on the sex chromosomes (X or Y) and display different inheritance patterns than traits located on autosomes.

Multiple alleles

The existence of more than two alleles for a particular gene in a population.

Blood types

A system of multiple alleles that determine the different blood types (A, B, AB, O) in humans.

X-linked recessive

Mode of inheritance where a recessive allele on the X chromosome causes a phenotype to be expressed in males with only one copy of the allele.

Multiple alleles

More than two alleles exist for a particular gene within a population.

Pedigree

A flowchart that shows the expression of a particular trait through multiple generations of a family.

Recombinant

An event where crossing over takes place during meiosis, resulting in the exchange of genetic material between homologous chromosomes and the formation of new combinations of alleles.

Gene mapping

The process of determining the relative positions of genes on a chromosome based on the frequency of recombination between them.

Parental gametes

Gametes that have the same combination of alleles as one of the parents.