bio - module 7

Genetics

The branch of biology concerned with heredity and variation of inherited characteristics.

"Blending" theory of inheritance

The genetic materials contributed by the male and female parents mix in forming the offspring, and the progeny inherits any characteristic as the average of the parents' values of that characteristic.

Inheritance of acquired characters

The belief that an organism acquires some traits during its lifetime and they are then passed on to the offspring.

Mendel's principles

The principles of inheritance demonstrated by Gregor Johann Mendel, including the principles of segregation and independent assortment.

Phenotype

The physical appearance of an organism, including its observable traits.

Genotype

The genetic makeup of an organism, referring to the alleles or variants of a gene carried by an organism.

Single Trait Crosses

determine the pattern of inheritance of single traits, also known as monohybrid crosses.

Alleles

Alternative forms of a gene that govern the variation of the same character and occupy corresponding positions on homologous chromosomes.

Homozygous

A true breeding organism having two identical alleles for a given characteristic.

Heterozygous

Having two different alleles for a given characteristic.

Hemizygous

A condition in which only one copy of a gene or DNA sequence is present in diploid cells.

Punnet Square

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

Testcross

A cross of an individual of unknown genotype for a particular characteristic with a homozygous-recessive individual for that same characteristic.

Mendel's First Law - the law of segregation

When an individual produces gametes, the alleles separate, so that each gamete receives only one member of the pair of alleles.

Mendel's Second Law - the law of independent assortment

Alleles of different genes get sorted into gametes independently of one another.

Chromosomal Basis of Inheritance

The concept that genes are located on chromosomes and the behavior of chromosomes during meiosis accounts for inheritance patterns.

Linked Genes

are located close together on the same chromosome and tend to be passed on together to a gamete.

Recombinants

Plants with a combination of traits not found in their parents due to crossing over and recombination of linked genes.

Crossing over

The exchange of segments between chromatids of homologous chromosomes during meiosis I.

Linkage Map

A map showing the arrangement of genes on the same chromosome based on recombination frequencies.

Map unit

A unit of measurement in a linkage map, equivalent to a recombinant offspring frequency of 1%.

Sex chromosome

A chromosome that determines the sex of an organism.

Autosome

Any chromosome that is not a sex chromosome.

Sex-linked inheritance

Inheritance of traits that are carried on the sex chromosomes.

X-linked recessive inheritance

Inheritance of recessive traits carried on the X chromosome.

Extranuclear inheritance

Inheritance patterns that do not adhere to Mendelian genetics, such as transmission through mitochondria or chloroplasts.

Maternal inheritance

Inheritance of traits associated with the female parent, often through mitochondrial or chloroplast genomes.

Mitochondria

Energy-converting organelles that evolved from prokaryotes and have their own genome.

Chloroplast

An organelle where photosynthesis takes place, believed to have originated from cyanobacteria.

Maternal inheritance in the four-o'clock plant

An example of non-Mendelian inheritance discovered by Carl Erich Correns, involving a gene named iojap that affects chloroplast ribosome assembly.

cross (hybridization)

the cross-fertilization of two different varieties/species

hybrid

the offspring of parents of two different varieties/species

f1 generation

the first generation resulting from a cross

f2 generation

the next generation of plants from self-fertilization of the f1 offspring

incomplete dominance

a type of inheritance in which one allele for a specific trait is not completely expressed over its paired allele in F1 hybrids; results in a third phenotype where the express physical trait is a combination of the phenotypes of both alleles

codominance

a cross between organisms with two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together

multiple alleles

occurrence of a gene that exists as three or more alleles in a population

pleiotrophy

the determination of more than one character by a single gene

epitasis

occurs when two or more different gene loci contribute to the same phenotype, but not additively; described as when one gene masks or modifies the phenotype of a second gene

polygenic inheritance

the additive effect of two or more gene loci on a single phenotypic characteristic