Genetics and Heredity

Heredity

Transmission of traits from one generation to the next.

Genetics

Study of heredity and the variation of inherited characteristics.

Gregor Mendel

Austrian monk and scientist who studied inheritance in garden peas.

Hybrid

Offspring of two different varieties.

P generation

True-breeding parents in a cross-fertilization.

F1 generation

Hybrid offspring of the P generation.

F2 generation

Offspring of the F1 generation resulting from self-fertilization or cross between two F1 hybrids.

Monohybrid cross

Cross involving one characteristic only.

Allele

Alternative versions of a gene.

Homozygous

Having two alleles that are the same.

Heterozygous

Having two alleles that are different.

Locus

Particular location of a gene on a chromosome.

Law of Segregation

States that paired unit factors (genes) must segregate equally into gametes.

Dominant allele

Allele that determines the physical appearance of a trait.

Recessive allele

Allele that only determines physical appearance if the other allele is also recessive.

Phenotype

Physical appearance of an organism.

Genotype

Genetic makeup of an organism for an allele.

Law of Independent Assortment

States that each pair of alleles segregates independently of other pairs during gamete formation.

Incomplete Dominance

Heterozygotes have an intermediate phenotype between the two homozygous phenotypes.

Codominance

Heterozygotes display each phenotype associated with each allele.

ABO Blood Group

Blood group system based on the presence of antigens on red blood cells.

Pleiotropy

Single gene influences phenotype of multiple characters.

Polygenic Inheritance

One character is controlled by many genes.

Sex-linked Genes

Genes located on sex-determining chromosomes.

Genotypes

Combinations of alleles present in an individual's DNA

Phenotypes

Physical traits or characteristics displayed by an individual

Punnett square analysis

A method used to predict the ratio of offspring genotypes resulting from a genetic cross

Carrier

An individual with a recessive allele who does not show the associated trait but can pass it on to offspring

X-linked Genes

Genes located on the X chromosome, such as those responsible for hemophilia and red-green color blindness

Incomplete dominance

A genetic situation in which one allele does not completely dominate another allele, resulting in a new phenotype

Pedigree Analysis

Study of the inheritance of a trait in a family over multiple generations using a pedigree chart

Mendelian Genetics

Study of how traits are inherited according to Gregor Mendel's principles

Monohybrid Crosses

Genetic crosses involving a single trait

Gene

Unit of heredity that is passed from parent to offspring and determines some characteristic of the offspring

Alleles

Different forms of a gene that can occupy a specific locus on a chromosome

Punnett square

A diagram used to predict the possible genotypes of offspring in a genetic cross

Diploid

Cells containing two sets of chromosomes, one set from each parent

Identical twins

Twins derived from a single fertilized egg that share the same genetic makeup

Gametes

Reproductive cells (sperm and egg) that carry one set of chromosomes

Offspring

The children or young of a particular parent or couple

Homozygous dominant

Having two identical dominant alleles for a particular gene (e.g., PP)

Homozygous recessive

Having two identical recessive alleles for a particular gene (e.g., pp)

Testcross

A cross between an organism with an unknown genotype and a homozygous recessive organism to determine the unknown genotype

Mendel's Law of Independent Assortment

The principle that different genes segregate independently of one another during the formation of gametes

Sex-Linked Genes

Genes located on the sex chromosomes that exhibit different patterns of inheritance in males and females

Pedigree analysis

The study of an individual's ancestry and family history in order to analyze the inheritance of traits

Cross

The process of cross-fertilization between two individuals to produce hybrid offspring