12.1 Inheritance of Genes Follows Mendelian Laws Flashcards
Blending vs. Particulate Inheritance
Blending inheritance suggests that hereditary determinants blend in the zygote, whereas particulate inheritance proposes that hereditary determinants are distinct, observable traits passed from parents to offspring.
Mendel’s Experiments & Garden Peas
Gregor Mendel conducted experiments with garden peas to study inheritance patterns. He meticulously recorded the traits of successive generations to understand how traits were passed from parents to offspring.
Generations: P, F1, F2
In Mendel’s experiments, the parental generation (P) refers to the original plants crossed. The first filial generation (F1) consists of offspring resulting from the P generation cross, and the second filial generation (F2) results from crossing F1 plants.
Monohybrid Crosses & 3:1 Ratios
Monohybrid crosses involve mating individuals that are heterozygous for one trait. Mendel observed a consistent 3:1 ratio of dominant to recessive traits in the F2 generation of his monohybrid crosses.
Diploid vs. Haploid
Diploid organisms have two sets of chromosomes, one from each parent, while haploid organisms have only one set of chromosomes.
Alleles: Homozygous, Heterozygous
Alleles are different forms of a gene. Homozygous individuals have two identical alleles for a particular gene, while heterozygous individuals have two different alleles.
Phenotype vs. Genotype
Phenotype refers to the physical trait expressed by an organism, while genotype refers to the genetic makeup of an organism, including its alleles.
Mendel’s Laws: Segregation & Independent Assortment
Mendel’s law of segregation states that two alleles for each trait separate during gamete formation. The law of independent assortment states that alleles of different genes assort independently during gamete formation.
Punnett Square
A Punnett square is a grid system used to predict the genotypes of offspring from a genetic cross between two parents.
DNA, Chromosomes, & Allele Segregation
DNA, the hereditary material, is organized into chromosomes. Alleles segregate as chromosomes separate during meiosis.
Probability Rules & Crosses
Probability is used to predict the likelihood of certain outcomes in genetic crosses. The multiplication rule is used for independent events occurring together, while the addition rule is used for events that can occur in two different ways.
Dihybrid Crosses & 9:3:3:1 Ratios
Dihybrid crosses involve mating individuals that are heterozygous for two traits. Mendel observed a consistent 9:3:3:1 phenotypic ratio in the F2 generation of his dihybrid crosses.
Pedigrees: Human vs. Pea Plants
Pedigrees are family trees that show the occurrence of traits in several generations. While pedigrees are more accurate with pea plants due to controlled breeding, they are also used to track inheritance patterns in humans.
Inheritance: Dominant vs. Recessive
Dominant alleles are expressed when present, while recessive alleles are only expressed when no dominant allele is present.
X-linked Traits: Dominant & Recessive
X-linked traits are carried on the X chromosome. X-linked dominant traits typically affect females, while X-linked recessive traits typically affect males.
