Mendelian Inheritance I Flashcards
What was the most widely favored explanation for passing of traits in the 1800s?
“blending”: hypthesis that genetic material from the two parents blends
What contradicts the blending hypothesis?
- Examination of populations contradicts this hypothesis
- Reappearance of traits, after skipping a generation, also contradicts this hypothesis
Why did Mendel use peas for his pea experiment?
- Many varieties with well-described characters
- Mating of plants can be controlled
- Easy to grow (short generation time, large number of offspring)
Mendel’s Pea Experimental Design
-ONLY chose to track characters that varied in an “either-or” manner
-used varieties that were “true breeding”
true breeding
plants that produce offspring of the same variety when they self-pollinate
Hybridization
mating two contrasting, true-breeding varieties
P (F0) generation
the generation of the true-breeding parents
F1 generation
the generation of hybrid offspring that stems from matings in the P generation
F2 generation
the generation that is produced when F1 individuals self-pollinate
Mendel’s Experiment
- P: Crossed parents that differed in an obvious character (purple pea flowers x white pea flowers)
- F1: One parent’s character disappeared (all plants had purple flowers)
- F2: The “lost” character reappeared in the next generation (purple and white flowers)
What did Mendel deduce from his results?
- Only the “purple flower factor” was affecting flower color in the F1 hybrids
- Called the purple flower color a dominant trait and white flower color a recessive trait
- “heritable factors” = genes
- “Particulate” hypothesis
What is the “particulate” hypothesis?
idea that parents pass on discrete heritable units (genes)
Alleles
alternative versions of genes account for variation in inherited characters
Heterozygous
an organism that has two DIFFERENT alleles (at a locus on homologous chromosomes) for a gene
Homozygous
an organism w/ two IDENTICAL alleles (at a locus on homologous chromosomes) for a gene
