Genetic Traits




Genotype: The types of the genes of an
organism
Phenotype: The observable
characteristics of an organism
Gametes: Haploid sex cells created for
sexual reproduction
Zygote: Diploid cell created by the fusion
of sperm and egg
Genetic Traits and Vocab


Dominant Gene: A gene that can be
expressed in the homozygous (2 copies)
or heterozygous condition (1 copy of
each).
Recessive Gene: A gene that is only
expressed in the homozygous (two copies)
condition. This gene can be masked by
the dominant gene.



Allele: Version of a gene (may be dominant or
recessive)
Homozygous: The state of having two identical
alleles of a particular gene (eg AA, aa).
Hybrid/Heterozygous: The state of having
two different alleles of a particular gene (eg Aa)
Mendelian Genetics:
Gregor Johann Mendel (1822-1884)

Augustinian monk, Czech Republic.

Foundation of modern genetics.

Studied segregation of traits in the garden
pea (Pisum sativum) beginning in 1854.

Published his theory of inheritance in 1865.

Mendel was “rediscovered” in 1902.
Some basic terminology:
Generations:
P = parental generation
F1 = 1st filial generation, progeny (offspring) of the P
generation
F2 = 2nd filial generation, progeny of the F1 generation (F3 and
so on)
Crosses:
Monohybrid cross = cross of two different true-breeding strains
(homozygotes) that differ in a single trait.
*Genetics etiquette - female conventionally is written first
Simple Dominance Examples:
Fig. 10.4, Mendel’s 7 garden pea characters.
(W)Widows Peak vs. Straight (w)
(E)Wet ear wax vs. Dry ear wax (e)
(F)Free Earlobe vs. Attached (f)
Six-digits (F)
Cleft chin (C)
Tongue Roll (T)
Hitchhiker’s Thumb (H)
Hand and Arm Crossing

Left hand clasped over right is dominant

Right arm folded over left is dominant
PTC


People who have the ability to taste PTC
are dominant to people who cannot
What is the benefit for having certain
taste?

About 40 percent of people cannot taste/smell
cyanide.