Early Concepts in Genetics
A. A ____________________ is any characteristic that can be passed from parents to offspring.
B. The scientific study of heredity is called genetics. Modern genetics began in the 1860’s
with he work of an Austrian monk and scientist named _________________________________.
He used pea plants to study how traits were passed from one ___________________________ to another.
Mendel’s Investigations:
An organism that receives different genetic information for a trait from each _____________________.
Mendel studied 7 traits in __________ plants. He chose these seven because each appeared in
two distinct forms. There was no intermediate color.
Each group was considered _____________________ because when allowed to self fertilize, each
produced only offspring with the same trait as the parent.
Mendel crossed 2 different pure bred plants:
He called the purebred plants the parental generation ____________.
Mendel’s P1 plants produced a generation of _____________________ offspring plants. Mendel
called these offspring the first filial, or first offspring generation _________________.
Mendel let the hybrid plants self fertilize and produce the next generation.
He called this generation the ____________________.
They were a 3:1 ratio:_______________________________________________________________
The F1 generation were all the same as only one of the ________________________ plants.
1. Mendel called a trait that showed up in a hybrid a _______________________ trait.
What is one of the dominant traits in pea plants?
2. A trait that did not show in a hybrid he called a _________________________ trait.
What is one of the dominant traits in pea plants?
D. Mendel hypothesized that each trait is controlled by something called a factor within
the organism. Scientist now use the word ______________________, instead of factor, to
indicate a genetic factor that controls a trait.
E. Mendel knew that two parents contribute to an organism’s inheritance. Therefore, each
organism must have _________________ factors for each trait.
Mendel also hypothesized that the two factors separate when ____________________ form.
What is the process for making gametes?
The gametes of an individual contain only one ____________________________ for each trait. During
fertilization, the single genes are joined to make a pair of offspring.
F1-generation plants
Mendel crossed SS (spherical seeds) with ss (dented seeds.)
All of the gametes of the spherical seeded parent have the S (dominant) allele
and all of the gametes of the dented seeded parent have the s (recessive) allele.
All of the F1 generation plants will have the genotype of Ss (heterozygous), and
all will be spherical seeded.
F1 generation
=
F2-generation plants
Mendel let the F1-generation plants self-pollinate to form a second generation
and he analyzed the seeds of the resulting F2 generation.
F2 generation
=
All F1-hybrid plants have the genotype Ss and all are spherical (dominant
characteristic). The recessive alleles segregate during gamete formation. As a
result, one out of four possible combinations of F2-generation plants will have the
homozygous recessive genotype (ss).
Goal: Determining the possible gametes made by the parent.
AA ___&___
Bb ___&___
bb ___&___
Gg ___&___
TT ___&___
ee ___&___
yy ___&___
Uu ___&___
Ss ___&___
Ww ___&___
Jj ___&___
Pp ___&___
Kk ___&___
Rr ___&___
cc ___&___
LL ___&___
Zz ___&___
hh ___&___
Goal: Determining the possible gametes made by the parents.
A heterozygous tall plant crossed with a purebred recessive short plant. (T)
Genotypes:
Gametes:
Parent 1 ________
Parent 1 ____&____
x
x
Parent 2 ________
Parent 2 ____&____
A hybrid tall plant crossed with a homozygous recessive short plant. (T)
Genotypes:
Gametes:
Parent 1 ________
Parent 1 ____&____
x
x
Parent 2 ________
Parent 2 ____&____
A homozygous recessive white cat crossed with a heterozygous pink cat. (P)
Genotypes:
Gametes:
Parent 1 ________
Parent 1 ____&____
x
x
Parent 2 ________
Parent 2 ____&____
x
x
Parent 2 ________
Parent 2 ____&____
Two purebred dominant fast cats. (F)
Genotypes:
Gametes:
Parent 1 ________
Parent 1 ____&____
A hybrid black cat crossed with a purebred recessive brown cat. (B)
Genotypes:
Gametes:
Parent 1 ________
Parent 1 ____&____
x
x
Parent 2 ________
Parent 2 ____&____
A heterozygous big tail cat crossed with a purebred recessive short tail cat. (T)
Genotypes:
Gametes:
Parent 1 ________
Parent 1 ____&____
x
x
Parent 2 ________
Parent 2 ____&____
A purebred recessive short giraffe crossed with a homozygous dominant tall giraffe. (G)
Genotypes:
Gametes:
Parent 1 ________
Parent 1 ____&____
x
x
Parent 2 ________
Parent 2 ____&____
x
x
Parent 2 ________
Parent 2 ____&____
Two purebred recessive sleepy dogs. (D)
Genotypes:
Gametes:
Parent 1 ________
Parent 1 ____&____