1. Gregor Mendel was an Austrian monk who performed experiments with garden peas and established the basic principles of genetics through his work. 2. Mendel showed that traits are passed from parents to offspring according to dominant and recessive alleles, and predicted inheritance patterns through experiments and statistical analysis. 3. Key terms and concepts that emerged from Mendel's work include genes, alleles, genotypes, phenotypes, monohybrid and dihybrid crosses, dominance, segregation, independent assortment, and his laws of inheritance. Mendel's findings formed the foundation of classical and modern genetics.

1. Genetics
Biology I Factoids

2. Factoid 124
• Section 9
• Gregor Mendel was an Austrian monk who
is known as the father of genetics due to
his work with garden peas. Since he was
into math, he wanted to know if there was
a way to calculate the offspring’s traits.

3. Factoid 125
• Mendel proved that if you cross a tall plant
with a short plant, all of the offspring would
be tall. Then if you crossed those tall
plants, 75% of them would be tall and 25%
would be short.

4. Factoid 126
• A gene carries encoded information about
specific traits. Each gene has a location
on a chromosome called a “locus.”

5. Factoid 127
• Alleles are various molecular forms of a
gene for the same trait. An allele usually
refers to a single letter, “T” for example.

6. Factoid 128
• Homozygous = Same letters; AA or aa for
example.
• Heterozygous – Different capitalization; Aa
for example

7. Factoid 129
• Homozygous dominant = AA
• Homozygous recessive = aa
• Heterozygous = Aa

8. Factoid 130
• Genotype is the sum of the genes (letters)
• Phenotype is how the genes are
expressed (words/descriptions)

9. Factoid 131
• Mendel’s Law of Dominance
• Some traits are dominant and others are
recessive.

10. Factoid 132
• A Punnett Square is a diagram used to
predict the outcome of a cross between
individuals.

11. Factoid 133
• Mendel’s Law of Segregation
• Half of your traits come from one parent
and the other half come from the other
parent.

12. Factoid 134
• In rabbits brown fur is dominant to white fur.
Predict the outcome between a homozygous
dominant brown rabbit and a white one.
• In flowers, red is dominant to white. Predict the
outcome between a heterozygous flower and a
homozygous dominant flower.

13. Factoid 135
• In bears, long fur is dominant to short fur.
Predict the outcome between a short furred
bear and one that is heterozygous.
• In some plants, tall is dominant to short.
Predict the outcome between two heterozygous
tall plants.

14. Factoid 136
• An organism is heterozygous or
homozygous dominant they look identical.
To determine which is which, you perform
a test cross.

15. Factoid 137
• If you cross your unknown (either
heterozygous or homozygous dominant)
with homozygous recessive and ANY
ONE of the offspring is recessive, then
your unknown organism is heterozygous.

16. Factoid 138
• A monohybrid cross involved only 1 trait at
a time. A dihybrid cross involves 2 traits.

17. Factiod 139
• Mendel’s Law of Independent Assortment
• Traits are not linked to one another and
you have and equal chance of getting
each gene independently of the others.

18. Factoid 140
• A dihybrid cross between two
heterozygous organisms for two
contrasting traits results in a 9:3:3:1 ratio.

19. Factoid 141
• In some species of plants, red flowers are
dominant to white flowers and tall plants
are dominant to short plants. Predict the
outcome between 2 heterozygous
organisms.

20. Factoid 142
• In incomplete dominance, the
heterozygous results in a blending of the
traits.
• RR = Red
• WW = White
• RW = Pink

21. Factoid 143
• In codominance the traits don’t blend but
both show up. The heterozygous results
in spotted or speckled off spring.
• FB
FB
= Black feathers
• FW
FW
= White feathers
• FB
FW
= Speckled feathers

22. Factoid 144
• Where there are more than 2 alternative
forms of a trait, it is said to have multiple
alleles.

23. Factoid 145
• Blood type is a common example of
multiple alleles.
• Type A = IA
IA
or IA
i
• Type B = IB
IB
or IB
i
• Type AB = IA
IB
• Type O = ii

24. Factoid 146
• Some traits actually ARE linked by sex.
These include baldness, color blindness,
and hemophilia.

25. Factoid 147
• Males are represented by XY. The X from
the mother and the Y from the father.
Sperm can carry either an X OR a Y
chromosome.
• Females are represented by XX. They
inherit and X from both parents. All eggs
carry an X chromosome.

26. Factoid 148
• XA
XA
– Normal female
• XA
Xa
– Normal female (but a carrier)
• Xa
Xa
– Affected female
• XA
Y – Normal male
• Xa
Y = Affected male

27. Factoid 149
• A pedigree shows the history of a trait in a
family.

28. Factoid 150
• Circles represent females.
• Squares represent males
• Horizontal lines represents a mating
• Vertical lines represent an offspring
• A triangle represents an abortion of
miscarriage.
• A diamond indicates unknown sex.
• Shaded in means affected
• A diagonal lines means dead.

29. Factoid 151
• All pedigrees must have a title, each
generation must be numbered with a
roman numeral, and each member must
be numbered.