The document discusses genes and alleles, genotypes and phenotypes, dominant and recessive traits, Mendelian and non-Mendelian inheritance patterns. It provides examples of inheritance crosses in pea plants, humans, birds and fish. Key differences are: a gene is a segment of DNA, an allele is a variant of a gene; genotype is the genetic makeup, phenotype is the physical traits; dominant alleles mask recessives but codominant alleles have joint effects. Non-Mendelian patterns like codominance do not follow Mendel's observations.

1. Traits and Inheritance
Heredity
Ignacio Anguera de Sojo
Colegio Real de Panamá

2. GENES AND ALLELES
Read Pg 92 -A great idea- and answer:
What is
the difference between a
GENE
and
ALLELE?

3. GENES AND ALLELES
ALLELE
A specific variation of a gene. The
allele can be dominant or
recessive.
GENE
Section of DNA that controls a
certain trait. Formed by 2 alleles
(♀ & ♂)

4. GENES AND ALLELES
ALLELE
Blue eyes, green eyes, type A
blood, black skin, white skin
GENE
Eye color, blood type, skin color

5. GENES AND ALLELES
Read Pg 92 and93 -A great idea- and answer:
What is
the difference between a
GENOTYPE
and
PHENOTYPE?

6. GENES AND ALLELES
GENOTYPE
Heritable genetic identity
PHENOTYPE
Description of your actual
physical characteristics

7. Genotype
RECESSIVE
Lowercase
DOMINANT
Capital

8. Genotype
HOMOZYGOUS
HETEROZYGOUS
tt TT
Tt
Homozygous
recessive
Homozygous
dominant

9. Genotype
Tall is dominant over short in pea
plants. Show the cross of a
homozygous short plant is crossed
with a homozygous tall plant.
♀:
♂:

10. Calculate Probabilities
Total number
of outcomes
Probability of an
event happening =
Number of ways
it can happen
100x

11. Calculate Probabilities
A bag contains 4 red marbles, 16
yellow marbles, 5 purple marbles, 16
blue marbles, and 10 green marbles.
 What is the probability of pulling out a red or a green
marble?
 What is the probability of pulling out a red marble?
Total number of outcomes
Probability =
Number of ways it can happen
=
4
4+16+5+16+10
100x

12. Genotype
Tall is dominant over short in pea
plants. Show the cross of a
homozygous short plant is crossed
with a homozygous tall plant.
♀: tt ♂: TT
t t
t
tt
tT
T
T T
TT
Probability:
Genotype
Phenotype
Tt =
4
4
100 = 100%
Tall =
4
4
100 = 100%

13. Practice!
A tall plant (TT) is crossed with a
tall plant (Tt).
♀:
♂:
Probability:
Genotype
Phenotype

14. Practice!
In humans, free-ear lobes are dominant
to attached. Two parented that are both
heterozygous free are expecting a child.
What are the chances that the child will
have free ear lobes or attached?
♀:
♂:
Probability:
Genotype
Phenotype

15. Non Mendelian Traits
*Patterns of inheritance, like Codominance, that do not follow Mendel’s
observations are called Non-Mendelian inheritance patterns.

16. Non Mendelian Traits
*Patterns of inheritance, like Codominance, that do not follow Mendel’s
observations are called Non-Mendelian inheritance patterns.

17. 3.4.5 Dominant alleles mask the effects of recessive alleles but co-dominant
alleles have joint effects
Dominant alleles always show
their encoded trait, when
present in an organism (they
mask recessive alleles)
Recessive alleles only express
their encoded traits when no
other alleles are present
• Dominant alleles code for
functional proteins, while
recessive alleles code for non-
functional proteins
Codominant alleles can have
joint effects if both are
present* *Patterns of inheritance, like Codominance, that do not follow Mendel’s
observations are called Non-Mendelian inheritance patterns.

18. Practice!
In a species of birds, incomplete
dominance between alleles for black (B)
and white (b) feathers is observed.
Heterozygotes are blue. If two blue
birds are crossed, what will be the
possible genotypes and phenotypes?
♀:
♂:
Probability:
Genotype
Phenotype

19. Practice!
In a certain fish, blue scales and red
scales are codominant. When a fish
has the genotype Bb, it has a
patchwork of blue and red scales.
What happens if you breed this fish
with a fish that only has Blue
Scales.
♀:
♂:
Probability:
Genotype
Phenotype