Traits and Inheritance

Heredity

Ignacio Anguera de Sojo

Colegio Real de Panamá

GENES AND ALLELES

Read Pg 92 -A great idea- and answer:

What is the difference between a

GENEand

ALLELE?

GENES AND ALLELES

ALLELEA specific variation of a gene. The allele can be dominant or recessive.

GENESection of DNA that controls a certain trait. Formed by 2 alleles (♀ & ♂)

GENES AND ALLELES

ALLELEBlue eyes, green eyes, type A blood, black skin, white skin

GENEEye color, blood type, skin color

GENES AND ALLELES

Read Pg 92 and93 -A great idea- and answer:

What is the difference between a

GENOTYPEand

PHENOTYPE?

GENES AND ALLELES

GENOTYPEHeritable genetic identity

PHENOTYPEDescription of your actual physical characteristics

Genotype

RECESSIVELowercase

DOMINANTCapital

Genotype

HOMOZYGOUS

HETEROZYGOUS

tt TT

Tt

Homozygous recessive

Homozygous dominant

Genotype

Tall is dominant over short in pea plants. Show the cross of a

homozygous short plant is crossed with a homozygous tall plant.

♀:

♂:

Calculate Probabilities

Total number of outcomes

Probability of an event happening =

Number of ways it can happen

100x

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 greenmarble?

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

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

4100 = 100%

Tall = 4

4100 = 100%

Practice!

A tall plant (TT) is crossed with a tall plant (Tt).

♀:

♂:

Probability:

Genotype

Phenotype

Practice!

In humans, free-ear lobes are dominantto attached. Two parented that are bothheterozygous free are expecting a child. What are the chances that the child will

have free ear lobes or attached?

♀:

♂:

Probability:

Genotype

Phenotype

Non Mendelian Traits

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

Non Mendelian Traits

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

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.

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

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