Non-Mendelian Genetics(Non-Mendelian Patterns of

Inheritance)-Incomplete dominance

-Codominance-Sex determination-Sex-linked traits

Roel R. Maraya

BEEdBSEd 4-1 (Natural Sciences)

January 19, 2010

Answer this!?

A homozygous round seed crosses with a homozygous

wrinkled seed. Give the genotype and the phenotype

of the offspring.

What if you marry an American man o woman? What do you think would be your children look like?

Think! Think! Think!

Non-Mendenlian Inheritance

is a general term that refers to any pattern of inheritance in which traits do not segregate in accordance with Mendel’s laws.

Incomplete Dominance

is a form of intermediate inheritance in which one allele for a specific trait is not dominant over the other allele.

Example

Remember!

“With incomplete dominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits.”

Codominancethe "recessive" & "dominant" traits

appear together in the phenotype of hybrid organisms.

•Both alleles contribute to the phenotype of the organism by showing up simultaneously (at the same time) in heterozygous individuals.

Example

R = allele for red flowers W = allele for white flowers red x white ---> pink RR x WW ---> 100% RW

Remember!

“With codominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together. ”

Sex Chromosomes

MALES: - have non-identical sex

chromosomes (XY).

FEMALES:- have identical sex

chromosomes (XX).

Sex Determination

Sex-linked traits

• This is also referred to as “x-linked traits”.

• These are determined by genes that are carried on the X chromosomes.

• This is determined also in the sex chromosomes of an individual.

Genotypes and Phenotypes of Color Blindness in

HumansGenotypes Phenotypes

1. XX Normal female

2. XXc Normal female,carrier of the

gene

3. XcX

c Color-blind female

4. XY Normal male

5. XcY Color-blind male

Sex-linked trait

Sex-influenced traits

• The traits produced here is not sex-linked, but is carried by the body chromosomes or AUTOSOMES.

– Example of this is Baldness.

Assignment # 1Directions: Answer the following questions. Write your

answers on a short bond paper. COPY and ANSWER.

1. Suppose a heterozygous woman (genotype XcX)

marries a color blind man (genotype XcY), determine

the phenotypes of their children using a Punnett square.

2. Suppose a color-blind woman (XcX

c) th a normal

marries a man with a normal vision (XY), determine the phenotypes of their children using a Punnett square.