Non-Mendalian Genetics

In a plant, long stems are dominant (L) to short stems (l). If a homozygous dominant flower and a homozygous recessive

plant are crossed, what would be the phenotypic ratio of their offspring?

Science Fact of the Day

• The protein Titin or connectin is the largest known protein with ~26,000 amino acids forming the polypeptide chain. This protein is responsible for muscle elasticity in the human body.

CO: I will predict possible genetic outcomes using Non-Mendelian

inheritance and pedigrees.

LO: I will take notes and draw a pedigree for a trait in a family.

REMEMBER:Mendel’s principles form the basis of the modern

science of genetics.

The inheritance of biological characteristics is

determined by specific segments of DNA called

genes.

Genes are passed from parents to their offspring.

Today we’re going to talk about a special case: sex-linked traits

• Remember: Each person inherits an X chromosome from mom and either an X or a Y from dad

• We use the letters X and Y to represent chromosomes (not alleles)

What do you think a “sex-linked” trait is? Examples?

Sex-linked traits

• Are traits that are determined by either the Y or X chromosome– If they are determined by the Y chromosome

they are referred to as “Y-linked”• Y-linked disorders are very rare and often cause

infertility in men

– If they are determined by the X-chromosome they are referred to as “X-linked”

X-linked dominant

• These conditions (such as vitamin D resistant rickets) are rare and can affect both men and women– Men are more affected than women– Both men and women can pass on the affected

chromosome to their children

In 18 words summarize these two diagrams.

X-linked recessive• These disorders (such as hemophilia and color

blindness) more frequently affect men than women– Both men and women can pass these traits on to

their children (at different rates)• An affected man/unaffected woman will have sons who

are unaffected and daughters who are carriers• An affected woman/unaffected man will have a 50%

chance of passing the trait. If she passes on her affected X chromosome, then her daughters will be carriers and her sons will be affected– This is why men are more likely to be color blind than women

How could you find out the chances that you have hemophilia

running in your family?

Pedigree chart: a chart that shows relationships within a family.

Let’s practice

1. Pedigree Worksheet together2. Flip knob—create your own pedigree chart

Bellwork• A geneticist studying fruit flies hypothesizes that short

wings are a recessive trait coded for by a single gene. Which observation is most likely to have led her to form this hypothesis? Why?

1. Flies have wing lengths ranging from very long to very short.

2. Flies with long wings are less likely to survive.3. Flies with long wings can produce offspring with

short wings.4. Flies with short wings prefer to mate with flies with

long wings.

Science Fact of the Day

CO: I will predict genetic outcomes using non-Mendelian inheritance.

LO: I will write notes and create a “baby” dominance with a partner

demonstrating both Mendelian and Non-Mendelian inheritance.

Types of Inheritance 1. Mendelian: genetic traits are controlled by a single gene

----- dominant or recessive; flower color

2. Sex-linked: genetic traits are controlled by the X or Y chromosome

-----X-linked recessive; colorblindness

3. Co-dominance: both alleles contribute to the phenotype equally (ex. Blood type)

4. Incomplete dominance: when the presence of both alleles leads to a blending of traits (ex. Red flower + white flower = pink flower)

5. Polygenic: when a trait is controlled by multiple alleles

Co-dominance• When the genotype is heterozygous, then both traits will

show up equally– Note: when writing we show this with two different capital

letters

Incomplete Dominance• When the genotype is

heterozygous, then the trait will be a blend of the two alleles

• Note: Sometimes, we write this by using an abbreviation of the trait in a capital letter (C =color) and the alleles as a superscript (CR = red flower) or subscript (CR).

• Sometimes, we just say the heterozygous trait is a blend.

Polygenic Inheritance• Multiple genes control the inheritance of traits

Both genes and the environment determine how traits are expressed in a population

Rest of the Day

1. Practice by completing the Make a Face Lab with a partner.

2. Remember, that you have homework for tomorrow

1. Watch and take notes over the video “What is Evolution?” by Stated Clearly. Come to class with at least 3 questions over the video http://youtu.be/GhHOjC4oxh8