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

CO:

LO:

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: January 7• Complete the Flipnob activity you started yesterday.• Copy the pedigree below. You must show who has

freckles by shading and label each person with their genotype.

Grandma Grandpa

Elizabeth David Fred Wilma Michelle Mickey Monica

John Sonny Barney Krista Janet

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

LO: I will draw a pedigree chart. I will write notes and answer

questions.

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. Vocab Strips: Read and sort the vocabulary words and definitions (use the pictures to help!)

2. Questions on the next slide.3. Homework:

– “What is Evolution?” by Stated Clearly– Watch video and write 3 facts you learned and 3

questions to share tomorrow in class.

Non-Mendelian InheritanceIn rabbits, white coat color (CW) and black coat color (CB) are

codominant, and both of these alleles are dominant over albino (c); heterozygotes (CWCB) are spotted.

1. Draw a Punnett Square that shows the genotypes of the offspring from a heterozygous black-coated rabbit and a homozygous white-coated rabbit?

Mrs. PigglyWiggly is a carrier of the sex-linked hemophilia allele, and Mr. PigglyWiggly is normal (as far as blood chemistry goes).

2. Draw a Punnet square that shows the theoretical genotypes among their children.

Non-Mendelian Inheritance

Spongebob loves growing flowers for his gal pal, Sandy. She loves the Poofkin flowers—red, purple, and blue! Interestingly enough, the Poofkin flowers display incomplete dominance in their genes for color.

1. Using “R” for red and “B” for blue, what would be the genotypes for the following phenotypes?

red: ______ purple: _____ blue: _____

2. Complete a Punnett square for a red Poofkin and a purple Poofkin.