1. Copy this down on your genetics notes from yesterday…. Gregor Mendel- Father of genetics

Please respond on page 178 Selena is told in science class that she inherits exactly ½ of her genes from each parent, but Selena says that she looks so much like her mother they could be twins. She says she also shares most of her mother’s personality traits and abilities and is not like her father at all. She believes she inherited more genes from her mother. Explain (In complete sentences) how she can resemble her mother more than her father even though she inherits exactly ½ her genes from each parent.

 Explain how genotype and phenotype differ and give an example of each.  Explain how homozygous and heterozygous are different and give an example of each.

Genetics

How does it work?  At the end of meiosis  4 daughter cells are produced  If female-4 eggs  If male-4 sperm  Each new sex cell only has 23 chromosomes

Chromosomes  In each of those 4 cells you have 23 chromosomes  Each of those chromosomes are made up of genes from your parent  Those genes determine what traits will get passed on

Passing Down Traits  Only 1 of the 4 egg cells and only 1 of the 4 sperm will make the baby  When the sperm and egg unite there are 46 chromosomes now = 46  So all of your mom’s traits won’t get passed down just half of them.

Heredity We know we get exactly ½ of our mom’s genes and ½ of our dad’s genes. Even if you look like one parent more than the other, you still have ½ of each!

 Your genes carry your traits (eye color, hair color, body shape, dimples, etc.)  Each trait is made up of two alleles (one from your mom and one from your dad)

a a a a a A A A A A  Only ONE of these 4 cells gets passed on

Vocabulary 1. Genotype : combination of alleles in your DNA (i.e. GG, gg, Gg) 2. Phenotype : the trait that shows up based upon the genotype (i.e. green eyes)

3. Homozygous : two of the same alleles. (HH, bb, AA, cc) 4. Heterozygous : two different alleles. (Hh, Bb, Aa, Cc) The dominant allele BLOCKS the recessive allele

Let’s Practice… Heterozygous or Homozygous??

Bb

ZZ

tt

Rr

The trait is eye color (b). Brown eyes are dominant to blue eyes Write the letter of the dominant trait.

The trait is eye color (b). Brown eyes are dominant to blue eyes Write the letter of the recessive trait.

The trait is eye color (b). Brown eyes are dominant to blue eyes Write the genotype for brown eyes.

The trait is eye color (b). Brown eyes are dominant to blue eyes Write the genotype for blue eyes.

The trait is eye color (b). Brown eyes are dominant to blue eyes Write out the homozygous, dominant genotype.

The trait is eye color (b). Brown eyes are dominant to blue eyes Write out the heterozygous genotype

The trait is eye color (b). Brown eyes are dominant to blue eyes Write out the homozygous recessive genotype

The trait is eye color (b). Brown eyes are dominant to blue eyes What is the phenotype for Bb?

The trait is eye color (b). Brown eyes are dominant to blue eyes What is the phenotype for bb?

The trait is eye color (b). Brown eyes are dominant to blue eyes What is the phenotype for BB?

Let’s Practice…  The trait is eye color (b). Brown eyes are dominant to blue eyes  1. Write the letter of the dominant trait.  2. Write the letter of the recessive trait.  3. Write the genotype for brown eyes.  4. Write the genotype for blue eyes.

Brown is dominant to blue  5. Write out the homozygous, dominant genotype.  6. Write out the heterozygous genotype.  7. Write out the homozygous recessive genotype.  8. Write the phenotype for #5.  9. Write the phenotype for #6  10. Write the phenotype for #7

Purple is dominant to green leaf color. (use the letter P when you cross them) If a homozygous purple plant is crossed with a green plant, what percentage of the offspring would have purple leaves?

1. Describe the genotypes given (use your notes). The first two are already done.  A. DD homozygous, dominant  B. Dd _heterozygous  C. Dd __________________  D. ss ______________________  E. Yy ______________________  F. WW ____________________

2. In humans, brown eye color (B), is dominant over blue eye color (b). What are the phenotypes of the following genotypes? In other words, what color eyes will they have?  A. BB ________________________  B. bb ________________________  C. Bb ________________________