Do Now

1.What is the difference between a dominant and recessive allele?

2.What do you already know about the words homozygous and heterozygous?

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Reviewing Dominant/recessive Homozygous and heterozygous Homozygous/heterozygous practice

Finish up our papers: about 20-30 mins

Agenda

Review

Remember, each chromosome is long sequence of DNA

Within the chromosome, there are many genes.

These genes are called Alleles.

They code for various traits.

Alleles

For example: An allele may code for eye color Another allele may code for height. 23 pairs of chromosomes – have all alleles.

Eye color

Height

Alleles are written as capital and lower-case letters

They each code for a specific trait.

Like Flower Colors: F – purple flowers. f – white flowers.

How are they shown?

Check for Understanding

Different chromosomes have different _________. alleles What are alleles? DNA sequences that code for a specific trait. How do scientists denote (write down) alleles? As capital and lower-case letters.

Types of Alleles

There are two types of Alleles: Dominant and Recessive

Dominant Allele (marked by a capital letter) Dominant alleles are always expressed. It covers up recessive allele.

F - purple flowers. What is Ff? Ff – purple flowers.

A recessive allele, is hidden whenever the dominant allele is present.

Recessive alleles express trait when there is no dominant allele.

Ex: f is recessive allele It codes for white flowers. ff? white plants.

Quick Practice

Circle the recessive alleles: A b C d e

Circle the dominant alleles: B C d E F

B - black hair. b - brown hair. What trait will Bb give you? Why?

What trait will bb give you? Why?

Homozygous vs Heterozygous

Homozygous alleles are alleles of the same kind. Fe: aa, DD, CC Can express dominant or recessive traits.

Heterozygous alleles are alleles that are different. Fe: Aa, Bb, Xx Will always show the dominant trait.

Group Work Circle the alleles that are homozygous recessive:

AA aa Aa BB Bb CC cc

Circle the alleles that are homozygous dominant: AA aa Aa BB Bb CC cc H- Hazel eyes. h – red eyes.

What will hh give you? HH?

Practice Time

Please work on the practice on the back of your sheets using your whisper voices.

Look up at me to show me that you are finished.