Thursday, May 28 th p. 296, 297

Thursday, May 28 th 296 5/28/15 Thurs. L.T.: I can use Punnett Squares, rules for reproduction, and genotypes and phenotypes to determine what % chances there are of passing a trait down from parents to offspring. DO NOW: There are definitely some rules with heredity (passing on traits) and sexual and asexual reproduction. Try making at least 3 rules from your understanding of yesterday’s class. ……………………….. Reflection: What is the highest % chance of 2 brown eyed parents having a blue eyed baby? Show your Punnett Square for evidence. 297 Title: Punnett Squares Phenotype: Genotype: ………………………………… Rules for Gene Expression: ………………………………….. Punnett Squares: DNA Gene Chromosome Alleles Inheritance Heredity Trait Dominant Recessive Phenotype Genotype

Reproduction Rules Sexual: All organisms have a set # of chromosomes. (Humans = 46, 2 sets of 23) Offspring will receive 50% of chromosomes from dad, and 50% from mom. (SO, that means 1 chromosome our of the set is from one parent.) Asexual: Daughters are genetic clones of mother

First, a short quiz… Select True or False (back up with evidence): 1. Genes are located on chromosomes. 2. Traits are all linked to genes. 3. You only have 1 gene for each trait. 4. It is possible for you to receive more DNA from 1 parent than the other. 5. Asexually reproducing organisms will have different DNA from mother to daughter.

How do we determine what traits the offspring will have? Things we need to know: Rules for reproduction (both sexually and asexually) Rules for gene expression (genotype/phenotype; dominant/recessive) How to use PUNNETT SQUARES

Genes and Gene Expression Phenotype: the result of your body doing what the gene says to do. In other words, your traits! Example: brown eyes, curly hair, tall height Genotype: the actual genes you have; your alleles Example: for eye color- the allele B and the allele b (Bb)

Eye Color Genotype Possibilities: BB, Bb, bb What do they mean? With your partner, see if you can come up with a rule as to WHY these genotypes result in these phenotypes. GenotypeBBBbbb Phenotypebrown blue

Dominant and Recessive Genes Rules: Dominant: dominant alleles will BLOCK the expression of recessive genes BB = brown Bb = brown Recessive: recessive alleles will be expressed ONLY in the absence of dominant alleles bb = blue

Quiz 1. A kid’s phenotype is brown eyes. What’s his genotype? 2. Both parents have blue eyes. What are their genotypes? 3. ChunDoong’s genotype is Bb for eye color. What color eyes does he have? (phenotype)

Punnett Squares Punnett Squares are about figuring out the % of all the possible combination of alleles parents can pass on to their children. Example: Dad’s genotype: BB Mom’s genotype: Bb Dad’s sperm no matter what has to contain the B allele. (Why?) Mom’s eggs are either going to contain the B allele or the b allele. (What % of her eggs will have the B? Why?) Now we use our understanding of sexual reproduction rules…