1. Genetics Vocabulary: Gene: A section of DNA that encodes a particular protein (ex: hair protein) Alleles: Different versions of a gene (ex: black hair vs. blond hair) Everyone has two alleles for each gene – one from each parent! Dominant: An allele that always shows up if you have it (ex: B = black hair) Recessive: An allele that only shows up if there is no dominant allele (ex: b) Genotype: The genetic make-up (combination of alleles) (ex: BB or Bb or bb) Phenotype: The characteristics or traits that show up (ex: your hair color)

2. Genetics Vocabulary: Genotype: The genetic make-up (combination of alleles) (ex: BB or Bb or bb) Phenotype: The characteristics or traits that show up (ex: your hair color) Dominant: An allele that always shows up if you have it (ex: B = black hair) Recessive: An allele that only shows up if there is no dominant allele (ex: b) Homozygous: Two of the same allele for a particular trait are present  Ex: RR (homozygous dominant) = Red wings  Ex: rr (homozygous recessive)= yellow wings Heterozygous: Two different alleles for a particular trait are present  Ex: Rr = red wings

3.  Homozygous and Heterozygous  Homozygous: Two of the same allele for a particular trait are present Ex: RR (homozygous dominant) = Red wings Ex: rr (homozygous recessive)= yellow wings  Heterozygous: Two different alleles for a particular trait are present Ex: Rr = red wings More Genetics Vocabulary Objectives for Class: Experiment with probability to see the diversity of offspring that can be made through sexual reproduction

4. Gregor Mendel – the “father” of genetics

5. Objectives for Class: Use Mendel’s Principle of Segregation to explain: How can children show traits that their parents don’t have? Use Punnett Squares to solve monohybrid crosses

6. Traits that Mendel studied:

7. Objectives for Class: Use Mendel’s Principle of Segregation to explain: How can children show traits that their parents don’t have? Use Punnett Squares to solve monohybrid crosses Check Your Homework… Parents are true-breeding aka homozygous 2a. All F1 offspring showed one trait – why?  They all showed the dominant phenotype because they all got a dominant allele from one parent 2b. They were all heterozygous 3. What happened in the F2 generation?  The recessive trait reappeared in ¼ of the offspring  How can we explain this?? Mendel’s 1 st Experiment

8. Mendel’s Law of Segregation  Alleles segregate (separate) during meiosis so each gamete gets only one allele a a A A a A a A Two choices for gametes: A or a

9. Another way to show this: AaaAAaAaAa AA a Aa Start w/ Diploid Cells Meiosis: Alleles separate into different gametes Punnett Squares show possibilites for fertilization Possible Gametes (Haploid) Possible Diploid Zygotes – develop into offspring Law of Segregation: Each gamete only gets ONE allele for each gene

10. Principle of Segregation (continued…)  This explains why the recessive trait reappears in the F2 generation… in ¼ of the offspring.

11. Punnett Squares (Predicting Probabilities) Tongue rolling (R) is dominant over non-tongue rolling (r) Two parents are both heterozygous. Write their genotypes! Mother is RrFather is Rr half of the sperm get each allele ½ of Mom’s eggs get the R allele ½ of Mom’s eggs get the r allele R r rR RR rr Rr

12. Predicting Probabilities This Punnett Square is used to PREDICT PROBABILITIES, NOT to tell you the actual numbers you will get! Probability of Tongue Rolling (RR or Rr) = ¾ or 75% Probability of Not rolling (rr) = ¼ or 25% R r rR RR rr Rr

13. Using Punnett Squares to predict the sex of a child  Mother’s genotype:  Father’s genotype:  Make a Punnett Square and fill it in Chances of girl (XX) = ½ or 50% Chances of boy (XY) = ½ or 50% X YX X XX XY XX XY

14. Do Now #2: (in your notebook)  What is one difference between these two cells?  Which chromosome is homologous to this one?  If we looked at human cells, how many pairs of homologous chromosomes would they contain?  Answer: 23 pairs (22 pairs plus the sex chromosomes) a a A A bb B B aa A A Cell 1 Cell 2

15. Meiosis with Two Different Genes on Two Different Chromosomes A B A A a a bb B B A A a a bb B B A B a b a b or… a B A b a B A b Four different possible gametes: ABabAbaB

16.  Alleles for different genes segregate independently during meiosis.  In other words: If a gamete gets A or a, this doesn’t effect whether it gets B or b. Any combo is possible: Parent: AaBb Possible gametes:ABAbaBab  This creates genetic diversity between gametes, and therefore a greater diversity of offspring. Mendel’s Discoveries: Law of Independent Assortment Objectives for Class: Use Punnett Squares to solve dihybrid crosses Use Mendel’s Principle of Independent Assortment to explain how genetic variation is created in individuals.

17. Example: Dihybrid Cross (Two Traits) (only write what’s in purple) Tall (T) is dominant over short (t) Black hair (B) is dominant over blond hair (b) Two parents are heterozygous for both traits: (1) Write the Parent Genotypes: TtBb x TtBb (2) What Gametes can they make? TBTbtBtb

18. Tall w/ Black hair = Tall w/ Blond hair = (3) Write the gametes along the sides of a BIG Punnett Square (4) Use the Punnett Square to calculate probabilities! TB Tb tB tb TBTbtBtb TTBb TtBB TtBb TTBB Ttbb TtBb TTbb TTBbTtBB TtBb ttBB ttBb ttbb ttBb Ttbb TtBb Short w/ Black hair = Short w/ Blond hair = 1/16 9/16 3/16