Genes & Alleles Genotype & Phenotype Homozygous & Heterozygous

1. Key to Heredity Genes & Alleles Genotype & Phenotype Homozygous & Heterozygous Created by Sima Mathew and Jennifer Dietz

2. Gregor Mendel known as:: THE FATHER OF GENETICS. - laid the foundations for the SCIENCE OF GENETICS through his study of inheritance patterns of traits in pea plants.

3. What is heredity or inheritance? • Passing of traits from parent to offspring or from one generation to the next. • Genes are the coded instructions that define our traits.

4. How are genes inherited? • Humans have 2 sets of chromosomes for a total of 46 chromosomes. Each parent contributes only 1 set of chromosomes to their child. • When a sperm cell (23 chromosomes) and an egg cell (23 chromosomes) join during fertilization, it results in a zygote (46 chromosomes).

5. What is a trait? • Notable feature or quality in a person. What are the two types of traits? • Physical traitsare traits that can be seen such as eye or hair color • Behavioral traitsdemonstrate the way one acts such as “the fetching behavior of golden retrievers”.

6. Phenotype • Phenotype is another word for physical trait (in other words, it describes how someone looks) • Examples of phenotypic words are: tall, short, brown hair, straight hair, fat, skinny, fair skin, freckles, etc. Can you think of anymore? On your notes, write at least 4 phenotypic words that describe YOU!

7. REMEMBER!! • Phenotype describes things you can see!!!

8. What do you think person’s phenotype would be?

9. How would you describe this phenotype?

10. Remember?? • REMEMBER: Mom gives you one half of your genes, and your dad gives you the other half…. • sperm + egg = YOU! Together, these two genes (one from mom and one from dad) represent your genotype • Each gene is represented by one letter.

11. Genotype • Genotype is the genetic makeup of an organism’s traits represented by letters Genotype codes for phenotype T = tall t = short

12. GENE Important vocab to know The factors that carry all traits = ALLELES Two different forms of the same gene =

13. Example • Gene = height • Alleles = tall; short

14. Example • Gene = eye color • Alleles = green, blue, brown

15. Example • Gene – hair texture • Alleles – straight, wavy, curly

16. Example • Gene – thumb • Alleles – hitchhiker’s thumb, straight thumb

17. Dominant vs. Recessive • Think of a person who never lets you talk during a conversation – that person DOMINATES the conversation. A Dominant Allele: allele that is expressed (the one that you see). A Recessive Allele: allele that is masked or hidden (not shown)

18. DOMINANT T RECESSIVE t Mendel's Key Terms Which allele is expressed over another and represented by a capital letter? Which allele is usually masked or appears less in the population and represented by a lowercase letter?

19. Dominant or Recessive? A F r h G t d

20. Check Yourself A – dominant F - dominant r – recessive h - recessive G - dominant t - recessive d - recessive

21. When both alleles are theSAMEit is called When the alleles areDIFFERENTit is called BB B bb homozygous for brown hair heterozygous for brown hair homozygous for red hair Mendel's Key Terms B = brown hair b = red hair b HOMOZYGOUS HETEROZYGOUS

22. Homozygous or Heterozygous? RR Jj tt Hh aa

23. Check Yourself RR - homozygous Jj - heterozygous tt - homozygous Hh - heterozygous aa - homozygous

24. PHENOTYPE – physical characteristics that you SEE Ex. Straight hair, red hair, freckles, lactose intolerant, tall, blue eyes Mendel's Key Terms You inherit two alleles for each gene (trait).1 from MOM! 1 from DAD! • GENOTYPE – genetic makeup represented by letters • Ex. RR, Tt, Ffgg, YyEePp

25. Mendel’s 1st Law of Inheritance • Principle of Dominance: when there is a dominant allele and a recessive allele inherited together for a particular gene, the dominant allelewill ALWAYS be expressed. B Brown b Dominant Brown hair allele Recessive red hair allele Express the dominant allele for brown hair