Genetics

1. Genetics

2. What is Genetics? • Genetics • The study of heredity • Heredity • The passing of traits from one generation to the next. • Inherit • Generation • Organisms that are descended from a common ancestor.

3. DNA • DNA • A chain of proteins that contains all of the information needed to create an organism.

4. DNA • Chromosome • A tightly wound bundle of DNA. • This is how DNA is stored in the nucleus of a cell.

5. DNA • Sperm and Egg Cells • When made, they each contain HALF of the number of chromosomes needed to make an organism. • When combined, they create an offspring with HALF of its mother’s chromosomes and HALF of its father’s chromosomes.

6. Genes • Gene • A portion of a chromosome that determines a trait. • Allele • The different versions of a gene. • Ex: With the GENE for hand dominance, the ALLELES are left and right.

7. Types of Genes • In the 1860’s, an Austrian monk named Gregor Mendel experimented with pea plants. • He discovered that genes have a dominant and recessive form.

8. Types of Genes • Dominant Gene • The “stronger” form of a gene that is always expressed when it is present. • Ex: being right handed • Recessive Gene • The “weaker” form of a gene that is ONLY expressed when the dominant gene is NOT present • Ex: being left handed

9. Genes • QUESTION: • If a child inherits a right handed allele from mom and a right handed allele from dad, which hand will the child write with? • QUESTION: • If a child inherits a left handed allele from mom and a left handed allele from dad, which hand will the child write with?

10. Genes • QUESTION: • If a child inherits a right handed allele from mom and a left handed allele from dad, which hand will the child write with?

11. Gene Expression • Phenotype • The way your genes are expressed physically • Ex: being left handed • Genotype • The way your genes code for your traits • Ex: hh will lead to being left handed

12. Gene Expression • Incomplete Dominance • When an organism has both of a gene’s alleles and a phenotype that is a mix of the two is expressed • Ex: skin color • Co-dominant Gene • When an organism has both of a gene’s alleles and a third phenotype is expressed • Ex: blood type

13. Punnett Squares • Punnett Squares are used to determine how likely it is that a certain trait will be passed on.

14. Punnett Squares A A • How to use a punnett square: • Make the square • Make a key • Add the parents • Cross the parents • Find the percents AA A AA Aa Aa a = 50% = 50% = 0% AA = right handed Aa = right handed aa = left handed = 100%

15. Punnett Squares • Question: A tall plant (TT) is crossed with a short plant (tt). What is the percent chance that the offspring will be tall? T T Tt t Tt = 0% = 100% = 0% TT= tall Tt= tall tt= short = 100% Tt Tt t

16. Punnett Squares • Question: A brown eyed parent (Ee) is crossed with another brown eyed parent (Ee). What is the percent chance that the offspring will be blue, green, or hazel eyed? e E EE E Ee EE= brown Ee= brown ee= not brown = 25% = 50% = 25% = 75% ee Ee e

17. Punnett Squares • Question: A parent with type A blood (AO) is crossed with a parent with type B blood (BO). What is the percent chance that the offspring will have type AB blood? O A AB B BO AB= Type AB AO= Type A AA= Type A BO= Type B BB= Type B OO= Type O = 25% = 25% = 0% = 25% = 0% = 25% = 25% = 25% OO AO O

18. Gender • The 23rd pair of chromosomes determines if the child is a boy or girl. • The mother always gives the baby an X chromosome. The father either gives an X or Y chromosome. • If the 23rd pair of chromosomes is XX, the baby is a girl. If it is XY, the baby is a boy.

19. Karyotypes • A karyotype is a picture of an organism’s chromosomes. • First, the chromosomes are extracted (removed) from the cell’s nucleus

20. Karyotypes • Next, the chromosomes are partnered up and photographed. Notice the 23rd pair of chromosomes. What gender is this person?

21. Karyotypes Notice the 23rd pair of chromosomes. What gender is this person?

22. Karyotypes Observe this karyotype carefully. Do you notice anything out of the ordinary? Trisomy- When there are 3 chromosomes in a partnership instead of 2. Trisomies lead to significant disorders, and sometimes cause miscarriages.

23. Pedigrees • A pedigree is a chart of an individual's ancestors which is used to analyze inheritance of certain traits.

24. Pedigrees • To read a pedigree, you use the following key:

25. Pedigrees • How many generations are represented in this pedigree chart? • How many carriers of the sickle cell anemia trait are in this family? • How many people in this family were born with sickle cell anemia? • From which parent did the second-generation children inherit the sickle-cell gene? • In which individual did sickle-cell anemia first show? • How are individuals IV - 1 and II - 2 related? • How many children did individuals II - 4 and II - 5 have? • According to this chart, is sickle cell anemia caused by a dominant or a recessive gene? Explain your answer.

26. Pedigrees • According to this chart, which family members are carriers of the hemophilia gene? • What gender are the people who are carriers of hemophilia? • According to this chart, which family members have hemophilia? • What gender are the people who have hemophilia? • Which chromosome do you think the hemophilia gene is carried on? • Why are all of the daughters of individuals II - 1 and II - 2 carriers of the gene?