1. 6.5 Traits and Probability

2. Quick Review
Gene – a piece of DNA that provides a set of instructions.
Trait - distinguishing characteristics that are inherited
Alleles – any of the alternative forms of a gene that occurs at a specific locus on a chromosome. Each gene has two alleles!
Homozygous – two of the same alleles at a specific locus
Heterozygous – two different alleles at a specific locus
Law of segregation – Mendel’s First Law
Organisms inherit two copies of each gene, one from each parent.
Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate during gamete formation.

3. Yy Quick Review Genotype Phenotype
Genotype – the genetic makeup of a specific set of genes
Phenotype – the physical characteristics, or traits
Genotype Phenotype Yy

4. Quick Review
Dominate allele – the allele that is expressed when two different alleles or two dominate alleles are present
Recessive allele - the allele that is only expressed when two copies are present
Ted Ed - Mendel

5. Mendel’s Laws Law of segregation – Mendel’s First Law
Organisms inherit two copies of each gene, one from each parent.
Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate during gamete formation.
Law of independent assortment – Mendel’s Second Law
Allele pairs separate independently of each other during gamete formation (meiosis).
Different traits seem to be inherited separately.

6. Punnett Squares
Punnett square – a grid system for predicting all possible genotypes resulting from a cross
Only show probability!

7. ? Punnett Squares What hair color could their child possibly have?
Remember:
The allele for
brown hair is
dominate.

8. ? BB? Bb? BB? Bb? Punnett Squares What hair color could
the child possibly have?
BB?
Bb? ?
BB?
Bb?

9. ? Punnett Squares What hair color could the child possibly have?
Let’s look at the possibilities.
BB x BB
BB x Bb
Bb x Bb ?

10. B B B B Punnett Squares BB x BB BB x Bb Bb x Bb
Homozygous - Homozygous
BB x BB
BB x Bb
Bb x Bb B B

11. Punnett Squares B B
BB x BB B B B B B B

12. Punnett Squares B B
BB x BB BB BB B B BB BB

13. B B BB BB B B BB BB Punnett Squares BB x BB Genotype: 4 BB; 0 Bb; 0 bb
Phenotype:
4 brown hair
100% chance of brown hair offspring BB BB B B BB BB

14. b B B b Punnett Squares BB x BB BB x Bb Bb x Bb
Heterozygous - Heterozygous
BB x BB
BB x Bb
Bb x Bb B b

15. Punnett Squares b B B B b b B b

16. Punnett Squares b B B BB Bb b Bb bb

17. b B B BB Bb b Bb bb Punnett Squares Genotype: 1 BB; 2 Bb; 1 bb
Phenotype:
3 brown hair; 1 blond hair
3:1
75% - brown
25% - blonde B BB Bb b Bb bb

18. B B B b Punnett Squares BB x BB BB x Bb Bb x Bb
Homozygous - Heterozygous
BB x BB
BB x Bb
Bb x Bb B b

19. Punnett Squares B B
BB x Bb B B B b B B

20. Punnett Squares B B
BB x Bb BB BB B b Bb Bb

21. B B BB BB B b Bb Bb Punnett Squares BB x Bb Genotype: 2 BB; 2 Bb; 0 bb
Phenotype:
4 brown hair
1:1
100% - brown
50% homozygous
50% heterozygous BB BB B b Bb Bb

22. Punnett Squares BB BB BB Bb ? BB Bb Bb Bb bb

23. Heterozygous – Heterozygous
Punnett Squares Bb Bb bb
Bb x Bb
Heterozygous – Heterozygous
25% chance of blonde hair
They had a blonde hair baby!

24. Crosses B B
Monohybrid cross – examine the inheritance of only one specific trait
homozygous – homozygous
heterozygous – heterozygous
heterozygous– homozygous BB BB B b Bb Bb

25. Crosses
Dihybrid cross- examine the inheritance of two different traits
6.17 p186

26. = Probability Probability number of ways a specific event can occur
number of total possible outcomes
Heredity patterns can be calculated with probability.
Explain how Mendel’s laws relate to probability.