1. Mendel & Inheritance
SC.912.L.16.1 Use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.

2. 1. Students will use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.
Mendel’s Law of Segregation: gene pairs separate when gametes (sex cells) are formed; each gamete as only one allele of each gene pair
Review:
Heterozygous = the two alleles are different (hybrid) Aa or Bb
Homozygous = the two alleles are the same (AA or aa)

3. 1. Students will use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.
Mendel’s Law of Independent Assortment: different pairs of genes separate independently of each other when gametes are formed
This means when chromosomes line up in homologous pairs during Metaphase I of meiosis that not ALL of moms chromosomes are on one side and not ALL of dads chromosomes are on one side – THEY ARE INTERMIXED!

4. 1. Students will use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.
Dominant Traits: shown with capital letters; controlling trait
Example: Brown hair over blonde hair; Huntington’s disease
Recessive Traits: shown with lowercase letters; hidden allele
Examples: Cystic fibrosis and Tay Sach’s – can be a carrier OR must have two recessives for it be expressed

5. 1. Students will use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.
Inheritance can be predicted using a Punnett square
Results show the probability of an offspring receiving that trait, and may be expressed in percent, ratios, or fractions
Genotype probability (genetic makeup of the organism):
TT – 25%, ¼ , or 1:4
Tt – 50%, ½, or 2:4 (1:2)
Tt – 25%, ¼ , or 1:4

6. 1. Students will use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.
Practice predicting Punnett square results. Express results for both genotype and phenotype (physical appearance of an organism)

7. 1. Students will use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.
Two Types of Crosses:
Monohybrid: Contains four boxes; a cross between two heterozygous would produce a 1:2:1 genotype ratio and a 3:1 phenotype ratio
Dihybrid: Contains sixteen boxes; a dihybrid cross involves two traits for each parent and a cross between two heterozygous parents would produce a 9:3:3:1 phenotype ratio

8. 1. Students will use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.
Dihybrid Cross:

9. 2. Student’s will identify, analyze, and/or predict inheritance patterns cause by various models of inheritance.
Patterns of Inheritance:
Sex Chromosomes: 23 pairs, XY = males, XX = females
Sex-Linked Traits: traits linked with particular sexes, X-linked traits are inherited on X chromosome from mother (examples: hemophilia, color-blindness, baldness); more common in males since females have another X
Multiple Alleles: presence of more than two alleles for a trait (eye color)
Polygenic Trait: one trait controlled by many genes (hair color, skin color); genes may be on the same chromosome or different chromosomes

10. 2. Student’s will identify, analyze, and/or predict inheritance patterns cause by various models of inheritance.
Patterns of Inheritance (Continued):
Codominance: phenotypes of both homozygous parents are produced in heterozygous offspring so both alleles are expressed (black + white chickens = checkered chicken; sickle cell anemia)
Incomplete Dominance: phenotype of a heterozygote is a mix of the two homozygous parents; neither allele is dominant, but combine to display both traits (white flower + red flower = pink flower)

11. 2. Student’s will identify, analyze, and/or predict inheritance patterns cause by various models of inheritance.
A pedigree may be used to show patterns of inheritance
squares = males and circles = females
shaded = affected, half- shaded = carrier