Mendel & Inheritance

SC.912.L.16.1 Use Mendel’s laws of segregation and

independent assortment to analyze patterns of inheritance.

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 pairReview:

• Heterozygous = the

two alleles are

different (hybrid) Aa or

Bb

• Homozygous = the

two alleles are the

same (AA or aa)

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!

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

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

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)

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

1. Students will use Mendel’s laws of

segregation and independent assortment

to analyze patterns of inheritance.

Dihybrid Cross:

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

on inherited on X chromosome from mother (examples: hemophilia,

color-blindness, baldness)

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

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)

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