Non-Mendelian Inheritance

Objectives

Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses and non-Mendelian inheritance (TEKS 6F) • Background Information • Explain the different types of non-Mendelian inheritance

• Incomplete dominance • Codominance • Multiple Alleles • Polygenic Traits • Sex-linkage

• Describe how to solve non-Mendelian inheritance

questions.

Background Information

• Every cell (living thing) has DNA

• Chromosomes are simply DNA wound up into a threadlike structure found in the nucleus (prokaryotes don’t have a nucleus).

• Genes are located on chromosomes

o genes control the TRAITS of the individual

• The number of chromosomes depends on

the species o Ex. Humans have 46

Background Information

• Humans have 46 chromosomes or 23 pairs of chromosomes • In each pair, you get one chromosome

from your mother and one chromosome from your father

• Out of the 23 pairs of chromosomes, 22

of those pairs are what we call autosomes.

• The last pair of chromosomes are called sex chromosomes or allosomes. • Females have two X chromosomes

(XX) and males have 1 X and 1 Y chromosome (XY)

This picture is called a karyotype: A display of someone's entire set of chromosomes/DNA. In other words, a display of someone's entire genome.

Background Information

• If a disease/condition is from a gene located on any of the 22 autosomes, and it’s recessive, it is called an autosomal recessive disease/condition. • Example: Cystic fibrosis is autosomal

recessive (gene is on chromosome 7) • If a disease/condition is from a gene

located on any of the 22 autosomes, and it’s dominant, it is called an autosomal dominant disease/condition. • Example: Huntington’s disease is

autosomal dominant (gene is on chromosome 4)

Background Information • If a disease/condition is from a gene

located on one of the sex chromosomes (usually the X because it has more genes), it is called a sex-linked (or X-linked or Y-linked ) disease/condition Sex-linkage can be recessive or dominant as well. • Example: Hemophilia is sex-linked • Hemizygous is the term given to

males with a sex-linked disease/condition located on the X-chromosome. They only have 1 X chromosome, therefore, if they receive the mutation (from their mother) they will have the disease/condition. Females, however, typically need two copies of the mutation (1 on each of their X chromosomes) unless the disease/condition is dominant.

Objectives

Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses and non-Mendelian inheritance (TEKS 6F) • Background Information • Explain the different types of non-Mendelian inheritance

• Incomplete dominance • Codominance • Multiple Alleles • Polygenic Traits • Sex-linkage

• Describe how to solve non-Mendelian inheritance

questions.

Non-Mendelian Inheritance

EduSmart video in class

Objectives

Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses and non-Mendelian inheritance (TEKS 6F) • Background Information • Explain the different types of non-Mendelian inheritance

• Incomplete dominance • Codominance • Multiple Alleles • Polygenic Traits • Sex-linkage

• Describe how to solve non-Mendelian inheritance

questions.

Incomplete Dominance & Codominance

First, determine if the description is describing incomplete dominance or codominance. Then, set up a key for each of the phenotypes listed in each set. Remember that the "medium" trait must always be heterozygous.

1. Birds can be blue, white, or white with blue-tipped feathers. - Codominance

- BB = blue - BW = white with blue tips - WW = white

2. Flowers can be white, pink, or red.

- Incomplete dominance - RR = red - Rr = pink - rr = white

Multiple Alleles

Blood type is a multiple allele trait. A person can have type A blood, type B, type AB (a type of codominance), or type O

A woman with type A blood (genotype AO) is married to a type B person (genotype BO). What proportion of their children will have: Type A: Type B: Type AB: Type O:

Sex-Linked

**In fruit flies, eye color is a sex linked trait. Red is dominant to white.** 1. What are the sexes and eye colors of flies with the following genotypes? X R X r _________ X R Y __________ X r X r __________ X R X R ____________ X r Y ____________ 2. What are the genotypes of these flies: white eyed, male ____________ red eyed female (heterozygous) ________ white eyed, female ___________ red eyed, male ___________ 3. Show a cross between a pure red eyed female and a white eyed male. What are the genotypes of the parents? ___________ and _______________ How many are: white eyed, male ____ red eyed, male ____ white eyed, female ____ red eyed, female ____