Non-Mendelian Inheritance

Size: px
Start display at page:

Download "Non-Mendelian Inheritance"

Transcription

1 Non-Mendelian Inheritance

2 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.

3 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

4 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.

5 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)

6 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.

7 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.

8 Non-Mendelian Inheritance EduSmart video in class

9 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.

10 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 bluetipped 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

11 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:

12 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