Genetics Beyond Mendel Types of Dominance 1 Complete

Genetics Beyond Mendel

Types of Dominance 1. Complete -1 gene masks the other (Tt…see Mendel) 2. Incomplete -Neither gene is dominant, neither is recessive. -The gene effect is mixed -We use 2 different letters for the homologous pair since neither is dominant.

Use a punnet square to predict offspring! Red Flower – RR White Flower - WW R W W RW RW RW TRY ME! Page 179 #8 Note: Use ‘W’ for white…not ‘b’! 100% PINK!!!

Types of Dominance 3. Co-Dominance -Neither gene is dominant or recessive -Gene effects are not mixed -Both genes are expressed at the same time! -Eg. Roan Cattle – Red hairs and white hairs LOOK AT ME…I’M ROAN!

Co-Dominance Cont. -Write C (for co-dominance) and a super script (R=Red, W=white) -Red haired = CRCR -White haired = CWCW -Red and White (Roan) =CRCW Use a punnet square to predict offspring: 1) Cross a white cow with a red bull X

CR CW C RC W CR C RC W 100% Roan!! C RC W 2) Cross a white cow with a roan bull

A Special Case – Blood Type • There are three alleles! A B O • A and B are co-dominant • O is recessive Predict offspring bloodtypes for: a) Heterozygous type A mother, type O father

Blood Type… Cont. A O O O AO OO 50% AO 50% OO b) Mother: AB; Father: Hetero type B c) Do Page 179, #9

Predicting Gender Two sex chromosomes determine gender: X & Y Female Genotype: XX Male Genotype: XY Predict the probability of a couple having a boy!

50% chance of having a boy! 50% chance of having a girl! Chew on this! Page 184, #12!

X-Linked Traits • All genes found on the ‘X’ chromosome are “linked”. • Many of the genes on the ‘X’ are not on the ‘Y’. • The ‘X’ is larger and has many genes that are not related to gender… (i. e. colour vision, blood clotting etc. )

Are you colour blind? WHAT DO YOU SEE?

X-Linked Traits • If a recessive gene is on the ‘X’: -In males it will always be expressed since there is no homologous pair on the ‘Y’. -Therefore (sorry guys) recessive, X-linked diseases are much more common in males!

Hemophilia – I can’t stop bleeding!! Since gender and the gene are important, both must be noted. • Dominant allele – H • Recessive allele – h • XH – dominant gene on ‘X’ • Xh – recessive gene on ‘X’ • Y – no gene on the ‘Y’

Hemophilia • Female genotypes XHXH – Normal XHXh – Normal but a ‘Carrier’ Xh. Xh – Hemophiliac (very rare) • Male genotypes XHY – Normal Xh. Y - Hemophiliac Predict the offspring for: -Mother carrier and a normal father!

• Try these! Page 200, Question 8, 9, 10 (a-f)