Genetics After Mendel

1. Genetics After Mendel

2. 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.

3. Use a Punnet square to predict offspring! Red Flower – RRWhite Flower - WW R R W 100% PINK!!! W

4. Try this one: • Bird feathers show incomplete dominance. For example, the gene for black feathers, B, may be incompletely dominant to the gene for white feathers, b. The heterozygous condition produces a bird with blue feathers. Determine the genotypic and phenotypic ratios that will result from each of the following crosses: A) blue x white B) black x blue C) blue x blue

5. Answers: A) 50% Bb (Blue); 50% bb (White) • 50% BB (Black); 50% Bb (Blue) • 25% BB (Black); 50% Bb (Blue); 25% bb (White)

6. 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 THERE’S NO NEED TO MOAN ABOUT BEIN’ ROAN!

7. Co-DominanceCont. -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 Punnett square to predict offspring: • Cross a white cow with a red bull X

8. CR CR CW 100% Roan!! CW 2) Cross a white cow with a roan bull

9. A Special Case – Blood Type • There are three alleles! A B O • A and B are co-dominant • O is recessive • FYI: +/- is the Rh factor (If the major Rh antigen is present, the person is Rh+; if not, they are Rh-) Predict offspring bloodtypes for: • Heterozygous type A mother, type O father

10. Blood Type… Cont. A O 50% AO 50% OO O O b) Mother: AB; Father: Hetero type B

11. Try these ones: • Mother: AB; Father: Hetero type B • Match the children and parents:

12. What’s your type? • AB universal plasma donors • AB+ universal recipients • O+ blood most needed • O- universal RBC donor

13. 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.)

14. Are you colour blind? WHAT DO YOU SEE?

15. X-Linked Traits • If a recessive gene is on the ‘X’: - always expressed in males - no homologous pair on the ‘Y’. - recessive, X-linked diseases are much more common in males!

16. 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’

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