King Henry VIII and his six wives

1. King Henry VIII and his six wives King Henry VIII of England married six times in an attempt to have a legitimate male heir to the English throne. Henry VIII blamed his wives for their inability to produce a son. Was Henry correct in blaming his wives? Explain.

2. Sex Determination in Humans: Phenotype: 50% female , 50% male Genotype:50% XX , 50% XY

3. Prince William and Kate Middleton The firstborn of Prince Williamand Kate Middleton will be heir to the throne, whether it’s a boy or a girl under the new succession rules.

4. Sex-Linked Inheritance • Sex linked traits: Occur in humans, for which genes are on the X chromosome. • Each X-chromosome in the female will have one allele for a gene for a total of 2 alleles per gene • Because Males have only one X-chromosome they will only have one allele for a particular gene. Female Male

5. Sex-Linked Inheritance • Types of inheritance: X-linked Dominant: dominant allele carried on one or both of the X-chromosomes will cause expression of the phenotype X-linked Recessive:recessive alleles must be present on bothX-chromosomes for a woman in order for the phenotype to be expressed, whereas a man only needs one recessive allele Recessive allele Dominant allele

6. Sex- Linked Disorders • There are various disorders that arise from sex-linked inheritance. (Note: the disorder is considered to be the phenotype). Haemophilia Severe Combined Immunodeficiency

7. Colour Blindness The gene that causes colour blindness is on the X chromosome.

8. Sex-linked Inheritance Problem: • Color blindness is an sex-linked recessive disorder. Suppose a heterozygous female (carrier) is crossed with a normal male. What would be the genotype and phenotype proportions of the F1 generation? Defective allele Xh X H Phenotype: 2 normal females 1 normal male 1 color blind male (XhY) X H X H Xh X H XH Y X H Y Xh Y Genotype: 25% XHXH 25% XH Y 25% XhXH 25% Xh Y