17.5 - Sex Linkage Flashcards
The inheritance of sex in humans What sex linkage means How to interpret pedigree charts
How many pairs of chromosomes do humans have?
23
What are autosomes?
22 pairs of identical chromosomes in males and females
What are sex chromosomes?
23rd pair
What are the two forms of sex chromosomes?
X and Y
Which sex chromosomes do females have?
XX
Which sex chromosomes do males have?
XY
What are sex-linked genes?
Genes located on X or Y chromosomes
Which chromosome carries most sex-linked genes?
X chromosome
Why do recessive X-linked alleles appear more in males?
No corresponding allele on Y chromosome
What is haemophilia?
X-linked recessive disorder affecting blood clotting
How is haemophilia inherited?
Faulty allele on X chromosome
Who is mainly affected by haemophilia?
Males
Why are females less affected by haemophilia?
Need faulty allele from both parents
Who do males inherit haemophilia from?
Mother
Who are carrier mothers?
Have one healthy and one haemophilia allele
Who can affected fathers pass haemophilia to?
Daughters
What are pedigree charts?
Visual method to track phenotypes and relationships
How are males represented in pedigree charts?
Squares
How are females represented in pedigree charts?
Circles
What does shading in a pedigree chart indicate?
Presence of a trait
