Examples of Sex-linkage Flashcards
List some examples of sex-linked characteristics
4
Colour blindness
Haemophilia
Duchenne muscular dystrophy
Eye colour in fruit flies
How many colours of light can a normal person see?
Three; Green, red and blue
What is the allele for normal vision?
N
Is the allele for normal vision recessive or dominant?
N (normal vision) is dominant
What is the most common type of colour blindness?
The inability to distinguish red from green
Where is the gene for colour vision located?
ON an X chromosome
What three genotypes can females have in relation to colourblindness?
XNXN
XNXn
XnXn
What is the genotype XNXn referred to as?
A carrier
What genotype is needed for a female to be colour blind?
XnXn
What are the two genotypes for males and colour blindness?
XNY
XnY
How many copies of the recessive allele do men need to be colour blind?
Only one
Why are males more likely to be colour blind?
As females need two copies of the recessive gene to be colour blind while males need only one copy
What is haemophilia?
Haemophilia is a bleeding disorder caused by the lack of a particular blood protein
What affect does haemophilia have on an individual?
Haemophiliacs suffer from frequent bleeding, often into the joints, they may bleed to death from a small cut without treatment
What causes haemophilia?
A gene located on the X chromosome
