Sex Linkage and Incomplete Dominance (Leaving Cert Biology): Flashcards
📚Flashcards
Practise the cards
15 cards from this deck
ShowHide
Practise the cards
15 cards from this deck
Definition of sex linkage
Definition of sex linkage
Characteristic controlled by gene on one of the sex chromosomes
Size comparison: X vs Y chromosome
Size comparison: X vs Y chromosome
X chromosome is much larger than Y chromosome
Most sex-linked traits are ___-linked
Most sex-linked traits are ___-linked
X-linked
Male sex chromosome genotype
Male sex chromosome genotype
XY
Female sex chromosome genotype
Female sex chromosome genotype
XX
Why males express X-linked recessive traits more
Why males express X-linked recessive traits more
Males only have one X chromosome, no allele on Y to mask it
Two examples of X-linked traits in humans
Two examples of X-linked traits in humans
Colour blindness and haemophilia
% of males worldwide with colour blindness
% of males worldwide with colour blindness
About 8%
What is haemophilia?
What is haemophilia?
Bleeding disorder from lack of blood clotting proteins
Can males be carriers of X-linked traits?
Can males be carriers of X-linked traits?
No, they either have the trait or don't
Definition of incomplete dominance
Definition of incomplete dominance
Both alleles expressed, creating intermediate phenotype
Cattle coat: red × white offspring phenotype
Cattle coat: red × white offspring phenotype
Roan coat (intermediate)
Cattle genotypes: RR, Rr, rr coat colours
Cattle genotypes: RR, Rr, rr coat colours
Red, roan, white
Snapdragon: red × white flower colour offspring
Snapdragon: red × white flower colour offspring
Pink flowers
F2 phenotypic ratio in incomplete dominance
F2 phenotypic ratio in incomplete dominance
1:2:1 (25%:50%:25%)