monohybrid crosses Flashcards
What is a monohybrid cross?
A genetic cross involving one trait.
What is complete dominance?
The dominant allele fully masks the recessive allele.
What is the phenotypic ratio for a heterozygous monohybrid cross?
3:1 (dominant : recessive).
What is incomplete dominance?
No allele is fully dominant; traits blend.
What is the phenotype of a red (RR) and white (WW) flower cross?
All pink (RW) flowers.
What is the phenotypic ratio of two heterozygous (RW) flowers crossed?
1:2:1 (red : pink : white).
What is co-dominance?
Both alleles are fully expressed.
What is the coat color of a red (RR) and white (WW) cattle cross?
Red and white patches (RW).
What is the phenotypic ratio when two heterozygous (RW) cattle are crossed?
1:2:1 (red : red-white patches : white).
What are the male and female sex chromosomes?
Male: XY, Female: XX.
What is the chance of having a boy or girl?
50% for each.
What determines a baby’s sex?
The father’s sperm (X or Y).
Why are males more likely to get sex-linked diseases?
They have only one X chromosome.
What are two examples of sex-linked diseases?
Haemophilia & color blindness.
What is the genotype of a normal female carrier of haemophilia?
XHXh.
What is the genotype of a male with haemophilia?
XhY.
Is cystic fibrosis sex-linked?
No, it’s on chromosome 7.
What is the genotype of a carrier?
Bb (heterozygous).
What is the chance of a heterozygous parent (Bb) and a normal parent (BB) having a child with CF?
0% (but 50% carriers).
How many alleles control blood type?
Three (IA, IB, i).
Which alleles are co-dominant?
IA and IB.
Which allele is recessive?
i
Can two blood type B parents have an O child?
Yes, if both are IBi.
Can a man with blood type AB be the father of a type O child?
no
