Slide Show Notes Flashcards
(30 cards)
What is the definition of linked genes?
Genes that are located on the same chromosome and do not assort independently.
What is the expected offspring ratio according to Mendel’s law of independent assortment?
1:1:1:1 ratio.
If results differ significantly from the expected ratio, what does this indicate?
The genes in question are located on the same chromosome.
Who discovered sex linkage and in what year?
T.H. Morgan in 1910.
What is a Barr body?
An inactive X chromosome in females.
What is the outcome when a white-eyed male fruit fly is crossed with a red-eyed female?
All F1 offspring have red eyes.
Why do more males than females show the recessive phenotype in sex-linked traits?
Males only need one copy of the recessive allele to express the trait.
What is the genotype of a normal male in terms of sex chromosomes?
XY.
Fill in the blank: Genes located on a sex chromosome are called _______.
sex-linked traits.
What is the effect of crossing over on linked genes?
It can disrupt linkage and create recombinant types.
What is the relationship between the distance of genes on a chromosome and crossing over frequency?
The farther apart two linked genes are, the greater the probability for crossovers.
What is the formula for calculating map distance between genes?
Map distance = (number of recombinant types / total number) x 100.
What does a 3:1 ratio in offspring indicate when analyzing traits?
The trait is likely dominant.
What is a key characteristic of recessive traits in pedigree analysis?
They may skip generations.
What is the significance of the genotype Xh for a female with hemophilia?
She has one copy of the hemophilia gene.
True or False: In sex-linked inheritance, fathers can pass the trait to their sons.
False.
What conclusion did Morgan reach regarding the gene for eye color?
It is located on the X chromosome.
What is the expected proportion of male progeny showing hemophilia if a carrier female marries a normal male?
1/2 of the males.
Fill in the blank: Crossing over occurs during _______.
Prophase I.
What type of inheritance pattern would show affected individuals in every generation?
Dominant inheritance.
In tortoiseshell cats, what causes the different colored patches of fur?
Random inactivation of one of the X chromosomes.
What is the expected phenotype ratio from a test cross of AaBb with aabb?
Parental types will always be greater than recombinant types.
What are examples of sex-linked traits in humans?
- Hemophilia
- Red-green color blindness
- Duchenne’s muscular dystrophy.
What does it indicate if two unaffected parents have an affected child?
The trait is likely recessive.
