Dihybrid Crosses
In Mendel’s cross of RRYY × rryy, this is the F2 phenotypic ratio.
What is 9:3:3:1 (round yellow:round green:wrinkled yellow:wrinkled green)?
He recognized the parallels between Mendel’s genes and the behavior of chromosomes.
Who is Walter Sutton?
When the heterozygote’s phenotype is intermediate between the two homozygotes, this is the pattern.
What is incomplete dominance (e.g., snapdragon flower color)?
The three alleles of the single ABO gene.
What is IA, IB, and i?
Gene interaction in which alleles at one locus mask the effects of alleles at a different locus.
What is epistasis?
Name all gamete genotypes an RrYy plant makes and their proportions, and the principle that guarantees it.
What is RY, Ry, rY, ry, each ¼, and independent assortment?
For independent assortment, the allele received for one gene has no influence on the allele received for the other.
This scientist discovered meiosis in 1883, but Mendel’s work was still overlooked until the early 1900s.
Who is Van Beneden?
In incomplete dominance, the F2 ratio from a monohybrid cross, and why it differs from 3:1.
What is 1:2:1, and the phenotypic ratio equals the genotypic ratio because the heterozygote is distinguishable?
This blood type can receive transfusions only from its own type.
What is type O because it has anti-A and anti-B antibodies?
In Labradors, these three genotypes all produce yellow fur.
What is BBee, Bbee, and bbee?
A round, yellow plant (RrYy) is crossed with a round, green plant (Rryy). What fraction of the offspring will be wrinkled and green, and what is the full phenotypic ratio?
What is 1/8 wrinkled green, and the phenotypic ratio is 3 round yellow:3 round green:1 wrinkled yellow:1 wrinkled green?
The particular site on a chromosome where a gene is located.
What is the locus?
Genotype LMLN gives this blood type, and this is the inheritance pattern it demonstrates.
What is type MN; codominance (both glycoproteins are present on the red blood cell surface)?
This blood type has no antibodies and can accept A, B, AB, or O.
What is type AB because it has antigens A and B, with no antibodies?
The E gene’s role in Lab coat color: what E permits and what ee does.
What is E permits pigment deposition; ee blocks it, so the B/b genotype can’t be seen?
Among F2 plants showing round, yellow seeds, this fraction is homozygous for both genes.
What is 1/9?
Only RRYY qualifies: 1/16 of all F2 out of the 9/16 that are round yellow.
Of Sutton’s parallels, this is the one that corresponds to Mendel’s principle of independent assortment.
What is the separation of one chromosome pair in meiosis independent of the separation of other pairs?
An individual carries at most two alleles of a gene, yet a population can have many. Name this and explain how the alleles differ.
What is multiple alleles; they differ at one or more points in their DNA sequence (e.g., single base-pair changes)?
A type A mother and type B father have a type O child. Give both parents’ genotypes.
What is mother IAi, father IBi?
The child must be ii, so each parent carries a recessive i.
Phenotypic ratio from BbEe × BbEe in Labradors, and the number of expected classes that is “lost.”
What is 9 black:3 brown:4 yellow; epistasis collapses 4 classes into 3 (the 3 + 1 ee classes combine)?
Two parents are crossed for two traits and produce 156 offspring in four groups: 89, 31, 28, and 8. What are the parents’ genotypes? If the four groups were about equal in size, what would the parents be, and what is that cross called?
What is RrYy × RrYy?
89:31:28:8 ≈ 9:3:3:1; a dihybrid cross. Equal numbers: RrYy × rryy, a test cross (dihybrid × double recessive).
At the same locus, different alleles of a gene differ in this way, and this is the possible consequence for the protein.
What is they differ in DNA sequence, which may cause functional differences in the encoded protein?
Red-flowered and white-flowered snapdragons show incomplete dominance. Predict the offspring of a pink × white cross.
What is 1 pink:1 white (½ heterozygous, ½ homozygous recessive)?
Explain what happens when a type A person receives type B blood, and why ABO shows three inheritance concepts at once.
What is anti-B antibodies in type A blood that bind the B antigens, so the donor cells clump; ABO shows multiple alleles, dominance (IA, IB over i), and codominance (IA with IB)?
A BbEe Lab is crossed with a bbee Lab. Give the expected offspring phenotypes and ratio.
What is 1 black (BbEe):1 brown (bbEe):2 yellow (Bbee, bbee)?