Mendelian and Non-mendelian Flashcards
What are Mendel’s three laws of inheritance?
Mendel’s laws include dominance (one allele masks another), segregation (alleles separate during gamete formation), and independent assortment (genes on different chromosomes inherit independently).
How do dominant and recessive traits differ in terms of inheritance and expression?
Dominant traits require only one allele for expression, while recessive traits require two copies of the allele to be expressed.
What is a test cross?
A test cross involves crossing an organism with a dominant phenotype (but unknown genotype) with a homozygous recessive organism to determine whether it is heterozygous or homozygous dominant.
How does a dihybrid cross demonstrate Mendel’s law of independent assortment?
A dihybrid cross (e.g., AaBb × AaBb) results in a 9:3:3:1 ratio, showing that genes for different traits are inherited independently if they are on separate chromosomes.
How can a Punnett square be used to predict genetic outcomes?
A Punnett square organizes parental alleles to show all possible offspring genotypes and their probabilities.
How does incomplete dominance differ from complete dominance?
In incomplete dominance, the heterozygote has an intermediate phenotype, unlike complete dominance, where the dominant allele fully masks the recessive allele.
Example: Red and white flowers producing pink offspring.
What is codominance, and how does it differ from incomplete dominance?
In codominance, both alleles are fully expressed, whereas in incomplete dominance, the heterozygote shows a blended trait.
Example: AB blood type.
What is epistasis, and how does it affect genetic expression?
Epistasis occurs when one gene masks or modifies the effect of another gene.
Example: Coat color in Labrador retrievers, where one gene controls pigment production and another determines deposition.
How does polygenic inheritance contribute to continuous traits like human height?
Polygenic traits result from the interaction of multiple genes, leading to a continuous variation in phenotypes rather than distinct categories.
What is pleiotropy, and how can a single gene influence multiple traits?
Pleiotropy occurs when a single gene affects multiple traits.
Example: Sickle cell anemia, where the mutation impacts red blood cells, circulation, and malaria resistance.
What are the genotypes of the parents in a cross between a purple-flowered pea plant and a white-flowered plant?
The purple-flowered parent must be heterozygous (Pp) because a homozygous dominant (PP) parent would not produce white-flowered (pp) offspring.
What is the probability that a child will inherit cystic fibrosis from two heterozygous parents?
25% (1/4) chance the child is affected (cc). 50% (2/4) chance the child is a carrier (Cc). 25% (1/4) chance the child is unaffected (CC).
What proportion of offspring will have round, yellow seeds in a dihybrid cross (RrYy × RrYy)?
9/16 (56.25%) will have round, yellow seeds (R_Y_).
What are the possible blood types of the other parent if a person with blood type A has a child with blood type O?
The parent with blood type A must have genotype IAi to pass the i allele. The other parent must be ii (blood type O).
What does it suggest if all male children in a family have an X-linked recessive disorder, but none of the females are affected?
The disorder is X-linked recessive, inherited from the mother (a carrier).
What phenotypic ratio will be observed when two pink-flowered plants are crossed?
25% Red (RR), 50% Pink (RW), 25% White (WW).
What are the possible blood types of children from a parent with AB blood type and a parent with blood type O?
50% Type A (IAi), 50% Type B (IBi).
What colors could puppies have from a cross between a black Labrador (BbEe) and a yellow Labrador (bbee)?
50% black (BbEe, Bbee), 50% yellow (bbee).
The ee genotype prevents pigment deposition, leading to yellow fur.
What type of inheritance does sickle cell anemia represent and why?
Pleiotropy—one gene mutation affects red blood cell shape, circulation, oxygen transport, and malaria resistance.
What is the probability that a son will have hemophilia if his mother is a carrier and his father is unaffected?
The son has a 50% chance of inheriting the X chromosome carrying the mutation (XhY).
