Question

1. which principle states that the inheritance of one trait does not affect the inheritance of another trait?

a. independent assortment
b. allele segregation
c. phenotypic ratio
d. dominance principle

1. why do sex - linked traits differ between males and females?

a. females have two x chromosomes, while males have one x and one y chromosome.
b. both males and females equally inherit sex - linked traits.
c. females have one x and one y chromosome.
d. males have two copies of the x chromosome.

1. which of the following statements about dominant alleles is true?

a. they are always expressed in the phenotype
b. they can be masked by recessive alleles
c. they overpower recessive alleles when present
d. they are only present in homozygous genotypes

Explanation:

Question 10

• Option a: Independent Assortment principle states that the inheritance of one trait is independent of another, meaning one trait's inheritance doesn't affect another's.
• Option b: Allele Segregation is about alleles separating during gamete formation, not about multiple traits' inheritance independence.
• Option c: Phenotypic Ratio is the ratio of observable traits in offspring, not a principle about trait inheritance independence.
• Option d: Dominance Principle is about dominant alleles masking recessive ones in a single trait, not about multiple traits.

• Option a: Females have XX chromosomes, males have XY. Sex - linked traits (often on X) are inherited differently because males have one X (so a single allele on X is expressed) and females have two Xs (can be heterozygous).
• Option b: Males and females do not inherit sex - linked traits equally due to different chromosome compositions.
• Option c: Females have XX, not XY.
• Option d: Males have one X chromosome, not two.

• Option a: Dominant alleles are not always expressed. For example, in a heterozygous genotype with a dominant and a recessive allele, the dominant is expressed, but if there are other factors or in some complex inheritance patterns, but generally, when present in a heterozygous (Aa) or homozygous dominant (AA) genotype, the dominant allele's trait is expressed. Wait, actually, the key is:
• Option b: Dominant alleles mask recessive alleles, not the other way around.
• Option c: When a dominant allele is present (in heterozygous or homozygous dominant), it will be expressed in the phenotype, overpowering the recessive allele (which is masked).
• Option d: Dominant alleles can be in heterozygous (Aa) or homozygous dominant (AA) genotypes.

Wait, re - evaluating:

• Option a: If the dominant allele is present (either in AA or Aa), it is expressed in the phenotype. So this is true.
• Option b: Recessive alleles are masked by dominant alleles, not the other way.
• Option c: "Overpower" is a bit of a non - scientific term, but the idea that dominant alleles are expressed when present (masking recessive) is correct, but option a is more accurate in terms of expression. Wait, no: In a heterozygous individual (Aa), the dominant allele is expressed, and in homozygous dominant (AA) it is also expressed. So dominant alleles are always expressed in the phenotype when present (in the genotype).
• Option d: Dominant alleles can be in heterozygous genotypes (Aa), so this is false.

Wait, maybe I made a mistake earlier. Let's re - check:

• Dominant allele: An allele that is expressed in the phenotype when present in either the homozygous (AA) or heterozygous (Aa) state.
• So option a: "They are always expressed in the phenotype" – when the dominant allele is present in the genotype (either AA or Aa), it is expressed. So this is true.
• Option b: Dominant alleles mask recessive alleles, so they can't be masked by recessive alleles.
• Option c: The term "overpower" is not the standard term, and the concept is that dominant alleles are expressed when present, but the wording of option a is more accurate about expression.
• Option d: Dominant alleles can be in heterozygous genotypes, so this is false.

So the correct answer is a.

Answer:

a. Independent Assortment

Question 11