7th Grade TCAP: Alleles and Offspring (7.LS3.3)

What does it mean if a trait is dominant?

• If the trait is present, then the trait is always expressed.

• If the trait is present, then the trait is never expressed.

• If the trait is absent, then the organism will not survive.

• If the trait is absent, then the organism will survive.

Answer explanation

A dominant trait is one that is expressed whenever it is present in an organism's genotype. This means that if the trait is present, it will always be visible in the organism's phenotype.

Tags

NGSS.HS-LS3-1

Which trait is an example of an inherited trait in humans?

• having short hair

• having blue eyes

• speaking English

• being polite

Answer explanation

Having blue eyes is an inherited trait, as it is determined by genetics. In contrast, having short hair, speaking English, and being polite are influenced by personal choices and environment, not inherited.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

What biological concept was Mendel studying when he crossed pea plants many times over many generations?

• imbalance in ecosystems

• predator-prey relationships

• dominant and recessive traits

• male and female genetic differences

Answer explanation

Mendel studied dominant and recessive traits by crossing pea plants, observing how traits were inherited across generations. This foundational work established the principles of genetics.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

What can be inferred about a plant with the genotype Rr?

• The red-flowered plant inherited a dominant allele from both parents.

• The white-flowered plant inherited a recessive allele from both parents.

• The red-flowered plant inherited a dominant allele from one parent and a recessive allele from the other parent.

• The white-flowered plant inherited a dominant allele from one parent and a recessive allele from the other parent.

Answer explanation

The genotype Rr indicates that the plant has one dominant allele (R) and one recessive allele (r). Therefore, it inherited a dominant allele from one parent and a recessive allele from the other parent, resulting in red flowers.

Tags

NGSS.HS-LS3-1

In peas, seed pods can be green (G) or yellow (g). The Punnett square shows a cross between a plant with green seed pods and a plant with yellow seed pods. Which statement explains why all offspring have green seed pods?

• A) All the offspring have the dominant allele.

• B) All the offspring have the recessive allele.

• C) Both parents have a dominant allele.

• D) Both parents have a recessive allele.

Answer explanation

All offspring have green seed pods because they inherit the dominant allele (G) from the green pod parent. Since G is dominant over g, the presence of G ensures all offspring display the green phenotype.

Tags

NGSS.HS-LS3-1

In pea plants, the allele for smooth peas is dominant (S). If a heterozygous smooth pea plant (Ss) is crossed with a homozygous smooth pea plant (SS), which are the possible genotypes the offspring could have?

• only SS

• only Ss

• Ss or SS

• ss or SS

Answer explanation

The cross between a heterozygous smooth pea plant (Ss) and a homozygous smooth pea plant (SS) can produce offspring with genotypes SS or Ss. Therefore, the possible genotypes are Ss or SS.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

What does the genotype for a trait BB represent?

• A. Each letter represents the dominant allele inherited from each parent.

• B. Both letters represent the dominant allele inherited from the mother.

• C. Both letters represent the recessive allele inherited from the father.

• D. Each letter represents the recessive allele inherited from each parent.

Answer explanation

The genotype BB indicates that both alleles are dominant, inherited from each parent. Therefore, choice A is correct, as it accurately describes the representation of the dominant alleles.

Tags

NGSS.HS-LS3-1

Which genotype represents a plant with short stems?

• tr

• tt

• TT

• Tt

Answer explanation

The genotype 'tt' represents a homozygous recessive condition, which results in short stems in plants. In contrast, 'TT' and 'Tt' would produce tall stems due to the presence of the dominant allele 'T'.

This trait will always be expressed if present because it will mask the expression of others

• stem cells
• heterozygous
• dominant
• recessive

Tags

NGSS.HS-LS3-1

Which genotype represents a homozygous recessive individual?

• AA

• Aa

• aa

• Ab