Question 1

What is considered a "black box in biology?

Accepted Answer

A "black box" in biology refers to processes or systems where only the input and output are known, but the internal mechanism or how the process works is not understood. This term is used to describe situations where the exact workings are either too complex to currently understand or have not yet been studied in detail.

Question 2

Which type of allele, or allelic combination, can be present in an individual without affecting phenotype?

Accepted Answer

A recessive allele can be present in an individual without affecting the phenotype if it is paired with a dominant allele, as the dominant allele will mask the expression of the recessive allele.

Question 3

Which of the following did Gregor Mendel not illustrate?

Accepted Answer

Mendel's work predated the discovery of chromosomes and their role in inheritance. His experiments with pea plants laid the foundation for the laws of inheritance, but he did not know that units of inheritance (genes) are located on chromosomes.

Question 4

Refer to the figure above and then answer the question that follows.
-In his basic experiments, Mendel began with true-breeding parental (P) plants. What did he see when he cross-fertilized P plants that had different traits?

Accepted Answer

Mendel observed that the offspring (F1 generation) of true-breeding parental plants with different traits exhibited only one of the parental traits, not a blend. This observation led to the principle of dominance.

Question 5

Refer to the figure above and then answer the question that follows.
-Before Mendel, people had observed inheritance of dominant and recessive traits by following many generations of plants and animals. What was different about Mendel's work?

Accepted Answer

Mendel's work was different because he meticulously counted and analyzed the results of his experiments mathematically, which allowed him to deduce the laws of inheritance.

Question 6

Crossing red flowering snapdragons with white flowering snapdragons yields seeds that grow into snapdragons with pink flowers. This suggests that:

Accepted Answer

The blending of red and white flower colors to produce pink flowers in snapdragons is a classic example of incomplete dominance, where neither allele is completely dominant over the other, resulting in a phenotype that is a mix of both parental traits.

Question 7

Cystic fibrosis (CF) is caused by a recessive allele. A child has CF, even though neither of his parents has CF. What can you conclude about the parents?

Accepted Answer

Since cystic fibrosis is a recessive condition, both parents must carry one copy of the recessive allele (heterozygous) to produce a child with CF, as neither parent shows the disease phenotype.

Question 8

In humans, "unattached earlobes are dominant over "attached earlobes. A woman and a man, both with unattached earlobes, have a child with attached earlobes. What is the probability their next child will have attached earlobes?

Accepted Answer

Since both parents have unattached earlobes but produced a child with attached earlobes, they must both be heterozygous (Aa) for the trait. The Punnett square for two heterozygous parents is Aa x Aa, which results in a 1/4 chance of an aa offspring (attached earlobes).

Question 9

If an individual exhibits a recessive trait, which of the following statements can you be sure of?

Accepted Answer

A recessive trait is expressed only when an individual has two copies of the recessive allele (homozygous recessive). This means its phenotype will differ from the phenotype of a homozygous dominant individual, who has two dominant alleles and expresses the dominant trait.

Question 10

Analyze the validity of the two statements below: Statement A: If an individual is heterozygous for a particular trait, it means that the individual carries two different alleles on a set of homologous chromosomes. Statement B: If an individual is heterozygous for a particular trait, that individual produces dominant gametes 50 percent of the time.

Accepted Answer

The answer of Analyze the validity of the two statements...

Question 11

Alleles that are dominant are:

Accepted Answer

The answer of Alleles that are dominant are:
...

Question 12

In the individual with genotype AaBB, what percentage of gametes will contain the A allele?

Accepted Answer

In the genotype AaBB, the A allele can be passed on from the Aa part of the genotype. Since gametes are formed through meiosis, each gamete gets one allele from each gene pair. Therefore, 50% of the gametes will contain the A allele (from the Aa pair), and the other 50% will contain the a allele. The BB genotype does not affect the distribution of the A allele.

Question 13

How many different types of gametes can be generated by an individual with genotype AaBB?

Accepted Answer

The individual with genotype AaBB can produce two types of gametes: AB and aB, because the Aa genotype can produce two different alleles (A and a), while the BB genotype can only produce one type of allele (B).

Question 14

The phenotypic ratio obtained in a dihybrid cross is 8:0:4:2. The number of offspring that are dominant for trait 1 and recessive for trait 2 is:

Accepted Answer

The phenotypic ratio of 8:0:4:2 indicates that there are no offspring that are dominant for trait 1 and recessive for trait 2.

Question 15

A "trihybrid cross would:

Accepted Answer

A trihybrid cross involves following three different traits in a genetic cross, typically to understand how multiple traits are inherited together.

Question 16

In Mendel's pea plants, yellow seeds are dominant to green seeds. Purple flowers are dominant to white flowers. Use Y and y for the seed color alleles, and P and p for the flower color alleles. Flower color and seed color assort independently. If a YyPp plant is crossed to a Yypp plant, what is the probability that the resulting plant will have the genotype Yypp? (Hint: Determine two separate probabilities, and use the rule of multiplication.)

Accepted Answer

The probability of Yy from Yy x Yy is 1/2, and the probability of pp from Pp x pp is 1/2. Multiplying these probabilities gives 1/2 * 1/2 = 1/4.

Question 17

In Mendel's pea plants, yellow seeds are dominant to green seeds. Purple flowers are dominant to white flowers. Use Y and y for the seed color alleles, and P and p for the flower color alleles. Flower color and seed color assort independently. A plant of unknown genotype with yellow seeds and purple flowers is crossed to a plant with green seeds and white flowers. The offspring all have yellow seeds, but some have purple flowers and some have white flowers. What is the genotype of the yellow-seeded, purple-flowered plant?

Accepted Answer

The yellow-seeded, purple-flowered plant must be homozygous dominant for seed color (YY) to ensure all offspring have yellow seeds, and heterozygous for flower color (Pp) to produce both purple and white flowers in the offspring.

Question 18

In Mendel's pea plants, yellow seeds are dominant to green seeds. Purple flowers are dominant to white flowers. Use Y and y for the seed color alleles, and P and p for the flower color alleles. Flower color and seed color assort independently. A true-breeding plant with green seeds and white flowers is crossed to a plant that is heterozygous for the genes for both phenotypes. What is the probability that the cross will yield a plant with green seeds and white flowers?

Accepted Answer

The answer of In Mendel's pea plants, yellow seeds are...

Question 19

In Mendel's pea plants, yellow seeds are dominant to green seeds. Purple flowers are dominant to white flowers. Use Y and y for the seed color alleles, and P and p for the flower color alleles. Flower color and seed color assort independently. If a plant that is heterozygous for both flower color and seed color genes is self-fertilized, what proportion of the offspring will have one of the dominant phenotypes, either the seed color or flower color, but not both?

Accepted Answer