Question 1

In the ABO multiple allele system, there are the following combinations of genotypes and phenotypes:

Accepted Answer

There are 6 genotypes (AA, AO, BB, BO, AB, OO) and 4 phenotypes (A, B, AB, O) in the ABO blood group system.

Question 2

Alternate forms of a gene are best described as _____.

Accepted Answer

Alleles refer to the alternate forms of a gene, which are responsible for producing different versions of a trait. Homologues are pairs of chromosomes that carry the same genes in the same order but may have different alleles. Loci refer to the specific location of a gene on a chromosome. Homozygous refers to having two identical alleles for a particular gene, while heterozygous refers to having two different alleles for the same gene.

Question 3

Methylmalonic acidemia is caused by _____.

Accepted Answer

Methylmalonic acidemia is characterized by the inability to properly metabolize amino acids and fats, specifically converting the amino acid methionine and the fatty acid derivative propionic acid into usable energy. This is due to a deficiency in the enzyme methylmalonyl-CoA mutase, which normally converts methylmalonyl-CoA into succinyl-CoA. Without this conversion, levels of methylmalonic acid build up in the body, leading to symptoms such as developmental delay, low muscle tone, poor feeding, and vomiting.

Question 4

The phenotype is _____.

Accepted Answer

The phenotype is the expression of a trait in an organism.

Question 5

Why did Mendel choose pea plants to experiment on?

Accepted Answer

Mendel chose pea plants to experiment on because offspring of pea plants are fertile, they have a number of different distinct traits, they are self-fertilizing, and they have a relatively short life cycle.

Question 6

Mendel's principle of segregation is directly related to an event that occurs in ______ of meiosis.

Accepted Answer

The principle of segregation refers to the separation of homologous chromosomes during anaphase I of meiosis, which results in the segregation of alleles into different gametes. Thus, the correct choice is C, which represents the stage of meiosis where this segregation occurs.

Question 7

In a cross between a true-breeding plant bearing smooth, yellow seeds and a true-breeding plant with wrinkled, green seeds, the offspring were all smooth and yellow. What is the genotype of the F₁ plants?

Accepted Answer

This is an example of a monohybrid cross, where only one trait (seed texture and color) is studied. In this case, the parental plants are true-breeding, so they can be represented by homozygous genotypes: SSYY for the smooth yellow-seeded plant and syy for the wrinkled green-seeded plant. The F1 generation shows a dominant phenotype: all plants are smooth and yellow. This means that the allele for smooth texture (S) and the allele for yellow color (Y) are dominant over the alleles for wrinkled texture (s) and green color (y), respectively. Therefore, the genotype of the F1 plants must be heterozygous for both traits: SsYy.

Question 8

Mendel's principle of independent assortment is directly related to an event that occurs in _____ of meiosis.

Accepted Answer

Mendel's principle of independent assortment states that the segregation of alleles for one gene is independent of the segregation of alleles for another gene. This occurs during metaphase I of meiosis when homologous chromosomes line up randomly at the equator of the cell, creating multiple possible combinations of alleles in the resulting gametes.

Question 9

Free earlobes are dominant to attached ear lobes and brown eyes are dominant to blue eyes. Ricardo has brown eyes and attached ear lobes. Ricardo's mother has blue eyes and free ear lobes. Ricardo's partner, Shanteel, has blue eyes and free ear lobes. Shanteel's mother has brown eyes and attached ear lobes. What is the probability that Ricardo and Shanteel will have a child who has blue eyes and attached ear lobes?

Accepted Answer

According to the given information, Ricardo is heterozygous for both traits (BbEe), while Shanteel is homozygous recessive for eye color and heterozygous for earlobe attachment (bbEe). 
The Punnett Square for their offspring is:

|   | B | b |
|---|---|---|
| e |Be |be |
| e |Be |be |

Therefore, there is a 25% probability that their child will have blue eyes and attached earlobes.

Question 10

In a cross involving incomplete dominance _____.

Accepted Answer

In incomplete dominance, the heterozygotes have a phenotype that is a blend of the two parental phenotypes, leading to identical phenotypic and genotypic ratios in the F2 generation.

Question 11

In his monohybrid crosses, Mendel deduced that one trait was recessive because _____.

Accepted Answer

Mendel observed that the recessive trait disappeared in the F1 generation but reappeared in the F2 generation, indicating it was masked by the dominant trait in the F1.

Question 12

A locus is best defined as _____.

Accepted Answer

A locus refers to the specific location of a gene on a chromosome.

Question 13

Independent assortment means that _____.

Accepted Answer

Independent assortment means that the segregation of one gene pair occurs as if no other gene pair was present. This suggests that the inheritance of one trait does not depend on the inheritance of another trait, and that the assortment of alleles for one gene is independent of the assortment of alleles for another gene.

Question 14

A pea plant with yellow peas is crossed with a pea plant that has green peas. The offspring include both yellow-pea and green-pea plants. The original plant with yellow peas must, therefore, have what genotype?

Accepted Answer

This is a classic example of a cross between two heterozygous individuals (one with Yy and one with yy). The Punnett square for this cross would result in 50% Yy (yellow) and 50% yy (green) offspring. Therefore, the original plant with yellow peas must have had a genotype of Yy.

Question 15

In a pedigree, a person whose symbol is filled in and who is associated with the roman numeral II _____.

Accepted Answer

A person whose symbol is filled in and associated with the roman numeral II is in the second generation of the pedigree. If the symbol is filled in, it means that the person is affected by the trait. Therefore, the best choice is A, which states that the person is affected by the trait and in the second generation.

Question 16

The offspring resulting from the cross of two red flowered plants are 3/4 red and 1/4 white. The most likely genotype of the red flowered plants is _____ .

Accepted Answer

The fact that the offspring are 3/4 red and 1/4 white suggests that one parent was homozygous dominant (RR) and the other was heterozygous (Rr). When the two are crossed, the Punnett square predicts that the offspring will be 3/4 red (RR or Rr) and 1/4 white (rr). Therefore, the most likely genotype of the red flowered plants is heterozygous (Rr). Option A (homozygous dominant) would result in all red offspring, while option C (homozygous recessive) would result in all white offspring, neither of which match the observed ratio. Option D (impossible to tell) is incorrect, as the observed ratio provides enough information to make a reasonable inference about the parent genotype.

Question 17

In a situation with codominant inheritance _____.

Accepted Answer

All of the choices are true. In codominant inheritance, both alleles are fully expressed, so there is no recessive phenotype. The principles of Mendelian inheritance are intact, and independent assortment can predict the genotypes and phenotypes of the offspring.

Question 18

In a monohybrid cross with complete dominance, the F₂ offspring should contain _____.

Accepted Answer

In a monohybrid cross with complete dominance, the F2 generation typically shows two phenotypes (dominant and recessive) and three genotypes (homozygous dominant, heterozygous, and homozygous recessive).

Question 19

Pedigrees _____.

Accepted Answer

Pedigrees provide information on the patterns of inheritance of a trait, can identify those at risk for a disease, can identify those at risk for transmitting a disease, and can be used to deduce the genotypes of parents. Therefore, all of these characteristics are true for pedigrees.

Question 20

A chi square test is done to determine _____.

Accepted Answer

A chi square test is used to determine whether the actual results of a cross match the expected results, which can help to determine how closely the observed data fits the theoretical patterns. This test is commonly used in genetics to test hypotheses about the inheritance of traits and to determine whether the results are statistically significant. The other choices are all related to genetic concepts, but they are not directly tested using a chi square analysis.

Quiz 3: Transmission of Genes From Generation to Generation