Question 1

Below are two statements. Which (if any) applies to the law of segregation? Which (if any) applies to the law of independent assortment? I: Phenotypes for long tails and big eyes are inherited separately in lab mice.
II: A baby mouse inherits a maternal red-eye allele and a paternal black-eye allele.

Accepted Answer

I: Independent assortment refers to the principle that genes for different traits can segregate independently during the formation of gametes. Statement I exemplifies this as it discusses the separate inheritance of two different traits (long tails and big eyes).II: Segregation refers to the principle that each individual has two alleles for each gene, which segregate from each other when gametes are formed, with each gamete receiving one allele. Statement II exemplifies this as it describes the inheritance of two different alleles for a single trait (eye color) from each parent.

Question 2

How is sex determined in most ants and bees?

Accepted Answer

In most ants and bees, sex is determined by the number of chromosomes an individual has. This system is known as haplodiploidy, where females are diploid (having two sets of chromosomes) and males are haploid (having only one set of chromosomes).

Question 3

Maternal inheritance patterns from generation to generation cannot be analyzed by simply studying the X chromosome in the way that paternal inheritance patterns can follow the Y chromosome because

Accepted Answer

The X chromosome is inherited from both the mother and the father (females inherit an X chromosome from each parent, while males inherit an X chromosome from their mother and a Y chromosome from their father), making it impossible to trace maternal inheritance patterns through the X chromosome alone in the same straightforward manner as paternal inheritance can be traced through the Y chromosome.

Question 4

If independent assortment did not occur, which of the following would be true?

Accepted Answer

Independent assortment is the process by which homologous chromosomes line up randomly during meiosis, resulting in the random separation of different genes into gametes. If independent assortment did not occur, genes for different traits would be inherited together as a pair, which means that the traits would be linked and would always appear together in offspring. This phenomenon is known as linkage.

Question 5

Sex-linked conditions are more common in men than in women because

Accepted Answer

Sex-linked conditions are caused by genes located on sex chromosomes, with the majority being on the X chromosome. Since men only inherit one X chromosome (from their mother), they only need to receive one copy of the recessive allele associated with the condition to be fully expressed. Women, on the other hand, have two X chromosomes and would need to inherit two copies of the recessive allele to be fully affected. Therefore, sex-linked conditions are more common in men than in women.

Question 6

What is meant by the statement that "male bees are fatherless"?

Accepted Answer

Male bees, also called drones, develop from unfertilized eggs laid by the queen bee. This means that they have no father, as there was no male contribution of genetic material in the fertilization of the egg.

Question 7

You are trying to determine the linkage map of a series of genes, X, Y, and Z, from Caenorhabditis elegans, a nematode worm commonly used in scientific research. From doing several crossover experiments, you know that the recombination frequency between X and Y is 11.5%, between Y and Z is 13%, and between X and Z is 25%. What is a possible sequence of these genes?

Accepted Answer

The sequence of genes can be determined by their recombination frequencies. The genes with the smallest recombination frequency (11.5% between X and Y) are closest together, while the genes with the largest recombination frequency (25% between X and Z) are furthest apart. Therefore, the sequence is X-Y-Z, where Y is between X and Z.

Question 8

The sex chromosome complement of a normal human female is

Accepted Answer

A normal human female has two X chromosomes, which is represented as XX.

Question 9

Blood samples are taken from the heel of newborn babies to test for a mutation in the PKU gene, which, if left untreated and in severe cases, can lead to mental retardation, reduced skin pigmentation, and seizures. Which concept is being illustrated by this example?

Accepted Answer

Pleiotropy refers to a single gene affecting multiple phenotypic traits. In this example, the mutation in the PKU gene can lead to mental retardation, reduced skin pigmentation, and seizures, indicating pleiotropic effects of this gene. Incomplete dominance, polygenic inheritance, and codominance do not accurately describe this scenario.

Question 10

Recessive X-linked traits are more likely to be expressed in a male fruit fly than a female fruit fly because

Accepted Answer

In fruit flies, males have only one X chromosome, while females have two. Therefore, any recessive trait on the X chromosome will be expressed in the male phenotype because there is no corresponding dominant gene on the other X chromosome to mask it. In contrast, the female phenotype may show the dominant gene and mask the recessive gene. This is known as X-linkage inheritance. The other choices, B and C, are not related to X-linkage inheritance and are incorrect.

Question 11

Suppose that an elephant with the genotype EEFfggHh reproduces with an elephant with the genotype eeFFGgHh. What is the probability that a baby elephant (called a calf) would have the genotype EeFFGghh?

Accepted Answer

To determine the probability of the calf having the genotype EeFFGghh, we analyze each gene pair separately:1. For the Ee genotype, one parent is EE and the other is ee, so all offspring will be Ee, giving a probability of 1.2. For the FF genotype, one parent is Ff and the other is FF, so the probability of an offspring being FF is 1/2 (the Ff parent can only pass on F 50% of the time).3. For the Gg genotype, both parents are Gg, so the probability of an offspring being Gg is 1/2 (since there's a 50% chance of getting G from one parent and a 50% chance of getting g from the other).4. For the hh genotype, one parent is Hh and the other is Hh as well, so the probability of an offspring being hh is 1/4 (since there's a 25% chance of getting h from both parents).Multiplying these probabilities together: 1 * 1/2 * 1/2 * 1/4 = 1/16.

Question 12

Given the sex determination system in bees, we can expect that

Accepted Answer

In bees, females are diploid and develop from fertilized eggs, thus they produce eggs through meiosis. Males, however, are haploid and develop from unfertilized eggs, so they produce sperm through mitosis, not requiring the reduction of chromosomes that occurs in meiosis.

Question 13

Justin has type A blood and his wife Brittany has type B blood. Justin's parents both have type AB blood, and Brittany's parents also both have type AB blood. What are the chances that Justin and Brittany's son Theodore has type A blood?

Accepted Answer

The answer of Justin has type A blood and his...

Question 14

A colorblind woman marries a man who is not colorblind. All of their sons, but none of their daughters, are colorblind. Which of the following statements correctly explains these results?

Accepted Answer

Color blindness is X-linked recessive, meaning the gene responsible for color vision is found on the X chromosome. Females have two X chromosomes, so in order to be colorblind, they must inherit two copies of the colorblindness allele. However, males only have one X chromosome, so if they inherit the colorblindness allele, they will be colorblind. Since the mother is colorblind, she must have one X chromosome with the colorblindness allele. If she passes that allele to her sons, they will be colorblind. The daughters, on the other hand, would need to inherit two copies of the colorblindness allele, which is less likely since their father does not have the colorblindness allele.

Question 15

According to scientists, about what percentage of men currently living in Central Asia may be descended from the Mongolian ruler Genghis Khan?

Accepted Answer

Studies have shown that approximately 8% of men living in Central Asia are descended from Genghis Khan, meaning that he and his male relatives likely had a significant impact on the gene pool in the region.

Question 16

In giraffes, long necks (N), long legs (L), dark spots (D), and the ability to digest maize (M) are all dominant traits. What possible genotype could a long-necked, short-legged, light-spotted, maize-digesting giraffe have?

Accepted Answer

The correct genotype for a long-necked, short-legged, light-spotted, maize-digesting giraffe is NnllddMM. This is because long necks (N) and the ability to digest maize (M) are dominant traits, which are represented by at least one dominant allele (N and M, respectively). Short legs and light spots are recessive traits, requiring two recessive alleles (ll and dd, respectively).

Question 17

Any gene located on a sex chromosome

Accepted Answer

Any gene located on a sex chromosome is called a sex-linked gene because it is linked to the sex chromosome.

Question 18

In some cats, black coat color (B) is dominant over brown (b) and a striped fur pattern (S) is dominant over a marbled fur pattern (s). You rescued a black striped cat from an animal shelter but could not determine its exact genotype. To do so, you mated the cat with a brown marbled cat. The mating produced 3 brown marbled, 2 brown striped, 2 black marbled, and 3 black striped. Immediately, you concluded the genotype of your rescued cat was

Accepted Answer

We can use the information from the offspring to determine that the brown marbled parent must be homozygous recessive (bbss). We know that the rescued cat must have at least one dominant allele for black coat color and at least one dominant allele for striped fur pattern, since it produced black striped offspring. The fact that it produced both black and brown offspring means it must be heterozygous for coat color. We can use a Punnett square to determine that the rescued cat must be heterozygous for both traits: BbSs.

Question 19

You prepare a human karyotype. Upon analysis, you find 22 pairs of chromosomes that are each of approximately equal length and also a single pair that has one chromosome longer than the other. What can you conclude from this information?

Accepted Answer

Humans have 23 pairs of chromosomes, with one pair being the sex chromosomes. Females have two X chromosomes, while males have one X and one Y chromosome. The presence of one chromosome longer than the other in the sex chromosome pair indicates that this cell came from a male organism. The length of the other pairs of chromosomes is not indicative of any particular genetic disease, and without further information about the cell type, we cannot conclude whether the cell is haploid or diploid.

Question 20

How many sex chromosomes are in a human gamete?

Accepted Answer

A human gamete contains only one sex chromosome, either X or Y, which determines the sex of the offspring when it combines with another gamete during fertilization.

Quiz 9: Patterns of Inheritance