Question 1

About two-thirds of the cells traveling to the developing cortex follow radial glia, and the remaining one-third move in a horizontal direction instead, without using radial glia to guide them.

Accepted Answer

This statement is true. Two-thirds of the cells traveling to the developing cortex follow radial glia, and the remaining one-third move in a horizontal direction instead, without using radial glia to guide them.

Question 2

Critical periods occur in many animals, such as the imprinting observed in geese, but has not yet been observed in humans.

Accepted Answer

Critical periods have been observed in humans, such as the development of language skills during early childhood.

Question 3

Which of the following is the best example of a phenotype?

Accepted Answer

A phenotype is a physical or observable trait of an organism, such as hair color, height, etc. Out of the given options, only A describes a physical trait (black hair) that is observable and can be classified as a phenotype. The other options describe genetic information or traits that may not be visible externally.

Question 4

Myelination of the human spinal cord and brain begins about 24 weeks following conception and is complete by the age of about 18 months.

Accepted Answer

Myelination in humans begins in the fetal stage but continues into adulthood, with significant myelination occurring into the second decade of life, not completing by 18 months.

Question 5

Because the heritability of height is 81 percent, and the heritability of adult body mass index (BMI) is 59 percent, we can conclude that genetics play a stronger role in the development of height than BMI.

Accepted Answer

The higher the heritability percentage, the stronger the genetic influence on a trait. Since the heritability of height is 81 percent and the heritability of BMI is 59 percent, we can conclude that genetics play a stronger role in the development of height than BMI.

Question 6

Joan has one APOE3 and one APOE4 allele. This means Joan is heterozygous for the APOE gene.

Accepted Answer

"Heterozygous" means having two different alleles for a particular gene, and Joan has one APOE3 allele and one APOE4 allele, so she is heterozygous for the APOE gene.

Question 7

The human genome contains about ________ protein-building genes.

Accepted Answer

The current estimate is that the human genome contains approximately 19,000 protein-coding genes. However, it is important to note that this number may change as scientific understanding and technology continue to advance.

Question 8

Healthy brain activity as we age appears to be quite independent of lifestyle, so there is little any of us can do to prevent declines in this area.

Accepted Answer

This statement is false. While some cognitive decline may be inevitable with age, engaging in regular physical and mental activity, maintaining a healthy diet, and managing stress can help to promote healthy brain function and potentially mitigate declines.

Question 9

An individual organism's observable characteristics are known as the genotype.

Accepted Answer

An individual organism's observable characteristics are known as the phenotype, not the genotype. The genotype refers to the genetic makeup of an organism.

Question 10

Which of the following is the best example of a genotype?

Accepted Answer

A genotype refers to the genetic makeup of an individual, and in this case, Anthony having two copies of a specific allele (APOE2) is the best example of a genotype. The other choices describe physical traits or characteristics that may be influenced by genetics, but they do not directly represent an individual's genetic makeup.

Question 11

The generation and maintenance of good brain health is less well understood than the mechanisms responsible for disease, especially among older adults.

Accepted Answer

The statement is true, as per the given information.

Question 12

The physical characteristics of an organism is referred to as its

Accepted Answer

Phenotype refers to the physical characteristics of an organism, such as its appearance, behavior, and traits. Genome refers to the organism's complete set of genetic material or DNA. Genotype refers to the specific genetic makeup of an organism. Chromosome refers to the organized structure of DNA and protein in cells.

Question 13

Females are much more likely than males to develop conditions influenced by genes that are located on the X chromosome, because they have two X chromosomes instead of one and therefore twice as much opportunity to experience problems with genes on those chromosomes.

Accepted Answer

Females have two X chromosomes, but one of these is typically inactivated in each cell, which means they do not have twice the opportunity to experience problems with genes on those chromosomes. Additionally, having two X chromosomes often provides a protective effect against X-linked recessive disorders, as the presence of a normal allele on one X chromosome can mask the effect of a recessive mutation on the other.

Question 14

Without contact with any other embryonic cells, a mesodermal cell will differentiate into skin.

Accepted Answer

Mesodermal cells have the potential to differentiate into a variety of cell types, but they require signals from neighboring cells to determine their specific fate. Without proper signaling, a mesodermal cell would not spontaneously differentiate into skin.

Question 15

How many chromosomes are typically present in human cells?

Accepted Answer

Human cells typically have 23 pairs of chromosomes, for a total of 46 chromosomes.

Question 16

How many chromosomes do human beings receive from each parent?

Accepted Answer

Human beings receive 23 chromosomes from each parent, for a total of 46 chromosomes.

Question 17

Which of the following species have the greatest number of genes in their genome?

Accepted Answer

Plants, particularly some species like wheat or certain flowering plants, have been found to have a significantly larger number of genes in their genomes compared to flies, yeast cells, and even human beings. This is due to factors such as polyploidy (having multiple sets of chromosomes), which is common in the plant kingdom and can result in a vast increase in the number of genes.

Question 18

The genetic instructions of an organism is known as the

Accepted Answer

The term "genetic instructions" refers specifically to an organism's DNA, which determines its characteristics and traits. Therefore, the correct answer is B) genotype. The other options, such as telomere and chromosome, are specific structures or components of DNA, while phenotype refers to an organism's physical appearance resulting from both genetic and environmental factors.

Question 19

The human genome has the greatest number of genes of all species studied to date.

Accepted Answer

While humans have a relatively large genome, with approximately 3 billion base pairs, the actual number of genes is not the highest among all species. For example, rice has a genome of only 389 million base pairs, but it has approximately 38,000 genes, compared to the estimated 20,000-25,000 genes in the human genome.

Question 20

Doctors recommend that those with phenylketonuria (PKU) adhere to the dietary restrictions associated with this condition throughout their lifetimes.

Accepted Answer

PKU is a genetic disorder that affects the body's ability to process the amino acid phenylalanine. People with PKU need to follow a low phenylalanine diet throughout their life to prevent cognitive impairment and other health problems. Doctors recommend strict adherence to this diet for optimal health outcomes.

Quiz 5: Genetics and the Development of the Human Brain