Question 1

Enzymes serve as ____.

Accepted Answer

Enzymes are biological catalysts that accelerate chemical reactions in the body without themselves being consumed during the reaction. They play a critical role in regulating metabolic pathways and chemical reactions in the body.

Question 2

Suppose all people with blonde hair have blue eyes and all people with dark hair have brown eyes. Which of the following would be the most likely explanation?

Accepted Answer

Hair and eye color being on the same chromosome suggests they are linked traits, which could explain why certain hair colors are consistently associated with specific eye colors in the population.

Question 3

In one family, all three children are homozygous for a recessive gene. What can be concluded about the parents?

Accepted Answer

The answer of In one family, all three children are...

Question 4

Almost all humans have 23 pairs of which of the following?

Accepted Answer

Humans have 23 pairs of chromosomes. Chromosomes are thread-like structures located within the nucleus of cells and carry genetic information in the form of DNA.

Question 5

RNA is:

Accepted Answer

RNA is a nucleic acid that is formed by copying (transcription) a portion of the genetic information stored in DNA. This results in a complementary copy of the DNA molecule, with the exception of the replacement of thymine (T) with uracil (U) in RNA. Therefore, RNA is not an exact copy of DNA, but a complementary copy of a single DNA strand.

Option A is incorrect because RNA is not an exact copy of DNA, despite sharing similar nucleotides.

Option C is incorrect because RNA is not a combination of many proteins, but a macromolecule composed of nucleotides.

Option D is incorrect because RNA is not the product of digesting DNA; rather, it is synthesized by RNA polymerase using a template strand of DNA.

Question 6

Chromosomes consist of large, double-stranded molecules of:

Accepted Answer

Chromosomes consist of large, double-stranded molecules of deoxyribonucleic acid (DNA), which carries the genetic information that determines the traits of an organism. RNA is also important in gene expression and protein synthesis, but it is not the main component of chromosomes. Autosomal genes and recombination genes are subsets of the genetic information carried within the DNA molecule.

Question 7

Suppose both the father and the mother are "heterozygous" for the gene that controls ability to curl the tongue lengthwise, and this gene is dominant. What can we predict about their children?

Accepted Answer

Since both parents are heterozygous, there are three possible genotypes for their offspring: homozygous dominant (able to curl), heterozygous (able to curl), or homozygous recessive (unable to curl). The offspring have a 75% chance of being able to curl their tongue and a 25% chance of not being able to curl their tongue. Therefore, the answer is D - they may be homozygous or heterozygous for ability to curl, or homozygous for inability.

Question 8

A trait not expressed when combined with a dominant trait is called a(n) ____ trait.

Accepted Answer

A recessive trait is not expressed when paired with a dominant trait. It only shows when paired with another recessive trait. Nurture refers to environmental factors, not genetic traits. Dominant refers to the expressed trait, not the one that is hidden. Homozygous refers to having two of the same alleles for a specific trait, but it does not necessarily determine whether the trait is dominant or recessive.

Question 9

Suppose "A" is a dominant gene for the ability to curl the tongue lengthwise, and "a" is a recessive gene for inability to do so. Which of the following couples can be certain that all their children will be able to curl their tongue lengthwise?

Accepted Answer

The father has two recessive alleles (aa) and the mother has two dominant alleles (AA), which means all their children will inherit one dominant allele from the mother and one recessive allele from the father, resulting in the ability to curl their tongue lengthwise (Aa).

Question 10

A person with two recessive genes is considered to be ____ for that trait.

Accepted Answer

A person with two recessive genes is considered to be homozygous for that trait. This means that both copies of the gene are the same and both carry the recessive allele.

Question 11

Suppose all people with blonde hair have blue eyes and all people with dark hair have brown eyes. If the genes for eye and hair color are on the same chromosome, then what would most likely happen if these chromosomes crossed over?

Accepted Answer

If the genes for eye and hair color are on the same chromosome, they are considered linked genes. During crossing over, alleles for each trait can exchange places. However, the closer the two genes are on the chromosome, the less likely they are to stray from each other during crossing over. Therefore, there is a chance that some offspring may inherit the linked traits together, but some may inherit them independently. So, hair and eye color could be inherited independently.

Question 12

Suppose "A" is a dominant gene and "a" is a recessive gene. One parent has genes Aa and the other parent has genes aa. What genes will the children probably have?

Accepted Answer

When one parent is Aa and the other is aa, the possible combinations for the offspring are Aa and aa, with each having a 50% probability.

Question 13

Suppose "A" is a dominant gene for the ability to taste phenylthiocarbamide and "a" is a recessive gene for inability to taste it. Which of the following couples could possibly have both a child who tastes it and a child who does not?

Accepted Answer

In the Aa x Aa (C) cross, there is a possibility of producing offspring with different genotypes: AA, Aa, and aa. Both AA and Aa genotypes have the dominant A allele which allows the ability to taste PTC. Therefore, if an AA or Aa individual is produced in this cross, they will be able to taste PTC. On the other hand, the aa genotype has two recessive a alleles, which means the individual will not be able to taste PTC. Therefore, if an aa individual is produced in this cross, they will not be able to taste PTC. Thus, it is possible for this couple to have one child who can taste PTC (AA or Aa) and another who cannot (aa).

Question 14

Chemically, what is the route from genes to their expression?

Accepted Answer

The route from genes to their expression is through the process of transcription and translation. Transcription involves the DNA being converted into RNA, which then serves as a template for protein synthesis during translation. Therefore, the correct order is DNA to RNA to proteins, making choice B the best answer.

Question 15

Biological catalysts that regulate chemical reactions in the body are called:

Accepted Answer

Enzymes are biological catalysts that regulate chemical reactions in the body. DNA and RNA are not catalysts, but rather genetic material, and nuclei are cellular structures that contain DNA.

Question 16

A strand of DNA serves as a template (model) for the synthesis of ____.

Accepted Answer

A strand of DNA serves as a template for the synthesis of RNA through the process of transcription. RNA serves as an intermediary in the synthesis of proteins through the process of translation. Chromosomes are structures made up of DNA and proteins that carry genetic information, but they are not directly synthesized from a DNA template. Carbohydrates are not synthesized from a DNA template at all.

Question 17

Suppose that adopted children are more similar to their biological parents than their adoptive parents in their preferences for a flavor of ice cream. Which of the following would be true?

Accepted Answer

The fact that adopted children are more similar to their biological parents than their adoptive parents in their preference for ice cream flavor suggests that genetics plays a significant role in determining this trait. Therefore, the heritability of this trait is likely high.

Question 18

Interruption of the production of RNA would directly affect which of the following?

Accepted Answer

RNA is involved in the process of protein synthesis, so interruption of RNA production would directly affect protein synthesis.

Question 19

Recessive genes manifest their effects only when the individual is ____ for them.

Accepted Answer

Recessive genes require two copies of the gene to be present (homozygous) in order to manifest their effects. If an individual only has one copy of the recessive gene (heterozygous), they will have the dominant trait instead.

Question 20

What are chromosomes composed of?

Accepted Answer

Chromosomes are composed of DNA, which is tightly packaged and associated with proteins to form a complex structure. RNA and carbohydrates do not play a major role in the composition of chromosomes.

Quiz 1: The Major Issues