Question 1

Gregor Mendel discovered the principles of genetics in his early experiments on

Accepted Answer

Gregor Mendel conducted his experiments on pea plants, observing the inheritance of specific traits, such as flower color and seed shape, through the process of cross-breeding. This led to his discovery of the principles of genetics, including dominant and recessive traits and the law of segregation.

Question 2

During formation of eggs and sperm, one member of each chromosome pair is transmitted to each progeny cell in a type of cell division called

Accepted Answer

During meiosis, cells undergo two rounds of division resulting in four haploid cells with unique combinations of chromosomes. This is what leads to genetic diversity in offspring. Gametogenesis is a general term for the formation of gametes (sperm and eggs) and encompasses the process of meiosis.

Question 3

Animal cells and most cells of higher plants are

Accepted Answer

Animal cells and most cells of higher plants are diploid, meaning they have two copies of each chromosome, one inherited from each parent.

Question 4

Eggs and sperm are

Accepted Answer

Eggs and sperm are haploid, meaning they contain half the number of chromosomes as a normal cell in the body. This is because during meiosis, the chromosome number is reduced by half to create gametes for sexual reproduction.

Question 5

Our fundamental knowledge about mutation, genetic linkage, and the relationships between genes and chromosomes was acquired largely from experiments on the

Accepted Answer

Experiments on the fruit fly Drosophila by Thomas Hunt Morgan and his colleagues in the early 20th century led to significant discoveries about mutation, genetic linkage, and the relationships between genes and chromosomes. These experiments laid the foundation for the modern field of genetics.

Question 6

DNA was identified as the genetic material in experiments done by

Accepted Answer

The experiments done by Avery, MacLeod, and McCarty in 1944 identified DNA as the genetic material. Mendel discovered the principles of inheritance, Chargaff discovered the base pairing rules in DNA, and Watson and Crick proposed the structure of DNA.

Question 7

Deduction of the structure of DNA was based on X-ray diffraction patterns obtained by

Accepted Answer

The deduction of the structure of DNA was based on X-ray diffraction patterns obtained by Wilkins and Franklin. They used X-ray crystallography to produce images of DNA fibers, which gave the first indications of a helical structure.

Question 8

DNA is a double helix with _______ base pairs per complete turn of the helix.

Accepted Answer

There are approximately 10 base pairs per complete turn of the DNA double helix. This is due to the way in which the nucleotide bases pair up and stack on top of each other, forming a repeating pattern that takes 10 base pairs to complete one full turn.

Question 9

In the base pairing within a DNA double helix,

Accepted Answer

In DNA base pairing, A always pairs with T (adenine with thymine) and G always pairs with C (guanine with cytosine). This is known as complementary base pairing. Purines (adenine and guanine) always pair with pyrimidines (thymine and cytosine). Choice A is incorrect as purines do not pair with purines. Choice B is incorrect as A always pairs with T, not U. Choice C is incorrect as A does not pair with G.

Question 10

When thymidine and adenosine interact within a DNA molecule, they form

Accepted Answer

Thymidine (thymine when part of DNA) and adenosine (adenine in DNA) form two hydrogen bonds when they pair within a DNA molecule.

Question 11

What is the complementary sequence to the following bases  5?-TCAAGG-3?

Accepted Answer

The complementary strand would be formed by pairing each base with its complementary base. A pairs with T, and C pairs with G. Therefore, the complementary sequence to 5ʹ-TCAAGG-3ʹ would be 5ʹ-CCTTGA-3ʹ. Option A contains the wrong base (U instead of T) and option B is identical to the original sequence. Option C is the correct complementary sequence. Option D contains the wrong base (U instead of T).

Question 12

DNA replicates

Accepted Answer

The correct answer is semiconservatively. DNA replication occurs in a semiconservative manner, meaning that each new DNA molecule consists of one original parental strand and one newly synthesized daughter strand. This was first demonstrated by the classic experiment by Meselson and Stahl in 1958.

Question 13

In Meselson and Stahl's experiment, cells were grown in media containing ¹⁵N in place of ¹⁴N, and then the cells' DNA was separated by equilibrium centrifugation. This experiment demonstrated that DNA

Accepted Answer

Meselson and Stahl's experiment demonstrated that DNA replication is semiconservative, meaning that each newly synthesized DNA molecule consists of one original (parental) strand and one newly synthesized (daughter) strand. This was shown by separating DNA in a density gradient after growing cells in a medium containing a heavy isotope of nitrogen, and then switching to a medium with a lighter isotope. The resulting DNA bands showed that the new DNA molecules were a mix of heavy and light isotopes, supporting the semiconservative model of replication. The experiment did not address the other options listed.

Question 14

RNA molecules that serve as templates for protein synthesis are called _______ RNAs.

Accepted Answer

Messenger RNAs carry the genetic information from DNA to the ribosome where protein synthesis takes place. Transfer RNAs bring the amino acids to the ribosome, and ribosomal RNAs are components of the ribosome itself. Small nuclear RNAs are involved in processing RNA.

Question 15

You have identified an unknown protein of approximately 1,500 amino acids. The minimum length of its mRNA is approximately

Accepted Answer

The answer of You have identified an unknown protein of...

Question 16

A codon is a

Accepted Answer

A codon is a sequence of three nucleotides on an mRNA molecule that codes for a specific amino acid or serves as a stop signal. It binds to a complementary sequence of three nucleotides on a tRNA molecule, called an anticodon, which carries the corresponding amino acid. Therefore, choice C is the correct answer as it describes the relationship between codons and tRNAs.

Question 17

Because the genetic code has more than one codon for most amino acids, the code is said to be

Accepted Answer

The term "degenerate" in this context means that multiple codons can code for the same amino acid, which is true for most amino acids.

Question 18

How many different RNA triplets specify amino acids?

Accepted Answer

There are 64 different RNA triplets, or codons, but only 61 code for amino acids. Three of them are stop codons, which signal the end of protein synthesis.

Question 19

Which of the following deletions will not change the reading frame of a gene?

Accepted Answer

A deletion of three nucleotides will only remove one codon (which consists of three nucleotides) from the gene sequence, but will not shift the reading frame. This is because the deletion will still maintain the triplet nucleotide code used to translate genetic information into proteins. A deletion of one or two nucleotides will cause a frameshift mutation, where the reading frame will shift by one or two nucleotides, resulting in a completely different amino acid sequence. A deletion of four nucleotides will cause the deletion of two codons, which will result in a frameshift mutation and a different amino acid sequence.

Question 20

Reverse transcriptase is an enzyme that catalyzes _______ synthesis.

Accepted Answer

Reverse transcriptase is responsible for the synthesis of DNA from an RNA template. Therefore, it catalyzes RNA-directed DNA synthesis.

Quiz 4: Fundamentals of Molecular Biology