Lesson 8 (Ch. 14-15) Reading Practice Quiz

Question 1

DNA is made up of ___.
Group of answer choices

nucleotides

amino acids

fatty acids

monosaccharides

Answer 1

The correct answer is nucleotides.

DNA is made up of nucleotides, which consist of three components: a phosphate group, a sugar (deoxyribose), and a nitrogenous base (adenine, thymine, cytosine, or guanine).

Amino acids are the building blocks of proteins, fatty acids make up lipids, and monosaccharides are simple sugars that are the building blocks of carbohydrates.

Question 2

DNA contains the sugar
_____
; RNA contains the sugar
_____

Answer 2

DNA contains the sugar deoxyribose.
RNA contains the sugar ribose.
The difference is that deoxyribose lacks one oxygen atom compared to ribose, which is why DNA is more stable than RNA.
Adenine and uracil are nitrogenous bases:

Adenine (A) is present in both DNA and RNA.
Uracil (U) is found only in RNA, replacing thymine (T), which is found in DNA.
So the correct distinction is:

DNA: Deoxyribose + Adenine, Thymine, Cytosine, Guanine
RNA: Ribose + Adenine, Uracil, Cytosine, Guanine

Question 3

Base pairs are held together by ___ bonds.
Group of answer choices

hydrogen

phosphodiester

polypeptide

hydrolytic

Answer 3

The correct answer is hydrogen bonds.

In DNA, the nitrogenous bases pair as follows:
- Adenine (A) pairs with Thymine (T) (via 2 hydrogen bonds).
- Cytosine (C) pairs with Guanine (G) (via 3 hydrogen bonds).

These hydrogen bonds help stabilize the double helix structure of DNA, though they are weak enough to allow the strands to separate during processes like DNA replication and transcription.

Let’s quickly review the other bond types:
- Phosphodiester bonds: Link the sugar and phosphate groups along the backbone of DNA and RNA.
- Polypeptide bonds: Form between amino acids in proteins.
- Hydrolytic bonds: Involve water molecules breaking down compounds.

Question 4

DNA replication is best described as ___.
Group of answer choices

semiconservative

conservative

error-free

dispersive

Answer 4

The correct answer is semiconservative.

In semiconservative replication, each new DNA molecule consists of one original (parent) strand and one newly synthesized strand. This ensures that the genetic information is accurately passed on to the next generation.

Here’s a quick breakdown of other terms:

Conservative: The original DNA molecule remains intact, and an entirely new molecule is synthesized (this doesn’t happen in nature).
Dispersive: DNA fragments are interspersed with both old and new DNA within each strand (an incorrect theory).
Error-free: While DNA replication is highly accurate, occasional errors can occur, though many are corrected by proofreading mechanisms.

Question 5

DNA is
transcribed
into RNA; RNA is
translated
into proteins.

Answer 5

This is the central dogma of molecular biology, which describes the flow of genetic information:

Transcription:

DNA is transcribed into RNA (specifically mRNA).
This process occurs in the nucleus (in eukaryotes) or the cytoplasm (in prokaryotes).
RNA polymerase reads the DNA template and synthesizes a complementary RNA strand.
Translation:

RNA (mRNA) is translated into proteins.
This occurs in the ribosome.
tRNA brings the appropriate amino acids based on the codons in the mRNA sequence to build a polypeptide (protein).
So, DNA → RNA → Protein reflects how genetic instructions are expressed.

Question 6

Match the type of RNA with its function.
Group of answer choices
Carries information from DNA in the nucleus to the ribosomes in the cytoplasm

mRNA
Carries amino acids to ribosomes. Has anticodons that match codons to indicate which amino acid should be added next in the sequence.

rRNA
Associated with the structure and function of the ribosome.

tRNA

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Answer 6

Here’s the correct matching of RNA types with their functions:

1. Carries information from DNA in the nucleus to the ribosomes in the cytoplasm
   Answer: mRNA (messenger RNA)
2. Carries amino acids to ribosomes. Has anticodons that match codons to indicate which amino acid should be added next in the sequence.
   Answer: tRNA (transfer RNA)
3. Associated with the structure and function of the ribosome.
   Answer: rRNA (ribosomal RNA)

Explanation:
- mRNA: Acts as the template for protein synthesis, carrying the genetic code from DNA.
- tRNA: Brings the correct amino acid to the ribosome based on matching anticodon-codon pairs.
- rRNA: A key component of ribosomes, facilitating the translation of mRNA into proteins.

Question 7

Codons are made up of how many bases?
Group of answer choices

three

one

two

four

Answer 7

The correct answer is three.

A codon is a sequence of three nitrogenous bases on mRNA that corresponds to a specific amino acid or a stop signal during translation. For example:

AUG: Start codon (also codes for methionine)
UAA, UAG, UGA: Stop codons
This three-base structure ensures that the genetic code can specify all 20 standard amino acids.

Question 8

Protein synthesis involves which of the following stages? (Mark all that apply)
Group of answer choices

initiation

elongation

termination

Answer 8

Protein synthesis involves the following stages:

Initiation: The ribosome assembles around the mRNA, and the first tRNA (carrying the start codon) pairs with the mRNA.

Elongation: The ribosome travels along the mRNA, and amino acids are added one by one to the growing polypeptide chain, facilitated by tRNA molecules.

Termination: The process ends when a stop codon is reached on the mRNA, signaling the release of the newly synthesized protein.

So, you would mark all three stages: initiation, elongation, and termination.

Question 9

Which of the following is NOT correct about ribosomes?
Group of answer choices

they are found in the nucleus

they are composed of rRNA and proteins

they facilitate complementary base pairing between mRNA and tRNA

they join amino acids together

Answer 9

The statement that is NOT correct about ribosomes is:

They are found in the nucleus.

Explanation:
Ribosomes are not found in the nucleus; they are located either in the cytoplasm or attached to the endoplasmic reticulum (forming rough ER). They can also be found within mitochondria and chloroplasts, but not in the nucleus.
The other statements are correct:
Ribosomes are composed of rRNA (ribosomal RNA) and proteins.
They facilitate complementary base pairing between mRNA and tRNA during protein synthesis.
They join amino acids together to form polypeptides (proteins).

Question 10

Unwinds DNA by breaking hydrogen bonds between base pairs.

[ Choose ]
Synthesizes a piece of RNA about 10 nucleotides long that allows nucleotides to be added to a 3’ OH end.

[ Choose ]
Prevents the overwinding of the DNA double helix ahead of the replication fork

[ Choose ]
Catalyzes the formation of a phosphodiester bond between the 3’-OH end of one nucleotide and the 5’ phosphate end of another nucleotide

[ Choose ]
Adds nucleotides one by one to the growing DNA strand that are complementary to the original DNA strand

Answer 10

Here are the correct choices for each description related to DNA replication:

Unwinds DNA by breaking hydrogen bonds between base pairs.
[Helicase]

Synthesizes a piece of RNA about 10 nucleotides long that allows nucleotides to be added to a 3’ OH end.
[Primase]

Prevents the overwinding of the DNA double helix ahead of the replication fork.
[Topoisomerase]

Catalyzes the formation of a phosphodiester bond between the 3’-OH end of one nucleotide and the 5’ phosphate end of another nucleotide.
[DNA Ligase]

Adds nucleotides one by one to the growing DNA strand that are complementary to the original DNA strand.
[DNA Polymerase]

Summary of Functions:
Helicase: Unwinds the DNA double helix.
Primase: Creates an RNA primer for DNA polymerase.
Topoisomerase: Relieves tension and prevents overwinding.
DNA Ligase: Joins Okazaki fragments on the lagging strand.
DNA Polymerase: Synthesizes the new DNA strand.