Chap 4:Genome Size and Packaging

Question 1

What is DNA?

Answer 1

Deoxyribonucleic acid, the principal molecule of biological heredity, a polymer of nucleotides

DNA forms a double helix structure.

Question 2

What are the components of a nucleotide?

Answer 2

A 5-carbon sugar, a nitrogen-containing base, and one or more phosphate groups

The sugar in DNA is deoxyribose.

Question 3

Define deoxyribose.

Answer 3

A 5-carbon sugar that lacks an oxygen atom on its 2’ carbon

It is different from ribose found in RNA.

Question 4

What are purines in nucleic acids?

Answer 4

Adenine and guanine, which have a double-ring structure

Purines pair with pyrimidines in DNA.

Question 5

What are pyrimidines?

Answer 5

Thymine, cytosine, and uracil, which have a single-ring structure

In DNA, thymine is used instead of uracil.

Question 6

What is a phosphodiester bond?

Answer 6

A bond that forms when a phosphate group in one nucleotide is covalently joined to the sugar unit in another nucleotide

It forms the backbone of the DNA strand.

Question 7

What is the 5′ end of a nucleic acid strand?

Answer 7

The end containing a free 5’ phosphate group

Question 8

What is the 3′ end of a nucleic acid strand?

Answer 8

The end that carries a free 3’ hydroxyl

Question 9

What does antiparallel mean in the context of DNA?

Answer 9

Strands oriented in opposite directions

Question 10

What is base pairing in DNA?

Answer 10

A pairs with T, and G pairs with C

This is crucial for the structure and function of DNA.

Question 11

How does the structure of DNA enable it to store information?

Answer 11

The sequence of nucleotides encodes genetic information

Only four nucleotides can create vast genetic diversity.

Question 12

What is the process of replication?

Answer 12

The process of copying DNA for genetic information transfer

Question 13

Define transcription.

Answer 13

The synthesis of RNA from a DNA template

Question 14

What is translation?

Answer 14

Synthesis of a polypeptide chain corresponding to the coding sequence in mRNA

Question 15

What is a ribosome?

Answer 15

A complex of RNA and protein that synthesizes proteins from amino acids as directed by mRNA

Question 16

What is a primary transcript?

Answer 16

The initial RNA transcript synthesized as a complement to the template DNA strand

Question 17

What is RNA processing?

Answer 17

Chemical modifications that convert the primary transcript into mature mRNA

Question 18

What is a 5′ cap?

Answer 18

Modification of the 5’ end of the primary transcript for mRNA stabilization and recognition

Question 19

What is polyadenylation?

Answer 19

The addition of a long string of adenine nucleotides to the 3’ end of the primary transcript

Question 20

What are exons?

Answer 20

Sequences left intact in mRNA after splicing, expressed in the protein

Question 21

What are introns?

Answer 21

Intervening sequences removed from the primary transcript during splicing

Question 22

What is alternative splicing?

Answer 22

The process where primary transcripts are spliced in different ways to yield different mRNAs

Question 23

How do RNA and DNA differ structurally?

Answer 23

1. RNA sugar is ribose; DNA sugar is deoxyribose
2. Thymine in DNA is replaced by uracil in RNA
3. DNA is double-stranded; RNA is usually single-stranded
4. DNA is typically longer than RNA

Question 24

What is the role of small nuclear RNA (snRNA)?

Answer 24

Involved in splicing, polyadenylation, and other nuclear processes

Question 25

What is the consequence of incorporating a nucleotide with a 3′–H group instead of a 3′–OH?

Answer 25

Subsequent elongation stops due to the lack of a free 3′–OH group

Question 26

What is the significance of a TATA box?

Answer 26

A DNA sequence in eukaryotic promoters that serves as a binding site for transcription factors

Question 27

What are the five types of noncoding RNA?

Answer 27

* ribosomal RNA (rRNA) * transfer RNA (tRNA) * small nuclear RNA (snRNA) * microRNA (miRNA) * small interfering RNA (siRNA) ## Footnote These types of noncoding RNA play various roles in the cell, particularly in translation and gene regulation.

Question 28

What is the function of ribosomal RNA (rRNA)?

Answer 28

Found in all ribosomes and is essential in translation. ## Footnote rRNA forms the core of ribosome structure and catalyzes protein synthesis.

Question 29

What does transfer RNA (tRNA) do?

Answer 29

Carries individual amino acids to the ribosomes in translation. ## Footnote tRNA molecules are crucial for translating the genetic code into proteins.

Question 30

What is the role of small nuclear RNA (snRNA)?

Answer 30

Involved in eukaryotic gene splicing, polyadenylation, and other processes in the nucleus. ## Footnote snRNA is part of the spliceosome, which is essential for mRNA processing.

Question 31

What is the function of microRNA (miRNA)?

Answer 31

Can destroy transcripts or inhibit translation. ## Footnote miRNA plays a significant role in post-transcriptional regulation of gene expression.

Question 32

What does small interfering RNA (siRNA) do?

Answer 32

Can also destroy transcripts or inhibit translation. ## Footnote siRNA is involved in the RNA interference (RNAi) pathway, which regulates gene expression.

Question 33

What are the additional functions of snRNA, miRNA, and siRNA?

Answer 33

They have other regulatory functions that are still not fully understood. ## Footnote The complexity of RNA regulation in eukaryotic cells continues to be an active area of research.

Question 34

What are introns in eukaryotic DNA?

Answer 34

Non-coding sequences that must be spliced out during mRNA processing. ## Footnote Introns are removed to produce a mature mRNA molecule that can be translated into a protein.

Question 35

Why can't bacterial cells properly splice out eukaryotic introns?

Answer 35

Because the eukaryotic DNA sequence contains introns, which the bacterial cell cannot splice out properly. ## Footnote This leads to incorrect protein production from the bacterial RNA transcript.