Unit 5: DNA, RNA, and Replication

Question 1

Parts of

DNA Nucleotide

Answer 1

Phosphate
Deoxyribose sugar
Nitrogenous base (A, T, C, or G)

Question 2

Parts of

RNA Nucleotide

Answer 2

Phosphate
Ribose sugar
Nitrogenous base (A, U, C, or G)

Question 3

Compare and contrast

Prokaryote and Eukaryote Chromosomes

Answer 3

Proks: one single, circular chromosome; smaller overall; “naked”
Eukaryotes: multiple linear chromosomes; very large; supercoiled by histones

Question 4

Define

Plasmid

Answer 4

Prokaryotic pieces of DNA that carry one or a few genes but are not part of its genome

Question 5

List

Nitrogenous bases

Answer 5

Adenine (A), Thymine (T), Uracil (U), Guanine (G), and Cytosine (C)

Question 6

State

Chargaff’s Rule (Complementary Base Pairing)

Answer 6

In DNA, the amounts of T and A are always equal, and the amounts of C and G are always equal

Question 7

Define

Purine

Answer 7

Nitrogenous base with double ring structure

Question 8

Define

Pyrimidine

Answer 8

Nitrogenous base with single ring structure

Question 9

Explain

Complementary Base Pairing

Answer 9

Purine (A or G) always bind with a pyrimidine (T, U, or C)
A, T, and U form two hydrogen bonds; C and G form three

Question 10

What attaches to each of the carbons in a nucleotide pentose?

Answer 10

C-1: Nitrogenous base
C-3: Hydroxyl group
C-5: Phosphate group

Question 11

How do nucleotides join together?

Answer 11

Dehydration reaction between hydroxyl group (C-3) and phosphate group (C-5)

Question 12

Which end of the molecule is this?

Answer 12

5’ end, because the phosphate is not bound to any more nucleotides

Question 13

Define

Antiparallel

Answer 13

DNA strands bind in opposite directions; that is, 5’ end of one strand binds to 3’ end of other strand

Question 14

Define

Supercoiling

Answer 14

DNA must wrap around proteins, which each interact to condense and ultimately keep DNA compact

Question 15

Define

Histone

Answer 15

Proteins around which DNA strands wind during coiling

Question 16

Define

Chromosome

Answer 16

A single molecule of DNA with its associated proteins

Question 17

Compare and contrast

DNA and RNA polymers

Answer 17

DNA: huge (millions of base pairs), double stranded
RNA: small (thousands of bases), single stranded

Question 18

Describe

Types of RNA

Answer 18

Messenger (mRNA): Single strand of RNA that has the same nucleotide sequence as the coding strand of DNA
Ribosomal (rRNA): Large, folded pieces of RNA that interact with proteins to form ribosomal subunits
Transfer (tRNA): Strands of RNA that fold back like a clover, which bring amino acids to ribosome

Question 19

State

The Central Dogma

Answer 19

DNA holds the genetic info, which is copied into mRNA. mRNA carries info to make specific protein
DNA → mRNA → Protein

Question 20

Define

Gene

Answer 20

Term has changed over time
Once met a hypothetical “unit of inheritance”
Later believed to mean a single stretch of DNA the coded for one protein
Now is a bit undefined; genes may code for multiple proteins or RNA

Question 21

Purpose of

DNA Replication

Answer 21

Make two sets of genome prior to a cell dividing

Question 22

Outline

The Process of DNA Replication

Answer 22

1. Initiation
2. Elongation
3. Termination

Question 23

Outline

DNA Replication: Initiation

Answer 23

All of the steps relating to starting replication.

• Helicase binds to DNA;
• Primers are added;
• DNA polymerase binds

Question 24

Function of

Helicase

Answer 24

Breaks hydrogen bonds between complementary base pairs in DNA; “unzips” DNA

Question 25

*Function of* **Primase**

Answer 25

Adds short RNA fragments onto single-stranded DNA

Question 26

*Function of* **RNA Primers**

Answer 26

DNA polymerase cannot bind to single stranded DNA and so primers allow segments of ssDNA to have complementary pairs

Question 27

*Outline* **DNA Replication: Elongation**

Answer 27

DNA Polymerases form the new strands of DNA using the original strands as templates; ligase forms phosphodiester bonds as needed

Question 28

*Function of* **DNA Polymerase**

Answer 28

Bring correct complementary base pair to existing DNA strand; Form phosphodiester bond between 3’ of newly formed DNA and the 5-C end of the new nucleotide

Question 29

*Describe* **Leading strand**

Answer 29

In DNA replication, the section of the DNA strand where a DNA polymerase is moving in the same direction as the helicase, thus forms a continuous new strand of DNA

Question 30

*Describe* **Lagging strand**

Answer 30

In DNA replication, the section of the DNA strand where DNA polymerase is forming new DNA in the direction away from the movement of the helicase

Question 31

*Define* **Okazaki fragment**

Answer 31

Short stretches of DNA formed by the movement of DNA polymerase away from the replication fork

Question 32

*Define* **Replication fork**

Answer 32

The area of DNA that is actively being replicated

Question 33

*Define* **Replication bubble**

Answer 33

The area of DNA that has been separated and new DNA strands have formed

Question 34

*Function of* **Ligase**

Answer 34

Form phosphodiester bonds between the 3’ and 5’ ends of Okazaki fragments

Question 35

*Describe* **DNA Replication: Termination**

Answer 35

Replication forks move outward, enlarging the replication bubble, until two bubbles join.