2.6: DNA and RNA

State the two types of nucleic acid.

Understanding: The nucleic acids DNA and RNA are polymers of nucleotides.

State the two types of nucleic acid.

Understanding: The nucleic acids DNA and RNA are polymers of nucleotides.

DNA: deoxyribonucleic acid

RNA: ribonucleic acid

Outline the parts of a nucleotide.

Understanding: The nucleic acids DNA and RNA are polymers of nucleotides.

A nucleotide is the monomer subunit of the nucleic acids. A nucleotide has three component parts:

1. a nitrogenous base

2. A 5-carbon sugar (ribose or deoxyribose)

3. A phosphate group

Identify and label carbons by number (for example, C1, C2, C3) on a nucleotide drawing.

Understanding: The nucleic acids DNA and RNA are polymers of nucleotides.

The carbons of the sugar component of the nucleotide are numbers clockwise, starting from the oxygen in the ring at the top and the phosphate group to the left.

Explain how nucleotides can connect to form a nucleic acid polymer.

Understanding: The nucleic acids DNA and RNA are polymers of nucleotides.

Nucleotides connect by creating covalent bonds between the sugar of one nucleotide and the phosphate group of another nucleotide in a condensation reaction.

State the names of the nitrogenous bases found in DNA and RNA.

Understanding: The nucleic acids DNA and RNA are polymers of nucleotides.

Cytosine (DNA and RNA)

Thymine (DNA only)

Guanine (DNA and RNA)

Adenine (DNA and RNA)

Uracil (RNA only)

Identify nitrogenous bases as either a pyrimidine or purine.

Understanding: The nucleic acids DNA and RNA are polymers of nucleotides.

Pyrimidine: single ring nitrogenous bases

Cytosine

Thymine

Uracil

Purine: double ring nitrogenous bases

Guanine

Adenine

State the complementary base pairing rules.

Understanding: The nucleic acids DNA and RNA are polymers of nucleotides.

A purine complementary base pairs to a pyrimidine.

In DNA and RNA, guanine bonds with

cytosine

In DNA, adenine bonds with thymine

In RNA, adenine bonds with uracil

Compare the structure of DNA and RNA.

Understanding: DNA differs from RNA in the number of strands present, the base composition and the type of pentose.

RNA

ribose

single stranded

A, G, C, U

DNA

deoxyribose

double stranded

A, G, C, T

Define "antiparallel" in relation to DNA structure.

Understanding: DNA is double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.

Adjacent molecules are oriented parallel to each other but oriented in opposite directions.

In DNA, one strand runs 5' to 3' and the complementary strand runs 3' to 5'

Outline the formation of a DNA double helix by hydrogen bonding between nitrogenous bases.

Understanding: DNA is double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.

Complementary DNA nucleotides form hydrogen bonds between the nitrogenous bases, forming two strands ("double") that wind around each other ("helix")

Identify the four bases of DNA based on the numbers of rings (purines or pyrimidines) and the number of hydrogen bonds it can form.

Understanding: DNA is double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.

Purines have two rings. If it can form 2 H-bonds it is adenine and if it can form 3 H-bonds it is guanine.

Pyrimidines have one ring. If it can form 2 H-bonds it is thymine and if it can form 3 H-bonds it is cytosine.

State the number of nitrogenous bases per complete turn of the DNA double helix.

Understanding: DNA is double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.

A complete turn is when one strand circles back on itself. There are 10 base pairs per turn of the helix.

Outline the role of Chargaff in the discovery of DNA structure.

Application: Crick and Watson's elucidation of the structure of DNA using model making.

Chargaff determined that there are equal numbers of A and T bases and G and C bases in a DNA sample.

Outline the role of Watson and Crick in the discovery of DNA structure.

Application: Crick and Watson's elucidation of the structure of DNA using model making.

Watson figured out how the nitrogenous base pairs could fit within a DNA double helix while maintaining a constant helix diameter.

Crick suggested that the DNA backbone was anti-parallel.

Outline the role of Franklin in the discovery of DNA structure.

Application: Crick and Watson's elucidation of the structure of DNA using model making.

Franklin took clear, detailed x-ray diffraction photos that provided clues to DNA structure.

Explain how Watson and Crick used model building to determine the structure of DNA.

Application: Crick and Watson's elucidation of the structure of DNA using model making.

Watson and Crick used model building to narrow down the possibilities for DNA structure and to eventually create an accurate representation of DNA that fit within the experimental evidence collected by Franklin and others.

Draw the basic structure of a single nucleotide (using circle, pentagon and rectangle).

Skill: Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons, and rectangles to represent phosphates, pentoses and bases.

Circle = phosphate group

Pentagon - ribose or deoxyribose sugar

Rectangle = nitrogenous base

Draw a simple diagram of the structure of RNA.

Skill: Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons, and rectangles to represent phosphates, pentoses and bases.

Single stranded

A, U, G, C

Ribose sugar

Draw a simple diagram of the structure of DNA.

Skill: Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons, and rectangles to represent phosphates, pentoses and bases.

Double stranded

A double H-bond to T

C triple H-bond to C

Anti-parallel

Deoxyribose sugar

Identify and label the 5' and 3' ends on a DNA or RNA diagram.

Skill: Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons, and rectangles to represent phosphates, pentoses and bases.

The 5' and 3' ends of a nucleic acid refer to the direction of the chain. In DNA, one strand will run from 5' to 3' and the complementary strand will run anti-parallel, from 3' to 5'.

The 5' end is identified by the presence of the phosphate group and the 3' end is identified as ending in the pentose sugar (ribose or deoxyribose).

List types of models used in science.

Nature of Science: Using models as representation of the real world- Crick and Watson used model making to discover the structure of DNA.

Mathematical Models

Use of math to describe and/or predict the behavior of a system

Computer Models

Computer programs that attempt to simulate the behavior of a system

Physical Models

Models of structures that can be carried, touched or held

Images

Diagrams used to represent a structure or process

Analogy

Comparisons for the purpose of explanation or clarification

State a common feature of models in science.

Nature of Science: Using models as representation of the real world- Crick and Watson used model making to discover the structure of DNA.

A model is a representation of a phenomenon, object or idea. Models are used to explain difficult concepts or to have tangible visualizations of structures. Models can be used to make and test predictions and to understand processes that are not easily observed.

List ways in which models are different from the structure or process they represent.

Nature of Science: Using models as representation of the real world- Crick and Watson used model making to discover the structure of DNA.

All models have limitations.

-variations in size

-simplification of complexity

-may be static representations of moving structures/processes

-do not represent all dimensions or variables