5a



Name____________________________________________ Date:________________ Period:____

DNA/RNA Structure Standards

5a. Students know the chemical structure of DNA, RNA, and protein.

1. Students know that all cells contain the molecule DNA which stores and transfers genetic information.

Prokaryotes store DNA in the _____________ Eukaryotes store DNA in the ____________

2. Students can describe the structure of DNA as a double stranded molecule consisting of nucleotides. The backbone of the DNA molecule consists of “sugar phosphate” units while the “rungs” consist of nitrogen-containing bases. [A, G, C, & T].

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3. Students can describe the structure of RNA as a single-stranded molecule consisting of the same A, G, and C nucleotides but with Uracil instead of Thymine.

4. Students can identify the two different types of RNA [mRNA and tRNA] and describe their functions.

Nucleic acids are polymers composed of monomers called nucleotides. Each nucleotide consists of three subunits: a five-carbon pentose sugar, a phosphoric acid group, and one of four nitrogen bases. (For DNA these nitrogen bases are adenine, guanine, cytosine, or thymine.) DNA and RNA differ in a number of major ways. A DNA nucleotide contains a deoxyribose sugar, but RNA contains ribose sugar. The nitrogen bases in RNA are the same as those in DNA except that thymine is replaced by uracil. RNA consists of only one strand of nucleotides instead of two as in DNA. The DNA molecule consists of two strands twisted around each other into a double helix resembling a ladder twisted around its long axis. The outside, or uprights, of the ladder are formed by the two sugar-phosphate backbones. The rungs of the ladder are composed of pairs of nitrogen bases, one extending from each upright. In DNA these nitrogen bases always pair so that T pairs with A, and G pairs with C. This pairing is the reason DNA acts as a template for its own replication. The bonds between the nitrogen bases are hydrogen bonds which are relatively weak allowing DNA to be separated for replication and transcription. RNA exists in many structural forms, many of which play different roles in protein synthesis. The mRNA form serves as a template during protein synthesis, and its codons are recognized by aminoacylated tRNAs. Protein and rRNA make up the structure of the ribosome.

DNA vs RNA

Proteins are polymers composed of amino acid monomers. Different types of proteins function as enzymes, transport molecules, hormones, structural components of cells, and antibodies that fight infection. Most cells in an individual organism carry the same set of DNA instructions but do not use the entire DNA set all the time. Only a small amount of the DNA appropriate to the function of that cell is expressed. Genes are, therefore, turned on or turned off as needed by the cell (regulated), and the products coded by these genes are produced only when required.

The base________________ pairs with _____________. The base ___________ Pairs with __________.

This is called complementary base pairs. Thus one strand of the DNA is complementary to the other strand (opposite/matching). 5’-----3’ 3’-----5’

The structure of DNA resembles a twisted ladder.

Which part of the nucleotide is found comprising the “rungs” of the ladder?

Which part of the nucleotide is found comprising the “frame” of the ladder?

The molecule transcribed/coded directly from DNA is represented by number __ and is called ____________________

The ____________________ can leave the _______________ through the ________________and enter the ___________________ because the molecule is _______________________ not _____________________.

Structure 2 is called a _____________ or _________________ because it carries an amino acid and can help ___________________ the genetic code. because it consists of three nucleotides. The structure 2 recognizes a __________________ because it has a complementary _________________.

Structure 3 is the building blocks of _________________.

Structure 4 is the __________________ which holds the messenger RNA so that translation using the transfer RNA can occur.

The bond labeled 5, formed between two amino acids, is known as a __________________________

Which of the following units are repeatedly joined together to form a strand of DNA?

1. amino acids

2. fatty acids

3. nucleotides

4. polysaccharides

The weakest bonds in a double-stranded molecule of deoxyribonucleic acid exist between the____________________________

(1) deoxyribose sugars (2) phosphate groups (3) nitrogenous bases (4) 5-carbon sugars

Molecules C, D, and E will combine to form part of _______________________________

1. DNA

2. RNA

3. a polysaccharide

4. a polypeptide

Structure B represents a molecule of ____________________________________

1. nuclear DNA

2. cytoplasmic DNA

3. ribosomal RNA

4. transfer RNA

How many codons are located on the messenger RNA molecule in the diagram?

The type of molecule represented at A is synthesized according to a template found in

1. DNA

2. RNA

3. dipeptides

4. amino acids

The process shown here would occur in the _____________________ of a cell

One similarity between DNA and messenger RNA molecules is that they both contain

1. the same sugar

2. genetic codes based on sequences of bases

3. a nitrogenous base known as uracil

4. double-stranded polymers

Which of the following features of DNA is most important in determining the phenotype of an organism?

1. the direction of the helical twist

2. the number of deoxyribose sugars

3. the sequence of nitrogenous bases

4. the strength of the hydrogen bonds

A portion of one strand of a DNA molecule has the sequence shown : ACCTGAAGG

Assuming there are no mutations in this portion of the DNA, what is the corresponding sequence on the complementary DNA strand?

1. ACCTGAAGG

2. GTTCAGGAA

3. TGGACTTCC

4. UGGACUUCC

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We Love DNA (to the tune of “Row, Row, Row Your Boat”)!

We love DNA

Made of nucleotides.

Sugar, phosphate and a base

Bonded down one side.

Adenine and thymine

Make a lovely pair.

Cytosine without guanine

Would feel very bare.

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