Biology-Lab 10-DNA BIOLOGY AND TECHNOLOGY • DNA AND RNA STRUCTURE

Key Concepts

- DNA (deoxyribonucleic acid) is a molecule found in all cells that stores the genetic information of the cell. RNA (ribonucleic acid) also exists in all cells and is a copy of the DNA that can be used in protein synthesis. -Both DNA and RNA are polymers composed of nucleotide subunits linked together in a chain. Genetic information is encoded in the sequence of the nucleotides. -Each nucleotide is composed of three parts: a five-carbon sugar, a nitrogen-containing base, and a phosphate group. In DNA, the five-carbon sugar is deoxyribose, and in RNA, the five-carbon sugar is ribose. The nitrogenous base in a nucleotide can vary and be one of five different kinds: adenine (A), guanine (G), cytosine (C), thymine (T; DNA only), and uracil (U; RNA only). -In a chain of nucleotides, the phosphate group of one nucleotide is bonded to the sugar group of the next nucleotide. Thus, alternating sugar and phosphate groups form a backbone, with the nitrogenous bases extending from it. -A DNA molecule consists of two strands of nucleotides twisted together to form a double helix. The two strands are linked in the middle by hydrogen bonds between nitrogenous base-pairs. In the base-pairs, C (cytosine) can only pair with G (guanine), and A (adenine) can only bond with T (thymine). In RNA, uracil (U) replaces thymine (T). -DNA carries the genetic information of the cell to daughter cells during reproduction. Each time a cell divides, it must first make copies of its DNA to pass on to daughter cells. This process is called DNA replication. -In DNA replication, the two strands of the DNA double helix unwind and separate at a site called the replication fork. Each of the two parental strands serve as templates for the synthesis of new strands. New nucleotides are added as dictated by the sequence of bases on the template strands. -RNA is synthesized using DNA as a template in a process called transcription. -In transcription, the DNA double helix unwinds, and an enzyme called RNA polymerase attaches to one strand of the DNA, called the template strand. The other strand of DNA is called the coding strand. RNA polymerase then moves along the DNA template strand and synthesizes an RNA copy of the DNA. After RNA polymerase passes by, the DNA strands rejoin and rewind.

Nitrogenous base

A nitrogen-containing organic molecule that forms part of a nucleotide; the nitrogenous bases adenine (A) and guanine (G) consist of two carbon-nitrogen rings, while the nitrogenous bases cytosine (C), thymine (T), and uracil (U) consist of one carbon-nitrogen ring.

In transcription, the enzyme RNA polymerase builds a strand of RNA along the A. template strand of DNA B. coding strand of DNA C. ribosome D. strand of amino acids

A. template strand of DNA

The two strands of nucleotides in a DNA molecule are held together by . A. sugar and phosphate bonding B. peptide bonds C. strong ionic bonds D. hydrogen bonds between base pairs

D. hydrogen bonds between base pairs

After DNA replication, each new daughter DNA molecule is composed of . A. two newly synthesized strands B. two parental strands C. one DNA strand and one RNA strand D. one parental strand and one newly synthesized strand

D. one parental strand and one newly synthesized strand

RNA polymerase

Enzyme that uses a DNA template to synthesize a molecule of RNA during transcription.

Deoxyribose

Five-carbon sugar found in the nucleotides of DNA; lacks an -OH group bonded to the 2' carbon.

Ribose

Five-carbon sugar found in the nucleotides of RNA.

Phosphate group

Functional group containing a phosphorus atom and four oxygen atoms (PO4) that is a component of nucleotides.

Overview

In this simulation, you will: -Examine DNA structure by labeling the components of a DNA molecule. -Label a DNA molecule undergoing DNA replication. -Label a DNA molecule undergoing transcription to produce RNA. -DNA is composed of two strands of nucleotides twisted together into a double helix shape

RNA (ribonucleic acid)

Molecule that consists of a strand of nucleotides and carries the genetic instructions of DNA to other parts of the cell for protein synthesis; RNA nucleotides contain the sugar ribose, a phosphate group, and one of four nitrogenous bases, adenine (A), guanine (G), cytosine (C), and uracil (U).

DNA (deoxyribonucleic acid)

Molecule that stores genetic material and consists of a double strand of nucleotides; DNA nucleotides contain the sugar deoxyribose, a phosphate group, and one of four nitrogenous bases, adenine (A), guanine (G), cytosine (C), and thymine (T).

Select all of the following that are components of DNA nucleotides.

Nitrogenous base Phosphate group Deoxyribose

DNA replication

Process by which DNA makes a copy of itself.

Transcription

Process that produces RNA using DNA as a template.

Double helix

Shape of a DNA molecule consisting of two strands twisted together, similar to a spiral staircase but with alternating major and minor grooves along the outside of the double helix.

Replication fork

Site on a DNA molecule where the double helix separates and unwinds to begin DNA replication.

Nucleotide

Subunit of DNA and RNA that consists of a five-carbon sugar bonded to a nitrogenous base and a phosphate group.

Coding strand

The strand in a DNA molecule that is not used as a template.

Template strand

The strand in a DNA molecule that is used to build a new DNA strand in DNA replication or an RNA strand in transcription.

What is the product of DNA replication?

Two daughter DNA molecules.

The process of forming RNA from a template strand of DNA is called

transcription