<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>0109 - Disclosure - DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>D2013Q2YTD</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0000911649</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2013-01-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="6 Months Ended" /><Label Key="Calendar" Id="1" Label="Jun. 30, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>us-gaap_AccountingPoliciesAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Accounting Policies [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D2013Q2YTD" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div style="font-size:10.0pt;font-family:Times New Roman;"&gt;
&lt;p style="TEXT-INDENT: -25.9pt; MARGIN: 0in 0in 0pt 25.9pt;"&gt;&lt;b&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold;" size="2"&gt;2.&lt;/font&gt;&lt;/b&gt;&lt;b&gt;&lt;font style="FONT-SIZE: 8.5pt; FONT-WEIGHT: bold;" size="1"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/font&gt;&lt;/b&gt; &lt;b&gt;&lt;font style="FONT-SIZE: 10pt; FONT-WEIGHT: bold;" size="2"&gt;DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES&lt;/font&gt;&lt;/b&gt;&lt;/p&gt;
&lt;p style="TEXT-INDENT: -25.9pt; MARGIN: 0in 0in 0pt 25.9pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="MARGIN: 0in 0in 0pt;"&gt;&lt;i&gt;&lt;font style="FONT-STYLE: italic; FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;Business&lt;/font&gt;&lt;/i&gt;&lt;/p&gt;
&lt;p style="MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 0.5in; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;Prior to the completion of the Asset Sale, the Company was a biotechnology company with a core mission of developing, commercializing and marketing innovative and proprietary products, services and solutions that preserve and enhance the quality of human health and wellness.&lt;/font&gt;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 0.5in; MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 0.5in; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;The Company supplied products, custom services and critical reagents used across the life science research and development markets. The Company&amp;#8217;s Genomic Antibody Technology&amp;#174; (&amp;#8220;GAT&amp;#8221;) was used in proteomic research, disease understanding and drug/biomarker discovery among academic, biotech, in-vitro diagnostic (&amp;#8220;IVD&amp;#8221;) and large pharmaceutical customers.&lt;/font&gt;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 0.5in; MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;As a result of the Asset Sale, the Company no longer owns its historical operating assets, and its past business operations have been discontinued.&lt;/font&gt;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="MARGIN: 0in 0in 0pt;"&gt;&lt;b&gt;&lt;u&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold;" size="2"&gt;Basis of Presentation and Interim Financial Statements&lt;/font&gt;&lt;/u&gt;&lt;/b&gt;&lt;/p&gt;
&lt;p style="MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;The accompanying unaudited consolidated interim financial statements of the Company have been prepared by the Company pursuant to the rules&amp;#160;and regulations of the Securities and Exchange Commission (&amp;#8220;SEC&amp;#8221;) regarding interim financial reporting. Accordingly, they do not include all the information and footnotes required by U.S. generally accepted accounting principles (&amp;#8220;GAAP&amp;#8221;) for complete financial statements and should be read in conjunction with the Company&amp;#8217;s Annual Report on Form&amp;#160;10-K for the fiscal year ended December&amp;#160;31, 2012.&amp;#160; In the opinion of management, the accompanying consolidated interim financial statements include all adjustments (all of which are of a normal recurring nature) necessary for a fair presentation of the results of operations.&amp;#160; The interim operating results are not necessarily indicative of the results to be expected for the entire year.&lt;/font&gt;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="MARGIN: 0in 0in 0pt;"&gt;&lt;b&gt;&lt;u&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold;" size="2"&gt;Revenue Recognition&lt;/font&gt;&lt;/u&gt;&lt;/b&gt;&lt;/p&gt;
&lt;p style="MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 26pt; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;Revenues composed of sales of immunoassay-based test kits and certain antibodies and immunochemical reagents are recognized upon the shipment of the product and transfer of title, or when related services are provided. Revenues associated with such products or services are recognized when persuasive evidence of an order exists, shipment of product has occurred or services have been provided, the price is fixed and determinable and collectability is reasonably assured. Management is required to make judgments based on actual experience about whether or not collectability is reasonably assured.&lt;/font&gt;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;Historically, the Company entered into contracts related to the production of custom antibodies, which provided for the performance of defined tasks for a fixed price, with delivery of the product upon completion of production. The standard time to complete a project was typically longer than 30 days but less than 12 months, and effort was expended over the life of the project. Revenues related to sales of custom antibody projects are recognized when a project&amp;#8217;s specifications have been met and the related materials have been shipped.&lt;/font&gt;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;Fees associated with products and services added on to a custom antibody project subsequent to delivery of the initial project are billed monthly and recognized as revenue as the services and other deliverables are provided.&amp;#160; Sales taxes collected from customers are presented net in the consolidated statement of operations.&lt;/font&gt;&lt;/p&gt;
&lt;p style="TEXT-ALIGN: center; MARGIN: 0in 0in 0pt;" align="center"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;The Company follows Accounting Standards Codification, (ASC) 605-25 &amp;#8220;&lt;i&gt;Revenue Recognition &amp;#8212; Multiple-Element Arrangements&lt;/i&gt;&amp;#8221; to determine the recognition of revenue under collaboration agreements that include multiple elements.&amp;#160; The deliverables under these agreements are evaluated to determine if they have stand-alone value and revenue is allocated to the elements based upon their relative selling prices.&amp;#160; Since the adoption of this standard, the Company has entered into one agreement with multiple-elements.&amp;#160; In the three months ended June&amp;#160;30, 2012, the Company recognized approximately $108 in revenue related to this agreement, which was comprised of $95 for materials shipped and $13 in consulting services provided.&amp;#160; In the six months ended June&amp;#160;30, 2012, the Company recognized approximately $1,028 in revenue related to this $1,250 agreement.&amp;#160; The amount recognized was comprised of $190 for materials supplied, $22 in consulting services provided and $816 in technology access fees.&amp;#160;&amp;#160; In November&amp;#160;2012, the Company announced this agreement had been terminated by Beckton Dickinson (BD) Diagnostics and that all revenues related to the initial $1,250 payment had been earned.&lt;/font&gt;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="MARGIN: 0in 0in 0pt;"&gt;&lt;b&gt;&lt;u&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold;" size="2"&gt;Use of Estimates&lt;/font&gt;&lt;/u&gt;&lt;/b&gt;&lt;/p&gt;
&lt;p style="MARGIN: 0in 0in 0pt;"&gt;&amp;#160;&lt;/p&gt;
&lt;p style="TEXT-INDENT: 25.9pt; MARGIN: 0in 0in 0pt;"&gt;&lt;font style="FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt;" size="2"&gt;The preparation of the consolidated interim financial statements requires management of the Company to make a number of estimates and assumptions relating to the reported amount of assets and liabilities, disclosure of contingent assets and liabilities at the date of the consolidated interim financial statements, and the reported amounts of revenues and expenses during the period. These estimates include those made in connection with assessing the valuation of accounts receivable, inventories, deferred tax assets and long lived assets. Actual results could differ from these estimates.&lt;/font&gt;&lt;/p&gt;
&lt;/div&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for the general note to the financial statements for the reporting entity which may include, descriptions of the basis of presentation, business description, significant accounting policies, consolidations, reclassifications, new pronouncements not yet adopted and changes in accounting principles.</ElementDefenition><ElementReferences>No definition available.</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://www.sdix.com/taxonomy/role/NotesToFinancialStatementsOrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
