ExtraLines in GridView

[Sergiy]

Hello, I have got the following style for my grid.

<Style TargetType="{x:Type t:RadGridView}" x:Key="OverrideDefaultGridViewStyle">
    <Setter Property="GridLinesVisibility" Value="None"/>
    <Setter Property="RowHeight" Value="50"/>
    <Setter Property="ColumnBackground" Value="White"/>
        <Setter Property="RowIndicatorVisibility" Value="Collapsed"/>
        <Setter Property="ShowGroupPanel" Value="False"/>
        <Setter Property="CanUserFreezeColumns" Value="False"/>
        <Setter Property="CanUserReorderColumns" Value="False"/>
</Style>

Could you explain, how can I get rid of extra lines (see attached file)?
These lines appear, when I am selecting cell(row). I think it's selected row.
How to disable selecting cell border (gray border)?
Thank You