Batch to Bash

I would like to translate this to a bash script.

The current Windows batch script is:

@ECHO OFF
:LOOP
CLS
ECHO AP Biology Lab Selector
ECHO -----------------------
ECHO Lab 2: Enzyme Catalysis
ECHO Q to Quit
ECHO.
:: SET /P prompts for input and sets the variable
:: to whatever the user types
SET Choice=
SET /P Choice=Type lab number:
:: The syntax in the next line extracts the substring
:: starting at 0 (the beginning) and 1 character long
IF NOT '%Choice%'=='' SET Choice=%Choice:~0,1%
ECHO.
:: /I makes the IF comparison case-insensitive
IF /I '%Choice%'=='2' GOTO Item1
IF /I '%Choice%'=='Q' GOTO End
IF /I '%Choice%'=='Quit' GOTO End
ECHO "%Choice%" is not valid!
PAUSE
ECHO.
GOTO Loop
:Item1
CLS
ECHO Starting program...
::do stuff
GOTO Again
:Again
CLS
GOTO Loop
:End

Any help would be great.