I'm in year 11 right now, but I remember that the most useful resource for the genetics topics are in the five senses education books: Success in Science 3 and 4
Hope that helps!!
There's a really good website about Genetics on the University of Utah(?) website. I'm not sure if I'm allowed to link you, but if you search around, you will find it. It has the basics of genes, chromosomes, mitosis/meiosis, etc. It's an awesome website and it's interactive. Our school is using it a lot.
Science in Focus are good, I used them in year 10.
But honestly you can piss away this subject because it is fairly easy and if you do Biology/or and science next year you will totally re-learn everything.