Science.Stumped.DNA help.

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Not a science teacher .Trying to figure this out for a supply lesson. Monday. We’ve done cells and structure Looking at nucleus and DNAthis week., Just about got chromosomes and genes sorted with regard to punett squares .But.... a) not sure how DNA tells cells to be whatever they are going to be. And how fits with chromosomes.
Which bit tells the black cat it’s a going to have fur cells and which bit it’s going to be black?
b) mutations- limitations ,how mutated can a gene get and what are it’s limits.
c) eye colour - always only blue and brown in science books. I have mixed race students with bright green, grey and black eyes. How am I explaining these.

Please help and tell me where to look.

Should you repost in The Staffroom?

what age kids?

Chromosomes are the DNA structures. Humans have 23 pairs. Different bits of the Dna on these chromosomes are the i dividual genes, lots in one chromosome. The DNA is copied into messenger RNA in the cell by transcription proteins (transcription) and the mRNA is converted into all the various proteins that make uo the orgnaism by other proteins. Thats how the genes code for different characteristics. Different genes will be active/turned on in different types of cells.

They used to think eye colour was controlled by 2 alleles ( versions of the same gene) one for brown, one for blue but it’s more complicated than that and involves several genes and alleles ghr.nlm.nih.gov/primer/traits/eyecolor
Mutations- Id check the spec to see exactly what they need to know - generally if a mutation is harmful, it decreases the individuals chance of surviving and reproducing and so that mutation would be rare in a population. If it is an advantage,the individual is more likely to survive and that mutation becomes more common. Mutations Change the structure of the protein the gene codes for and so can affect its action or prevent it from working g at all.
As for the fur cell thing - I don’t think they really k ow. - all cells contain the same DNA and different genes are switched on and off depending on other factors which affects the role of the cell.
Hope that helps

Thanks Itold. I will blame on proteins.
It’s year 11’s. I know what ai have to teach but it’s those other questions they ask...I hate not having proper subject knowledge.
Calop - I thought it was the other way round, Good to know about transcription.
Will also have a look at staff room.
Thank you.

Re: fur cells.

When the kitten is developing as an embryo there are various signals set up telling which cells what to be.

The genes in these cells will then be switched on or off as required.

One of those genes (if the correct allele is present in the kitten) will be the gene (or genes) for black pigment (which will be a protein), this will be made in cells where it is switched on.

Transcription (DNA to mRNA) happens in the nucleus, the mRNA leaves the nucleus, as it's only one gene long so many times smaller than the DNA, and is then Translated into protein (with every 3 letters of DNA representing one amino acid).