Download 2-3 DNA to Proteins - Lighthouse Christian Academy

UNIT 1:
REPRODUCTION
UNIT A IN YOUR GRADE 9 SCIENCE 9 PROBE TEXTBOOK
2.3 From DNA to Proteins
(pg. 42)

The nucleus contains the chromosomes which are
made of DNA. DNA contains the instructions for the
body. How does the body read the instructions and
build the body?
Lets understand DNA
o
o
Shape – DNA is made up of nucleotides (Fig 1 pg 42). The
nucleotides pair up to form ladder rungs. There are four
types: Adenine (A) goes with Thymine (T), Cytosine (C)
goes with Guanine (G). The ladder shape then twists to
form a helix.
Copying – DNA can unzip and then new nucleotides attach
to each side of the original. In the end you end up with
two new DNA each with half of the original in them. (see
page 43)
Lets understand DNA
o
o

Genetic Code – So how do the base pairs (A, T, C, G)
contain information? In three letter “words” called
codons. Each codon codes for the production of 1 of 20
amino acids. A chain of amino acids is a protein.
Genes – All of your DNA is organized into 23
chromosomal pairs. These are like encyclopedias that
contain instructions on how to make all the proteins in a
body part. A single gene is the instructions for how to
make a single protein.
https://www.youtube.com/watch?v=8kK2zwjRV0M
How does the Genetic code
become a body part?
Finding the right gene – First the DNA unwinds the
chromosome so that a copy of the needed gene can be
made. This is copy is called RNA (ribonucleic acid). RNA
is similar to DNA except it is only one strand.
o RNA to Ribosome – The RNA then leaves the nucleus and
attaches to a ribosome which “reads” the code on the
RNA.
o Ribosome builds the Protein – As the RNA reads the
code it attaches the amino acids in the order listed. This
builds the protein.
o
Gene Variation

Not everyone looks the same. This is because the
instructions in the genes can vary slightly from person
to person.

You have two copies of each gene, one from your Mom
and one from your Dad. One of these will show up and
the other will be hidden (recessive).