Transcript DNAsc9 - SD57 Mail

A
very large molecule, found in the
chromosomes of all cells
 Carries the genetic code - all the instructions
for the structure and functioning of the cell
(and the whole organism)
A
long complex
molecule in the
shape of a double
helix (twisted
ladder)
 Made of two strands
of smaller molecules
called nucleotides
 Each
nucleotide has 3
parts: sugar, phosphate,
and a nitrogenous base
 There are 4 different
nitrogenous bases: adenine
(A), guanine(G), thymine
(T) and cytosine (C)
 Phosphate
and sugar
form the sides of the
ladder
 Pairs of bases form the
rungs of the ladder
 A always pairs with T
C always pairs with G
 A,T,C,and
G form 3 letter codes called
“codons”
 Each 3 letter word codes for one amino acid
 Amino acids are the building blocks of
proteins
 So, DNA has instructions for building all the
proteins a cell needs
 Each
strand of DNA contains many genes
 A gene contains many nucleotides
 Each gene carries the code for one protein
 DNA
can make exact
copies of itself
 This is necessary so that
all new cells get all the
information they need
 DNA replication happens
in the nucleus
 The molecule unzips, and
new nucleotides are
attached making 2
identical molecules
 DNA
can’t leave the nucleus, so copies of
its code are made
 RNA is the messenger molecule that
carries the code from the nucleus to the
cytoplasm
 RNA is a single strand and contains only
one gene
 RNA bases are AUCG
A
ribosome attaches to a strand of
messenger RNA
 The ribosome reads the code 3
nucleotides at a time
 Amino acids are attached in the
correct order to assemble the protein
Proteins have many important functions in the
body. Some examples:
 Enzymes to control chemical reactions in
cells
 Hormones to carry messages through the
body
 Structural proteins that make up body parts
 Blood proteins like hemoglobin and
antibodies