Download DNA Notes How was the DNA Model Formed? 1) In the 1950`s a

DNA Notes
How was the DNA Model Formed?
1) In the 1950’s a biochemist named Erwin Chargaff found that the amount of adenine (A) in DNA
always equaled thymine (T), as is the same for cytosine (C) and guanine (G). Soon after this discovery
was known as Chargaff’s Rule:
A=T
G= C
2) Soon after a young chemist named Rosalind Franklin created images of DNA using a technique known
as X-ray diffraction. Franklin used X rays to create images on film and found that the general shape of
DNA is a spiral shape
3) In 1953 ___James_ ___Watson__, an American biochemist, and ___Francis__ ___Crick____, an
English physicist, worked together in Cambridge, England to develop a model for DNA. Watson and Crick
were the first scientist to discover the true shape of DNA.
*DNA stands for _ Deoxyribonucleic Acid __.
Shape of DNA:
It is the blueprint of life.
DNA has a very distinct shape. It is arranged in a form of a helix. A helix is a
shape of a coiled spring. However, a DNA molecule is a double helix
What is DNA made up of?
DNA is made up of subunits called nucleotides.
Each nucleotide is composed of 3 parts:
a. Deoxyribose- a 5 carbon sugar
b. A phosphate group
c. A nitrogen base
Nitrogen Bases:
Adenine – Thymine
Cytosine – Guanine
*All living things have the
Same 4 bases, but the order matters!
Nucleotide:
What does the letters in your DNA code for?
Your DNA sequence is a message for your cells to make specific
proteins. It is essentially like a recipe so your cells know what
ingredients to put into your proteins. The proteins that are
made allow you to express the specific traits that you inherit.
A gene is a piece of DNA that codes for a particular protein.
How DNA makes a copy of itself
One of the unique characteristics of DNA is that it can copy
itself using one of the strands as a template. DNA can
replicate and match base pairs to make complementary
strands
EX:
Strand 1: A T C C G T A G C
Strand 2
____________________
Strand 1:
T T G A T C T C C
Strand 2
____________________
Changes in Genes
-
Sometimes mistakes happen when DNA is copied, similar to how we might make a typo.
-
_mutation_ - change in DNA sequence. Sometimes they are random, and sometimes they are
caused by external factors called mutagens.
-
__mutagens_ - cause mutations. Examples include x-rays, UV light, chemicals in cigarettes
-
Types of Mutations
o
Substitution – a base is _switched_ in the sequence
o
Deletion – a base is __removed__ from the sequence
o
Insertion – a base is __added__ to the sequence