Download The Earth - Mr. Shanks` Class

MOLECULAR GENETICS
N O V E M B E R 2 ND 2 0 1 5
GENERAL ANNOUNCEMENTS
• Reminder: My name is Ms. M! (M for McAvella)
• Feedback Box
• University Inquiries
KW CHART!
• Form groups of 4
• On your chart paper, create the following table:
GENETICS
K
W
E.g. Our genes contribute E.g. What
to what make us different diseases/disorders are
from one another
genetically related?
• In the K column, list everything you and your group
members know about the topic
• In the W column, list everything you would like to
know about the topic
LEARNING GOALS
• Students will learn about nucleotides, the monomer
of DNA molecules, and how they are bound to form
strands
• Students will understand how complementary base
pairing can lead to the formation of two
polynucleotide strands that twist to form a double
helix
WHAT IS DNA?
• Deoxyribonucleic acid (DNA)
• DNA is the hereditary material – passed on from
generation to generation
• Contains information that controls the production of
proteins
• Has to be able to replicate itself with great accuracy
STRUCTURE OF DNA
• Structure: DNA is made up of repeating units of
nucleotides (monomer)
• Nucleotides are composed of the following 3
components:
1. A sugar group
2. A phosphate group
3. A nitrogenous base
1. SUGAR GROUP
In DNA, the sugar group is a deoxyribose sugar
The sugar group is a five-carbon molecule
2. PHOSPHATE GROUP
The deoxyribose sugar binds with phosphate at both
its 3’ and 5’ (three prime and five prime) carbons
3. NITROGENOUS BASE
• A nitrogenous base attaches to the deoxyribose
sugar group
• There are two different forms of nitrogenous bases:
1. Pyrimidines
2. Purines
3. NITROGENOUS BASE
Thymine and Cytosine
are pyrimidines
Adenine and Guanine
are purines
PYRIMIDINES – CHEMICAL STRUCTURE
Thymine and Cytosine
Have a single ring
PURINES – CHEMICAL STRUCTURE
Adenine and Guanine
Have two fused rings
DNA NUCLEOTIDE*
Recall: consists of a phosphate group, sugar group
and nitrogenous base
DRAW A NUCLEOTIDE
NUCLEOSIDE VS. NUCLEOTIDE
• A sugar + a nitrogenous base = nucleoside
• A sugar + a nitrogen base + phosphate = nucleotide
• Phosphorylating a nucleoside makes a nucleotides
PRIMARY STRUCTURE
• Each nucleotide is attached to the next by a
phosphodiester bond
• The phosphodiester bond is the linkage between the
3’ carbon atom of one sugar molecule and the 5’
carbon atom of the next
• Think: Phospho (phosphate) + diester (two esters)
• This bonding creates a polynucleotide (multiple
nucleotides) strand
DRAW
SUGAR PHOSPHATE BACKBONE
• Each polynucleotide strand has a backbone of
alternating phosphate groups and sugars called the
sugar phosphate backbone
BINDING OF TWO STRANDS
• Complementary base pairing: nitrogenous bases on opposite
strands pair through hydrogen bond formation such that
Adenine pairs with Thymine
Cytosine pairs with Guanine
• A-T held by 2 hydrogen bonds
• C-G held by 3 hydrogen bonds
Question: Which pair do you think is stronger?
CHARGAFF’S RULE
• The amount of adenine in any sample of DNA is
equal to the amount of thymine
AND
• The amount of cytosine is always approximately
equal to the amount of guanine
Question: are purines binding to one another and
pyrimidines binding to one another?
ANTIPARALLEL
• Antiparallel: The two strands run in opposite
directions
• Each strand will have a 5’ end and a 3’ end
• The 5’ end of one strand lies across from the 3’ end
of the complementary strand
• The 5’ and 3’ come from the numbering of the
carbons on the deoxyribose sugar
ANTIPARALLEL – ANALOGY
• This is similar to how sports teams face in a different
direction when they shake hands at the end of a game
• Let’s say the goalie is always at the front of the line (5’)
• And the coach is always at the back of the line (3’)
DRAW
SECONDARY STRUCTURE – DOUBLE
HELIX
• The two bound polynucleotide strands twist around
each other to form a double helix
http://www.johnkyrk.com/
http://www.dnatube.com/video/3447/DNA-doublehelix
LEARNING GOALS
• Students will learn about nucleotides, the monomer
of DNA molecules, and how they are bound to form
strands
• Students will understand how complementary base
pairing can lead to the formation of two
polynucleotide strands that twist to form a double
helix
QUESTIONS!
• How many bonds between A-T? C-G?
• What kind of bonds are these?
• What is a nucleotide and what is a nitrogenous
base?
• Are the two polynucleotide strands that twist
around each other identical?
ROSALIND FRANKLIN*
• In groups of 4/5 you will read a short
section on an article about Rosalind
Franklin
• The sections are as followed:
1. A crucial contribution
2. Her education
3. A passionate woman
4. An unhappy time
5. On to better things
• Summarize an important fact or two
about the section you read
• Pick one group member to read this
to the class
TOMORROW: DNA EXTRACTION!
• You can read through the instructions tonight if that
would help you in working your way through the
mini-lab