Transcript DNA: The Molecule of Heredity

DNA: The Molecule
of Heredity
DNA Structure
• Deoxyribonucleic
acid.
• A macromolecule
composed of two
strands of monomers
called nucleotides.
• These strands are
joined in the middle
by hydrogen bonds.
• The strands twist
around one another
forming a double
helix. Twists to the
right.
http://cancergenome.nih.gov/media/DNAKit_illustration_image.jpg
Nucleotide Structure
• 5-C sugar –
deoxyribose
• Phosphate
group
• Nitrogen
containing base
-4 of two types
–
–
–
–
Adenine
Guanine
Cytosine
Thymine
http://www.msu.edu/course/isb/202/ebertmay/drivers/nucleotide.jpg
Types of Nitrogen Bases
• Pyrimidines –
have one ring in
their structure
– Thymine
– Cytosine
• Purines – have two
rings in their
structure
– Adenine
– Guanine
http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/images/DNAbases.jpg
Nitrogen Base Pairing
• Bases pair in a
specific pattern.
• A purine always
bonds to a
pyrimidine
– Adenine bonds to
thymine.
– Guanine bonds
to cytosine.
Nitrogen Base Pairing
• The bases are held
together by weak
hydrogen bonds.
• The sides of the DNA
ladder are composed of
alternating sugar and
phosphate and are
called “backbones”.
Functions of DNA
• DNA must be able to copy itself exactly.
This process is called REPLICATION
-
- Enzymes control the process.
• DNA is the molecule of heredity.
- It provides instructions for cell functioning
and is a blueprint for the production of proteins
that do the work of the cell.
Replication – Overview
 DNA “unzips” down its
H-bonds
 One strand then acts as
a template for the
production of a new
strand
 Each new DNA
molecule has one old
strand of nucleotides
and one new strand.
Control Of Cell Activities
• DNA is copied
into RNA.
(Transcription)
• RNA in turn
controls the
production of
proteins.
(Translation)
• Proteins then do
the work of the
cell.
RNA
• Like DNA, Ribonucleic acid is also made up
a sugar, phosphate group and nitrogen
bases. But there are some major differences-• The sugar in RNA, is Ribose.
• RNA is single stranded
• the nitrogen bases consist of Uracil (U),
Adenine (A), Guanine (G) and Cytosine (C).
• Uracil and Adenine = Base Pair
• Guanine and Cytosine = Base Pair
TAKS PRACTICE: Question 1
Question 2
4 DNA passes information to RNA during the
process of —
F transcription
G active transport
H regeneration
J osmosis
Question 3
5 Which of the following must occur before DNA
replication can take place?
A Translation of DNA into amino acids
B Separation of the DNA molecule into codons
C Transformation of DNA into RNA
D Separation of the DNA double helix
Question 4
3 If a cat has 38 chromosomes in each of its body
cells, how many chromosomes will be in each
daughter cell after mitosis?
F 11
G 19
H 38
J 76