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Warm UP
• Illustrate how the chromosome
number in a sexually reproducing
organism with 8 chromosomes
remains constant from one generation
to the next by drawing a model of
meiosis and showing the TOTAL
number of chromosomes in each
stage, the steps, and the products for
male and female.
Warm Up
• Deoxyribonucleic acid, the material
that contains the information that
determines inherited characteristics
• One of the four possible bases in a
string of DNA—it pairs with adenine
• A subunit of DNA that consists of a
sugar, a phosphate, and a nitrogenous
base
• The complement to guanine
Warm Up
• What letters represent the four bases?
• Using X-ray diffraction, what did
Rosalind Franklin show the shape of
DNA to be?
• Watson and Crick built a DNA model
like a ……
• The sides of the DNA “ladder” are
made of…….
• The “rungs” of the DNA ladder are…..
Pick Up Warm Up
• On the back of your warm up,
answer the following:
• What are the phenotypes based
on the genotypes:
Ggbb ____________________
ggBB ____________________
ggbb ____________________
GgBb ____________________
Warm Up
• A male rabbit with the genotype
GGbb is crossed with a female
rabbit with the genotype ggBb.
• Determine the phenotypes and
proportions in the offspring.
Warm Up
• How many out of 16 have grey fur and
black eyes?
• How many out of 16 have grey fur and
red eyes?
• How many out of 16 have white fur
and black eyes?
• How many out of 16 have white fur
and red eyes?
DNA
What is DNA
• Deoxyriboneucleic
Acid:
a genetic code (like a
blueprint) for making
new cell parts, new
cells, or an entirely
new organism.
• DNA wraps around
protein cores and
forms chromosomes
found in the nucleus of
eukaryotic cells.
History of DNA
• 1952 – Rosalyn Franklin discovered that DNA is
made up of 2 chains of molecules arranged in a
spiral form.
History of DNA
Chargaff’s Rule:
-Adenine always equals amount of Thymine.
A=T
-Guanine always equals amount of Cytosine.
G=C
Chargraff’s Rule
History of DNA
• 1953 – James Watson and Francis Crick
constructed the first model of DNA and win the
Nobel Peace Prize.
DNA Structure
• DNA is often called a
“double helix” or “twisted
ladder.”
• The sides are made of
phosphate and
deoxyribose-sugar
molecules.
• The middle (rungs) are
made of nitrogenous base
pairs (adenine/thymine,
guanine/cytosine).
Four Nucleotides
• Nucleotide: combination
of a phosphate
molecule, deoxyribosesugar molecule & a
nitrogenous base.
The Four:
Adenine
Thymine
Cytosine
Guanine
Complementary Bases
Remember Chargaff’s Rule:
The complementary
strand/sequence to
G-A-T-T-A-C-A would be…
DNA Replication
• Before any cell
can make a
copy of itself, all
the DNA must
be copied!
• This is called
DNA
replication.
DNA Replication
• An enzyme opens the strands of DNA so that
they become single stranded.
• Complimentary nucleotides come fill in the
missing strand.
• Two DNA strands are formed.
Let’s Model DNA
• Have students stand in two lines that spiral like a
DNA molecule. Each line should hold string.
• Students should hold cards labeled A, T, C, or G to
represent the nucleotide pairs.
• Have the two lines move away from each other to
model how the DNA molecule separates into two
strands.
• Have free standing students pair up with matching
A, T, C, or G cards to show how the open strands
replicate.
• This one example of how models can be similar to
yet different from the natural occurrences they
represent.
http://www.classzone.com/books/ml_science_share/vis_sim/chm05_pg141_
protein/chm05_pg141_protein.html
Making Proteins
• Groups of three nitrogenous bases are
a code (codon) for making specific
amino acids
• Strings of amino acids form proteins
• RNA (riboneucleic acid) makes a
temporary DNA copy
Genes: sections of DNA on
chromosomes that
control production of proteins for
specific traits such as:
hair color, eye color, dimples,
freckles….
RNA vs. DNA
Differences:
Similarities:
• Are nucleic acids
• Contain nitrogenous
bases
• Contain phosphate &
sugar molecules
Deoxyribose Sugar
DNA
RNA
Double
strand
Single strand
Thymine
Uracil
Deoxyribose- Ribose-sugar
sugar
Types of RNA
• messengerRNA or mRNA:
comes from nucleus w/ genetic
information for protein synthesis
(mirror image of DNA strand).
• transferRNA or tRNA: carries
matching amino acids to
ribosomes.
• ribosomalRNA or rRNA:
constitutes 50% of a ribosome,
decodes mRNA for tRNA to pickup matching amino acids.