The molecule of heredity
Test: Feb. 11
Quiz on today’s lesson, tomorrow
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
DNA structure
DNA function
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

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Inheritance
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
Mitosis/Meiosis
Replication
Protein synthesis
Punnett Squares
DNA vs. RNA
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Organisms have 2 different types of
cells
 Body (somatic) cells: skin, liver, brain
 Sex cells (gametes): sperm and egg
Because sperm and egg need to meet
and combine their chromosomes to
form a new individual, they have ½
the number of chromosomes as body
cells
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DNA is made up of nucleotides. Each
nucleotide of DNA consists of:
A sugar “deoxyribose”
 A phosphate
 A nitrogenous base:

 Adenine
 Cytosine
Thymine
Guanine
PLEASE SKETCH THIS IN YOUR NOTES
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PLEASE SKETCH THIS IN
Double-helix/spiral ladder
YOUR NOTES
Sugar-phosphate “backbone”
Bases are rungs of ladder
Long sequences of bases make up genes
DNA is located in
nucleus of a cell.
the ________
 While in the nucleus
it is in the form of
chromosomes .
 Chromosomes
contain the genes
 Different species
have different amounts
of chromosomes.
Humans = 46

23
46
23
Quiz on yesterday’s lesson (10 min. maximum)
When finished, bring to front.
“SSR” Silent Sustained Reading (20 minutes)
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2.
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Read pages: 101-103, 110 - 112
Notes on Mitosis and Meiosis (20 min.)
Homework (can start at end of class if time):
4.
5.
1.
2.
Finish SSR assignment if you didn’t finish in the 20
min. given in class
Do text pages:
- 103, #1-4
- 112 #1 & 4
- 114 #7 - 9
Turn in HW
2. Genetics Video Clip (10min)
www.unitedstreaming.com
1. Meiosis and crossing over
2. Karyotypes
HW:
Replication and Protein Synthesis Worksheet
1.
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Mitosis is the division of a cell into body cells.
Meiosis is the division of a cell into sex cells.
http://www.pbs.org/wgbh/nova/miracle/divi_
flash.html
eye color
locus
eye color
locus
hair color
locus
hair color
locus
From Dad
From Mom
PLEASE SKETCH THIS IN YOUR NOTES
homologous pairs
Tetrad, homol. pairs together
PLEASE SKETCH THIS IN YOUR NOTES
Tetrad
This causes genetic
variation
n=23
human
sex cell
n=23
sperm
n=23
2n=46
haploid (n)
diploid (2n)
n=23
Crossing-over
occurs at this
stage
PLEASE SKETCH THIS IN YOUR NOTES
n=23
n=23
4 genetically different
gametes are produced
SEX CELLS/HAPLOID (N)
23
 12
 4
 20
 10
 22
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BODY CELLS/DIPLOID (2N)
46
 24
 8
 40
 20
 44
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Review chromosome number
Examine karyotypes
Discuss chromosomes and genes/inheritance
Begin protein synthesis
HW: Study for quiz on everything we’ve
covered in this unit through today. Closednote quiz.
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Nondisjunction is when the chromosomes
don’t split evenly in meiosis, resulting in too
many or too few chromosomes in the sperm or
egg.
Examples of diseases/conditions caused by
non-disjuction:
Down’s Syndrome = 47
 Turner’s Syndrome = 45
 Klinefelter’s Syndrome = 47
http://www.biostudio.com/d_%20Meiotic%20Nondisju
nction%20Meiosis%20I.htm
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Normal Human
Karyotype:
 46 chromosomes
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44 autosomes
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23 pairs
22 pairs
2 sex chromosomes

1 pair
 XX = female
 XY = male
First 30 minutes:
 Take Quiz and submit to front desk -10 min
 Protein Synthesis and Genetics – 30 min
 Homework: Read textbook pages 117-123 and
127-132. Make flashcards of all bold words.
Bring to next class
Protein Synthesis: How DNA turns the base
sequence into proteins
DNA  RNA  Protein
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It is important for the same DNA to be found
in all new daughter cells (created from
mitosis).
 This is done through replication – the
copying of DNA
DNA holds the instructions for the
manufacturing of protein.
 This is done through protein synthesis –
the making of proteins from the
instructions coded by the sequence of bases
in the DNA
http://www.biostudio.com/demo_freeman_protein_synthesis.htm
First 35 minutes:
 Take Quiz and submit to front desk -10 min
 Read textbook pages 117-123 and 127-132.
Make flashcards of all bold words. Bring to
next class. Finish for HW if needed
 Begin Genetics – 25 min
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Organisms are a product of the genes they
receive from their parents. These genes make
proteins, such as pigments, that make
individuals who they are/what they look like –
to an extent…..
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Genes – segment of DNA that codes for
a trait
Alleles – different versions of a gene:
 Allele for brown eyes, allele for blue
eyes
 Both genes code for hair color, but
have different versions
Letters are used to indicate alleles. Ex. B, b
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Homozygous – an individual who has the
same alleles for a trait. Ex. 2 genes for cystic
fibrosis
Heterozygous – an individual who has
different alleles for a trait. Ex. One gene for
cystic fibrosis, one for normal
Dominant – The allele that is expressed
 Recessive – The allele that is not expressed when
paired with a dominant. Only expressed when
paired with another recessive gene
Ex) Heterozygous brown mouse (Bb)
1. how do you know brown is the dominant
phenotype?
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2. How do you know to use the letter “B” or “b”
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Parent generation = P
Offspring of P generation = F1
Offspring of F1 generation = F2
Cross a homozygous dominant purple flower
with a homozygous recessive white flower. Give
the F1 genotype and phenotype percents.
Purple = PP, white = pp
Phenotype:
_______ % ___________
_______ % ___________
Genotype:
________% Hom. Dom.
________% Het.
________% Hom. Rec.
Cross Bb x Bb
2. Give the F2 of BB x bb
3. Cross a heterozygous black mouse with a white
mouse. Give the F1
4. Cross a homozygous dominant black mouse
with a white mouse. Give the F2.
5. Cross two carriers (Nn) for cystic fibrosis
6. Cross a normal (NN) with an affected (nn) for
cystic fibrosis.
7. Cross a normal with a carrier for tay-sachs
*When finished with correct answers checked by a
teacher, pair up with someone who needs help.
1.