Transcript Meiosis - najicschoolbus

3-5-10
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IN
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What are gametes?
Define Meiosis
3-05-10
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Through
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Genetic disorders
Explain Part A pg. 431
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OUT
Read 498-502
Complete the meiosis
worksheet
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5. In cocker spaniels, black B is dominant over
red b. Solid color S is dominant over white
spotting s. A red male was mated to a black-andwhite female. They had five puppies, as follows:
one black, one red, one black and white, and two
red-and-white.
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A. What genetic principle explains the
phenotypes of these offspring?
B. Write a one or two paragraphs to describe
how that principle worked in this cocker
spaniel family. Include the following terms;
gene, phenotype, dominant trait, recessive
trait, chromosome, allele, genotype
Open your book to page 496
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With your group divide two genetic disorders
between pairs
Read and take notes about your decided
disorder
Share your information with the other pair
Check with my notes to see you have all
important information
Case studies of two genetic
disoders
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Huntington’s disease- a dominant genetic
disorder that causes degeneration of the
central nervous system.
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Symptoms occur after 35
NO cure
Disease causes the brain and nerves to slowly
shutdown for up to 15 years, then person dies
Genotype Hh or HH
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Cystic fibrosis -- a recessive genetic disorder
that affects the respiratory system.
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Symptoms show at birth
Lungs are clogged with thick mucus
Affects digestive system as well because of mucus
Possibilities range between races
Genotype cc
NO cure, person usually dies at a young age
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However, antibiotics, vapor therapy, and chest thumping help
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Other genetic disorders to research:
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Down syndrome
Sickle-cell
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Would you test to see if you and your partner
carry genetic disorders?
What are the advantages of knowing you
have alleles for genetic disorders?
What are the disadvantages of knowing you
have alleles for genetic disorders?
Understanding Patterns of
Inherited Patterns
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Gametes -- How genetic information is
passed on from one generation to the next
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Sperm(male) Egg(Female)
Only have half the information
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23 Chromosomes
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Meiosis --- process that reduces the amount
of genetic information in a cell by half.
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How gametes are produced
VERY important process, because it reduces the
amount of genetic information so that it doesn’t
continue to build up
Explains why patterns of inheritance often are
predictable
Meiosis: The Mechanism
behind patterns of inheritance
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In all cells(46 chromosomes), chromosomes
are in pairs; This is called diploid (2n)
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For each pair;
one chromosome from mom
one chromosome from dad
Gamete(23 chromosomes) only contain 1
chromosome from each pair; This is called
haploid (n)
MOM
n
n
2n
DAD
Chromosome from dad n
Chromosome from mom n
DNA synthesis: each chromosome doubles
2n
Cell begins to divide in half
Cell division 1
n
n
Cell division 2
n
Cell division 2
n
n
n
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Before meiosis, each chromosome doubles; DNA
synthesis
First cell division occurs and doubled chromosomes
separate
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Each offspring cell contains one doubled chromosome
Second cell division occurs and doubled cell
separates into two cells
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Results in a total of 4 offspring cells (daughter)
Each offspring cell contains one chromosome from original
pair
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Principle of segregation --- during meiosis,
chromosome pairs separate so that each of
the two alleles for any given trait appears in a
different gamete.
Gg
G
Gg
g
G
g
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Watch DVD “Meiosis” and add additional
notes to help with you understanding of the
concept
Meiosis web animation
Tracking Genes through
Meiosis
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Use figure 11.9, your journal notes, and
modeling clay to track how meiosis affects
the distribution of the 4 chromosomes.
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1. On a large sheet of paper, draw circles to
represent a cell undergoing meiosis. On the last set
of four circles. Refer to page 500
2. Use modeling clay to form 2 pairs of
chromosomes about as thick as a pencil. Make one
pair longer than the other.
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Red is from female parent
Blue is from male parent
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3. Use the letters provided and press them gently
into clay.
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C= cream eye c= tan eye
W= white wing w=spotted wing
Eye color on long chromosome and Wing color on short
chromosome
4. Place your chromosome models in the large
circle at the top of your sheet of paper
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5. Prior to meiosis, the chromosomes
replicate. Make more clay models with labels
to represent this step.
6. Using your cell diagram circles, move your
chromosome models through the process of
meiosis.
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In your journal, draw the chart you created
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7. Answer the following questions:
A. In your model, what is the genotype of each
sperm for eye color and wing color?
B. What other genotypes are possible?
C. At what point would you change how you
positioned your chromosome models to obtain the
other possible genotypes?
Interphase
Interphase (synapse)
Meiosis I
Meiosis II
Interphase (synapse)
Interphase (synapse)
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Crossing-over
Meiosis I
Meiosis II