Biology Chapter 11

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Biology Chapter 11

• Introduction to Genetics Mendel and Meiosis

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IQ 1
1. How many chromosomes would a sperm or an egg
contain if either one resulted from the process
of mitosis? 2. If a sperm containing 46
chromosomes fused with an egg containing 46
chromosomes, how many chromosomes would the
resulting fertilized egg contain? Do you think
this would create any problems in the developing
embryo? 3. In order to produce a fertilized egg
with the appropriate number of chromosomes (46),
how many chromosomes should each sperm and egg
have?
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Section 11-4 Meiosis
I. MEIOSIS A. Meiosis process of
_________________________ in which the number of
chromosomes per cell is cut in 1/2 and the
homologous chromosomes that exist in a diploid
cell are separated. (and produce haploid
cells)   B. Purpose
Reduction Division
Form gametes (egg and sperm)
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• II. DIPLOID AND HAPLOID CHROMOSOME NUMBER
•  
• A. During ________________ the genetic material
  from one parent combines with genetic material
  from another
• Example A fruit fly has 8 chromosomes
• A set of 4 came from the female fly
• A set of 4 came from the male fly

fertilization
B. The two sets of chromosomes are said to be
 
homologous a female chromosome has a
corresponding male chromosome.
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Diploid (2n)

• C. contain both sets of
  homologous chromosomes
• D. contain 1 set only
• Male gamete
• Female gamete
•  

Haploid (n)
Sperm (n) 23 chromosomes
Egg (n) 23 chromosomes
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Question If we start with a diploid cell, how do
we get an organism that produces haploid
gametes? Answer   Example what if    

Meiosis (aka reduction division) 1 replication
2 divisions
8
46
Human
Fruit fly
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92
8
Duplicated chromosomes
46
8
46
Duplicated chromosomes
4
4
4
4
23
23
23
23
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PROCESS OF MEIOSIS (DIVIDED INTO 2 STAGES
MEIOSIS I IIINTERPHASE growth, DNA
synthesis, protein production, organelle
production
A. Meiosis I    
1.
homologous chromosomes
pair up (Form tetrads)

2. nucleoli disappear  

3. nucleus disappears
4.
crossing-over occurs portions of chromatids
exchange genetic material
2n (diagram 277)
prophase I
 
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Crossing-Over
Crossing Over exchange of genetic material
between homologous chromosomes
Go to Section
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Crossing Over
Go to Section
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Crossing Over
Crossing-Over
Go to Section
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metaphase I
1. homologous pairs (tetrads) line up at the
equator
   2. spindles attach to chromosomes independent
assortment occurs
  anaphase I
1. spindles pull the homologous chromosomes
toward opposite ends of the cell
Key point homologous pairs separate, cell now
haploid
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    Telophase I
1. Nuclear membranes reform
  2. cell begins to separate into two
new haploid cells     3. 2 haploid daughter
cells
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Meiosis I
Figure 11-15 Meiosis
Section 11-4
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with its corresponding
homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward
the opposite ends of the cell.
Go to Section
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Meiosis I
Figure 11-15 Meiosis
Section 11-4
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with its corresponding
homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward
the opposite ends of the cell.
Go to Section
15
Meiosis I
Figure 11-15 Meiosis
Section 11-4
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with its corresponding
homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward
the opposite ends of the cell.
Go to Section
16
Meiosis I
Figure 11-15 Meiosis
Section 11-4
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with its corresponding
homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward
the opposite ends of the cell.
Go to Section
17
B. Meiosis II (similar process as mitosis no
replication)
Prophase II
Metaphase II
Anaphase II
Telophase II/ Cytokinesis
n
n
n
n
RESULT 4 haploid daughters that are
genetically different!!
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Meiosis II
Figure 11-17 Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
Go to Section
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Meiosis II
Figure 11-17 Meiosis II
Section 11-4
Prophase II
Metaphase II
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
Anaphase II
Telophase II
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
Go to Section
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Meiosis II
Figure 11-17 Meiosis II
Prophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
Metaphase II
Anaphase II
Telophase II
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
Go to Section
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Meiosis II
Figure 11-17 Meiosis II
Section 11-4
Prophase II
Metaphase II
Anaphase II
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
Telophase II
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
Go to Section
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Meiosis II
Figure 11-17 Meiosis II
http//www.sumanasinc.com/webcontent/anisamples/ma
jorsbiology/meiosis.html
Section 11-4
Prophase II
Metaphase II
Anaphase II
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
Telophase II
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
Go to Section
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IV. GAMETE FORMATION (refer to page 278) A.
Males 1.   2. male gametes produced by a
process called _________________   B. Females 1.
4 haploid cells are produced but only
1-haploid cell is a 3-produce     2.
female gametes produced by a process called
_______________
The 4 haploid cells (gametes) sperm
spermatogenesis
viable egg
polar bodies caused by uneven cytoplasmic
division
oogenesis
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Chapter 18 Sexual Reproduction, Meiosis, and
Genetic Recombination
Figure 18-10 Gamete Formation
(a) In the male, all four haploid products of
meiosis are retained and differentiate into
sperm. (b) In the female, both meiotic divisions
are asymmetric, forming one large egg cell and
three (in some cases, only two) small cells
called polar bodies that do not give rise to
functional gametes. Although not indicated here,
the mature egg cell has usually grown much larger
than the oocyte from which it arose.
1999 by Addison Wesley LongmanA division of Pearson Education
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V. COMPARING MITOSIS AND MEIOSIS A. Mitosis
results in the production of two genetically
identical diploid cells, whereas meiosis produces
four genetically different haploid cells.
http//biologyinmotion.com/cell_division/
4 haploid cells
2 diploid cells
gametes
Body cells
2
1
1
1
 
Sexual reproduction
Growth, replacement, repair, asexual reproduction
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Section 11-1 Standards addressed CA 3.b.
Students know the genetic basis for Mendels laws
of segregation and independent assortment.
National 7 2.c. Students know an inherited trait
can be determined by one or more genes. 7.2.d.
Students know plant and animal cells contain many
thousands of different genes and typically have
two copies of every gene. The two copies (or
alleles) of the gene may or may not be identical,
and one may be dominant in determining phenotype
while the other is recessive. B1. 2.d. Students
know new combinations of alleles may be generated
in a zygote through the fusion of male and female
gametes (fertilization). Key Ideas What is the
principle of dominance? What happens during
segregation?
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INTRODUCTION TO GENETICS   I. The work of Gregor
Mendel A. the scientific
study of heredity   B. Heredity    II.
Gregor Mendel's Peas A. In the 1800's,
_____________________________ (an Austrian Monk)
conducted the first scientific study of heredity
using pea plants.   B. Pea plants contain both
male (pollensperm) and female (eggs)
reproductive parts.  
Genetics

Passing genes from generation to generation
Gregor Mendel

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Flowering Plant Structures Pea Plant
C. _______________ Joining of male and female
reproductive cells
Fertilization
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D. _________________ a pea plant whose pollen
fertilizes the egg cells in the very same
flower.   1. Mendel discovered that some
plants ___________ for certain traits   2.
Trait Example seed color, plant
height   3.True breeding (a.k.a. pure)

Example Short
plants that self pollinate for
generations always produce offspring that
were pure for shortness.
Self-pollination
Bred True
Specific Characteristics
Peas that are allowed to self-pollinate produce
offspring identical to themselves
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Cross Pollination
Self pollination
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  E.
_______________ male sex cells from one
flower pollinate a female sex cell on a
different flower.
Cross-pollination
F. Mendel manually cross pollinated pea plants,
removing the male parts to ensure no
self-pollination would occur. Through a series of
experiments, Mendel was able to make discoveries
of basic principles of heredity. 1. principle
of 2. principle of 3. principle of
Dominance
Segregation
Independent Assortment
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III. Experiments Mendel performed
A.  Mendel studied __ different traits in pea
plants each with 2 contrasting characters. (refer
to page 264)   B.  Each trait Mendel studied was
controlled by one gene.   C.  Different forms of
a gene (trait) Example Gene for plant height
has 2 alleles
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Alleles
Dominant T tall Recessive t short
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Mendels Seven Crosses on Pea Plants
Figure 11-3 Mendels Seven F1 Crosses on Pea
Plants
Section 11-1
Seed Shape
Flower Position
Seed Coat Color
Seed Color
Pod Color
Plant Height
Pod Shape
Round
Yellow
Gray
Smooth
Green
Axial
Tall
Wrinkled
Green
White
Constricted
Yellow
Terminal
Short
Round
Yellow
Gray
Smooth
Green
Axial
Tall
Go to Section
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Mendel Experiment 1
TALL
SHORT
tt
TT
TALL
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Conclusion
genes
        individual factors (now known as
_________)           the factors
 ________________________________ some alleles
are dominant (expressed traitwritten as a
capital letter ex. T) some are recessive
(hidden/masked trait written as a lower case
letter ex. t)    From these conclusions, Mendel
wanted to continue his experiments to see what
happened to the recessive trait  
did not blend
Principle of Dominance
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Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
Go to Section
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Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
Go to Section
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Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
3 tall 1 short
Go to Section
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Conclusion         ___________________________
The reappearance of the recessive allele
indicated that at some point the allele for
shortness separated from the allele for tallness.
Mendel suggested that the alleles separated
during the formation of the sex cells
(gametes).During meiosis.    
Principle of Segregation
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 IV. PROBABILITY AND PUNNETT SQUARES
The likelihood that a particular event will occur
          A. Probability         B.
Probability Example 1 If you
flip a coin, what is the probability of landing
on heads? Probability (side that has a
head on it) (
opportunities on a coin head or tails)   Example
2 If you flip a coin 3 times what is the
probability of landing on heads? Probability
 
of times a particular event occurs of
opportunities for the event to occur ( of trials)
1
2
2
½ x ½ x ½ 1/8
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A. Each flip is       B.  The      
C. The principles of probability can be used
to  
independent of the next. Past outcomes do not
affect future ones. Similar to alleles that
segregate randomly, like a coin flip.
larger the number of trials the closer you get to
the expected outcomes
predict the outcomes of genetic crosses.
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IV.  PUNNETT SQUARES Use of Punnett squares help
determine the probable outcomes of genetic
crosses.   New vocabulary to help with Punnett
squares  -Homozygous    -Heterozygous
  -Genotype   -Phenotype -Hybrids

Having 2 identical alleles (TT, tt)
Having 2 different alleles (Tt)
Genetic makeup of an organism (TT, tt, Tt)
Physical appearance (tall or short)
The offspring resulting from a cross between
parents of contrasting traits
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        Example of a Punnett square Parent
(P) cross homozygous tall( ) x homozygous
short( )    
tt
TT
t
t
T
Tt
Tt
T
Tt
Tt
F1 offspring
  Probability of producing homozygous tall
offspring? Probability of producing hybrid?
 
0/4
4/4
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• IV.  PROBABILITY AND SEGREGATION
• For fun, lets cross F1s to see if Mendels
  assumptions about segregation are correct
• Tt x Tt
•  
•  

T
t
T
TT
Tt
t
tt
Tt
If the alleles segregate during meiosis, then the
probable outcomes will be TT Tall Tt S
hort tt Ratio tallshort  
1/4
3
2/4
1
31
1/4
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Mendel was correct in his assumptions about
Segregration
Conclusion
IV. PROBABILITY AND INDEPENDENT
ASSORTMENT A. Mendel wondered if one pair of
alleles affected the segregation of another pair
of alleles.    B.The two factor cross Mendel
crossed RRYY x rryy (P)(akatwo trait cross)
All offspring are
Do round seeds have to be yellow?
Hybrid (RrYy) (F1)
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A.   Then he crossed the hybrids (F1) RrYy
x RrYy   Punnett square formatting rules for
2 trait crosses 1. Determine the possible
gametes produced by the parents. 2
methods   a.    F- RrYy O-
I- L-
irst two
(RY)
(Ry)
utside two
(rY)
nside two
(ry)
ast two
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  a.  Use a punnett square. One trait on top and
the other trait on the side. Parent 1
RrYy Parent 2 RrYy  
y
Y
y
Y
RY
Ry
R
Ry
RY
R
ry
r
rY
ry
rY
r
Possible gametes Possible
gametes
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2. Place one parents gametes at the top of a
16-Punnett square and the other parents gametes
on the side of the 16-Punnett square.  
RY
Ry
ry
rY
RRYY
RRYy
RrYY
RrYy
RY
RRYy
RRyy
RrYy
Rryy
Ry
rY
RrYY
rrYy
RrYy
rrYY
rryy
rrYy
Rryy
ry
RrYy
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Section 11-3
Probability RY (round and yellow) Ry
(round and green rY (wrinkled and yellow)
ry (wrinkled and green)   Phenotype Ratio
  Conclusion
9/16
3/16
3/16
1/16
9331
Alleles for seed shape independently assort.
Go to Section
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Independent assortment
Genes for different traits can segregate
independently during the formation of gametes
    This is true if the traits you are
studying   Just by chance all 7 of Mendels
traits were on different chromosomes.
are located on different chromosomes
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Summary of Mendels Principles
1. The inheritance of biological
characteristics is determined by individual units
known as genes. Genes are passed from parents to
their offspring. 2. In cases in which two or more
forms (alleles) of the gene for a single trait
exist, some forms of the gene may be dominant and
others may be recessive. 3.  In most sexually
reproducing organisms, each adult has two copies
of each gene one from each parent. These genes
are segregated from each other when gametes are
formed. 4. The alleles for different genes
usually segregate independently of one another.
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Summary of Gregor Mendels Work
Gregor Mendel
concluded that
experimented with
Factors determine traits
Alleles are separated during gamete formation
Some alleles are dominant, and some alleles
are recessive
Pea plants
which is called the
which is called the
Law of Dominance
Law of Segregation
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Beyond Dominant and Recessive Alleles
  Key idea Some alleles are neither dominant nor
recessive, and many traits are controlled by
multiple alleles or multiple genes.  Ex. Four
Oclock flowers (see next slide)
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Incomplete Dominance in Four Oclock Flowers
Incomplete Dominance One allele is
_______________ dominant over another. Therefore
the phenotype in the heterozygous is somewhere
__________ the two homozygous phenotypes.
not completely
in between
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Incomplete Dominance in Four Oclock Flowers
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equally
Codominance both alleles contribute _________
to the phenotype. Ex. Cholesterol    
Mutliple Alleles Genes that have
_____________ alleles. This does not mean an
individual can have more than two alleles, but
that there are more than two alleles in the
_______________ for a given trait.  
Ex. Rabbit coat color, blood type
more than two
population
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Multiple Alleles and Codominance
3 Alleles iA, iB, I iA and iB are
codominant iA, iB both dominate over i
Blood Type/Phenotype
BO BB
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Polygenic Inheritance The interaction of many
genes controls one trait. It is usually
recognized in traits that show a
____________________ such as skin color, height,
and body weight.
range of phenotypes
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(No Transcript)
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Applying Mendels Principles.  Mendels
principles do not apply only to plants.  
Thomas Hunt Morgan 1. In the early ________,
Morgan (a nobel prize winning geneticist) decided
to look for a model organism to advance the study
of genetics. 2. He studied the _____________,
Drosophila melanogaster. 3. This specimen was a
good choice because   _______ and can be kept
in a small place   produce ___________ of
offspring   has only _________ of
chromosomes   they can produce a new
_______________ every 4 weeks  
1900s
fruit fly
tiny
hundreds
4 pairs
generation
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Fruit Flies (Drosophila melanogaster)
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Genetics and the environment
Genes alone ______________________ the
characteristics of an organism. The interaction
between genes and the ________________are
necessary. Ex. Consider the height of a
sunflower. Genes provide a plan for the
development of a sunflower but the condition of
the soil, climate, and water availability will
also influence the height of the sunflower.
do not determine
environment
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11-5 Gene Linkage and Gene Maps Standards
addressed CA B1 3.b students know the genetic
basis forMendels laws of segregation and
independent assortment. B1 3.d. Students know
how to use data on frequency of recombination at
meiosis to estimate genetic distances between
loci and to interpret genetic maps of
chromosomes.   Key concept What structures
actually assort independently?
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Actually ________________________ do assort
independently just as Mendel had suggested but
the _______ on the chromosomes can be
____________.   A. Linked genes 1. Genes
located on the _________ chromosome 2.
Inherited _____________ 3. Do not undergo
___________________ they don't follow Mendel's
law (Just by chance all the traits Mendel
studied were located on separate
chromosomes...none were linked.)
the chromosomes
genes
linked together
same
together
independent assortment
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B. Linkage group all the genes on a
_____________ If there are ___ pairs of
chromosomes then there are ____ linkage groups.
Humans have ____ pairs of chromosomes therefore
____ linkage groups
chromosome
4
4
23
23
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III. Crossing Over A.     If two genes are found
on the same chromosome, does it mean that they
are linked forever? NO!   Crossing over
produces ___________________   B.
Recombinants individuals with ________________
_ of genes
  recombinants.
new combinations
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IV. Gene Mapping A. Sturtevant stated that
 crossing over occurs ________________ along
the linkage groups.  the _______________ the
genes are from each other the ______________ they
will cross over  using the ______________________
_ (how often crossing over occurs), a gene
_______ can be made for each chromosome
randomly
further
more likely
frequency of recombination
map
68
B. Gene map the __________________ on a
chromosome Example gene a and gene b
cross over 20 gene a and gene c cross over
5 gene b and gene c cross over 75  
positions of genes
A
C
B
chromosome
69
Figure 11-19 Gene Map of the Fruit Fly
Exact location on chromosomes
Chromosome 2