Meiosis and Heredity
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Transcript of Meiosis and Heredity
MEIOSIS10.1
Making gametes…
http://waynesword.palomar.edu/lmexer2a.htm
Review Questions1. 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?
46 chromosomes
46 + 46 = 92; a developing embryo would not survive if it contained 92 chromosomes.
Sperm and egg should each have 23 chromosomes.
Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htmFamily http://babyhearing.org/Parenet2Parent/index.asp
Remember from Chapter 1:CHARACTERISTICS OF LIVING THINGS ALL LIVING THINGS __________
REPRODUCE
ASEXUAL REPRODUCTIONBacteria reproduce using__________________________________
Budding & regeneration are used by plants and animals to reproduce asexually (mitosis)
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookmito.html
http://fig.cox.miami.edu/~cmallery/150/mitosis/c7.13.2.hydra.jpg
Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm
BINARY FISSION
BINARY FISSION & MITOSIS
Produces cells that are __________ copies of parent cell
identical
ADVANTAGES OF ASEXUAL REPRODUCTION
Can make offspring faster
Don’t need a partner
http://www.mrgrow.com/images/cutting.jpg
DISVANTAGES OF ASEXUAL REPRODUCTION
ALL ALIKE
Species CAN’T change and adapt
One disease can wipe out whole population
http://www.mrgrow.com/images/cutting.jpg
SEXUAL REPRODUCTION
Combines genetic materialfrom 2 parents (sperm & egg)so offspring aregenetically __________ from parents
DIFFERENT
Family image from: http://babyhearing.org/Parenet2Parent/index.asp
ADVANTAGES OF SEXUAL REPRODUCTION
Allows for variation in population
Individuals can be different
Provides foundation for EVOLUTION
Allow species to adapt to changes intheir environment
http://naturalsciences.sdsu.edu/classes/lab8/spindex.html
EGG + SPERM
If egg and sperm had same number of chromosomes as other body cells . . . baby would have too many chromosomes!
http://www.angelbabygifts.com/Image by Riedell Image by Riedell
http://www.acmecompany.com/stock_thumbnails/13217.forty-six_chromosomes.jpg
MEIOSIS is the way…to make cells with ½ the number of chromosomesfor sexual reproduction
http://waynesword.palomar.edu/lmexer2a.htm
HOMOLOGOUS CHROMOSOMESImage modified by Riedell • SAME SIZE
• SAME SHAPE• CARRY GENES for the SAME TRAITS
• BUT ______________! (Don’t have to have the SAME CHOICES)
http://sps.k12.ar.us/massengale/genetics%20tutorial.htm
NOT IDENTICAL
DIPLOID & HAPLOIDMost cells have 2 copies of each chromosome = ______________
(one from mom; one from dad)
All BODY (___________) cells are diploid
DIPLOID 2n
HOMOLOGOUSCHROMOSOMES
= SOMATIC
DIPLOID & HAPLOIDSome cells have only one copy of each chromosome = _____________
All sperm and egg cells are haploid
HAPLOID 1n
MITOSIS• Makes ___ cells genetically _________ to parent cell & to each other
• Makes ___ cells• Makes __________• Used by organisms to: increase size of organism, repair injuries, replace worn out cells
http://waynesword.palomar.edu/lmexer2a.htm
2identical
2n
SOMATIC (body)
MEIOSIS• Makes ____ cells genetically different from parent cell & from each other
• Makes _____ cells• Makes ______________
• Used for ____________
4
1n Germ cellsOR Gametes (sperm & eggs)
sexual reproduction
http://waynesword.palomar.edu/lmexer2a.htm
WHAT MAKES MEIOSIS DIFFERENT ?
1. SYNAPSIS & CROSSING OVER (PROPHASE I)
2. SEGREGATION & INDEPENDENT ASSORTMENT
(ANAPHASE I)
3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT…
ONLY COPIES DNA ONCE
WHAT MAKES MEIOSIS DIFFERENT ?
1.Homologous chromosomes pair up during ________________
= ______________SYNAPSIS
Images modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
This group of FOUR (4)chromatids is called a_________________TETRAD
PROPHASE I
WHAT MAKES MEIOSIS DIFFERENT?
1. Exchange of DNA betweenhomologous pairs = _____________during PROPHASE I
CROSSING OVER
Allows shuffling of genetic material
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
CROSSING
OVER
Image modified by Riedell
• Allows for_________________in different combinations
• After crossing over, chromatid arms are________________ anymore
http://sps.k12.ar.us/massengale/genetics%20tutorial.htm
rearranging of DNA
NOT IDENTICAL
WHAT MAKES MEIOSIS DIFFERENT ?
2.Separation during ANAPHASE I
INDEPENDENT ASSORTMENT
Separates gene choices and allows shuffling of genetic material
SEGREGATION &
SEGREGATION(Anaphase I)
SEGREGATION & CROSSING OVERtogether make even more combinations
http://waynesword.palomar.edu/lmexer2a.htm
INDEPENDENT ASSORTMENT
http://fig.cox.miami.edu/~cmallery/150/mitosis/c13x9independent-assortment.jpg
INDEPENDENT ASSORTMENTat ANAPHASE I
Lots of different combinations are possible!This is why you don’t look exactly like your brothers and sisters even though you share the same parents!
WHAT MAKES MEIOSIS DIFFERENT ?
Crossing over Segregation Independent assortment
are ALL ways MEIOSIS results in =______________________________
So daughter cells are ______________from parents and from each other
differentGENETIC RECOMBINATION
WHAT MAKES MEIOSIS DIFFERENT ?
3. Skip INTERPHASE II (No S) CELL DIVIDES TWICE, BUT … ONLY COPIES ITS DNA ONCE
G1 G2S P M A T C
G1
MITOSIS:
MEIOSIS:
S G2 P M A T CP M A T C
( I )
( II )
Go to Section:
Meiosis I
Section 11-4
Figure 11-15 Meiosis
Go to Section:
Meiosis I
Section 11-4
Figure 11-15 Meiosis
Meiosis I
Go to Section:
Meiosis I
Section 11-4
Figure 11-15 Meiosis
Meiosis I
Go to Section:
Section 11-4
Figure 11-15 Meiosis
Meiosis I
Go to Section:
Section 11-4
Figure 11-15 Meiosis
Meiosis I
Go to Section:
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe 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.
Section 11-4
Figure 11-17 Meiosis II
Go to Section:
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe 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.
Section 11-4
Figure 11-17 Meiosis II
Go to Section:
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe 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.
Section 11-4
Figure 11-17 Meiosis II
Go to Section:
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe 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.
Section 11-4
Figure 11-17 Meiosis II
Go to Section:
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe 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.
Section 11-4
Figure 11-17 Meiosis II
Ways Meiosis is different?• Homologous pairs match up & trade DNA
(SYNAPSIS & CROSSING OVER) in PROPHASE I
•SEGREGATION
& INDEPENDENT ASSORTMENT in Anaphase I
create genetic recombination• Skipping INTERPHASE II- (Dividing TWICE but copying DNA once)
produces 1n cells
The Work of Gregor Mendel
10.2
http://www.jic.bbsrc.ac.uk/germplas/pisum/zgs4f.htm
http://sps.k12.ar.us/massengale/genetics%20tutorial.htm
Transmission of characteristics from _______________________is called ___________________.
The science that studies _____characteristics are _________ from onegeneration to the next is called___________________
heredity
Genetics
parents to offspring
howpassed on
The __________________ is _________________,
a monk whose _________ of genetic traits was the beginning of our _________________ of _____________________.
Gregor Mendel
http://www.jic.bbsrc.ac.uk/germplas/pisum/zgs4f.htm
Father of Genetics
study
understandinghow genes work
Mendel designed
____________ using
__________ in the
monastery garden
_______ part of flower makes
___________ (sperm)
__________ part of flower makes
_______ cells
Pea plants
Pollen
http://www.cedarville.edu/academics/education/resource/schools/chca/2scideb/debwebpv.htm
http://hus.yksd.com/distanceedcourses/YKSDbiology/lessons/FourthQuarter/Chapter11/11-1/images/MendelExperiment.gif
experiments
MALE
FEMALE
egg
In pea plants, the pollen normally joins with an egg from the _______ plant (=_______________ ) so seeds have “_________________”
Self pollination
http://hus.yksd.com/distanceedcourses/YKSDbiology/lessons/FourthQuarter/Chapter11/11-1/images/MendelExperiment.gif
same
ONE parent
MENDEL’S PEA EXPERIMENTS
Mendel started his experiments with peas that were _________________
= if allowed to _________________ they would produce ____________________ to themselves.
http://hus.yksd.com/distanceedcourses/YKSDbiology/lessons/FourthQuarter/Chapter11/11-1/images/MendelExperiment.gif
true breeding
self pollinate
offspring identical
MENDEL’S PEA EXPERIMENTSMendel ____________________making parts and ____________from _______ plant.
This allowed him to_____________ plantswith ______________ characteristics and ________ the results
http://hus.yksd.com/distanceedcourses/YKSDbiology/lessons/FourthQuarter/Chapter11/11-1/images/MendelExperiment.gif
different
removed pollenadded pollen
another
cross-breed
study
A _____________________ is called a ____________
Mendel ______________ in peas.
specific characteristic
trait
Pearson Education Inc,; Publishing as Pearson Prentice Hall
studied 7 traits
MENDEL’S EXPERIMENTS
____ generation (_________)
____ generation
(______= offspring)
___ generation
P1
F1
F2
parental
filial
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
Section 11-1
Principles of Dominance
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
Section 11-1
Principles of Dominance
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
Section 11-1
Principles of Dominance
When Mendel ______________ PLANTS with 2 ______________ traits:(EX: Tall crossed with short)
He always found same pattern: 1. ONLY ______ trait ____________
in the ____ generation BUT . . .
2. ___________ trait ____________ in the ____ generation
in a _________ ratio
ONE showedF1
F2
3:1
crossed PURE contrasting
Missing returned
PATTERNS ARE THE KEY
Image modified from:http://www.laskerfoundation.org/rprimers/gnn/timeline/1866.html http://www.accessexcellence.org/AB/GG/mendel.html
Mendel decided that there must be a __________________ that ________each trait and that
__________ must be able to _______ the other.
pair of FACTORS
one factor
control
HIDE
We now know that Mendel’s ________________ carried onthe pair of________________
_________________
factors are geneshomologouschromosomes
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
________ gene _______ for atrait are called ___________.ALLELES
http://sps.k12.ar.us/massengale/genetics%20tutorial.htm
DIFFERENT
CHOICES
__________________ = An allele that ________ the presence of another allele
__________________ = An allelethat __________________ the
presence of another allele
DOMINANT
RECESSIVE
HIDES
is hidden by
DOMINANT/RECESSIVE_____________ allele is represented by a
____________ letter.(usually the first letter of the trait)
____________ allele is represented by the SAME
_________________ letter.
EX: Tall = ______
Short =______
capital
lower-case
T
t NOT S for short
Dominant
Recessive
HOMOZYGOUSHETEROZYGOUS
When both alleles in the pair are the _______, the organism is _______________ or __________
EX: ____ or ___
When both alleles in the pair are _____________, the organism is
_________________ or _____________
Ex: ____
HETEROZYGOUS HYBRID
HOMOZYGOUS PURESAME
TT tt
DIFFERENT
Tt
PHENOTYPE/GENOTYPE
The ________________ of an organism is its _____________
The ____________ of an organism is
its _____________
GENOTYPE
PHENOTYPE
genetic makeup
appearance
Why did the recessive trait disappear in the F1 generation and reappear in the F2?
Image modified from:http://www.laskerfoundation.org/rprimers/gnn/timeline/1866.html
The pattern corresponds to the ____________ of ______________ during____________________MEIOSIS
movementchromosomes
REMEMBER
_____________
chromosomes
________________
during
ANAPHASE I
= _________________SEGREGATIONImage modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
HOMOLOGOUS
SEPARATE
____ offspring __________ an allele for tallness from their _______ parent and an allele for shortness from their ________ parent.
The F1 plants ALL ___________ but are ___________ an
allele for _________
TALL
Images from: BIOLOGY by Miller & Levine; Prentice Hall Publishing ©2006
SHORT
LOOK TALL
F1 received
carrying shortness
alleles are separated when the F1 plants ______________
When these gametes recombined to make the F2 generation, the _____________ trait _______________ in ¼ of the offspring
EXPLAINING the F1 CROSS
LAW OF ___________________SEGREGATION
Image from: BIOLOGY by Miller & Levine; Prentice Hall Publishing ©2006
recessive
made gametes
reappears
MAKING A CROSS for only a __________ trait =____________________MONOHYBRID CROSS
ONE GENE
MAKING A CROSS with ___________________=____________________DIHYBRID CROSS
TWO gene traits
LAW OF __________________________
the factors are distributed to gametes independently of other factors
INDEPENDENT ASSORTMENT
Image modified from: http://anthro.palomar.edu/mendel/mendel_1.htm
PROBABILITY & PUNNETT SQUARES
10.2
Tossing Coins - Mini Activity• If you toss a coin, what is the
probability of getting heads? Tails? • If you toss a coin 10 times, how many
heads and how many tails would you expect to get? – Working with a partner, have one person
toss a coin ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.
1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?
2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?
Results will vary, but should be close to 5 heads
and 5 tails.
The results for 20 tosses may be closer to the predicted 10 heads and 10 tails.
3. If you compiled the results for the whole class, what results would you expect?
4. How do the expected results differ from the observed results?
The results for the entire class should be even
closer to the number predicted by the rules of probability.
The observed results are usually slightly
different from the expected results due to
Experimental error.
It can be written as a:
Fraction ____
Percent ____
Ratio ___
____________________is the __________ that a
particular _________________
PROBABILITY
1/4
25%
1:4
likelihoodevent will occur
COIN FLIPThere are 2 possible
outcomes:
HEADS TAILS
capital
http://www.arborsci.com/CoolStuff/CoinFlip.jpg
The chance the coin will land on either one is:
____ ____ ____
Alleles segregate randomly just like a coin flip. . . So we can use probability to predict outcomes of genetic crosses.
1/2 50% 1:2
PROBABILITIES_____ outcomes ______ affect _________ones
_____________works ______ in ___________ a ________ number of events.
If last coin flip was heads… there is still a 50/50 chance the next flip will be heads too.
The more flips. . . The closer results will be to
the expected 50:50 average.
PAST DON’T FUTURE
Probability best predictinglarge
DOMINANT/RECESSIVE_____________ allele is represented by a
____________ letter.(usually the first letter of the trait)
____________ allele is represented by the SAME
_________________ letter.
EX: Tall = ______
Short =______
capital
lower-case
T
t NOT S for short
Dominant
Recessive
HOMOZYGOUSHETEROZYGOUS
When both alleles in the pair are the _______, the organism is _______________ or __________
EX: ____ or ___
When both alleles in the pair are _____________, the organism is
_________________ or _____________
Ex: ____
HETEROZYGOUS HYBRID
HOMOZYGOUS PURESAME
TT tt
DIFFERENT
Tt
PHENOTYPE/GENOTYPE
The ________________ of an organism is its _____________
The ____________of an organism is
its _____________
GENOTYPE
PHENOTYPE
genetic makeup
appearance
MAKING A CROSS for only a __________ trait =____________________
A Punnett square for a MONOHYBRID CROSS looks like this:
MONOHYBRID CROSSONE GENE
PUNNETT SQUARESare used to show possible offspring
from a cross between 2 parents
_______________ go at top and on left side
Boxes show _______________________________
T T
T
t
possible offspring combinations
Parent alleles
1. ___________ what _________________ are2. ________correct__________ square __________3. ______ possible_______________________4. ______ boxes with _____________________5. Determine ____________of_____________& ____________
STEPS FOR MAKING CROSSES
Figure out parent allelesChoose Punnett sizePut in parent gametesFill in offspring combinations probabilities phenotypes
genotypes
IN PEA PLANTS
Tall is dominant over short
TALL = ____
SHORT = ____T
tLET’S MAKE A CROSS!
PURE TALL PURE SHORTX
PURE TALL parentWhat are the parent alleles?
T T _________
T T
HOMOZYGOUS
What gametes can it make?
PURE SHORT parent What are the parent alleles?
t t _________
t t
HOMOZYGOUS
What gametes can it make?
GENOTYPE _____ PHENOTYPE _______
_____ of the offspring
____ %
___/4
will be
T T
t
t
T t T t
T t T t
Tt TALL
ALL
100
4
HYBRID TALL parents What are the parent alleles?
T t _________
T t
HETEROZYGOUS
What gametes can it make?
GENOTYPES
¼ = _____
½ = _____
¼ = _____
T t
T
t
T T T t
T t t t
PHENOTYPES ____ or ____% _________ ____ or ____% _________
TT
75
Tt
tt
3/41/4 SHORT
TALL25
PRACTICE MAKING GAMETES for a MONOHYBRID CROSS
Tall = ____ Round seeds = ___
Short = ____ Wrinkled seeds = ___
T
tR
r
Homozygous Tall parent =
What gametes can it produce?
What are the possible gametes?
T T
T T
PURE wrinkled parent =
What gametes can it produce?
What are the possible gametes?
rr
r r
Heterozygous Round parent =
What gametes can it produce?
What are the possible gametes?
R r
R r
Hybrid Tall parent =
What gametes can it produce?
What are the possible gametes?
Tt
T t
DIHYBRID CROSSES(2 traits)
http://mac122.icu.ac.jp/BIOBK/BioBookgenintro.html
Mendel also asked the question?
Does the gene that determines if a seedis round or wrinkled have anything todo with the gene for seed color?
Must a seed that is yellow also be round?
MAKING A CROSS with ___________________=____________________
A Punnett square for a DIHYBRID CROSS looks like this:
DIHYBRID CROSSTWO gene traits
Section 11-3
Figure 11-10 Independent Assortment in Peas
1. ___________ what _________________ are2. ________correct__________ square __________3. ______ possible_______________________4. ______ boxes with _____________________5. Determine ____________of_____________& ____________
LET’S MAKE A DIHYBRID CROSSHOMOZYGOUS
ROUND YELLOW
rryy
HOMOZYGOUSWRINKLED GREEN
Figure out parent allelesChoose Punnett sizePut in parent gametesFill in offspring combinations probabilities phenotypes
genotypes
RRYY
LAW OF __________________________
the factors are distributed to gametes independently of other factors
INDEPENDENT ASSORTMENT
Image modified from: http://anthro.palomar.edu/mendel/mendel_1.htm
r r y y
HOMOZYGOUS WRINKLED GREEN
PRACTICE MAKING GAMETESWHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE?
Each gamete shouldget one of each kindof gene
___________ ____________ _____________ _____________r y r y r y r y
R R Y Y
HOMOZYGOUS ROUND YELLOW
PRACTICE MAKING GAMETESWHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE?
Each gamete shouldget one of each kindof gene
___________ ____________ _____________ _____________R Y R Y R Y R Y
ry ry ry ry
RY
RY
RY
RY
100% of offspring = _______ genotype _______________________ phenotype
RrYyROUND YELLOW
RrYy RrYy RrYy RrYy
RrYy RrYy RrYy RrYy
RrYy RrYy RrYy RrYy
RrYy RrYy RrYy RrYy
R r Y y
HETEROZYGOUSROUND YELLOW
PRACTICE MAKING GAMETESWHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE?
Each gamete shouldget one of each kindof gene
___________ ____________ _____________ _____________R Y r y r Y R y
R r Y y R r Y y
HETEROZYGOUSROUND YELLOW
HETEROZYGOUSROUND YELLOW
MAKE ANOTHER CROSS
X
POSSIBLE PARENT GAMETES?
RY ry RyrY
RY Ry rY ry
RY
Ry
rY
ry
Sign of a ______________________ cross is a_____________ ratio in offspring.9:3:3:1
____ Round & Yellow
____ Round & green
____ Wrinkled & yellow
____ wrinkled & green
9
3
3
1
RRYY RRYy RrYY RrYy
RRYy RRyy RrYy Rryy
RrYY RrYy rrYY rrYy
RrYy Rryy rrYy rryy
heterozygous dihybrid
__________ratio is a clue that it’s a ____________________________cross
____ ____________ TRAIT 1 ; ____________ TRAIT 2 ____ ____________ TRAIT 1; _____________ TRAIT 2
____ ____________ TRAIT 1; _____________ TRAIT 2
____ ____________ TRAIT 1; _____________ TRAIT 2
9
3
3
1
9:3:3:1
HETEROZYGOUS TWO gene
dominant dominant
dominant recessive
recessive dominant
recessive recessive
PRACTICE MAKING GAMETESfor DIHYBRID CROSSES
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html
pure round & pure tall = __________
____ ____ _____ ______
What gametes can it produce?
What are the possible gametes?
R R T T
R T R T
R T R T
Heterozygous Tall = __________
& pure round
____ ____ _____ ______
What gametes can it produce?
What are the possible gametes?
T t R R
T R T R
t R t R
Hybrid tall = __________
& pure wrinkled
____ ____ _____ ______
What gametes can it produce?
What are the possible gametes?
T t r r
T r T r
t rt r
Heterozygous tall = __________
& hybrid round
____ ____ _____ ______
What gametes can it produce?
What are the possible gametes?
T t R r
T R T r
t rt R
Gene Linkage & Polyploidy10.3
Genetic Recombination
New combination of genes created by _________________ and __________________________
Formula __n = possible gamete combinations
n = number of _________________________
CROSSING OVERINDEPENDENT ASSORTMENT
CHROMOSOME PAIRS
2
Example: peas have 7 chromosome pairs.27 = _____ possible combinations.128 x 128 = __________ possible
combinations after fertilization
Humans have ___ chromosomes
223 x 223 = ____+ trillion after fertilization!
12816,384
23
70
GENE LINKAGE
Genes located ________ to each other on the same chromosome will usually travel ___________ during gamete formation
Exceptions to Mendel’s law of ________________________________.
CLOSE
TOGETHER
INDEPENDENT ASSORTMENT
Genes A and B (a and b) are close together and are more likely to travel together during gamete formation.
Chromosome Maps
Maps show relative____________ of genes
Crossing over occurs more often between genes that are ______________
Chromosome maps created by using ______________________
POSITIONS
FAR APART
CROSSOVER DATA
Letters show relative position of genes
Crossing over is much more likely to occur between A and ___ than
A and ____
C
B
___________________One or more ____________ of chromosomes
_______________ organisms would be 3n
_____________ in humans and rarely occurs in animals
Sometimes in earthworms and __________________
POLYPLOIDY
EXTRA SETS
LETHAL
GOLDFISH
TRIPLOID
Polyploidy1/3 of all ________________________ are
polyploid
Commercial wheat, commercial oats (6n)
Commercial sugar cane (8n)
Polypoloidy plants often have increased ______ and vigor.
FLOWERING PLANTS
SIZE
TRY THIS! Sample Data for Genes A, B, C, & D.・ Draw a line 1 cm longer than
the greatest crossover frequency making a mark every cm.
・ 1% crossover frequency = 1 cm・ Start with the gene pair farthest
apart and plot their letters on the line. (B and D)
・ Plot genes A and C on your line next. They should be between B and D. ・
Use the crossover frequencies to see how far they are from
each gene (AD = 4%, so A is 4 cm from D)