Meiosis and Heredity

MEIOSIS
10.1
Making gametes…
http://waynesword.palomar.edu/lmexer2a.htm

Review Questions
1. How many chromosomes would a sperm or an egg contain if
either one resulted from the process of mitosis?
46 chromosomes
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?
46 + 46 = 92; a developing embryo would not survive if it
contained 92 chromosomes.
3. In order to produce a fertilized egg with the appropriate
number of chromosomes (46), how many chromosomes should
each sperm and egg have?
Sperm and egg should each have 23 chromosomes.

Remember from Chapter 1:
CHARACTERISTICS OF LIVING THINGS
ALL LIVING THINGS __________
Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm
Family http://babyhearing.org/Parenet2Parent/index.asp
REPRODUCE

ASEXUAL REPRODUCTION
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookmito.html
Bacteria reproduce using
__________________________________
http://fig.cox.miami.edu/~cmallery/150/mitosis/c7.13.2.hydra.jpg
Budding & regeneration are used by plants
and animals to reproduce asexually
(mitosis)
Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm
BINARY FISSION

BINARY FISSION & MITOSIS
Produces cells that are __________
identical
copies of parent cell

ADVANTAGES OF
Can make offspring
faster
Don’t need a partner
http://www.mrgrow.com/images/cutting.jpg

DISVANTAGES OF
ALL ALIKE
Species CAN’T
change and adapt
One disease can wipe
out whole population
http://www.mrgrow.com/images/cutting.jpg

SEXUAL REPRODUCTION
Family image from: http://babyhearing.org/Parenet2Parent/index.asp
Combines genetic material
from 2 parents (sperm & egg)
so offspring are
genetically __________
DIFFERENT
from parents

ADVANTAGES OF
SEXUAL REPRODUCTION
Allows for variation in population
Individuals can be different
Provides foundation for EVOLUTION
Allow species to adapt to
changes in
their environment
http://naturalsciences.sdsu.edu/classes/lab8/spindex.html

http://www.Image by Riedell Image by Riedell angelbabygifts.com/
EGG + SPERM 
If egg and sperm had same number of
chromosomes as other body cells . . .
baby would have too many chromosomes!
http://www.acmecompany.com/stock_thumbnails/13217.forty-six_chromosomes.jpg

MEIOSIS is the way…
to make cells
with ½ the
number of
chromosomes
for sexual
reproduction

HOMOLOGOUS CHROMOSOMES
Image modified by Riedell • SAME SIZE
• SAME SHAPE
• CARRY GENES for the
SAME TRAITS
• BUT NOT ______________!
IDENTICAL
(Don’t have to have the
SAME CHOICES)
http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

DIPLOID & HAPLOID
Most cells have 2 copies of each chromosome
= ______________
DIPLOID 2n
(one from mom; one from dad)
HOMOLOGOUS
CHROMOSOMES
= SOMATIC
All BODY (___________) cells are diploid

DIPLOID & HAPLOID
Some cells have only one copy of each
chromosome = _____________
HAPLOID 1n
All sperm and egg cells
are haploid

MITOSIS
• Makes ___ 2
cells genetically
_________ identical
to parent cell &
to each other
• Makes ___ 2n
cells
• Makes __________
SOMATIC (body)
• Used by organisms to:
increase size of organism,
repair injuries,
replace worn out cells http://waynesword.palomar.edu/lmexer2a.htm

MEIOSIS
• Makes ____ 4
cells
genetically different from
parent cell & from each
other
• Makes _____ cells
• Makes ______________
1n
Germ cells
OR Gametes (sperm & eggs)
sexual
reproduction
• Used for ____________

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 ________________
PROPHASE I
= __S_Y_N__A_P_S_I_S____
This group of FOUR (4)
chromatids is called a
____T_E__T_R_A_D_______
Images modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif

WHAT MAKES MEIOSIS
DIFFERENT?
1. Exchange of DNA between
homologous 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
rearranging of DNA
• Allows for_________________
in different combinations
• After crossing over, chromatid arms
are________________ anymore
NOT IDENTICAL

WHAT MAKES MEIOSIS
DIFFERENT ?
2.Separation during ANAPHASE I
SEGREGATION &
Separates gene choices and allows
shuffling of genetic material

SEGREGATION & CROSSING OVER
together make even more combinations

http://fig.cox.miami.edu/~cmallery/150/mitosis/c13x9independent-assortment.jpg

at 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
=______________________________
GENETIC RECOMBINATION
So daughter cells are ______________
different
from parents and from each other

WHAT MAKES MEIOSIS
DIFFERENT ?
3. Skip INTERPHASE II (No S)
CELL DIVIDES TWICE, BUT …
ONLY COPIES ITS DNA ONCE
MITOSIS:
G1 S  G2  P  M  A  T C
MEIOSIS:
S G2 P M A T C
G1       
P  M  A  T 
C
( I )
( II )

Go to
Section:
Meiosis I
Section 11-4
Figure 11-15 Meiosis

Section 11-4
Go to
Section:
Figure 11-15 Meiosis
Meiosis I

Prophase II Metaphase II Anaphase II Telophase 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.
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.
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

Transmission of characteristics from
_______________________parents to offspring
is called
___________________.
heredity
The science that studies _____
how
characteristics are _________ passed on
from one
generation to the next is called
___________________
Genetics

The __________________ is
_________________,
Gregor Mendel
a monk whose _________ of
genetic traits was the beginning of
our _________________ of
_____________________.
http://www.jic.bbsrc.ac.uk/germplas/pisum/zgs4f.htm
Father of Genetics
study
understanding
how genes work

http://hus.yksd.com/distanceedcourses/YKSDbiology/lessons/FourthQuarter/Chapter11/11-1/images/MendelExperiment.gif
Mendel designed
____________ experiments
using
__________ Pea plants
in the
monastery garden
_______ part of flower makes
Pollen
___________ (sperm)
__________ part of flower makes
_______ cells
http://www.cedarville.edu/academics/education/resource/schools/chca/2scideb/debwebpv.htm
MALE
FEMALE
egg

In pea plants, the pollen normally joins
with an egg from the _______ same
plant
(=_______________ Self pollination
) so seeds have
“_________________”
ONE parent

MENDEL’S PEA EXPERIMENTS
Mendel started his experiments with
peas that were _________________
true breeding
= if allowed to
_________________
self pollinate
they would produce
____________________
offspring identical
to themselves.

MENDEL’S PEA EXPERIMENTS
Mendel ____________________
removed pollen
making parts and ____________
from _______ plant.
another
This allowed him to
_____________ cross-breed
plants
with ______________
different
characteristics and
________ the results
added pollen
study

A _____________________ specific characteristic
is
called a ____________
trait
Mendel ______________ in peas.
studied 7 traits
Pearson Education Inc,; Publishing as Pearson Prentice Hall

MENDEL’S EXPERIMENTS
P1
F1
____ generation
(_________)
____ generation
(______= offspring)
___ generation
F2
parental
filial

Section 11-1
Principles of Dominance
P Generation F1 Generation F2 Generation
Tall Short Tall Tall Tall Tall Tall Short

crossed PURE
When Mendel ______________ PLANTS
with 2 ______________ contrasting
traits:
(EX: Tall crossed with short)
He always found same pattern:
1. ONLY ______ trait ____________
ONE showed
F1
in the ____ generation BUT . . .
Missing returned
2. ___________ trait ____________ in
F2
3:1
the ____ generation
in a _________ ratio

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 __________________ pair of FACTORS
that
________control
each trait and that
__________ one factor
must be able to
_______ HIDE
the other.

We now know that Mendel’s
________________ factors are genes
carried on
the pair of________________
homologous
chromosomes
_________________

________ gene
_______ for a
trait are called
__A_L_L_E_L_E_S___.
DIFFERENT
CHOICES

DOMINANT
__________________ = An allele that
________ HIDES
the presence of another
allele
__________________ RECESSIVE
= An allele
that __________________ is hidden by
the
presence of another allele

DOMINANT/RECESSIVE
_____________ Dominant
allele is represented by a
____________ capital
letter.
(usually the first letter of the trait)
____________ Recessive
allele is represented by the
SAME
lower-case
_________________ letter.
EX: Tall = ______
T
t NOT S for short
Short =______

HOMOZYGOUS
HETEROZYGOUS
When both alleles in the pair are
the _______, SAME
the organism is
_______________ or __________
HOMOZYGOUS PURE
TT tt
EX: ____ or ___
When both alleles in the pair are
_____________, DIFFERENT
the organism is
_________________ HETEROZYGOUS or _____________
HYBRID
Tt
Ex: ____

PHENOTYPE/GENOTYPE
The ________________ genetic makeup
of an organism
is its _____________
GENOTYPE
appearance
The ____________ of an organism is
its _____________
PHENOTYPE

Why did the recessive trait disappear
in the F1 generation and reappear in
the F2?
The pattern corresponds
to the ____________ of
______________ during
____M_E__IO__S_IS__________
http://www.laskerfoundation.org/rprimers/gnn/timeline/1866.html
movement
chromosomes

REMEMBER
_____________
chromosomes
________________
during
ANAPHASE I
= _S_E__G_R__E_G__A__T_I_O__N_
HOMOLOGOUS
SEPARATE

F1 received
____ offspring __________ an allele for
tallness from their _______ TALL
parent and an
allele for shortness from their ________
SHORT
parent.
The F1 plants ALL ___________
but are ___________ an
allele for _________
LOOK TALL
carrying
shortness
Images from: BIOLOGY by Miller & Levine; Prentice Hall Publishing ©2006

EXPLAINING the F1 CROSS
LAW OF __S_E_G__R_E_G__A_T__I_O_N____
alleles are separated
when the Fplants
1 ______________
When these gametes recombined to make the
Fgeneration, the _____________ recessive
trait
2 _______________ in ¼ of the offspring
Image from: BIOLOGY by Miller & Levine; Prentice Hall Publishing ©2006
made gametes
reappears

MAKING A CROSS for
only a ONE __________ GENE
trait =
M__O__N_O__H_Y__B_R_I_D__ C__R_O__SS

MAKING A CROSS with
___________________=
TWO gene traits
D__IH__Y_B__R_I_D_ _C_R__O_S_S____

LAW OF
__________________________
the factors are distributed to gametes
independently of other factors
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?
Results will vary, but should be close to 5 heads
and 5 tails.
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?
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?
The results for the entire class should be even
closer to the number predicted by the rules of probability.
4. How do the expected results differ from the
observed results?
The observed results are usually slightly
different from the expected results due to
Experimental error.

PROBABILITY
____________________
is the __________ that a
likelihood
event will occur
particular _________________
It can be written as a:
Fraction ____
1/4
Percent ____
25%
Ratio ___
1:4

COIN FLIP
http://www.arborsci.com/CoolStuff/CoinFlip.jpg
There are 2 possible
outcomes:
HEADS TAILS
capital
The chance the coin will land on either one is:
1/2 50% 1:2
____ ____ ____
Alleles segregate randomly just like a coin
flip. . . So we can use probability to
predict outcomes of genetic crosses.

PROBABILITIES
PAST DON’T FUTURE
_____ outcomes ______ affect _________ones
If last coin flip was heads… there is still a 50/50
chance the next flip will be heads too.
Probability best predicting
_____________works ______ in ___________
a ________ number of events.
large
The more flips. . . The closer results will be to
the expected 50:50 average.

PHENOTYPE/GENOTYPE
The ________________ genetic makeup
of an organism
is its _____________
GENOTYPE
appearance
The ____________of an organism is
its _____________
PHENOTYPE

MAKING A CROSS for
only a ONE __________ GENE
trait =
____________________
A Punnett square for
a MONOHYBRID
CROSS looks like
this:
MONOHYBRID CROSS

PUNNETT SQUARES
are used to show possible offspring
from a cross between 2 parents
Parent alleles
_______________ go at
top and on left side
Boxes show
____________
___________________
T T
T
t
possible
offspring combinations

STEPS FOR MAKING CROSSES
Figure out parent alleles
Choose Punnett size
Put in parent gametes
Fill in offspring combinations
1. ___________ what _________________ are
2. ________correct__________ square __________
3. ______ possible_______________________
4. ______ boxes with _____________________
5. Determine ____________probabilities of_____________&
phenotypes
____________
genotypes

IN PEA PLANTS
Tall is dominant over short
TALL = ____
SHORT = ____
T
t
LET’S MAKE A CROSS!
PURE TALL X PURE SHORT

PURE TALL parent
What are the parent alleles?
T T _________
 
T T
HOMOZYGOUS
What gametes
can it make?

PURE SHORT parent
t t _________
 
t t
HOMOZYGOUS
What gametes
can it make?

ALL
_____
of the
offspring
____ %
___/4
will be
T T
t
t
T t T t
T t T t
100
4
Tt TALL
GENOTYPE _____ PHENOTYPE _______

HYBRID TALL parents
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
TT
3/4
75
1/4 SHORT
Tt
tt
TALL
PHENOTYPES ____ or ____% _________
25
____ or ____% _________

PRACTICE MAKING GAMETES
for a MONOHYBRID CROSS
Tall = ____ T
Round seeds = ___
R
Short = ____ t
Wrinkled seeds = ___
r

What are the possible gametes?
Homozygous Tall parent =
What gametes can it produce?
T T


T T

PURE wrinkled parent =


rr
r r

Heterozygous Round parent =

R r

R r

Hybrid Tall parent =

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 seed
is round or wrinkled have anything to
do with the gene for seed color?
Must a seed that is yellow
also be round?

MAKING A CROSS with
___________________=
TWO gene traits
DIHYBRID ____________________
CROSS
A Punnett square for
a DIHYBRID
CROSS looks like
this:

Section 11-3
Figure 11-10 Independent Assortment in Peas

LET’S MAKE A DIHYBRID CROSS
HOMOZYGOUS
ROUND YELLOW
HOMOZYGOUS
WRINKLED
GREEN
RRYY
1. ___________ what _________________ are
2. ________correct__________ square __________
3. ______ possible_______________________
4. ______ boxes with _____________________
5. Determine ____________of_____________&
____________
rryy
Figure out parent alleles
Choose Punnett size
Put in parent gametes
Fill in offspring combinations
probabilities phenotypes
genotypes

WHAT ARE THE POSSIBLE GAMETES
THIS PARENT CAN MAKE?
HOMOZYGOUS
WRINKLED GREEN
r r y y
Each gamete should
get one of each kind
of gene
___________ ____________ _____________ _____________ r y r y r y r y

HOMOZYGOUS
ROUND YELLOW
R R Y Y
Each gamete should
of gene
___________ ____________ _____________ _____________ R Y R Y R Y R Y

ry ry ry ry
RY
RY
RY
RY
RrYy RrYy RrYy RrYy
RrYy RrYy RrYy RrYy
RrYy RrYy RrYy RrYy
RrYy RrYy RrYy RrYy
RrYy
100% of offspring = _______ genotype
ROUND YELLOW
_______________________ phenotype

HETEROZYGOUS
ROUND YELLOW
R r Y y
Each gamete should
of gene
___________ ____________ _____________ _____________ R Y r y r Y R y

MAKE ANOTHER CROSS
HETEROZYGOUS
ROUND YELLOW
HETEROZYGOUS
ROUND YELLOW
X
R r Y y R r Y y

POSSIBLE PARENT GAMETES?
RY ry rY Ry

RY Ry rY ry
____ Round &
Yellow
RY
Ry
rY
ry
Sign of a ______________________ cross is a
____9__:3_:_3_:_1___ ratio in offspring.
____ 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

9
3
3
1
dominant dominant
dominant recessive
recessive dominant
recessive recessive
____ ____________ TRAIT 1 ; ____________ TRAIT 2
____ ____________ TRAIT 1; _____________ TRAIT 2
____ ____________ TRAIT 1; _____________ TRAIT 2
____ ____________ TRAIT 1; _____________ TRAIT 2
__________ratio is a clue that it’s a
____________________________cross
9:3:3:1
HETEROZYGOUS TWO gene

for DIHYBRID CROSSES
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html

R R T T
pure round & pure tall = __________




R T R T R T
R T
____ ____ _____ ______

T t R R
Heterozygous Tall = __________
& pure round


T R T R


t R t R
____ ____ _____ ______

T t r r
Hybrid tall = __________
& pure wrinkled


T r T r


t r t r
____ ____ _____ ______

Heterozygous tall = __________
& hybrid round

T t R r

T R T r


t R t r
____ ____ _____ ______

Gene Linkage & Polyploidy
10.3

Genetic Recombination
New combination of genes created by
_________________ CROSSING OVER
and
INDEPENDENT __________________________
ASSORTMENT
Formula __n = possible gamete combinations
n = number of _________________________
CHROMOSOME PAIRS
2

Example: peas have 7 chromosome pairs.
27 = _____ 128
possible combinations.
128 x 128 = __________ 16,384
possible
combinations after fertilization
Humans have ___ 23
chromosomes
223 x 223 = ____+ 70
trillion after fertilization!

GENE LINKAGE
Genes located ________ CLOSE
to each
other on the same chromosome
will usually travel TOGETHER
___________
during gamete formation
Exceptions to Mendel’s law of
________________________________.

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
____________ POSITIONS
of genes
Crossing over occurs more often
between genes that are ______________
FAR APART
Chromosome maps created by using
______________________
CROSSOVER DATA

Letters show relative position of genes
Crossing over is much more likely to
occur between A and ___ C
than
A and ____
B

POLYPLOIDY
___________________
One or more EXTRA ____________ SETS
of chromosomes
_______________ TRIPLOID
organisms would be 3n
_____________ LETHAL
in humans and rarely
occurs in animals
Sometimes in earthworms
and __________________
GOLDFISH

Polyploidy
1/3 of all ________________________ FLOWERING PLANTS
are
polyploid
Commercial wheat, commercial oats (6n)
Commercial sugar cane (8n)
Polypoloidy plants often have increased
______ and vigor.
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)

Meiosis and Heredity

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