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10.1 Cell Growth
Key Concept - What problems does growth cause for
cells and how does cell division solve the problem?
Limits to Cell Growth
Larger cell= more demands the cell’s DNA
Larger cell = more trouble moving nutrients
in across cell membrane
Larger cell= more trouble moving wastes
out across cell membrane
10.1 Cell Growth
Limits to Cell Growth
Larger cell: more demands cell’s DNA
DNA, “overload”
Library metaphor: as the town gets larger,
too many people are trying to check out the
same books. Better to build another library!
10.1 Cell Growth
Limits to Cell Growth
Problems Exchanging Materials
•Food, Oxygen, and Water need to get in
through cell membrane (surface area)
•Wastes need to leave the cell through the
membrane (surface area)
•Amount of nutrients needed and waste
produced depends on volume.
10.1 Cell Growth Limits to Cell Growth
Problems Exchanging Materials
Food, Oxygen, and Water get in through cell membrane (surface area)
Wastes need to leave the cell through the membrane (surface area)
Amount of nutrients needed and waste produced depends on volume.
Problem: as volume increases, surface area
increases
But not as quickly as volume increases
10.1 Cell Growth Limits to Cell Growth
Problems Exchanging Materials
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10.1 Cell Growth Limits to Cell Growth
Ratio of Surface Area to Volume
Problem: as volume increases, surface area
increases
But not as quickly as volume increases
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10.2 CellDivision
Prokaryotes: just separate into two
Eukaryotes: Two stages
mitosis division of nucleus
cytokinesis dividing cytoplasm in two
Chromosomes:
Only visible during cell division
At other times chromatin
At cell division, chromosomes have been
duplicated, and so are seen as two sister
chromatids
Chromosomes
• Only visible
during cell division
•At cell division,
chromosomes have
been duplicated and
are seen as two
sister chromatids
•joined at
centromere
Chromosomes:
DNA twisted together
with proteins
histones
Then twisted again and
again into chromatids
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Cell Cycle
Interphase: time between
divisions
cell growth
duplication of genetic
material
Mitosis: nucleus and
chromosomes divide
Cytokinesis: cytoplasm divides
Cell
Cycle
Cell Cycle
Interphase: time
between divisions
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Cell Cycle
Prophase:
Chromatin organizes
into chromosomes.
Nuclear membrane
breaks up
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Cell Cycle
Metaphase:
Chromosomes line
up along cell equator
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Cell Cycle
Anaphase:
Chromosomes
separate toward
opposite poles
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Cell Cycle
Telophase: Nuclear
membrane reformes.
Cytokinesis begins.
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Cell Division: Mitosis
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Cell Division: Mitosis
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Work of Gregor Mendel
Genes and Dominance
Trait a specific characteristic (color, height)
that varies from individual to individual
Mendel crossed plants with different colors
Hybrids are offspring of parents with different traits
F1 first generation of that cross
Mendel expected F1 offspring to be a blend of parent
traits
Instead, all the offspring had characteristics of one
parent
Work of Gregor Mendel
Genes and Dominance
Trait a specific characteristic (color, height)
that varies from individual to individual
Mendel crossed plants with different colors
Hybrids are offspring of parents with different traits
F1 first generation of that cross
Mendel expected F1 offspring to be a blend of parent traits
Instead, all the offspring had characteristics of one parent
Genes chemical factors that determine one
trait
Alleles different forms of that gene
Dominance some alleles are dominant,
some are recessive.
Work of Gregor Mendel
Seed
Shape
Round
Seed
Color
Seed Coat
Color
Flower
Position
Pod
Shape
Pod
Color
Smooth
Green
Axial
Tall
Short
Yellow
Gray
Wrinkled Green
White
Constricted
Yellow
Terminal
Round
Gray
Smooth
Green
Axial
Yellow
Plant
Height
Tall
Work of Gregor Mendel
P Generation
Tall
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Work of Gregor Mendel
Segregation
What happened to the recessive alleles?
P Generation
Tall
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Work of Gregor Mendel
Segregation
What happened to the recessive alleles?
P Generation
Tall
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Work of Gregor Mendel
Segregation
What happened to the recessive alleles?
The F1 Cross
How did the recessive traits disappear and then
reappear?
SEGREGATION in formation of sex cells or
gametes, alleles are separated. Each gamete
carries only one copy of each gene.
F1 plant produces two types of gametes one with
the allele for tallness and one for the allele for
shortness.
11.2 Probability and Punnett
Squares
•EXPLAIN how geneticicsts use the principles
of probability
•DESCRIBE how geneticists use Punnett
squares
Probaility and Punnett
Squares
Genetics and Probability
Probability can be used to predict the outcome of genetic crosses
The ratio of probability that an allele will be
expressed
Is proportional to the number of offspring
expressing that allele.
Probaility and Punnett
Squares
Punnett Squares
are used to determine the possible gene combinations from a genetic
cross
The Punnett square can be used to predict the ratio
of offspring
Punnett Square vocabulary:
•Homozygous has two identical alleles for a given trait (ie tt
or TT)
•Heterozygous has two different alleles for the trait (ie Tt)
•phenotype physical characteristic (Tall Tt or TT)
•genotype genetic make up (TT is different than Tt)
Probaility and Punnett
Squares
Punnett Square
Probaility and Punnett
Squares
Punnett Square
Probaility and Punnett
Squares
Punnett Square
Probaility and Punnett
Squares
Punnett Square
Probaility and Punnett
Squares
Punnett Square
Probaility and Punnett
Squares
Punnett Square
Phenotype:
tall
Phenotype:
tall
Phenotype:
tall
Phenotype:
short
Probaility and Punnett
Squares
Probability and Segregation
Did segregation occur?
The recessive gene that had been hidden in the F1
generation reappeared in the F2 generation.
The ratio was 3 tall plants to 1 short plant
Probaility and Punnett
Squares
Probabilities Predict Averages
Just as in a coin flip
The larger the sample, the more likely the result will
match the prediction
11.3 Exploring Mendelian
Genetics
Independent Assortment
Alleles segregate during gamete formation
Do they segregate independently?
Does the gene for seed color (Yellow, Y or Green, y)
have anything to do with the gene for seed shape
(round, R or Wrinkled, r)?
11.3 Exploring Mendelian
Genetics
Independent Assortment
Two Factor Cross: F1
First Mendel crossed an rryy plant with an RRYY
plant
That cross produced all RrYy offspring
What would happen in the next generation (F2)?
Would there be any Ry or rY plants?
Or would the dominant and recessive alleles stick
together?
11.3
Exploring
Mendelian RY
Genetics
rY
ry
RRYY RRRy
RrYY
RrYy
Ry
RRYy
RRyy
RrYy
Rryy
rY
Independent
Assortment
Genes for different
Traits segregate
ry
independently
RrYY
RrYy
rrYY
RrYy
Rryy
rrYy
Independent
Assortment
Two-Factor
Cross: F2
RY
Ry
rrYy
rryy
11.3 Exploring Mendelian
Genetics
Summary of Mendelian Principles
• Inheritance determined by genes passed
from parents to offspring
• Genes may be dominant or recessive
• Adult has two copies of each gene, one
from each parent
• Alleles for different genes usually segregate
independently
11.3 Exploring Mendelian Genetics
Beyond Dominant and Recessive
Some alleles are neither dominant nor
recessive
Incomplete Dominance Heterozygous offspring
show a phenotype somewhere in between the
two homozygous phenotypes (pink four
o’clocks)
Codominance both alleles contribute to the
phenogype of the organism (roan cattle have
both red and white hairs)
11.3 Exploring Mendelian Genetics
Beyond Dominant and Recessive
Some alleles are neither dominant nor
recessive
Multiple Alleles More than two alleles possible
(coat color in rabbits)
PolygenicTraits controlled by more than one
gene (human eye color, human skin color)
11.3 Exploring Mendelian Genetics
Applying Mendel’s Principals
Drosophila:
Often used in genetic research
Fruit fly produce a new generation of hundreds
of offspring every 14 days
Human applications
Albinism controled by one gene
Skin pigment is dominant, Albinism is recessive
Pigmented parents have an albino child.
What is the chance that the next child will be albino?
Skip to Tuesday
Focus Week
11.4 Meiosis and
11.5 Linkage and Gene Mapping
Due Thursday (in class work - not homework)
11.4 p 278 q 1 - 5
11.5 p 280 q 1 - 4
Homework
Study for final
80% of questions will come from study guide and
standardized test prep (end of each chapter)
Normal human body cells each contain 46
chromosomes. The cell division process that
body cells undergo is called mitosis and
produces daughter cells that are virtually
identical to the parent cell.
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?
11.4 Meiosis
GOALS
Contrast the chromosome number of body cells
and gametes
Summarize the events of meiosis
Contrast meiosis and mitosis
HOW TO EXPLAIN MENDEL’S OBSERVATIONS
Organisms inheirit a single copy of each gene
from each parent
Offspring’s gametes contain only one set of each
gene
11.4 Meiosis
Chromosome Number
Homologous: two genes that belong to the same
pair
i.e. Fruit flies have 8 chromosomes, four
homologous pairs, 4 chromosomes from each
parent
Diploid: containing both sets of homologous
chromosomes
2N
11.4 Meiosis
Chromosome Number
Homologous: two genes that belong to the same pair
i.e. Fruit flies have 8 chromosomes, four homologous pairs, 4
chromosomes from each parent
Diploid: containing both sets of homologous chromosomes
2N (i.e. 2N = 8)
Gametes: contain only a single set of
chromosomes (therefore genes)
And so are called
Haploid: containing only one set of
chromosomes N (i.e. N=4)
11.4 Meiosis
Phases of Meiosis
Meiosis: reduction division. Chromosome
number cut in half by separating homologous
chromosomes of diploid cell
Meiosis I
Each chromosome is replicated
Homologous chromosomes pair up
forming tetrad joined at centromere
homologous chromosomes separate
Meiosis II
11.4 Meiosis
Phases of Meiosis
Meiosis: reduction division. Chromosome number cut in half
by separating homologous chromosomes of diploid cell
Meiosis I
Each chromosome is replicated
Homologous chromosomes pair up
forming tetrad joined at centromere
homologous chromosomes separate
Meiosis II
No duplication of genetic material
Chromosomes (only half of the diploid number)
line up and chromatids separate
11.4 Meiosis
Phases of Meiosis - Meiosis I
Interphase I
DNA
replication,
forming
duplicate
Chromosome
s.
11.4 Meiosis
Phases of Meiosis - Meiosis I
Interphase I
DNA
replication,
forming
duplicate
Chromosome
s.
Prophase I
Metaphase I
Each
Spindle fibers
chromosome attach to the
pairs with
chromosomes.
corresponding
homologous
chromosome to
form a tetrad.
Anaphase I
The fibers pull
the homologous
chromosomes
toward the
opposite ends of
the cell.
11.4 Meiosis
Phases of Meiosis - Meiosis I
Interphase I
DNA
replication,
forming
duplicate
Chromosome
s.
Prophase I
Metaphase I
Each
Spindle fibers
chromosome attach to the
pairs with
chromosomes.
corresponding
homologous
chromosome to
form a tetrad.
Anaphase I
The fibers pull
the homologous
chromosomes
toward the
opposite ends of
the cell.
11.4 Meiosis
Phases of Meiosis - Meiosis I
Interphase I
DNA
replication,
forming
duplicate
Chromosome
s.
Prophase I
Metaphase I
Each
Spindle fibers
chromosome attach to the
pairs with
chromosomes.
corresponding
homologous
chromosome to
form a tetrad.
Anaphase I
The fibers pull
the homologous
chromosomes
toward the
opposite ends of
the cell.
11.4 Meiosis
Phases of Meiosis - Meiosis II
Prophase II
Meiosis I results in
two haploid (N)
cells, each with
half the number of
chromosomes of
Metaphase II
Anaphase II
The chromosomes
line up in a similar
way to the
metaphase in
mitosis.
The sister
chromatids
separate and move
toward opposite
ends of the cell.
Telophase II
Meiosis II results in
four haploid (N)
daughter cells.
11.4 Meiosis
Phases of Meiosis - Meiosis II
Prophase II
Meiosis I results in
two haploid (N)
cells, each with
half the number of
chromosomes of
Metaphase II
Anaphase II
The chromosomes
line up in a similar
way to the
metaphase in
mitosis.
The sister
chromatids
separate and move
toward opposite
ends of the cell.
Telophase II
Meiosis II results in
four haploid (N)
daughter cells.
11.4 Meiosis
Phases of Meiosis - Meiosis II
Prophase II
Meiosis I results in
two haploid (N)
cells, each with
half the number of
chromosomes of
Metaphase II
Anaphase II
The chromosomes
line up in a similar
way to the
metaphase in
mitosis.
The sister
chromatids
separate and move
toward opposite
ends of the cell.
Telophase II
Meiosis II results in
four haploid (N)
daughter cells.
11.4 Meiosis
Phases of Meiosis - Meiosis II
Prophase II
Meiosis I results in
two haploid (N)
cells, each with
half the number of
chromosomes of
Metaphase II
Anaphase II
The chromosomes
line up in a similar
way to the
metaphase in
mitosis.
The sister
chromatids
separate and move
toward opposite
ends of the cell.
Telophase II
Meiosis II results in
four haploid (N)
daughter cells.
11.4 Meiosis
Crossing-over
During Meiosis I,
11.4 Meiosis
Crossing-over
During Meiosis I, homologous
chromosomes may, “cross-over,”
11.4 Meiosis
Crossing-over
During Meiosis I, homologous
chromosomes may, “cross-over,” and
exchange portions of their chromatids.
11.4 Meiosis
Gamete Formation
•In male animals, meiosis produces four
haploid (1N) sperm cells
•In female animals one of the haploid egg cell
receives most of the cytoplasm
the remaining, “polar bodies,” do not
participate in reproduction
11.4 Meiosis
Comparing Mitosis and Meiosis
•Mitosis two
genetically
identical diploid
cells
•Meiosis four
genetically
different haploid
cells
11.5 Gene Linkage and Mapping
Some genes appear to be
inherited together, or
“linked.”
If two genes are found on
the same chromosome,
does it mean they are
linked forever?
11.5 Gene Linkage and Mapping
1. In how many places can
crossing over result in genes A
and b being on the same
chromosome?
2. In how many places can
crossing over result in genes A
and c being on the same
chromosome?
Genes A and e?
3. How does the distance
between two genes on a
chromosome affect the
chances that crossing over will
recombine those genes?
11.5 Gene Linkage and Mapping
1. Identify the
structures that
actually assort
independently
2. Explain how gene
maps are produced
Independent assortment:
Genes are assorted
independently
But what about genes on the
same chromosome
11.5 Gene Linkage and Mapping
Gene Linkage
Mendel worked with 7 characteristics
Six of them happened to be on different
chromosomes
The one pair on the same chromosome were
so far apart on the chromosome that they
appeared to assort independently.
11.5 Gene Linkage and Mapping
11.5 Gene Linkage and Mapping
Gene Linkage
1910 Morgan’s research on fruit flies
Studied 50 traits
Many (red-eyed, short winged) appeared to
be, “linked.”
Grouped into four linkage groups
Four chromosomes
Conclusion: It is chromosomes, not
individual genes, that assort
independently.
11.5 Gene Linkage and Mapping
Gene Maps
Are those linked genes linked forever?
No, crossing over may separate linked genes.
1911 Sturtevant (student of Morgan)
hypothesis:
The farther genes are from eachother
The more likely they will be separated by cross-over
Produced gene map using recombination rates