Monohybrid Crosses

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Mitosis VS Meiosis
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Significance of cell reproduction
Unicellular Organisms reproduce by a type of
cell division called binary fission.
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Multicellular organisms- growth and repair upon
cell division, also the production of sex cells.
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Chromosomes -Carriers of genetic material found
in nucleus -Made up of DNA -Information is copied
and passed to future generations
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Usually exist as chromatin -long, winding
strands which condense into chromosomes
before dividing Humans have 46 chromosomes in
body cells, 23 in sex cells
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Meiosis

• Similar in many ways to mitosis
• However there are several differences
• Involves 2 cell divisions (mitosis only has one)
• Results in 4 cells with 1/2 the normal genetic
  information that are not identical (mitosis
  results in 2 cells)

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Vocabulary

• Diploid (2N) - Normal amount of genetic material
• Haploid (N) - 1/2 the genetic material.
• Meiosis results in the formation of haploid
  cells.
• In Humans, these are the Ova (egg) and sperm.
• Ova are produced in the ovaries in females
• Process is called oogenesis
• Sperm are produced in the testes of males.
• Process is called spermatogenesis

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Comparison of Mitosis Meiosis
Page 276
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Meiosis Phases

• There are 2 phases Meiosis I, Meiosis II.
• Meiosis I.
• Prior to division, amount of DNA doubles

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Crossing Over

• During metaphase 1 homologous chromosomes line-up
  along the metaphase plate
• Areas of homologous chromosomes connect at areas
  called chiasmata

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Crossing over contd.

• Crossing Over of genes occurs now
• Segments of homologous chromosomes break and
  reform at similar locations.
• Results in new genetic combinations of offspring.
• This is the main advantage of sexual reproduction

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Chromosome reduction

• During anaphase 1, each homologous chromosome is
  pulled to opposite sides of the cell. Unlike
  mitosis, THE CENTROMERES DO NOT BREAK.

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Meiosis I continued

• Nuclei may or may not reform following division.
• Cytokenesis may or may not occur

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Meiosis II

• DNA does not double
• Chromosomes randomly line-up along metaphase
  plate like regular mitosis.
• During anaphase 2, CENTROMERES BREAK and each
  chromosome is pulled to opposite sides of the
  cell.
• Nuclei reform and cytokenesis usually occurs
  (although it is often unequal).

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Overview of Meiosis
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Introduction to Genetics
Genetic variation within the White-cheeked
Rosella
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Heredity Genetics 1. Heredity The passing of
traits from parents to offspring 2.
Genetics Study of heredity 3. Inherited
characteristics are called traits
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Gregor Mendel was the first person to predict how
traits are transferred.Austrian monk who
studied garden peas
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-Mendel transferred pollen from plant to plant
and then studied resulting peas-Studied only
one trait at a time- Mendel is called the
father of genetics
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Mendel used pea plants because - they reproduce
sexually - have both male and female
gametes in the same flower - fertilization could
be controlled
http//www2.edc.org/weblabs/WebLabDirectory1.html
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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
Gray
Smooth
Green
Axial
Tall
Round
Yellow
Constricted
Terminal
Short
Wrinkled
Green
White
Yellow
Round
Yellow
Gray
Smooth
Green
Axial
Tall
Go to Section
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Phenotypes Genotypes

• Phenotype appearance of an organism
• Example short, tall, green, yellow
• Genotype gene combination of an organism
• Example tt, TT, Tt, gg, GG, Gg

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Heterozygous the 2 alleles are
differentExample Tt -heterozygousHomozygous
the 2 alleles are the sameExample TT means
homozygous dominant, and tt means homozygous
recessive
Heterozygous Homozygous
Livestock http//www.parkelivestock.com/semensale
s.htm http//www.mcrobertsgamefarm.com/buffalo/w
hite_buffalo.htm
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Traits can be dominant or recessive Dominant
traits exhibited trait, written with 1 or 2
capital letters Example TT, Tt Recessive
traits inhibited trait (not expressed unless
homozygous), written with lowercase letters
Example tt
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Monohybrid Crosses

• Crosses that differ by a single trait
• Example Tall pea plant x short pea plant
• The first generation produced offspring
  resembling only one parent
• Example all tall pea plants

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Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Tall
Tall
Short
Tall
Short
Tall
Tall
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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The second generation produced 3/4 of peas were
tall 1/4 of peas were short

• Mendel concluded that each trait has 2 factors
• -Factors are now called alleles
• - Organisms inherit one allele from mother
  and one allele from father

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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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Tt X Tt Cross
Section 11-2
Go to Section
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Tt X Tt Cross
Section 11-2
Go to Section
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Probability the chance or percentage of chance
of a trait being exhibited
Now you know that the probability of a heads-up
landing when you flip a coin is 1/2. What is
the probability of getting tails if you flip it
again? - It is still 1/2. The two events do
not affect each other. They are independent!
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Mendel Revisited

• Quick Review
• Genotype genetic code for traits TT Tt tt
• Phenotype physical appearance
• Homozygous, heterozygous, dominant, recessive
• Punnett Square
• TT x tt
• Tt x Tt

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• Law of Dominance
• In a cross of parents that are pure for
  contrasting traits, only one form of the trait
  will appear in the next generation.
• Offspring that are hybrid for a trait will have
  only the dominant trait in the phenotype.
• TT (tall) x tt (short) all Tall

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• Law of Segregation
• During the formation of gametes (eggs or sperm),
  the two alleles responsible for a trait separate
  from each other. Alleles for a trait are then
  "recombined" at fertilization, producing the
  genotype for the traits of the offspring.
• Tt (tall) x Tt (tall) 75 Tall, 25 short
• alleles act independently
  

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Incomplete dominance Incomplete
dominance-neither allele is Dominant or
recessive Example- white flowers X red
flowers pink flowers-a mixture or blend of the
parent colors
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Codominanceoffspring shows phenotype of neither
parent both alleles are dominant Example- bay
horse x white horsed roan horse- both hair
colors are present
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Multiple alleles more than 2 alleles control a
traitExample-blood type in humans a. blood
type is determined by presence or absence of
proteins on the surface of red blood
cellsExamples- A, B, AB, O
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Genotype PhenotypeAA, Ao A bloodBB, Bo B
bloodOO O blood
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To determine the blood types of possible
offspringParents A blood, O bloodGenotypes
AA, AO OO
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Calico Cats

• Calico is not a breed of cat, but an unusual
  coloring occurring across many breeds
• Virtually all calico cats are female
• a male calico is a genetic anomaly and usually
  sterile
• Producing calico kittens through selective
  breeding also is nearly impossible due to
  unpredictable actions of genes and chromosomes
  when cells multiply in a feline fetus

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Sex linked alleles controlled by genes located
on sex chromosomes -usually carried on the X
chromosomes -Females XX, males XY -If trait is
X-linked, males pass the trait on to all their
daughters, but none to their sons -mothers have
50/50 chance of passing it to all their
childrenExamples-colorblindness
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Colorblindness,Hemophilia, MD

• Colorblindness recessive disorder where a
  person cant distinguish between certain colors.
• Hemophilia blood clotting disorder
• Muscular Dystrophy deterioration of the
  skeletal muscle. Children rarely live past early
  adulthood.

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Colorblindness test

• http//www.geocities.com/Heartland/8833/coloreye.h
  tml

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Aneuploidy

• Abnormal of chromosomes
• Trisomy aneuploidy of the 1st 22 pairs of
  chromosomes
• Autosomes 1st 22 pairs of chromosomes.
• Turners Syndrome XO 1/2000. Females that lack
  ovaries, shorter, and live normal lives.
• Klienfelters syndrome 1/500 males XXY taller
  than avg., longer limbs, sterile

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Karyotype

• A chart of all 23 pairs of chromosomes
• Tell the sex of the child
• Aneuploidy yes/no

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Pedigree Analysis