Genetics, Meiosis, Mitosis

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Genetics, Meiosis, Mitosis
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Mitosis

• Produces daughter cells with 46 chromosomes
• Used in growth and repair

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Mitosis

• DNA is duplicated
• Doubled chromosomes form from duplicated DNA
• Each cms has 2 identical chromatids

Chromatid
Chromatid
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Mitosis Metaphase
Chromosomes line up in a single row.
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Chromosomes separate Each chromatid becomes a
single chromosome
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Meiosis

• Reduce the chromosome number to half that of body
  cells
• Produce gametes
• Egg
• Sperm

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Meiosis Metaphase
Chromosomes line up in a double row.
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Chromosomes separate Each each daughter cell gets
doubled chromosomes
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Doubled Chromosomes Separate in Second Meiotic
Division
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Double Filed Chromosomes

• Daughter cells receive ONE of each cms pair
• Daughter cells receive ONE allele for most traits
• New combinations of alleles possible

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Gene

• A unit of heredity that controls the development
  of one trait
• Made of DNA

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Allele

• Member of a paired gene
• One allele comes from each parent
• Represented by a single letter

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Examples of Alleles
Dwarfism D Normal height d
DD Dwarfism Dd Dwarfism dd Normal height
Dwarf Band
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Dominant Recessive Alleles

• Dominant alleles are expressed
• Recessive alleles are not expressed in the
  presence of a dominant allele
• Recessive alleles are only expressed if both
  recessive alleles are present

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Homozygous

• Both alleles alike
• AA or aa

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Heterozygous

• Alleles are different
• Aa

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Genotype

• Genetic make up
• Represented by alleles
• DD Dd are genotypes for dwarfism

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Phenotype

• A trait
• Genotype determines the phenotype
• Dwarfism is a phenotype

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Codominant

• Two different alleles are both dominant
• A allele for type A blood
• B allele for type B blood
• AB results in type AB blood

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Karyotype

• Picture of chromosomes from an individual

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Homologous Chromosomes

• Chromosomes of the same pair
• Karyotypes are usually arranged with homologous
  chromosomes paired together

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Mutation

• Change in a gene or chromosome
• Causes an abnormal trait

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Mutagen

• Agent that causes mutations

Cigarette smoke Pesticides X-rays Ulatraviolet
light Nuclear radiation
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Homologous chromosomes line up in a double file
in metaphase I of meiosis
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Homologous Pairs Separate
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Four Gametes With Single Chromosomes
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Fertilization
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Nondisjunction
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Trisomy
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Sex Chromosomes
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Sex Chromosomes

• Male have Xy
• Male gametes have either X or y
• Females have XX
• Female gametes have X

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Autosomes

• Chromosomes 1-22

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X-Linked Traits

• Alleles are on the X chromosome
• Females have two alleles
• Males have one allele
• Only one X chromosome

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Normal Male
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Normal Female
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Trisomy 21Down Syndrome
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Down Syndrome

• Large tongue
• Flat face
• Slanted eyes
• Single crease across palm
• Mental retardation
• Some are not

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Maternal Age Down Syndrome
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Trisomy 18Edward Syndrome
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Edward Syndrome

• Heart defects
• Displaced liver
• Low-set ears
• Abnormal hands
• Severe retardation
• 98 abort
• Lifespan lt 1 year

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Trisomy 13Patau Syndrome
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Patau Syndrome

• Cleft lip and palate
• Extra fingers toes
• polydactylism
• Defects
• Heart
• Brain
• Kidneys
• Most abort
• Live span lt 1 month

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Klinefelter Syndrome
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Klinefelter Syndrome

• Breast development
• Small testes
• Sterile
• Low intelligence
• Not retarded

Klinefelter Website
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Turner Syndrome
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Turner Syndrome

• Short
• Not go through pruberty
• Produce little estrogen
• Sterile
• Extra skin on neck

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Fetal Testing
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Sickle Cell Anemia

• RBCs sickle shaped
• Anemia
• Pain
• Stroke
• Leg ulcers
• Jaundice
• Gall stones
• Spleen, kidneys lungs

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Sickle Cell Anemia

• Recessive allele, s codes for hemoglobin S
• Long rod-like molecules
• Stretches RBC into sickle shape
• Homozygous recessive, ss have sickle cell anemia
• Heterozygous, Ss are carriers

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Hemophilia

• Blood clotting impaired
• Recessive allele, h
• carried on X cms
• X-linked recessive trait
• More common in males

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Albinism

• Lack of pigment
• Skin
• Hair
• Eyes

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Enzyme
Amino Acids
Melanin Pigment
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PKU Disease

• Phenylalanine excess
• Mental retardation if untreated

Mollys Story
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Enzyme
Phenylalanine
Tyrosine
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A man woman are both carriers (heterozygous)
for albinism. What is the chance their children
will inherit albinism?
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Man Aa
Woman Aa
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Aa
AA
Aa
aa
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Genotypes
1 AA, 2Aa, 1aa
Phenotypes
3 Normal 1 Albino
Probability
25 for albinism
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A man woman are both carriers (heterozygous)
for PKU disease. What is the chance their
children will inherit PKU disease?
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p
P
P
p
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Genotypes
1 PP, 2Pp, 1pp
Phenotypes
3 Normal 1 PKU disease
Probability
25 for PKU disease
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A man with sickle cell anemia marries a woman who
is a carrier. What is the chance their children
will inherit sickle cell anemia?
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s
S
s
s
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Genotypes
2 Ss, 2ss
Phenotypes
2 Normal (carriers) 2 Sickle cell
Probability
50 for Sickle cell
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A man with heterozygous dwarfism marries a woman
who has normal height. What is the chance their
children will inherit dwarfism? Dwarfism is
dominant.
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d
d
D
d
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Genotypes
2 Dd, 2dd
Phenotypes
2 Normal 2 Dwarfs
Probability
50 for Dwarfism
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X-linked Recessive Traits

• Alleles are on the X chromosome
• Inheritance pattern different in males and females

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A man with hemophilia marries a normal woman who
is not a carrier. What is the chance their
children will inherit hemophilia? Hemophilia is
X-linked recessive.
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XH
XH
Xh
XH Xh
XH Xh
XHy
XHy
y
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Genotypes
2 XH Xh, 2XHy
Phenotypes
2 Carrier Females 2 Normal Males
Probability
O for Hemophilia
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A normal man marries a normal woman who is a
carrier for hemophilia. What is the chance their
children will inherit hemophilia?
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Xh
XH
XH
y
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Xh
XH
Genotypes
XH XH , XH Xh, XHy, Xhy
XH
XH XH
XH Xh
Phenotypes
2 Normal Females 1 Normal Males 1 Male Hemophiliac
XHy
Xhy
y
Probability
50 for Male Hemophilic 0 for Female Hemophilic
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The End