Transcript Genetics - Aurora City Schools

Chapter 9 – Patterns of Inheritance
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Primitive civilizations -- domestication of
plants and animals, important demonstration
of early genetic engineering, lead to
agricultural development
Gregor Mendel -- laid down the foundation for
the field of genetics (early 1800s)
(http://science.discovery.com/videos/100-greatest-discoveries-shorts-genetics.html )
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Morgan (1900s) – used fruit flies to identify
chromosomes as region of cell where genes are
stored in the cell
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Modern Genetics
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Populations Genetics - Evolution
Oncology, oncogenes and Cancer
Genetic Disease and Gene Therapy
Recombinant Technology (e.g., crop resistance,
animal breeding, etc...) http://www.youtube.com/watch?v=YXPnQvcqHkg
DNA Fingerprinting
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Genetics – the study of inheritance (the
transmission of traits from one generation to
the next)
Mendel’s Experiments:
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He performed controlled breading experiments
Pea plants have distinct characteristics that are
passed on from one generation to the next in
determined mathematical ratios
Traits: (see picture)
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He experimented on peas with monohybrid
crosses (following the inheritance of one single
trait when two heterozygous parents are
crossed).
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Different morphological traits come in two's (e.g.,
smooth or wrinkled seed), must be 2 particles
inside the cell that determine the morphological
trait, (Today we know theses are alleles =
alternative forms of a gene)
Relationships exist between alleles, most common
is dominance (an allele that is more powerful than
the other allele of the same gene). Recessive alleles
are masked by the dominant ones
Law of segregation - alleles segregate on gametes
(today we know – because the gametes are
haploid, they carry only one copy of each gene)
Law of independent assortment – during gamete
formation (meiosis), alleles of DIFFERENT traits
are arranged independently from one another
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Solving monohybrid problems with dominant and
recessive inheritance
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Solving dihybrid cross problems (crossing two traits
at a time where the parents are heterozygous to both
traits)
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To study human inheritance, human pedigrees
are used – a chart to follow a certain trait over
several human generations.
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You must be able to determine the type of
inheritance by using human pedigrees
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Recessive disorders:
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Albinism – lack of pigment in skin, hair and eyes
Cystic fibrosis – excess mucus in lungs, digestive
tract and liver
Sickle-cell disease – sickled blood cells, damage to
many tissues
(Pamela’s story: http://www.nhs.uk/Conditions/Sickle-cell-anaemia/Pages/Introduction.aspx
The disease: http://www.youtube.com/watch?v=9UpwV1tdxcs )
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Dominant disorders:
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One type of Alzheimer’s disease – mental
deterioration
Huntington’s disease – mental deteioration,
uncontrollable movements
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More often the inheritance patterns are more
complex than simple dominant and recessive
inheritance.
Incomplete dominance – a form of intermediate
inheritance in which one allele for a specific trait is
not completely dominant over the other allele. This
results in a combined phenotype. (ex.: red and
white snapdragons will have pink flowered
offspring)
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Codominance – It occurs when both of the
contributions of both alleles are visible and do
not over power each other in the phenotype
(ex.: A and B blood groups)
Pleiotropy -- occurs when a single gene
influences multiple phenotypic traits (ex. Sickle
cell disease)
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Polygenic inheritance – A simple phenotypic
characteristic is inherited by the interaction of
at least two genes. (Ex. Skin color in humans)
The frequency of the traits with polygenic
inheritance follow the shape of a bell curve.
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Many characteristics result from the
combination of heredity and environment (skin
color, weight, height)
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Genes occupy specific loci on chromosomes
and it is the chromosomes that undergo
segregation and independent assortment
during meiosis.
Because of the chromosomal theory, if genes
are located on the same chromosome, they are
inherited together and not independently from
one another – linked genes
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Chromosomes that are responsible for the
determination of the gender – sex
chromosomes
In humans and most mammals XX determines
a female and XY determines a male.
In other organisms there may be a different
system of sex chromosomes.
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Genes that are located on either the X or Y
chromosomes are sex linked
These genes are inherited differently in males
and females because the X and Y chromosomes
do not carry the same genes.
Genetic disorders that have genes on the X
chromosome show up more frequently in
males than females. While Y-linked disorders
only show up in males.
Males get their X chromosome from their
mother.
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You must be able to solve genetic problems with
sex-linked inheritance in traditional genetic
problems and in pedigrees.