Download Heredity Chpt 11

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Inheriting Trait
Heredity is the passing of traits from parent to
offspring
Genetics is the study of how traits are inherited
through the interactions of alleles
Alleles are the different forms of a trait that
make up a gene pair
 Alleles separate in the sex cells during meiosis
and results with one allele is being donated by
each parent for the traits they carry
Gregor Mendel, 1856, Austrian
monk studied how traits were
transferred to offspring
 Studied pea plants and 7 traits
 Used scientific method and
mathematics to predict offspring
traits
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When plants always produce the same
traits generations and generation they are
called purebreds
He noticed when he crossed purebreds
with different traits they always produce
one of the traits by one parent. He called
these hybrids
 For example: crossed purebred tall pea
plants with purebred short pea plants
and always got tall plants
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Cross pollination techniques allowed Mendel
to cross the tall and short purebreds
The result was always tall plants
Mendel called the tall form the Dominate
factor while the short form was called
Recessive factor
In the first generation the short trait
disappeared , while the tall trait dominated
over the short
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Punnett square is a tool to help predict the
possible outcomes of traits
Mendel used capital letters to represent each
allele that were dominate (TT) representing
tall purebred .
He used small letters for the same alleles that
were recessive(tt) short plants
Two alleles that are the same are called
homozygous (both above are homozygous)
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Heterozygous refers to an organisms
with 2 different alleles Tt
Tt represents a crossbred plant with
one allele (Tall) and one allele (short)
 The offspring is tall because the tall
allele dominates over the short
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Genotype is the genetic make up of an
organism
TT, tt and Tt represents the genetic make up of
pea plants dealing with tall and short plants
 Actual alleles present in an organisms
Phenotype represents the actual appearance of
the offspring
 TT would appear tall, Tt would appear tall, tt
would appear short
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On the top of square, one parent has both
alleles above the square, one each in each
section
The vertical side has one parent has both
alleles, one each in each section
Each square in grid is filled with one allele
from each parent
Probability of offspring can be calculated
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1. traits are controlled by alleles on
chromosomes
2. An allele’s effect is dominant or
recessive
3. When a pair of chromosomes
separates during meiosis, the
different alleles for a trait move into
separate sex cells
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When 2 homozygous parent show
intermediate phenotypes it is called
Incomplete Dominance
Occurs when some pure white flowers cross
with pure red flowers and phenotype of
offspring is pink
When cross the pink flowers, the result was
some pink, white and red flowers on 2nd
generation
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Some traits are determined by more than 2
alleles
A trait that is controlled by more than two alleles is
said to be controlled by multiple alleles
Traits controlled by multiple alleles produce more
than three phenotypes
Blood type is determined by 3 alleles
A, B, O blood alleles
O is recessive homozygous OO
AB both A and B is expressed
A blood type could be AA, or AO
B blood type could be Bb or BO
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Groups of gene pairs acts together to produce
a trait
Effect of many genes acting on a trait effect a
wide variety of phenotypes
Eye color, height, skin color are examples
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Chromosomes disorders can occur because of
wrong numbers of chromosomes produced
during meiosis
Down syndrome is a result of 3 copies of
chromosome 21
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In order for a recessive disorder to show
up, both parents may have the hidden
recessive gene but not shown in one or
either parent
Cystic fibrosis is homozygous recessive
disorder
 Disorder produces thick mucus in
lungs that make it hard to breath
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Females are designated XX(both
alleles for sex are the same)
Males XY (X or Y alleles can be
donated )
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Sex linked gens is an allele on a sex
chromosome
Color blindness is a recessive disorder caused
on X allele
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Female would be color blind if both X alleles are
present
Male will be color blind if the X allele is present
Males most generally are color blind
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http://www.youtube.com/watch?v=yEIM4jm
K1F0&feature=related
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Dominate sex linked disorders are rare and
result when a person inherits at least on
dominant sex linked allele
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Vitamin D rickets is an example where kidneys can’t
absorb adequate amounts of phosphorus leading to
soft bones, teeth
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Represent a tool to follow traits of family
Squares represent male
Circles represent females
Affected traits are colored in
You can follow traits thru family history and
compare if it is a sex linked
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Genetic engineering is the experimenting with
biological and chemical methods to change the
DNA that makes up a gene
Help in medicine, genetic crops have been
completed with genetic engineering
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Recombinant DNA: inserting a useful
segment of DNA from one organism into
bacterium
 Insulin for diabetics is a result of
recombinant DNA
Gene Transfer: replace abnormal
genetic material with normal genetic
material
Genetically Engineered Plants: finding
the genes that produce desired traits in
one plant and inserting those into a
different plant