Genetics - DVUSD
Transcript of Genetics - DVUSD
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GeneticsThe study of genes and the
inheritance of traits
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THE STUDENTS WILL:
■ Explain how traits are inherited■ Identify the role of Gregor Mendel
in the History of Genetics■ Use a Punnett Square to predict
the results of crosses.■ Compare and Contrast the
difference between an individual’s genotype and phenotype.
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Vocabulary:
■ Heredity Phenotype■ Allele Homozygous■ Genetics Heterozygous■ Hybrid■ Dominant■ Recessive■ Genotype
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Inheriting Traits
■ Nose shape, eye color, and any other physical features are some of the traits that are inherited from parents.
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An organism is a collection of traits, all inherited from its
parents.
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Heredity
■ The passing of traits from the parent to the offspring
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• Generally, genes on chromosomes control all the traits that show up in an organism.
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Alleles
■ The different forms of a trait that a gene may have are called alleles
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- When a pair of chromosomes separates during meiosis, alleles for each trait also separates into different sex cells
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Important!
Every sex cell has one allele for each trait….
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What is Genetics?
The study of how traits are inherited through the interactions of alleles is the science of Genetics.
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Gregor Mendel- Father of
Genetics
-Austrian monk/ teacher-Began experimenting with garden peas in 1856-Made use of Scientific Method-First to use the Mathematics of Probability to explain heredity.-First to trace one trait through several generations.-Died in 1884 (work unnoticed)-His work was rediscovered in 1900
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Genetics in Garden
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Genetics in a Garden
-Each time Mendel studied a trait, he crossed two plants with different expressions of the trait and found that the new plants all looked like one of the two parents.
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Genetics in a Garden
Mendel called these new plants HYBRIDS because they received different Genetic information or different alleles, for a trait from each parent.
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Genetics in a Garden
An organism that always produces the same traits generation after generation is called a PUREBRED.
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■ HybridAn offspring that
was given different genetic information for a trait from each parent.
■ PurebredAn offspring that
always produces the
same traits generation after
generation.
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Mendel’s cross between tall pea plants yielded all tall pea plants
X =
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His cross between small pea plants yielded all small pea plants.
X =
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Mendels’ cross between tall pea plants and small pea plants yielded all tall pea plants.
X =
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Mendel then crossed these second generation tall pea plants and ended up with 1 out 4 being small.
X =
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DOMINANT AND RECESSIVE
TRAITS
■ Recessive Traits:Describes a trait thatis covered over, or dominated, byanother form of that trait and seems to disappear.-Weaker Trait
● Dominant Traits: Describes a trait that covers over, or dominates another form of that trait.-Stronger trait
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Traits compared by Mendel
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Using Probability to Make
Predictions
-A branch of mathematics that helps you predict the chance that something will happen.
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■ Mendel also dealt with Probability
■ Worked with a large number of plants to make his predictions accurate.
■ Studied almost 30, 000 pea plants over a period of 8 years.
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PUNNETTE
SQUARES
-A handy tool used to predict results in Mendelian genetics.
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Punnett
Squares
-Letters represent dominant and recessive alleles
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HOW?
-An upper case letter stands for a dominant letter.
- A lower case letter stands for a recessive allele
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Alleles
■ B – is considered a dominant allele
■ b – is considered a recessive allele
BB – is dominant
Bb or bB – is dominant
bb - is recessive
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GENOTYPE & PHENOTYPE
■ Genotype- genetic makeup of an organism
Ex. BB (Homozygous Dominant)■ Phenotype- the way an
organism looks and behavesEx. Black Fur
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Alleles Determine Traits
■ Most cells in your body have 2 alleles for a trait.
■ These alleles are located on chromosomes within the nucleus of cells.
Example:Trait- HeightT - allele would be for Tallt - allele would be for short
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Alleles determine Traits
■ Homozygous- an organism with 2 alleles that are the same
Ex. TT ( Tall), BB (Blonde Hair), tt, bb
■ Heterozygous- an organism with 2 different alleles for a trait.
Ex. Tt, Bb