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Genetics

Study of heredity

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True breeding

All children have same traits

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Hybrid

Kids whose parents had different traits

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Trait

A specific characteristic

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Gene

DNA code for a trait

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Allele

The gene options

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Fertilization

Sperm meeting egg

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Gamete

Sex cell (sperm or egg)

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Zygote

Cell when sperm and egg meet

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Gregor Mendel

Austrian monk born 1822
Studied genetics and taught high school
Keep meticulous quantitative data

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Gregor Mendel's experiment on pea plants

Very short reproductive lines
Simple control of offspring
Many obvious traits
Able to selectively breed or self pollinate

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(Mendel's crosses) p

The two parent plants
Two different true breeding (yellow and green)

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(Mendel's crosses) F1

The first generation (p x p)
All offspring have same allele (green)

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(Mendel's crosses) f2

Second generation (f1 x f1)
1/4 of offspring have a different allele than parents (3/4 green and 1/4 yellow)

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(Mendel's conclusions) An individuals characteristics (traits) are determined by

Factors (genes) that are passed from one parent generation the next

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(Mendel's conclusions) an individual gets

One allele from each parent

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(Mendel's conclusions) principle of dominance

Some alleles are dominant (always appear) and others are recessive (hidden by the dominant)

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(Mendel's conclusions) Law of segregation

During gamete formation the alleles for each gene separate from each other, so that each gamete carries only one allele for each gene

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Homozygous

Having two of the same alleles

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Heterozygous

Having two different alleles

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Phenotype

The appearance of the individual

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Genotype

The allies in their genes (DNA)

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Probability

The chance that a particular event will occur

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Allies are represented by

Letters

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Alleles (referring to Punnett square)

= genotype = phenotype = probability

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Genotype ratio 1:2:1

Always homozygous dominant : heterozygous: homozygous recessive

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Phenotype ratio

Dominant to recessive

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Two factor cross

A huge Punnett square with 4 columns and 4 rows
Looks at how two different traits are inherited together

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Dihybrid

Both parents are heterozygous for both traits
Phenotype ratio 9:3:3:1 ratio

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Independent assortment

Genes for different traits can segregate independently during formation of gametes (this gets way more complicated)

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Mendel's principles

Inheritance of biological characteristics is determine by individual units called genes which are passed from parents to offspring
Where two or more forms (alleles) of the gene for a single trait exits, some alleles may be dominant and others may be recessive
In most sexually reproducing organisms each adult has two copies of each gene - one from each of their parents. These genes segregate from each other when gametes are formed
Alleles for different genes usually segregate independently of each other

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Incomplete dominance

Neither allele is dominant
Heterozygous phenotype is a mix
Example: red and white = pink
(Allele letters are both capital)

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Codominance

Neither allele is dominant
Heterozygous phenotype is a mix
Example: red and white = roan(candy cane)
(Allele letters are both capital)

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Multiple alleles

There are more than two options
Example = rabbit coat color

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Polygenic traits

Several genes produce many different traits
Human skin color
Four different genes control the trait

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Environmental affects

The environment can affect gene expression and influence genetically determine traits

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Meiosis

Process by which gametes are formed
Contain half the normal number of chromosomes as somatic cells
Known as "haploid" and number of chromosomes in this state is represented as "n = ____"
Diploid number is represented as "2n = ______"

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Mechanics of meiosis

Cause genetic reshuffling to occur at random and can result in genetic reshuffling producing new allele combinations