LS Chapter 5: Genetics and Heredity
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Genetics and Heredity
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_____________________
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The passing of traits from parents to offspring
_____________________
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The study of how traits pass through generations
_____________________
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The _____________________
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1800’s (so much biology in the 1800’s!)
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Austrian (NOT AUSTRALIAN) monk
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Worked in the monastery garden
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Background in math and science
Mendel’s Experiment
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Used _____________________
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Controlled the way that the pollinated (reproduced)
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Mated plants for a certain trait until they were _____________________ (a.k.a. _____________________)
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True-breeding organisms __________________________________________
He then mated 2 of the true-breeding plants together to form _____________________
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Hybrids are __________________________________________
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Example: Purple and white plant mated together, the offspring are hybrids
Mendel’s First Generation
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Mendel _____________________ plants together
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Each was true-breeding for 1 form of a certain trait
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Name: ______________________________
Example: True-breeding _____________________x true-breeding _____________________
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All of the offspring are considered to be _____________________
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All of them were _____________________
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Mendel hypothesized that the __________________________________________
Mendel’s Second Generation
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Mendel then took 2 of the offspring (_____________________) and _____________________
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For every _____________________ plants, there was _____________________one (_____________)
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The _____________________
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The same thing happened whenever he mated 2 of the hybrids together
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Not only that, it happened whatever trait he tried (height, seed shape, etc.)
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Mendel’s Conclusions
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From the experiment, Mendel concluded that __________________________________________
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He called the trait that covered the other up the _____________________
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He called the trait that was covered up by the dominant on the _____________________
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Correcting misconception: The dominant trait is not better, nor is it necessarily more common
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All “dominant” means is that it can cover up the recessive trait
Genes and Alleles
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While __________________________________________, he correctly guessed that something would be
found to explain inheritance
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A __________________________________________
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The different forms of a trait (ex. purple and white) are controlled by different forms of a single gene, called
alleles
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Ex. Gene for flower color
Example: Gene for flower color has alleles for purple and white
__________________________________________and __________________________________________
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We symbolize the _____________________and the _________________________________________
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Example: Dominant: _____________________; Recessive: _____________________
The _____________________Dominance and recessiveness are indicated by capital and lowercase.
Practice: Dominant or Recessive
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Are the following dominant or recessive?
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A-_____________________
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b-_____________________
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C-_____________________
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D-_____________________
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e-_____________________
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A note on the letters: Exaggerate if the capital and lowercase look similar!
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Inheritance of alleles
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Zz
You have __________________________________________in each body cell
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During _____________________, the chromosomes are sorted into _____________________, each
with __________________________________________as body cells
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When sperm and egg come together (______________), you get 23 chromosomes from mom and 23 from dad
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This means that, for each trait, _____________________
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The _____________________ _____________________ (segments of DNA) for traits
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They _____________________though
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Genotype and Phenotype
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_____________________=the genes (_____________________) that an organism has
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Example: __________________________________________
Think _____________________, _____________________
Practice: Genotype/Phenotype
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Example: _____________________
_____________________=The expression of the genotype (i.e. the _____________________of the organism)
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You can get an allele for blue eyes from your mom and brown eyes from your dad
Indicate whether the follow show a genotype or a phenotype:
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AA-_____________________
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Blue-_____________________
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Aa-_____________________
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Bb-_____________________
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Tall-_____________________
Homozygous vs. Heterozygous
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Because we inherit 2 alleles that may be either dominant or recessive, there are 3 combinations that they can
take
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Dominant-Dominant (_____________________)
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Dominant-Recessive (a.k.a. _____________________)
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“Homo” means “same”
When they have __________________________________________, we call them _____________________
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Ex. aa
When an organism has _______________________________for a trait, we call them _____________________
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Ex. Aa
Recessive-Recessive (_____________________)
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Ex: AA
“Hetero” means “different”
We combine the term “homozygous” with whether it is dominant or recessive
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AA=__________________________________________
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aa=__________________________________________
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Heterozygous is only one dominant and one recessive
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Aa=_____________________
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aA=_____________________
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____________________________________________________________________________________
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Indicate whether the following are homozygous dominant, homozygous recessive, or heterozygous
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SS-_____________________
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Nn-_____________________
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uu-_____________________
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mM-_____________________
Genotype/Phenotype, Homozygous/Heterozygous, Dominant/Recessive
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If there is ___________________________________, they will express the _____________________
Practice: Homozygous vs. Heterozygous
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Blue eyes (b) are recessive to brown eyes (B). With that in mind answer these questions:
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If a person has a genotype of Bb, what color eyes do they have?
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A person has blue eyes (phenotype). What is their genotype?
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A person is homozygous dominant for eye color. What is their genotype? What is their phenotype?
Predicting Offspring Traits
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There is no way to know for certain what offspring will look like.
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However, we can get a _____________________of what traits they may get.
_____________________
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A __________________________________________of offspring inheriting a certain trait.
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Shows _______________________________________________________________
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Note that it shows __________________________________________
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Note: Usually we’d flip this so the capital is in front because it is dominant
Thought Experiment: Coin flip
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If I flip a coin what is the percent chance it will be heads?
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If it comes up heads, what is the chance that the next flip will also be heads?
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If it comes up heads 100 times in a row, what is the chance that the 101st flip will also
be heads?
Using probability in genetics
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If a couple is having a child, what is the chance that it will be a boy?
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If a couple has 3 boys, what is the chance that their next child will be a girl?
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If there is a 50% chance of a child inheriting a genetic disorder and the couple has 1 healthy child, what is the
probability their next child will have the disorder?
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How to make a Punnett Square
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DRAW IT HERE:
Because there are 2 alleles for each trait for each parent, we
will draw a grid that is 2x2
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We will then put one parent’s alleles on the top
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It does not matter which parent (at least to me…)
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We will then put the other parent’s alleles on the left side
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These correspond to the possibilities of the sperm and eggs
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Then, bring the ones on top down each column and the ones
on the left across each row
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Example
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Another Example
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A person with genotype Gg and a person with genotype GG mate. What are the possible genotypes of the
children?
Brown hair is dominant to blonde hair. If a man heterozygous for brown hair (Bb) has a child with a blonde
woman (bb), what is the chance that the child will have blonde hair?
One more Example
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Brown eyes are dominant to blue eyes. A man and woman, each heterozygous for brown eyes, are expecting a
child. What is the probability that the child will have brown eyes? What about blue eyes?
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You Try It
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Free earlobes are dominant to attached earlobes. Harry, who is homozygous dominant for earlobes, has a child
with Ginny who is homozygous recessive for her earlobes. Answer the following questions:
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What is Harry’s genotype?
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What is Harry’s phenotype?
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What is Ginny’s genotype?
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What is Ginny’s phenotype?
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What is/are the possible genotype(s) and phenotype(s) that their children could have?
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Show your Punnett Square Below: