DO NOW: How could all of these puppies come from the same parents? (Write down your answer)
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Transcript of DO NOW: How could all of these puppies come from the same parents? (Write down your answer)
DO NOW: How could all of these puppies come from the same parents? (Write down your answer)
Patterns of Inheritance: Genetics
Modern genetics began in 1860’s
• Czech Monk- Gregor Mendel
• Playing with peas in his garden
“THE MAN”
Gregor Mendel
• Used peas to study how physical traits passed from parent to offspring - heredity
• Mendel measured 7 traits in peas, each trait with 2 forms.
Examples of two Pea traits (Shape & Color) that Mendel studied
How did Mendel do all this?• Step 1: Identify true
breeding plants
• When pure plants are self-fertilized, they ALWAYS produce offspring identical to the parent generation after generation.
• How could you ensure self pollination?
• Mendel crossed true breeding plants with two distinct traits using cross-fertilization.
Hybrids
• Offspring of two different true-breeding varieties.
• P – parental generation• F1 – offspring of P
generation• F2 – offspring of self
fertilized or cross fertilized members of F1 generation
Mendel’s 1st RuleThe Law of Segregation:
• For each trait (i.e. pod color or plant height) an individual has 2 factors
• The 2 factors may be the same or different
• When making kids, each parent will contribute only 1 factor
• The 2 factors a parent has will separate when making a kid (Meiosis)
The Law of Segregation
• Each parent will pass on 1 factor during sex (gamete production)
• Kids get 1 factor (for each trait) from each parent...
Factors
The Factors
• Each individual has 2 factors for each trait…pod color, height, eyes, hair...
• If both factors for a trait are the same, you are homozygous for that trait…
• If you have 2 different factors for a trait, you are heterozygous for that trait
How to Label these factors?
• G for Green pods
• Y for yellow pods
• B for brown hair
• x for blond hair
But…we don’t do this!!
The Factors
• You have 2 factors, but only 1 factor for each trait is typically used (expressed)..
• This is the dominant factor
• The other one is the recessive factor
So; How we do Label the factors?
• Dominant factor is written in
upper case… i.e. “B”
• Recessive factor in lower case, using the dominant abbreviation.. i.e. “b”
• B is for brown hair (which is dominant)
• b is for blond
Mendel’s Factors = Genes
• Every normal human has thousands of genes
• Each gene describes the information for one human trait.
• You have two genes for each trait
• Where are these genes located?
How to Predict which factor you’ll give your
kids? • Each parent has 2 factors for each trait
• But, each gamete you produce has only 1 factor for each trait
• Which factor goes to which kid?
• Best described by a Punnett Square
Punnett Square..• Used to predict how offspring will get
their share of factors…
• Parents mate (x): BB X bb
• What possible offspring will each make?
B B
b
b
FemaleGametes
Male Gametes
Possible Offspring…. Or, F1 Generation
B B
b
b
Bb Bb
Bb Bb
Each F1 Offspring has the same traits for hair color… Bb
Try this one!
In summer squash, white fruit color is dominant to yellow fruit color.
What would the genotype and phenotype be for the F1 generation if the parental cross was homozygous white and yellow?
Another Example..Trait for Seed Shape (S)
Text pg 181
Mendel’s 2nd Law
Law of Independent Assortment:• Factors for each trait segregate into gametes
independently of each other• The factor for hair color (B or b) will segregate
independently of the factor for height (T or t)• Consider a dihybrid cross… Two traits at once
• Example: Say Parents are Bbtt x bbTT
Dihybrid Cross
• If a Bbtt male mates with a bbTT female?
• What are the possible gametes for each?
Male Bbtt x
Female bbTT
Bt bt
bT
bT
BbTt bbTt
BbTt bbTt
gametes
gametesNew individuals (with two factors for each trait)
So What?
• What does Mendel and his Peas have to do with you?
• Chromosomes and Heredity…
On Chromosomes• We each have 46
chromosomes in each cell
• 23 chromosomes came from Mom, 23 from Dad
• Each chromosome contains hundreds of genes…
An example using the FISH techniqueof identifying the location of one geneon a chromosome.
Gene location on Chromosomes