Genetics amp You Something to keep in mind as we begin our discussion on genetics Your traits are a combination of your genetic material DNA and the environment around you For Example ID: 752920
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Slide1
Chapter 11
Introduction to GeneticsSlide2
Genetics & You
Something to keep in mind as we begin our discussion on genetics
…
Your traits are a combination of your genetic material (DNA) and the environment around you.For Example: Why are people from poor countries often short? MalnutritionBecause of this…The physical appearance of an individual cannot always be directly linked to an individual’s genetic makeup.Slide3
Nature vs. Nurture
What can we use to study how the environment affects the expression of our genes?Slide4
Gregor Mendel
Considered the
“Father of Genetics”
Performed Experiments to Study HeredityHeredity – the passing of traits or characteristics from parent to offspringIn his experiments Mendel used Pea Plants.Why?Slide5
Mendel’s Pea Plants
Cheap & Readily Available
Easy to Grow & Don’t Move (easy to contain & control/manage)
Grow fast –study multiple generationsControl their breeding/reproductionCharacteristics were easy to study because they came in easily identifiable pairs. Round vs. Wrinkled Pea Shape Tall vs. Short Pea Plants Green vs. Yellow Pea PodsSlide6
Mendel’s Experiment
Mendel controlled the reproduction of his pea plants so he could study heredity.
He did this by:
Removing the Stamen (male) Contains the Anther Pollen = Plant Sperm Carpel (contains the stigma, style, ovary) – female reproductive structuresCrossed Plants that showed the same traits only.Created “true or pure bred” linesSlide7
Mendel’s Experiment
Once Mendel had his true or pure bred lines, he could cross plants that had
different
traits.What did Mendel look for? Patterns!Slide8
Observations
So what did Mendel observe when he performed his experiments?
________________ X ___________________
All _________________________
____________________ x ______________________
Ratio
3 ( ) __________________: 1 ( )
_________________Slide9
Dominant vs. Recessive
Traits like pea shape are said to be either
dominant
or recessive.A recessive trait become hidden by a dominant trait.In Mendel’s cross which trait was dominant?Which trait was recessive?How do we know recessive traits are present & get passed down?Slide10
Mendel didn’t know anything about Genes!
Gene – segment of DNA that codes for a specific protein which controls a trait.
Genes can exist in more than one form!For example Round or Wrinkled are 2 forms of the gene or protein for seed shape.We call these different forms of a gene: allelesEach parent has 2 alleles for each trait BUT only gives one to the offspring!Which one? That’s all chance!Slide11
Probability & Genetics
Diploid Organisms have 2 copies of each numbers chromosome.
Remember, chromosomes of the same shape and size are called:
Homologous ChromosomesHomologous Chromosomes carry the same genes but can have different forms or alleles of these genes.For Example: Both chromosomes 18 carry the gene that controls the shape of your hair line. (one chromosome 18 came from mom & one from dad) 18 A – Widow’s Peak 18 B – No Widow’s PeakSo, which one will you pass on to your child?Slide12
Probability & Genetics
Scientists can make
predictions
about which traits will get passed onto offspring & therefore what offspring might look like. The study of these predications is called probability.Probability Expressed as a fraction or a percent. Equation: # of times a specific event occurs total # of possible outcomes can be either dependent
or
independentSlide13
Inheritance of Alleles
Mendel crossed plants that differed in
one
gene/trait: pea shape.This type of cross is called a monohybrid cross.________________ X ___________________All _________________________
____________________ x ______________________
Ratio
3 ( ) __________________: 1 ( ) _________________Slide14
Generations & Punnett Squares
The plants involved in the 1
st
cross are called the parental or P generation.The offspring of the P generation are called the F1 generation.The offspring of the F1 generation are called the F2 generation.Punnett SquareCapital Letter represents the: Dominant AlleleLowercase Letter represents the: Recessive AllelePlace each parent’s allele combinations across the top & side of the box & fill in the squares.Slide15
Genotypes & Phenotypes
Both RR pea plants & Rr peal plants look round, but are they the same genetically?
Round is called a
phenotype = physical appearanceRr or RR is called a genotype = actually genes or alleles of an individualTwo Types of Genotypes Homozygous = two identical alleles (RR or rr) Heterozygous = two different alleles (Rr)Slide16
Genotypes & Phenotypes
Classify the following as either a genotype or phenotype.
For each genotype determine if it is homozygous or heterozygous.
RR Round RrSlide17
Genotypes, Phenotypes, & Punnett Squares
Every time you make a Punnett Square you
MUST
indicate both the Phenotypic & Genotypic Ratios!Let’s do an Example: homozygous round pea X heterozygous round pea