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Chapter 11 Introduction to Genetics Chapter 11 Introduction to Genetics

Chapter 11 Introduction to Genetics - PowerPoint Presentation

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Chapter 11 Introduction to Genetics - PPT Presentation

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

pea amp called plants amp pea plants called mendel trait traits study recessive shape alleles genes gene dominant cross

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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