Chapter 9
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Chapter 9. Genetics. 9.1 The Work of Gregor Mendel. Mendel – crossed pea plants to study and understand genetics Most pea plants self pollinate ( true breeding ) Mendel forced plants to cross pollinate (have 2 plants). Studied 7 traits of pea plants pg 176.

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Chapter 9

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Chapter 9

Chapter 9

Genetics


9 1 the work of gregor mendel

9.1 The Work of Gregor Mendel

  • Mendel – crossed pea plants to study and understand genetics

    • Most pea plants self pollinate (true breeding)

    • Mendel forced plants to cross pollinate (have 2 plants)


Chapter 9

  • Studied 7 traits of pea plants pg 176.

  • Took the plants that had different traits and crossbreds them (hybrids)


The f1 cross

The F1 Cross

  • First Filial (parent cross, produce the F1, then cross the F1 making an F2)

    • Law of segregation: Segregation of alleles occurs during the formation of gametes, sex cells.

    • Pg 177

    • Law of Independent Assortment – factors for individual characteristics are not connected. Assort independently of each other.


Came to 2 conclusions after the breeding

Came to 2 conclusions after the breeding

  • Genes, segment of DNA, occurs in pairs, controll heredity. Visual form called alleles. (noted as “factors”)

  • Found that some of the alleles are dominant and some are recessive.

    • Dominant trait always uppercase (TT, Tt)

    • Recessive always lowercase (tt)


9 2 probability and punnett squares

9.2 Probability and Punnett Squares

  • Punnett square – table representation of crossing alleles

    • TT or tt – homozygous – same alleles

    • Tt – heterozygous – different alleles

    • Phenotype – physical look, all tall (TT, Tt) have same phenotype.

    • Genotype – based on alleles. (TT, and Tt) are different now.


Probability

Probability

  • Penny = ½ = .50

  • A cross results in 787 pink flowers and 277 white flowers. If we cross the same P generation, the probability will be the same)


Chapter 9

  • Dominant Recessive

  • Curled Up Nose Roman Nose

  • Clockwise Hair Whorl Counter-clockwise Hair Whorl

  • Can Roll TongueCan't Roll Tongue

  • Widow's PeakNo Widow's Peak

  • Facial DimplesNo Facial Dimples

  • Able to taste PTCUnable to taste PTC

  • Earlobe hangsEarlobe attaches at base

  • Middigital hair (fingers)No middigital hair

  • No hitchhiker's thumbHitchhiker's thumb

  • Tip of pinkie bends inPinkie straight

  • Oval faceSquare face

  • Cleft chinno cleft chin

  • Broad eyebrowSlender eyebrow

  • Separated eyebrowsJoined eyebrows

  • Long eyelashesShort eyelashes

  • Almond eyesRound eyes

  • FrecklesNo freckles

  • Wet-type earwax Dry-type earwax

  • Left thumb on top of

    interlocking fingersRight thumb on top of interlocking fingers


Chapter 9

Punnett Squares pg 182


Homozygous x homozygous

Homozygous x homozygous


Homozygous x heterozygous

Homozygous x heterozygous

  • AA x Aa


Hetero x hetero

Hetero x hetero


Summary of mendel s principles pg 272

Summary of Mendel’s Principles pg 272

  • Some alleles are neither dominant nor recessive, and many traits are controlled by multiples alleles or multiple genes.

  • Incomplete Dominance– when one allele is not necessarily dominant (red and white flowers produce pink)

  • Codominance – both alleles contribute to the phenotype.

  • Multiple alleles – within the population of the species there are more than just 2 types of alleles. Coloration in Rabbits

  • Polygenic Traits – having many genes, traits controlled by 2 or more genes. Skin color in humans.


Chapter 9

Incomplete Dominance


Chapter 9

  • We'll use "F" for the flower color allele. FR = allele for red flowers FW = allele for white flowers red x white -------> red & white spotted flowers FRFR  x FWFW ----> 100% FRFW


Codominance

Codominance

  • Problems


Explore punnett squares

Explore Punnett Squares!!

  • http://www.geocities.com/CapeCanaveral/Hall/1410/lab-B-19.html


Dihybrid cross two traits

Dihybrid cross – two traits


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