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Genetics PowerPoint PPT Presentation

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Genetics. Investigation 9-2. Quick Review. The traits in a population of walkingsticks change over the course of several generations. Green Brown Green-brown How can that kind of change happen?. Inheritance. Passing genetic information from one generation to the next

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Investigation 9-2

Quick review

Quick Review

  • The traitsin a population of walkingsticks change over the course of several generations.

    • Green

    • Brown

    • Green-brown

  • How can that kind of change happen?

  • Inheritance


    Passing genetic information from one generation to the next

    (why offspring grow up pretty much looking like their parents)

    • You inherited alleles from your parents, larkeys inherit alleles from their parents, and the same is true of every other living thing on Earth.

    Gregor mendel

    Gregor Mendel

    • The pioneer on inheritance

    • He spent years growing thousands of plants and animals, observing closely to see how similar they were to their parents.

    Gregor mendel cont

    Gregor Mendel (cont.)

    • His most important work was done with pea plants

    • All of his pea plants had flowers, but there was variationin the feature of color.

    • Some had the trait of purple flowers, some had the traitof white flowers.

    • When both parent pea plants had purple flowers, the offspring has purple flowers. (same with white)

    • With one purple & one white parent, some offspring had purple flowers and some had white flowers

    • He reasoned the offspring must inheritsomething from each parent to determine color, but didn’t live to find out the answer.





    • Inheritance unfolds inside the cell

    • Everything is made of cells and that’s where the information describing how to make you resides

    • Cells have smaller structures inside that perform functions essential to life.

    • One of interest is the nucleus.



    • Inside the nucleus is the inheritance messenger, DNA.

    • DNA molecules are coiled again and again into structures called chromosomes.

    • Chromosomes carry the message of inheritance.



    • Nucleus of a cell from the larkey.

    • There are 8 chromosomes, looking a little like bent hot dogs of different lengths.

    • Chromosomes always come in pairs.

    • Our larkey has 4 pairs of chromosomes, rather than eight different ones.



    • Look at these 2 dark areas. Both chromosomes in a pair have dark areas in the exact same location.

    • The dark areas are called alleles .

      (alleles aren’t really dark-its used to represent the location of the alleles on the chromosomes)


    • The2 alleles on the paired chromosomes work together.

    • Together they constitute a gene.

    • A gene (2 alleles working together) controls a trait.

    • This gene could be the one that determines the larkey’s eye color, or perhaps the pattern of its fur.



    • Nuclei contain chromosomes

    • Chromosomes come in almost identical pairs

    • Chromosomes have specific active locations called alleles.

    • The two alleles in identical locations on paired chromosomes constitute a gene.


    • Each larkey feature is controlled by one gene.

    • Each of the four genes is on a different chromosome.

    • The gene for appendages (legs) is the 2 (A) alleles.

    • Eye color (E)

    • Fur pattern (F)

    • Tail (T)


    • Both uppercase and lowercase letter Es are alleles for eye color

    • The alleles are the code that determines the traits of the larkey

    • This chart is the larkey genetics code

    • The alleles for legs are aa (so on)



    • The combination of alleles in an organism’s chromosomes is the organism’s genotype.

    • The genotype lists the paired alleles that are particular to that organism.

    • The previous chart is the genotype of one of the larkeys in the yammer


    • Alleles don’t all have equal influence in determining traits.

    • Some alleles have more influence.

    • Dominant allele—more-influential alleles and are represented by an uppercase letter

    • Recessive alleles—less-influential and are represented by a lowercase letter


    Identify the two alleles for each feature as dominant or recessive

    Leg length –

    Eye Color—

    Fur pattern—



    • The left column has the 4 alleles this larkey got from its mother.

    • The right column has the 4 alleles it got from its father.

    • Use the transparency 6 to fill in the Genotype box.

    • The middle column shows all the possible combinations of alleles in the genes for each of the 4 features and the traits that results from each combination.


    • What alleles make up our larkey’s gene for leg length?

    • What trait does that produce in our larkey?

      (draw the legs on the larkey)

    • Do the other features, adding the traits to the torso.



    • This is what the larkey with this genotype looks like.

    • PHENOTYPE—the way it looks

    Genetics vocabulary

    Genetics Vocabulary

    The offspring of organisms often grow up to look like one or both of their parents. This is because offspring inherit information from their parents that directs their development.

    The inherited information is located in the _____________ of every cell in the organism. The information is coded in the huge ______________ molecule. The huge molecules are coiled into compact hot dog–shaped structures called ______________. ________________ are always present in almost identical pairs. Locations on chromosomes that affect features of organisms are called ______________. A gene is composed of _____________.

    An organism’s unique combination of genes is its . The traits produced

    by an organism’s genes is its _____________. Alleles that have more influence in

    determining traits are _____________alleles. Alleles that have less influence in determining

    traits are ______________alleles.



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