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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.

    GENOTYPE color

    • 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

    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 recessivelarkey 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.

    PHENOTYPE recessive

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

    • PHENOTYPE—the way it looks

    Genetics vocabulary
    Genetics Vocabulary recessive

    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.

    chromosome recessive