Genetics Experiments With Pea Plants Gregor Mendel Genetics Experiments With Pea Plants

Mendel Noticed Pea Plants varied by: height, color of flowers, position of flowers, seed color, seed shape, pod color, pod shape

Mendel Hypothesized

Mendel Hypothesized Variations in pea plant appearance was due to something (some information) passed along during reproduction by the parent plants.

Mendel’s Experimental Design

Mendel’s Experimental Design Mendel raised pea plants to “breed true,” I.e. tall only produced tall, short only produced short

Mendel’s Experimental Design Mendel raised pea plants to “breed true,” I.e. tall only produced tall, short only produced short Mendel crossed one true-breeding variety with the alternate true-breeding variety, e.g. tall x short

P1 Tall X Short

P1 Tall X Short F1 All Tall

P1 Tall X Short F1 All Tall F2 3/4 Tall 1/4 Short

Mendel Hypothesized That something was passed from parents to offspring to determine height; he called this an allele

P1 Tall X Short T t F1 All Tall T F2 3/4 Tall 1/4 Short

Mendel Hypothesized That something was passed from parents to offspring to determine height; he called this an allele Further, since the t allele was “hidden” in the F1, but reappeared in the F2, plants must have a pair of alleles for each trait.

P1 Tall X Short TT tt F1 All Tall Tt F2 3/4 Tall 1/4 Short T? tt

When an organism had a pair of alleles the same, e. g When an organism had a pair of alleles the same, e.g. TT or tt, he called this homozygous When an organism had an unlike pair of alleles, e.g. Tt, he called this heterozygous These terms refer to an organism’s genotype The appearance of the organism he called it’s phenotype

Practice Vocab Ex. Plant Height Genotype Phenotype Pure or Hybrid Homozygous/ Heterozygous

More practice Ex. Flower color Genotype Phenotype Pure or Hybrid Homozygous/ Heterozygous

Mendel proposed several principles regarding his findings If an organism is heterozygous and only one phenotype appears, this is the dominant phenotype, the alternate is the recessive phenotype When an organism reproduces, allele pairs must segregate and only one member of each allele pair is passed along to the next generation.

Solving Genetic Problems T T t t t T T t T X t = T t F1

Punnett Square

TT X tt t t Genotype 4/4- Tt Phenotype 4/4- Tall Tt Tt Tt Tt T

Practice Space

Test Cross What is the genotype of a short pea plant?______ What is the genotype of a tall pea plant?_____ or _____ Mendel developed a way of testing whether the tall plant is homozygous or heterozygous. It was the test cross

Test Cross problem T_ X tt

Independent Assortment The inheritance of any characteristic is independent of the inheritance of any other characteristic. Ex. The inheritance of height is independent from pea color. Mendel provided evidence for this through dihybrid crosses.

Dihybrid Cross TtPp X TtPp To solve this problem you can use a 16 block punnett square or the Forkline method.

16 Block Punnett Square

Fork Line Method

Ex. TtPp X TtPp

Practice with Fork Line Method

Practicing Punnett Squares

Inheritance patterns that Mendel did not know about Incomplete dominance Codominance Multiple alleles Polygenic Inheritence Sex Linkage

Incomplete Dominance Incomplete dominance does not involve an allele that masks recessive allele. Instead there is a blending of the two alleles. Ex. Red flower X White flower =Pink Cross Two Pink flowering plants

Example Cross a two pink flowering plants RW X RW

Codominance Codominance does not involve an allele that masks recessive allele. Instead both alleles show in the phenotype Ex. Brown horse X White horse =Spotted Cross a brown horse with a spotted horse

Codominance Exmple Cross a brown horse with a spotted horse. BB X BW

Multiple Alleles Some phenotypes can be determined by more than two alleles. Ex. ABO Blood type Genotypes Phenotypes AA - A Blood Type AO - A Blood Type BB - B Blood Type BO - B Blood Type OO - O Blood Type AB - AB Blood Type

Blood Type Problems Cross a heterozygous A blood type with a heterozygous B blood type iAiO X iBiO

Polygenic Inheritance The inheritance of some characteristics are determined by more than two alleles. Ex. Skin color, eye color, height, and noses. Phenotypes of polygenic inheritance are a result of the blending of many genes.

Sex Linkage Who determines the sex of the baby? How would a gene found on the X chromosome be inherited and expressed differently in males vs. females?

Sex Inheritance X Y X XX XY XX XY

Sex Linked Problems X-Linked Color Blindness is carried on the X Chromosomes. It is recessive. What are all of the different possible combinations of genotypes an individual could have?

Sex Linkage Problem Cross a Colorblind male with a woman who is a carrier for colorblindness. XcXC X XcY

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Practice Sex Linkage Problems