Monohybrid & Dihybrid Crosses

Mendel proposed that traits observed in pea plants resulted from a combination of "factors" inherited from each parent. His description of these "factors" can be considered the first scientific definition of the role of —

• ribosomes

• meiosis

• genes

• cell nuclei

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Mendel's early work with pea plants demonstrated a significant genetic discovery. The crossing of homozygous tall pea plants with homozygous short pea plants always resulted in tall plants and demonstrated that tallness in pea plants is a trait that is —

• blended

• dominant

• mutated

• recessive

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The physical expression of a genetic trait is called a

• mutation

• genotype

• crossing over

• phenotype

Start with the P generation with the following genotypes (AA x aa). Based on classical Mendelian inheritance, how will a cross between two homozygous parents, one dominant, one recessive, influence future generations?

• The F1 generation will show an even split between the dominant phenotypes and the recessive genotype.

• The F1 generation will show the dominant trait and future crosses will continue to produce genotypes expressing the dominant trait.

• Although the F1 generation will all show the dominant trait, the offspring will all be heterozygous and increase the chances of future variation.

• The F1 generation will show a mix of the dominant phenotype and recessive phenotype and over generations, the recessive trait will increase in number.

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Using the chart shown, correctly identify how the genotype would be written for a heterozygous round seed shape.

• RR

• Rr

• rr

• rR

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A couple has three brown-eyed children. The parents are brown-eyed (Bb). The allele for brown eyes is dominant over the allele for blue eyes. They believe the fourth child they have will be blue-eyed. Which statement below explains what actually will happen?

• The couple will have a blue-eyed fourth child.

• The couple will have a brown-eyed fourth child.

• They have a 75% chance of having a blue-eyed child.

• They have a 25% chance of having a blue-eyed child.

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Who is the father of genetics? 

• Charles Darwin 
• Gregor Mendel
• Dimitri Mendeleev 
• Hans Krebs 

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Objective #5

(B-brown eyes & b-blue eyes)

Cross (Dad)Bb X (Mom)BB.

List the possible genotypes from this cross.

• BB, Bb, bb

• BB

• BB, Bb

• bb,Bb

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Mendel established the Law of Segregation. Each gamete produced by a parent contains only _______allele for a trait.

• 1

• 2

• 3

• 4

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What is another way of saying "purebred"?

• homozygous
• dominant
• recessive
• heterozygous

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