Sept 14 (Mendelian Genetics II) [_/13]
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What is a gene?
A section of DNA that contains instructions for a specific trait or function.
Example: A gene in a pea plant can help determine flower color, such as purple or white.
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What types of gametes are made in a monohybrid cross?
In a monohybrid cross, each gamete carries one allele for the single gene being studied.
Example: A heterozygous Pp parent makes two types of gametes: P and p.
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What is meant by a filled shape? What about an unfilled shape? [Pedigree]
● / ■ Filled shape = the person has the trait being studied.
○ / □ Unfilled shape = the person does not have the trait being studied.
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What is an allele?
A different version of a gene.
Example: For a flower-color gene, P is the purple allele and p is the white allele.
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What gametes in a dihybrid cross?
In a dihybrid cross, gametes contain one allele from each of the two genes being studied.
Example: An AaBb parent can make 4 types of gametes: AB, Ab, aB, and ab.
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Homozygous dominant pedigree?
Homozygous dominant: The person has two dominant alleles (AA).
Example: If the pedigree tracks a dominant trait, an AA person is affected (filled).
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What is a test cross (draw)?
Test cross: A cross used to determine an organism’s unknown genotype by breeding it with a homozygous recessive organism.
Example: Cross an unknown purple plant (P_) with a white plant (pp) to find out whether the purple plant is PP or Pp.
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[Pedigrees] What does a circle denote? What does a square denote?
In a pedigree:
○ Circle = Female
□ Square = Male
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Homozygous recessive pedigree?
Homozygous recessive: The person has two recessive alleles (aa).
Example: If the pedigree tracks a recessive trait, an aa person is affected (filled).
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What makes a particular pattern of inheritance Mendelian?
A pattern is Mendelian when a trait is controlled by one gene with dominant and recessive alleles that follow Mendel’s laws of inheritance.
Example: In Mendel’s pea plants, purple flowers (P) are dominant over white flowers (p), so PP and Pp are purple, while pp is white.
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How do we label generations?
In a pedigree, generations are labeled with Roman numerals:
I = 1st generation
II = 2nd generation
III = 3rd generation
IV = 4th generation
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What is a monohybrid cross?
Monohybrid cross: A genetic cross that studies the inheritance of one trait.
Example: Crossing two pea plants (Pp × Pp) to study only flower color.
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What do generations show us?
Generations indicate different levels of a family over time, such as grandparents → parents → children.
Example: I = grandparents, II = parents, III = children.