11.2 Study Guide Flashcards
(15 cards)
What are Mendels Two Laws of Heredity?
- Law of Segregation
- Law of Independent Assortment
What is “independent assortment” in meiosis?
The random segregation of different chromosome pairs into gametes, ensuring a wide variety of genetic combinations in offspring.
What is an exception to the Law of Independent Assortment?
If genes are linked they do not randomly segregate
What is a Dihybrid Cross?
a mating experiment between two organisms that are both heterozygous for two different traits.
What are the four steps to setup and use of a Punnett Square to determine Mendelian Genotype and Phenotype ratios?
- Write the Parent Genotypes
- Use FOIL to determine the potential Gamete Genotypes of each parent
- Line up the Genortype options for one parent on the side of the square and the other on the top of the square
- Fill in offspring and determine genotypic and phenotypic ratios
What is the Probability of A OR B if A and B are mutually exclusive events?
p(A or B) = p(A) + p(B)
The probability of either A or B is equal to the probability of A plus the probability of B
What is the probability of A AND B if A and B are independent but happen at the same time?
p (A and B) = p(A) x p(B)
The probability of both A and B is equal to the probability of A times the probability of B
What are the steps for setting up and using a Forked Line Diagram to determine genotype and phenotype ratios?
- Identify the traits and their alleles
- Establish the probabilities for each trait
For example, in a dihybrid cross where two heterozygous parents are crossed (e.g., AaBb x AaBb), the probability of inheriting the dominant allele is 3/4 and the recessive allele is 1/4 for each trait.
- Create the forked lines
Draw a series of lines, each representing a trait or a combination of traits. At the beginning, write the probabilities for the parental genotypes. For each subsequent line, branch out the probabilities for each possible allele combination.
- Multiply probabilities along each path
Multiply the probabilities along each path through the forked lines to determine the probability of obtaining a specific genotype or phenotype.
- Combine probabilities to find overall ratios
Sum the probabilities of all possible paths to obtain the overall ratios of different genotypes and phenotypes in the offspring.
What are polygenic traits?
Inherited characteristics where more than one gene is involved in determining the phenotype.
Do polygenic traits involved just two or many possibilities?
Many
Examples are hair color, eye color and height
Height is a polygenic trait but _______also significantly affects height in childhood.
Nutrition
What is an Epistatic Gene?
A gene that influences or modifies the expression of another gene (Hypostatic Gene).
What is a Hypostatic Gene?
A gene whose expression is affected by the epistatic gene.
Epistatic Traits
Epistatic traits occur when expression of one gene (the “hypostatic” gene) is influenced or masked by the presence or absence of another gene (the “epistatic” gene).
This means the phenotype associated with the hypostatic gene can be altered by the epistatic gene.
The epistatic gene can either completely mask the effect of the hypostatic gene (leading to a different phenotype) or partially modify it.
Example: In albinism, a recessive epistatic gene (lack of pigment production) masks the expression of genes that would otherwise produce skin and hair pigment.
Why were pea plants a lucky and wise choice to study genetics by Mendel?
- Relatively simple genetically
a. Most characteristics controlled by a single gene- with each gene having two alleles when one is completely dominant over the other - Pea plants are available in many varieties with distinct heritable features
- Mendel had strict control over the mating of the plants
