Mendelian Genetics Flashcards
Testcross
A way to determine if an organisms is heterozygous or homozygous for a dominant trait.
What is the forked-line method?
It is a method to do a trihybrid cross by using forked lines to “track” the inheritance.
Chromosomal theory of inheritance.
Genetic material is contained in chromosomes.
Locus
A location on a chromosome where a specific gene is located.
Allele
A variant of a given gene.
Product law
The probability of two independent events occurring simultaneously is equal to the product of the two individual probabilities.
How to classify two chromosomes as homologous chromosomes?
Same length and centromere position.
During meiosis, they pair up.
Contain identical order of gene loci.
Sum law
The probability of obtaining a single outcome, where the outcome can be achieved by two or more events, is equal to the sum of the probabilities of the individual events.
With probability, predictions of possible outcomes are based on what? Why?
Large sample sizes. A small sample size may give abnormal ratios and influence probability. These variations are due to chance.
What happens to chance deviation as sample size increases?
It diminishes.
Chance deviation
Deviations from expected results are due to chance.
What are Mendel’s hypothetical ratios based on?
Each allele is dominant or recessive.
Segregation is unimpeded.
Independent assortment takes place.
Fertilization is random.
What should you remember when predicting or analyzing genetic outcomes?
Independent assortment and random fertilization are susceptible to deviations due to chance.
Chance deviation diminishes as sample size increases.
MP: Unit factors in pairs.
Genetics characters are controlled by unit factors existing in pairs in individual organisms.
MP: Dominance/Recessiveness
When two different unit factors are present in an individual, one is dominant and one is recessive.
MP: Segregation
During the formation of gametes, paired unit factors separate randomly so that each gamete has an equal likelihood of receiving it.
MP: Independent assortment
During gamete formation, segregating unit factors assort independently of each other, meaning the assortment of one does not influence another.
Null hypothesis
There is no real difference between the real and measured values. Any difference is due to chance.
What does it mean when you reject the null hypothesis?
The observed deviation is not due to chance alone.
What does it mean when you fail to reject the null hypothesis?
The observed deviation is due to chance.
Chi-square analysis
A method to determine the validity of the null hypothesis.
What do the symbols mean in chi-square analysis?
o: observed values
e: expected values, from ratios
(o-e): d, deviation
Degrees of freedom
It is the number of categories minus 1.
How to determine degrees of freedom?
The number of categories are the number of different phenotypes possible. Minus this value by 1.
Why is degrees of freedom important?
The more categories there are, the more deviation is expected due to chance.
How to determine probability for a given chi-square and degrees of freedom?
Use external table. Find correct degrees of freedom row and find cell containing chi-square value.
p<0.05
Observed deviation is due to chance less than 5% of the time. Reject null hypothesis.
p>0.05
Observed deviation is due to chance more than 5% of the time. Fail to reject null hypothesis.
Pedigree
A family tree indicating the inheritance of a specific trait.
Consanguineous
Parents are closely related.
Monozygotic twins
Identical twins. Same embryo.
Dizygotic twins
Fraternal twins. Different embryos.
Proband
The person in which the trait is first noticed.
Characteristic of autosomal recessive traits
Skip generations.
Characteristic of autosomal dominant traits
Present in every generation.
Wild type
Trait which is most common or expected in a species.
Transposable element
DNA sequence that can change its position within a genome.
