Chapter Two: Genetics & Inheritance Flashcards
What did Gregor Mendel’s work conclude? (5)
- Each parent contributes one factor of each trait shown in offspring (alleles)
- The two alleles contribute equally to offspring traits
- The blending theory was discounted
- Males & females contribute equally to offspring traits
- Acquired traits are not inherited.
What made Mendel’s work unique? (3)
- Methodical approach to a definite problem
- Use of clear-cut variables
- Application of statistics to a biological problem
Law of Dominance
One of the factors for a pair of inherited traits will be dominant and the other recessive, unless both factors are recessive
Law of Segregation
Paired alleles separate during gamete formation with each gamete receiving either one trait or the other
Law of Independent Assortment
When gametes are formed, alleles assort independantly
Genotype
Specific genetic makeup; written in terms of alleles.
Trait
Inheritable characteristic
Monohybrid cross
Cross examining ONE trait
Dihybrid Cross
Cross examining TWO traits
Test Cross
Cross used to determine if a parent is homozygous or heterozygous for a dominant trait. The parent is crossed with a heterozygous recessive individual
Product Rule of Probability
The chances of a gamete having multiple traits is the product of their individual chances.
Codominance
Two equally dominant alleles are expressed independantly
Polygenetic Inheritance/Multiple Allele Inheritance
More than one gene is responsible for a trait, results in continuous variation within the population.
Lethal Alleles
Allele that causes death to an individual during embryonic development.
Dominant & Recessive
Probability
The chance of an event occurring.
Theoretical Probability Formula
Probability = # of likely outcomes/total # of outcomes
Rules of Probability (3)
- The actual outcome will have a ratio closer to the predicted probability as # of trials increase
- Past outcomes don’t affect future outcomes
- The chance that two or more independent events will occur at the same time is equal to the product of their individual chances
Why are males more likely to get sex-linked traits than females?
Males only have one X-chromosome, so the allele is always expressed. Females, having two X-chromosomes, appeal to the rule of dominance.
Pedigree
Tool designed to show inherited phenotypes and can be used to logically deduce genotypes as well.
Autosomal Dominant disease
Disease is passed from father to son (not sex-linked)
Males and Females affected with roughly the same probability
Autosomal Recessive Disease
Males and females equally likely to be affected.
The recurrence risk to the unborn sibling is 25%
Non-Disjunction
An accident of Mitosis or Meiosis where a tetrad (Meiosis) or a pair of sister chromatids (Mitosis) fail to separate properly.
Deletion
A chromosomal fragment is lost.
Duplication
A chromosome fragment reattaches to its homologous chromosome, creating a duplicate sequence.
Inversion
A chromosomal fragment reattaches it is’s original chromosome in the reverse sequence.
Translocation (2)
- Insertions: a chromosomal fragment is attached to a non-homologous chromosome
- Exchanges: homologous chromosome pairs exchange chromosomal fragments
Karyotype
Collection of photographs of chromosomes during mitosis, arranged in homologous pairs snd placed in order of descending size.
Aneuploidy
An abnormal chromosome number:
Trisomy (+1)
Monosomy (-1)
Incomplete Dominance
The dominant trait does not completely mask the recessive trait.
