Chapter 3 Flashcards
What is a gene?
An inherited factor (region of DNA) that helps determine a characteristic.
What is an Allele?
One of two or more alternative forms of a gene (like A or a).
What is a locus?
A specific place on a chromosome occupied by an allele/gene.
What is a genotype?
Set of alleles possessed by an individual organism (like AA, Aa, or aa)
What is a heterozygote?
An individual organism possessing two different alleles at a locus (Aa).
What is a homozygote?
An individual organism possessing two of the same alleles at a locus (AA or aa).
What is a phenotype or trait?
The appearance or manifestation of a characteristic.
What is a characteristic/character?
An attribute or feature possessed by an organism.
What is Dominance?
One dominant allele (A) can “hide” the phenotype of a recessive allele (a).
What is a dominant allele?
Mask the effect of the other alleles (capital letter, like A).
What is a recessive allele?
An allele whose effect is masked (small letter, like a).
What is True-breeding?
Both alleles are the same (same as homozygous).
-Homozygous dominant (AA)
-Homozygous recessive (aa)
What is the difference between cross-fertilizing and self-fertilizing?
In cross-fertilization, there are two different organisms. In self-fertilization, it is the same organism.
What is a Filial (F1 and F2)
The generations after the parent generation.
P= parental, first generation
F1= second generation
F2= third generation
What is a testcross?
If you have an organism with a
dominant phenotype, but you don’t know the genotype, you cross it with a known genotype (usually homozygous recessive) to determine the unknown genotype
What is the Wildtype?
The most prevalent allee in a “wild” population (+).
What is the difference between a locus and
an allele?
A locus is a place on a chromosome where genetic information encoding a characteristic is located. An allele is a version of a gene that encodes a specific trait.
What is the difference between
genotype and phenotype?
A genotype is the set of alleles possessed by an individual organism, and a phenotype is the manifestation or appearance of a characteristic.
When did Gregor Mendel publish?
In 1865
What were the keys to Mendel’s success?
- A good model organism
- Small number of traits examined
- Easily differentiated characteristics controlled by a single gene
- His math, counting results, and writing everything down.
What are Monohybrid Crosses?
Cross between two parents that
differ in a single characteristic. The hybrid of two individuals with homozygous genotypes which result in the opposite phenotype for a certain genetic trait
*Looking at one trait (gene) at a time
What were the 4 conclusions of monohybrid crossing?
1: one character is encoded by two genetic
factors.
2: two genetic factors (alleles) separate when
gametes are formed.
3: The concept of dominant and recessive
traits.
4: Two alleles separate with equal probability
into the gametes.
What is the Principle of Segregation (Mendel’s first law)?
Each individual diploid organism possesses two alleles for any particular characteristic. These two alleles segregate when gametes are formed, and one allele goes into each gamete.
What is the Concept of Dominance?
When two different alleles are
present in a genotype, only the trait encoded by one of them―the “dominant” allele―is observed in the phenotype.
What explains monohybrid crosses?
The Principle of Segregation (The symbols in genetic crosses correspond to alleles on chromosomes).
What is a Punnett square?
A convenient way to trace the
probabilities of particular genotypes/phenotypes occurring
from a particular cross.
What is probability?
The likelihood of the occurrence of
a particular event. Used in genetics to predict the outcome of a genetic cross
What are the two probability rules?
- The multiplication rule
- The addition rule
What is the Multiplication rule?
Calculates the total probability of
two or more events that are
dependent on each other.
(Probability of two fours AND
then a five is 1/6x1/6x1/6 =
1/216)
What is the Addition rule?
The addition rule calculates the total
probability of two or more events that are not dependent on each other.
(The total probability of rolling either a three OR a four is 1/6 + 1/6 =2/6 = 1/3).
What is a Dihybrid Cross?
Examine two traits (or genes for Mendel) at a time. Led to The Principle of Independent Assortment.
Experimentally, dihybrids are similar to
monohybrid crosses: two plants that are
either homozygous dominant or homozygous recessive for TWO traits are crossed to give an F1 heterozygote. This plant is self-fertilized to give F2 progeny.
What is the Principle of Independent Assortment?
States that alleles of two or more different genes assort independently from one another
What did Sutton do?
Chromosomal Theory of Heredity. Sutton explained everything by chromosomes, meiosis, and fertilization.
What are the Common Ratios for phenotypes and genotypes?
Also common is the 9:3:3:1 ratio, which is a classic Mendelian ratio for dihybrid crosses.
What is a Branch Diagram?
What are the gamete combinations?
Total number of combinations that can occur in gametes = 2^n
(n= haploid number of chromosomes). Example that humans have 23 chromosomes, so they have 2^23 gametes.
How are the principles of segregation and independent assortment related, and how are they different?
Both the principle of segregation and the
principle of independent assortment refer to
the separation of alleles in anaphase I of
meiosis. The principle of segregation says that
these alleles separate, and the principle of
independent assortment says that they
separate independently of alleles at other loci.
How is probability of dihybrid crosses found?
What is statistics?
Provides a way to accept or reject hypotheses in an unbiased manner. In other words, we can accept a hypothesis if certain statistical criteria are met.
What does the Chi-Square Test determine?
It determines the expected numbers based on hypothesis.
What is the Chi-Square Goodness of Fit?
Indicates the probability that the difference between observed and expected values is due to chance.
When do the Observed and Expected values of a Chi-Square test match?
When the x^2 value is to the left of 0.05.
When do the Observed and Expected values of a Chi-Square test not match?
The more the x^2 value is less than 0.05
What are the steps of a Chi-Square problem?
First find the x^2 value, then find the degrees of freedom (n-1). Then determine the level of significance with these values and the chart.
How is the expected value found in Chi-Square Test?
Multiplying the ratio of the expected proportion to the total number observed.
What is a pedigree?
Pictorial representation of a family history, a family tree that outlines the inheritance of one or more characteristics
What is a proband?
The person from whom the pedigree is initiated.
What is an Autosomal dominant trait?
AA or Aa would be affected and aa would not be affected. Aa is the more common genotype of someone with the condition. Examples are Huntington’s disease, Waardenburg syndrome.
What is an Autosomal recessive trait?
AA would be unaffected, two normal alleles. Aa would be a carrier, with one affected allele. aa would be an affected individual. Examples include sickle cell anemia, cystic fibrosis, albinism.
What is the difference between sex-linked and autosomal traits?
Sex-linked traits are due to genes that occur on the chromosomes that determine sex, while autosomal traits are due to genes that occur on any of the other chromosomes
What are the symbols used in a pedigree?
How are relationships shown in a pedigree?
