Chapter 3

Father of genetics

Gregor Mendel

What did Mendel study?

Pisum sativum

How was Mendel's work revolutionary for the time?

he used an experimental approach and analyzed results mathematically

Gene

an inherited factor, encoded in DNA, that helps determine a characteristic

Allele

one of two or more alternative forms of a gene

Locus

specific place on a chromosome occupied by an allele

Genotype

set of alleles possessed by an individual organis

Heterozygote

an individual organism possessing two different alleles at a locus

Homozygote

an individual organism possessing two of the same alleles at a locus

Phenotype/trait

the appearance or manifestation of a characteristic

Characteristic

an attribute or feature possessed by an organism

Monohybrid cross

cross between two parents that differ in a single characteristic

P generation

parental - first gen of a cross

F1 generation

first filial - offspring of the P generation

F2 generation

second filial - offspring of self-fertilized F1 generation

Mendel's First Conclusion

one character is encoded by two genetic factors

Mendel's Second Conclusion

two genetic factors (alleles) separate when gametes are formed

Mendel's Third Conclusion

the concept of dominance

Mendel's Fourth Conclusion

two alleles separate with equal probability into the gametes

Principle of Segregation

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.

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

Law of Dominance

hybrid offspring will only inherit the dominant trait in the phenotype. The alleles that are suppressed are called the recessive traits while the alleles that determine the trait are known as the dominant traits.

Law of Independent Assortment

A pair of traits segregates independently of another pair during gamete formation. As the individual heredity factors assort independently, different traits get equal opportunity to occur together. (the inheritance of one pair of genes is independent of inheritance of another pair)

Law of Segregation

During the production of gametes, two copies of each hereditary factor segregate so that offspring acquire one factor from each parent. Allele pairs segregate during the formation of gametes and re-unite randomly after fertilization. (every individual organism possesses two alleles and only one allele is passed onto the offspring)

Sutton

chromosomal theory of heredity

Backcross

a cross between an F1 genotype and either of the parental genotypes

Testcross

cross between an organism with an unknown genotype and an organism with a recessive phenotype

Probability

the likelihood of the occurrence of a particular event
# of times a particular event takes place/# of all possible outcomes

Multiplication Rule

the probability of two or more independent events taking place together is calculated by multiplying their independent probabilities

What must be true for the multiplication rule to be used

the outcome of one event must not influence the outcome of the other

Addition Rule

the probability of any of two or more mutually exclusive events is calculated by adding the probabilities of the events

What must be true for the addition rule to be used

the events whose probability is being calculated must be mutually exclusive; one event excludes the probability of the other

Conditional Probability

additional info that modifies or conditions the probability

Wild Type

the most common allele for a characteristic usually found in the wild, symbolized by one or more letters and a plus sign

Chi-square goodness-of-fit

evaluates the role of chance in producing deviations between observed and expected values