MENDELIAN GENETICS

Gene

basic unit of heredity

allele

alternate form of a gene at a given locus

locus

site on a chromosome where a gene is located

Genotype

alleles possessed by an organism, typically represented by two letters

Phenotype

physical expression of a trait

Autosome

any non-sex chromosomes

Heterozygous

have two different alleles for a given gene, designated with capital and lowercase letter, Dd

Homozygous

have two identical alleles for a given gene

Heterozygous dominant

Aa

Homozygous dominant

DD

Homozygous recessive

dd

Dominant

allele (trait) that confers same phenotype whether the individual is homozygous or heterozygous for a trait; denoted with capital letter

Recessive

allele (trait) that appears “latent” or non-expressed when the individual is heterozygous (has the dominant trait); denoted with a lowercase letter

Genetic cross

intentional breeding or mating of two parent organism to study how traits are transmitted to their offspring

P generation

original parents in a cross. (Original parents)

F1 generation

offspring resulting directly from breeding of P generation. (Children of the P generation)

F2 generation

offspring resulting directly from breeding of F1 generation.

Monohybrid cross

A _____ looks at one characteristic.

Monohybrid cross

cross between parents that differ in a single characteristic

Paired unit factors (genes)

each trait is controlled by a pair of unit factors, with one factor inherited from each parent.

Law of Dominance

In a pair of unit factors, one unit is dominant and will mask the presence of the other allele (the recessive) for the same trait characteristic

Law of Segregation

During gamete formation, the paired factors segregate randomly so

that each gamete receives only one factor.

test cross

A _____ used when you have an organism with a dominant phenotype

Dihybrid cross

cross between parents that differ in for two characteristics.

Law of independent assortment

alleles for different genes (e.g., eye color vs hair color) segregate independently of one another during gamete formation (meiosis)

Probability

likelihood of an event happening

Product Law

AND = MULTIPLY

Sum Law

OR = ADD

binomial probability

_____ is used when you're asked for exactly X successes among N offspring.

Forked-lined Method

_____ can be used for dihybrid, trihybrid, and larger crosses by breaking them into individual monohybrid crosses.

9:3:3:1

Dihybrid phenotype

Monohybrid genotype

1:2:1

Monohybrid phenotype

3:1

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