BIOL 111 Inheritance and Genetics

What was Mendel’s experimental design?

he observed 7 traits with 2 discrete forms and determined which were dominant and recessive to find occurrence ratios

What is true-breeding?

a plant that always produces the same phenotype when self pollinated

What is a monohybrid cross?

a cross between two individuals that differ in only one trait

What is the law of segregation?

each individual has two factors per trait that separate/segregate when gametes form

Where are genes located during meiosis?

at a specific locus on a pair of homologous chromosomes

In a monohybrid cross, what are the common ratios for genotypes and phenotype?

genotypes: 25% homozygous dominant trait, 50% heterozygous dominant trait, and 25% homozygous recessive trait

phenotypes: 75% dominant trait and 25% recessive trait

What is a dihybrid cross?

a cross between two individuals that differ in two traits

What is the product rule?

the probability of two independent events both occurring is the product of their individual probabilities

What is the sum rule?

the probability of either of two mutually exclusive events is equal to the sum of their individual probabilities

What makes an allele dominant or recessive? And what is its definition?

gene dosage: dominance reflects whether the cell can get by on half the usual protein dose

Why are recessive genes considered nonfunctional?

recessive alleles often have a mutation that causes a loss of function

What is haplosufficiency?

when one functional copy makes enough protein to produce a normal phenotype

What is haploinsufficiency?

when one functional copy doesn’t make enough protein and produces an altered phenotype

What is complete dominance?

when a heterozygote shows the dominant phenotype

What is incomplete dominance?

when a heterozygote presents an intermediate phenotype that is mixed or blended

What is codominance?

when both alleles are expressed equally

What is a genotype?

the allele combination an individual carries

What is a phenotype?

the observable trait produced by a genotype

What is the classic phenotypic ration that comes from a dihybrid cross?

9:3:3:1

How would you solve for the probability of either aa or Aa?

using the addition rule

How would you solve for the probability of aa and tt?

the multiplication rule

What are lethal alleles?

certain genotypes that are lethal to individuals and where removing lethal genotypes changes phenotypic ratios

What does it mean to be hemizygous?

individuals only contain one X chromosome

What is a common inheritance pattern?

affected males inherit from mothers, but cannot pass x-linked traits to their sons and only daughters inherit the x-linked allele

What is gene linkage?

when genes positioned close together on the same chromosome tend to be inherited together

What is true of linked genes?

they do not follow the classic ratios and produce excess parental combinations and fewer recombinant combinations

What is x-inactivation?

a mosaic phenotype that occurs in females

How do you determine dominant traits in a pedigree analysis?

dominant traits do not skip generations and one parent must always have the trait

How do you determine recessive traits in a pedigree analysis?

they can skip generations and unaffected parents can have affected offspring

How do you determine autosomal traits in a pedigree analysis?

males and females are equally likely to be affected by a trait and fathers can pass the trait to their sons

How do you determine x-linked traits in a pedigree analysis?

males are more commonly affected than females and fathers cannot pass the trait onto their sons

What is mitochondrial inheritence?

when females with mitochondrial mutations can pass genes to every one of her offspring

What is polygenic inheritence?

when multiple genes influence a trait

What is a map unit (centimorgan)?

the distance representing a 1 percent chance of recombination

What is independent assortment?

when genes separate without influencing each other because they are usually on different chromosomes