molecular - genetics, inheritance, and pedigree

law of dominance

in a heterozygote, one allele may conceal the presence of another

law of segregation

in a heterozygote, two different alleles segregate from each other during the formation of gametes

law of independent assortment

each gene’s two alleles are transmitted independently and randomly to each gamete

gene

a discrete unit of inheritance controlling a trait

allele

a variant within a gene, each individual has two per gene

locus

a specific place or region of the genome

genotype

the genetic makeup of an individual for a specific trait

phenotype

the physical expression of a trait by an individual

dominant

an allele whose phenotype will always express

recessive

an allele whose phenotype only expresses in the absence of a dominant allele

heterozygous

an individual who has two different alleles for a specific gene

homozygous

an individual who has two identical alleles for a specific gene

wild type (wt)

the most common allele in a given population

variant

an alternative allele from the wild type

monohybrid cross

beginning with two tru breeding organisms, we cross them to produce heterozygotes (F1)

3:1

what is the ratio of phenotypes in a monohybrid cross?

dihybrid cross

beginning with two organisms that are true breeding for two traits, we cross them to produce double heterozygotes (F1)

9:3:3:1

what is the ratio of phenotypes in a dihybrid cross?

anaphase 1

one copy of each chromosome is assorted at random into each gamete during which phase?

prophase 1

genes within each chromosome assort semi independently in which phase?

recessive

_____ variant alleles are commonly loss of function

dominant

_____ variant alleles are commonly gain of function

22

how many pairs of autosomes in a human?

autosomal dominant inheritance

all individuals with this are affected

50%

what is the chance that each child of affected autosomal dominant parents will be affected?

autosomal recessive inheritance

individual must have two copies of this allele to be affected, those with one copy are carriers

25%

what is the chance that each child of affected autosomal recessive parents will be affected?

x linked recessive inheritance

50% of male children of carrier mother affected, female children of carrier mother are unaffected, female children of carrier mother and affected father are affected

x linked dominant inheritance

all children of affected mother have 50% chance of being affected; females are 100% and males are 0% from affected father; females are 100% and males are 50% in both parents affected

incomplete dominance

heterozygotes are the intermediate

codominance

heterozygotes express both traits fully

incomplete penetrance

only some individuals of a given genotype will express the aberrant phenotype, common in inherited cancer syndromes

variable expressivity

one genotype produces a variety of phenotypes, marfan syndrome or neurofibromatosis

haplotype

a set of alleles in different genes that are usually inherited together

polygenic traits

multiple loci contributing to one overall phenotype

pleiotropy

one gene controlling seemingly unrelated phenotypes

genetic mosaicism

specific portions of the body have different genetic make up than the rest of the person

chimerism

two different genotypes present due to fusion of two zygotes