LP3 Extensions of Mendelian Genetics

LP = lecture packet

What are the two postulates of mendelian genetics?

1) chromosomes segregate and independent assortment during gamete formation 2) gene are present on homologous chromosomes

complete dominance

hetzygote express same phonotype as one fo the homozygotes

incomplete dominance

hetzygote has an intermediate phenotype between homozygotes

codominance

hetzygote has phenotype that simulatenously expressed the phenotypes of both homozygotes

what is multiple alleles

when more than two alleles present for a given locusw

why can multiple alleles only be studied in populations?

one individual can only have two alleles, so to study all alleles, must have more than one individual.

can the recessive allele of blood gene make antigen?

no

lethal allele

a lethal allele is one that causes death @ early stages so genotype doesn’t appear in progeny. affects mendelian ratio, so can ID that way

recessvie lethality

when 2 copies of lethal allele produce phenotype that leads to death

dominant lethality

when 1 copy of lethal allele produces phenotype that leads to death

gene interaction

when effects of genes at one locus depends on the presence of genes around other loci

epistasis

expression of one gene or gene pair masking or modifying the effect of another gene pair. modifies 9:3:3:1

how many categories can epistasis affect?

one or more of the 4.

if gene C is necessary for the function of gene P (gene C came “first”, which gee is epistatic to the other?

gene C is epistatic to gene P

dominant epistasis

when dominant allele at one loci masks an allele at the second loci

dominant vs epistasis: masks genes at the SAME loci

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dominant vs epistasis: masks genes at the DIFFERENT loci

epistasis

recessive epistasis

when 2 copies of recessive allele at one locus masks other gene

dominant epistasis

when 1 copy of dominant allele at one locus masks other gene

recessive duplicate epistasis

when both genes need one dominant allele at both loci for a particular phenotype

what does it mean if a phenotype never breeds true?

the genotype is heterozygous

incomplete penetrance

les than 100% individuals having a particular gentoype express the expected phenotype

what compound is essential to adding the terminal sugar to prdouce A or B antigen in blood?

Compound H

Bombay Phenotype

type O due to incomplete H substance

proband

first person in family to have a genetic condition