Simple Inheritance Patterns Flashcards
do most mutations in your genome affect phenotype?
no, they are not “functional” mutations
describe functional mutations; how are they transmitted?
affect phenotype; can only be transmitted to the next generation if they are in the “germline” cells of the organism
describe the “germ line”
lineage of cells set aside during development to differentiate into gametes in the adult
when is the germ line established?
when the embryo is patterned during development, like any other cell type
rest of the cells (besides germ line cells)
somatic cells
mutations that occur in the germline during meiosis give rise to…
mutant gametes
if the mutation in the germline is functional, what does the gamete give rise to?
a new “mutant” individual with a new phenotype after fertilization and development
when do mutations occur during mitosis?
any point in an individual’s life
consequence of mutations that occur in a differentiated cell that is no longer dividing (or dividing very little)
won’t alter an organisms phenotype, even if they are “functional mutations”
consequence of mutations that occur during mitosis in a cell that keeps dividing
will create a population of cells with a different “genotype” than the rest of the organism
describe “genetic mosaics”
individuals in which a subset of cells have acquired new mutations (we are all one), a lot of the mutations are not “functional” and don’t affect phenotype
what happens if a functional mutation occurs during mitosis early in development?
may give rise to a genetic mosaic with a mosaic phenotype
if a functional mutations occurs during the first cell division of a zygote, what is the result?
the resulting individual’s cells will carry the mutation and display the phenotype
if a functional mutation affects the germline cells, what is the result?
the mutation can get passed on to the next generation
results of functional mutations in the “cell cycle checkpoint genes” of dividing cells (skin cells, breast tissue, lung tissue)
can lead to cancer (a type of genetic mosaicism)
if your parents have cancer, you won’t automatically inherit their cancer. why?
the series of mutational “hits” that ultimately cause most cancers are in somatic cells (not germline)
why then does cancer have a heritable aspect?
you do inherit any mutational “hits” transmitted from your parents in their germline cells that make cancer more likely
are phenotypes caused by heritable functional mutations always transmitted perfectly to offspring? why?
no, because of sexual reproduction
describe the blending hypothesis
old idea that traits simply mix like paint colors to give a variety of intermediate forms
describe the particulate hypothesis
traits transmitted as distinct units
Mendel’s 4 part model for particulate inheritance
1) different versions of the same gene, called alleles account for differences in a trait between individuals
2) for each gene an individual inherits two alleles, one from each parent
3) if the two alleles an individual has are different, one will determine the appearance, it is “dominant”
4) an individual only passes on one allele to its offspring, which allele a particular offspring gets is random (law of random segregation)
“dominant”/“recessive” alleles
rare, not the best way to describe it
Mendel’s main insight
explained the inheritance patterns he saw over generations as ratios/percentages
no matter how many alleles Mendel looked at at once, how did they behave?
the behaved statistically independently; they were unlinked and assorted independently
