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
define trait/character
any aspect of the form or function of an organism (may or may not be determined by genes)
define phenotype, give an example
a particular measurable “state” for a character; character is hair color, phenotype is black hair color
what is phenotype determined by
may or may not be determined by genes (could be from the environment) but for this class, phenotype is determined by genes
define wild type phenotype
the most common likely original and ancestral phenotype during a given time frame
define gene
transcribed DNA sequences and their associated CREs that contribute to the form and function of an organism (analogous to trait or character)
define allele
a particular version of a gene, with or without mutations (analogous to phenotype)
define genotype (specific)
the two alleles of a gene present in an individual
define genotype (general)
all the alleles of all genes in an individual
what is the dominant allele (simple Mendelian gene)
the functional, wild type allele
what is the recessive allele (for simple Mendelian genes)
the “broken” allele (caused by a loaf of function mutation)
when does complete mendelian dominance of one allele work?
ONLY works if one good copy is enough to create the dominant phenotype (half dose of a gene’s product is as good as a full dose)
many genetic disease/ disorders that behave like simple Mendelian traits are mutations in what kind of genes?
tissue-specific effector genes
describe the term “carriers”
heterozygous for the dominant, functional wildtype allele and the broken, recessive allele
why is incest a bad idea?
we are all carriers of pathological and/or deadly recessive mutation alleles
basis of Mendel’s “law of random segregation”?
due to independent assortment of homologous chromosomes during meiosis
genes are on _____, alleles are on ______
chromosomes; homologous chromosomes
what does crossing over during meiosis ensure?
independent assortment of genes, even when they are on the same chromosome
