Inheritance Flashcards
how was inheritance believed to behave before Mendel
a range of blending from mother and father (equal contributions)
what was predicted to happen if the blending hypothesis was correct
a freely mating population would make way to genetically uniform individuals (all the same)
what does blending hypothesis fail to explain
how traits reappear fully developed after skipping a generation
what is an allele
contrasting alternatives of a gene which can be dominant or recessive
what is a phenotype
the observable properties of an individual
what is a genotype
the genetic makeup of an individual gamete usually with reference to a specific characteristic
difference between genotype and genome
genome- an organisms complete set of DNA with all its genes and noncoding DNA
what is the location on a chromosome that holds the allele called
the gene locus, indicated by placing a line on a chromsome
what is the P generation
the parental generation (homozygous)
what is the F1 generation
the offspring of the P generation (most often heterozygous)
why does each gamete only have one gene
because gametes are haploid
(at fertilization you get the same gene but not always the same allele)
what does particulate inheritance mean
that alleles are discrete unchanging traits that can be passed down
what is Mendel’s first law of inheritance
alleles of a gene segregate independently of each other during gamete formation
(the law of independent segregation)
what is the principle of independent assortment
the alleles of one has nothing to do with the allele of the other (in dihybrid crosses RRYY)
what is incomplete dominance
genes have different degrees of dominance and recessiveness in relation to each other
how do we show incomplete dominance in the genotype
use superscripts to show there is no implication that one is dominant over the other (often times are blended)
example of multiple alleles
blood type
different types are denoted I with superscripted A or B, and lowercase i for type O
what is codominance
when they express both alleles simultaneously without any blending (blood type AB)
what is epistasis
when the activity of one gene influences the activity of another
(one gene can mask the expression the alleles in another gene ex: if pigment cannot be deposited into skin despite whatever allele it ahs for colour none will show)
what is polygenetic inheritance
when two or more genes affect the outcome of a single trait
(typically phenotypes show in a bell curve, ex: height, weight, skin colour, etc)
what is pleiotropy
when a single gene affects more than one characteristic of an organism
what is probability
the extent to which an event is likely to occur (ranges from 0-1)
what is the product rule
when two or more events are independent the probability that they will both occur is calculated by multiplying their individual probabilities together
what is the sum rule
when two or more events are mutually exclusive (cannot both happen) the probability that either will occur is calculated by adding their individual properties
which is the heterogametic sex
males, XY
which is the homogametic sex
females, XX
which chromosome has a larger number of genes on it
the X chromosome
what is it called when something i linked to the X-chromosome
x-linked
what are other unlinked chromosome called
autosomes
what is a Barr body
an inactivated X-chromosome only found in females (because they have two)
what is it called when an x chromosome is inactivated
lyonization
what can lyonization lead to
few whole body effects due to selective inactivation of the X-chromosome throughout the body (patchy placement of things like colour or sweat glands)
what is the SRY gene
a gene linked to the Y- chromosome
what is the SRY gene responsible for
it is the switch that directs the development towards maleness at an early stage in embryo development (if inactivated will continue to female)
what are carriers
women that are heterozygous for a certain disease
they don’t express the disease due to a dominant allele suppressing it but they can pass the disease
why is it only/almost always male offspring that inherit an x-linked disease
they will always get an x from their mother (if it is the recessive/disease carrying allele there is nothing to suppress it)
why do we use pedigree charts
to determine if a human trait is dominant or recessive and autosomal or x-linked (we can’t experiment on humans so we look at family trees)
how to determine if a trait is autosomal
affects males and females equally
when is a trait autosomal dominant
when there are no carriers (everyone who has it displays it), and no skipping of generations
how to determine if it is x-linked
shown predominantly in the male population
