Ch 14 Flashcards
Model for genetic transmission in the 1800s
“blending” hypothesis, like paint colors mixing
plant utilized by Mendel
pea plant
why did Mendel choose peas
they are available in many varieties, they have short generation time, have large numbers of offspring, and you can strictly control mating between individuals
a character
a heritable feature that varies among individuals such as flower color
trait
each variant for a character, such as purple or white flowers
reproductive organs of a pea plant
located in a flower, each plant has both pollen producing organs (stamens) and egg-producing organs (carpel), peas usually self-fertilize
which characters would Mendel only track
character that occurred in distinct, alternative forms, ex purple or white flowers
P
parental generation
F1
First filial generation offspring
true-breeding plants
self-pollinated over many generations, and had only produced the same variety as the parent plant, utilized by Mendel
hybridization
the crossing of two true breeding varieties
latin word for son
filial
F2
second filial generation
as for the size of his samples, Mendel usually kept them very
large
Dominant Pea traits
Purple flower, Axial flower, yellow seed, round seed, inflated pod, green pod, tall stem
Recessive Pea traits
White flower, terminal flower, green seed, wrinkled seed, constricted pod, yellow pod, dwarf stem
what Mendel called genes
heritable factor
four parts of Mendel’s model
- alternative versions of genes account for variations in inherited characters
- for each character, an organism inherits two copies of gene, one for from each parent
3.if the two alleles at a locus differ, then one, the dominant allele, determines the organism’s appearance; the other, the recessive allele, has not noticeable effect on the organism’s appearance
4 (law of segregation) the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes
law of segregation
the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes
alternate versions of a gene
an allele
Punnett square
handy diagrammatic device for predicting alleles
homozygous
an organism that has a pair of identical alleles for a character; breeds true
heterozygous
an organism that has 2 different alleles for a gene
phenotype
organism’s appearance or observable traits
genotype
organism’s genetic makeup
testcross
breeding organisms of unknown genotype
monohybrids
the F1 progeny produced in Mendel’s crosses of true-breeding parents, meaning that they were heterozygous for one particular character in the cross
monohybrid cross
cross between such heterozygous monohybrids
dihydbrid
an individual heterozygous for two characters being followed in a cross
dihybrid cross
a cross between F1 hybrids
key ratio in assortment in single allele
3:1
dependent assortment
genes connected
independent assortment
genes are unconnected
dihybrid ratio
9:3:3:1
law of independent assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation
when does the law of independent assortment only apply
genes (allele pairs) located on different chromosomes
independent events
events not affected by previous events
multiplication rule
to determine probability, we multiply the probability of one event (one coin coming up heads) by the probability of the other event (the other coin coming up heads)
the addition rule
the probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual properties
in order to find probability in dihybrid crosses
find the probabilities of the individual characteristics and use the multiplication rule
what di the rules of probability give us
the chance of various outcomes, cannot predict with certainty actual outcomes
the larger the sample size
the closer the results will match the prediction
one character dependent on more than one gene
pod shape; determined by two genes
alleles can show different degrees of what
dominance and recessiveness
complete dominance
the phenotypes of the heterozygote and the dominant homozygote are indistinguishable
incomplete dominance
neither alleles is completely dominant, F1 hybrids have a phenotype somewhere between those of two parent varieties
codominance
two alleles affect the phenotype in separate, distinguishable ways
codominance example in humans
M and N in blood cells , MM only M molecule, NN only N molecule, M and N both means both M and N molecules
do dominant and recessive alleles actually interact
no, it just means one’s effects overpower another’s effects in the phenotype only, both still function
is a gene dominant and recessive at all levels
no, its is subjective based on how deep you look, a gene may be dominant phenotypically, but codominant on the molecular level
Tay Sachs
child must be homozygous, brain cells do not properly metabolize lipids, brain accumulates fats, child dies young, however is codominant on molecular level, recessive allele still produces faulty enzyme just counteracted by correct enzyme produced by dominant allele
most genes exist in how many allele forms
more than 2
alleles of ABO blood groups
IA-codominant with IB, IB-codominant with IA, i-recessive,O
pleion
more in Greek
pleiotrophy
most genes exist in more than 2 allele forms
epistasis
Greek for standing upon: the phenotypic expression of a gene at one locus alters that of a gene at a second locus
all epistatic interaction produce ratio variations of
9:3:3:1
quantitative characters
characters vary in the population in graduations along a continuum
quantitative variation usually indicates
polygenetic inheritance
polygenetic inheritance
an additive effect of two or more genes on a single phenotypic character (the converse of pleiotrophy where a single gene affects several phenotypic characters)
what else affects phenotype other than genotype
environmental factors
norm of reaction
the range of phenotypic possibilities due to environmental influences
for some characters like blood type, the norm of reaction has
no breadth whatsoever; given genotype mandates specific phenotype
multifactorial
characters that have many factors both genetic and environmental, collectively influencing phenotype
phenotype
can refer to specific characters or all of its aspects
genotype
can refer to alleles for a specific genetic locus or an organism’s entire genetic makeup
what did Mendel call alleles
particles
the human generation span is about
20 years
why humans are bad for genetic research
the long human generation span, the ethicality of breeding people, humans produce relatively few offspring
pedigree
family tree describing the traits of parents and children across the generations
key for pedigree tree
square=male circle=female colored in=affected by trait under study #first born on the left and last on the right
albinism is
recessive
heterozygotes are called (in reference to their ability to pass a recessive trait onto their offspring)
carriers
consanguineous mating
(same blood) when close relative mate, the probability of passing on recessive traits increases greatly
recessive traits (distribution)
not evenly, often pockets of higher frequency
the most common lethal genetic disease
cystic fibrosis-chloride transport channels absent, resulting mucus builds up, lead to poor nutrient absorption of nutrients from the intestines, chronic bronchitis, and recurrent bacterial infections.
sickle-cell disease
most common among people of African descent, misshapen red blood cells
achondroplasia
dominant allele dwarfism
Huntington’s disease
degenerative disease of the nervous system which lays dormant until the middle of one’s life
processes that can detect Tay-Sachs Disease or other genetic disorders
amniocentesis, takes amniotic fluid from embryo to look for certain molecules
ultrasound and fetoscopy
new method for finding escaped fetal cells in mother’s blood
or chorionic villus sampling, sucks out tiny parts of the placenta
fetoscopy
needle- thin tube inserted into uterus which contains a viewing scope and fiber optics
PKU
treatable with special diet, cannot metabolize phenylpruvate, accumulates in blood and causes disability
