Lecture 4 (Mendelian Genetics and Beyond) Flashcards
blending hypothesis
a genetic material from the two parents blend together
particulate hypothesis
parents pass on discrete heritable units (gene)
P generation
True breeding parents
F1 Generation
Hybrids (determines the dominant allele)
F2 Generation
children of hybrids
Homozygous
2 of the same allele for a character (PP)
Heterozygous
2 different alleles for a gene (Pp)
hybrid
heterozygous
True Breed
homozygous
genotype
what are the alleles
phenotype
what is the physical appearance of the individual
locus
a specific position on a chromosome where a particular gene is located
Understanding dominant vs recessive alleles
instead of there being a specific locus for the recessive allele, there might instead just be the absence of the enzyme that prevents it from making the dominant allele which then results in the recessive allele
character
a heritable feature that varies among inviduals
trait
each variant of a character (for example different colors)
test cross
you mate the mystery individual with a homozygous individual based on the results you figure out the alleles for the mystery individual
law of segregation
2 alleles for one gene will separate in gamete formation
law of independent assortment
states that one pair of alleles separates independently of another pair of alleles (for a different gene) during gamete formation
the multiplication rule
use when you have one individual and want to figure out the chances of multiple events
the addition rule
add fractions together when you want to know the chance of any number of separate events occurring in one individual
dominant allele
usually makes a functional protein
recessive allele
usually does not make a functional protein
complete dominance
occurs when the phenotypes of the heterozygote and the dominant homozygote are identical (Ex: both Pp and PP produce a purple color)
Incomplete dominance
the phenotype of the heterozygotes is somewhere between the phenotypes of 2 parental variants (think blending hypothesis)
codominance
2 dominant alleles affect the heterozygote in separate distinguishable ways (for example: blood)
pleiotropy
most genes have multiple phenotypic effects
Sickle cell disorder
recessive disorder
abnormal RBC shape
cause damage to spleen, respiratory problems, chest pain, fatigue, pale skin, increased chance of infections, stroke, death
PKU (Phenylketonuria)
recessive disorder
inability to break down phenylalanine
can cause intellectual disabilities, seizures, fair skin, musty odor, mood disorders, ADHD
Cystic Fibrosis
recessive disorder
inability to transport Cl- ions outside the cell
causes build up of mucus in lungs, blocked pancreatic and bile ducts, infections in chest and sinuses, problems absorbing nutrients from food, infertility
albinism
recessive disorder
inability to produce a pigment named melanin
causes vision problems, and usually a lack of skin pigmentation
huntington’s disease
dominant disorder
a misshapen protein builds up in brain
causes lack or coordination, dementia, heart disease, seizures, depression
achondroplasia
dominant disorder
a misshapen protein involved in repressing bone growth that is always active
dwarfism with short arms and legs, a large head, a normal sized torso, frequent ear infections, breathing problems
polydactyly
extra fingers/toes
KEEP IN MIND THAT DOMINANT ALLELES ARENT NECESSARILY MORE COMMON THAN RECESSIVE ALLELES
haplosufficiency
having only one normally functioning allele is enough to be completely healthy
haploinsuffiency
having only one normally functioning allele isnt enough to be healthy
epistasis
a gene at one locus alters phenotypic expression of a gene at a second locus
polygenic inheritance
an additive effect of 2 or more genes on a single phenotype
quantitative characters
those that vary in population along a continuum
multifactorial characters
have polygenic and environmental influences on phenotypes
how does temperature affect the phenotype
a sensitive allele whose product is functional only at certain temperatures
in some animals, temperature determines the sex of the offspring
how does environment impact phenotypes?
a child’s environment or access to nutrients and proper education could affect their intelligence or height (nutrients)
hydrangeas color changes based on the soil acidity
Himalayan rabbits the color of their fur changes based on cold temperatures. present in all the body but turned on only where it is cold (nose, ear, feet)
