Chapter 12 Flashcards
Gregor Mendel
Austrian monk
mathematician (1860s)
studied pea plants
“factors”
F1 and F2 generations
Factors
genes
homologous chromosomes
Locus
location of gene
Allele
alternate form of gene
character (color) and trait (pur vs white)
True-breeding
bred trait for generations (multiple generations of purple and white)
used for hybridization
parental generation
F1
First filial generation
offspring of hybridization
F2
Second filial generation
offspring of hybrids
different traits often reappear
Mendel’s model of inheritance
Alternative forms of genes exist (alleles represented by letters)
Organisms inherit 2 alleles (one from each parent)
Dominant and recessive alleles
Dominant alleles
represented by capital letter
if present masks recessive
not “better” or “stronger”
Recessive alleles
will be masked by dominant
unless both alleles are recessive
may be carried into generation
Gametogenesis
Separation of alleles
Zygosity
degree of allelic similarity of Homo chromos
homo or hetero zygous
Homozygous
both alleles the same
dominant or recessive
AA, aa
Heterozygous
both alleles different
Aa (carrier)
Phenotype
visible appearance
Genotype
Actual alleles for trait
Monohybrid cross
one trait inheritance
follow sperm and egg
all combinations
complete dominance
punnett squares
Test cross
when you don’t know if PP or Pp
b/c both purple phenotype
perform test cross with pp
Dihybrid cross
two trait inheritance follow sperm and egg
independent assortment
all combination of gametes
Probability of events
ranges from 0 ->1
independent events
multiplication rule
event 1 and event 2
ex: P sperm and p egg
1/2 x 1/2 = 1/4
Addition rule
event 1 or event 2
ex: P sperm; p egg
OR p sperm; P egg
1/4 +1/4 = 1/2
Law of segregation
mendel had not knowledge of chromosomes
1 trait must be masked and carried into F2
each plant has 2 factors
1 factor dominates other
factors separate during gametogenesis.
Law of independent assortment
mendel had no knowledge of meiosis
distinct traits do not affect each other
dependent and independent assortment
Dependent assortment
both traits dominant or recessive
prediction -> 3:1
Independent assortment
all gamete combinations tracked
prediction -> 9:3:3:1
during metaphase, 2nd source of genetic variation
color does not affect smoothness
Pedigree analysis
chart of family history
emphasis on one trait
squares (M) circles (F)
shaded (affected)
infer genotypes from previous generations and current offspring
Autosomal dominant
genotypes of “WW” or “Ww”
rarer (no widows peak;ww)
Autosomal recessive
more common (cannot taste PTC)
must inherit “tt”
Autosomal recessive disorders
Tay-sachs disease: lack certain enzyme build up in lysosome
Cystic Fibrosis: affects Cl- channels creates thick mucus
Albinism
Sickle cell disease: sickle cell trait ; heterozygote; malaria resistance
Autosomal dominant
Osteogenesis imperfecta: weakened/brittle bones, collagen synthesis
Huntington disease: neurological disorder, degeneration of brain cells
Incomplete dominance
Intermediate phenotype
3 phenotypes possible
ex: red + white = pink
Codominance
Heterozygote
alleles equally expressed
AB blood type
Multiple allels
several allelic forms exist, you can only have 2
Epistatic interactions
interaction between gene factors, one gene overrides another
