genetics Flashcards
gene
segments of DNA that code for basic units of heredity
allele
alternate version of a gene
monohybrid cross
study one characteristic
testcross
determines if dominant trait is homozygous or heterozygous by crossing with recessive
dominant
expressed
recessive
hidden
genotype
genetic makeup
phenotype
expressed physical traits
homozygous
all the same, eg. AA, aa
heterozygous
mixed, eg. Aa
incomplete dominance
F1 hybrids have appearance that is between that of 2 parents
Eg. red x white = pink flower
codominance
phenotype of both alleles is expressed
Eg. red hair x white hairs = roan horses
multiple alleles
gene has 2+ alleles
Eg. human ABO blood groups
crossing over explains
why some linked genes get separated during meiosis
recombination frequency
frequency of production of offspring with new combo of genes from parents
#recombinants/#offspring x 100%
linkage map
genetic map that is based on % of crossover events
phenotypic plasticity
how genes are expressed can change due to environment
Eg. twins, one goes to space and one goes to earth
karyotype
person’s complete set of chromosomes
monohybrid cross
focuses on one characteristic, 1:2:1 (genotypic), 3:1 (dominant to recessive)
dihybrid cross
focuses on two characteristics, 9:3:3:1
monohybrid heterozygous ratio
3:1
heterozygous dihybrid cross ratio
9:3:3:1
female chromosome pair
XX
male chromosome pair
XY
eggs chromosome
X
sperm chromosome
X or Y
what genes do fathers pass onto their kids?
X-linked genes to daughters, but not sons
what gene do males express on
recessive trait on the single X
linked genes located on
same chromosome
how are linked genes inhertied
together during cell division
If linked genes results do not follow Mendel’s Law of Independent Assortment
then the genes are probably linked
relation between crossing over and recombination frequency
the further apart 2 genes on same chromosome, the higher the probability of crossing over and the higher the recombination frequency
50% recombination represents
far apart on same chromosome or on 2 different chromosomes
Gene mapping and recombination frequency
1 map unit = 1% recombination frequency
Express relative distances along chromosome
deletion
removes chromosomal segment
disjunction
repeats a segment
inversion
reverses segment with a chromosome
translocation
moves a segment from one chromosome to a nonhomologous chromosome
duplication
Gregor Mendel
Austrian monk
Brought experimental and quantitative approach to genetics
Bred pea plants to study inheritance
why did Mendel study peas
Control mating (self- vs. cross-pollination)
Many varieties available
Short generation time
P (parental) generation
true breeding plants
F1 (first filial) generation
offspring
F2 (second filial) generation
F1 offspring
Law of Segregation
the 2 alleles for each character separate during gamete formation
mendel’s principles
Alternate version of genes (alleles) cause variations in inherited characteristics among offspring.
For each character, every organism inherits one allele from each parent.
If 2 alleles are different, the dominant allele will be fully expressed; the recessive allele will have no noticeable effect on offspring’s appearance.
Law of Segregation
punnett square
Device for predicting offspring from a cross
law of independent assortment
Each pair of alleles segregates (separates) independently during gamete formation
Eg. color is separate from shape
Rule of Multiplication
probability that 2+ independent events will occur together in a specific combination 🡪 multiply probabilities of each event
Rule of Addition
Probability that 2+ mutually exclusive events will occur 🡪 add together individual probabilities
Complete Dominance
Mendel’s simple genetics - classic pea crosses
heterozygote and homozygote for dominant allele are indistinguishable
blood transfusion rule
must match blood type
what happens if incompatible blood is mixed
clumping and death
rh factor
protein found on RBC’s (Rh+ = has protein, Rh- = no protein)
Polygenic Inheritance
the effect of 2 or more genes acting upon a single phenotypic character
Nature and Nurture
both genetic and environmental factors influence phenotype
Pedigree
diagram that shows the relationship between parents/offspring across 2+ generations
Autosomal Recessive genetic disorders
Cystic fibrosis (CF)
Tay-Sachs disease
Sickle-cell disease
Phenylketonuria (PKU)
autosomal dominant genetic disorders
Huntington’s disease (HD)
Lethal dominant allele
pleiotropy
one gene is able to affect multiple phenotypic characteristics
epistasis
phenotypic expression of one gene affects that of another
