Mendelian Genetics Flashcards
alleles
different forms of same trait
true breeding plants
always give same type of offspring when self pollinated
hybrid/hybridization
Have two different alleles for a trait
Monohybrid cross
tracks the inheritance of single trait
P generation-
(parental generation)- two true-breeding parents
with contrasting alleles
F1 generation-
(first filial)- hybrid P offspring
F2 generation
allowing F1 generation to self pollinate
Homozygous
organism having a pair of identical alleles for a character
Phenotype-
organism’s appearance (purple or white)
Heterozygous
organism having two different alleles for a gene
Genotype
genetic makeup (PP, pp, Pp) (homozygous dominant,) (homozygous recessive,) (heterozygous [always dominant])
blending inheritance-(false)
fluids of parents, carrying the traits, would blend together during reproduction to form intermediate hybrids.
Give an example that proves blending inheritance false
the F1 generation would have pale purple flowers, and it does not
Law of segregation
during meiosis, the two alleles of a gene separate into separate gametes
If the two alleles differ
dominant allele is fully expressed in the organism’s appearance, while the recessive allele is masked
What accounts for variations?
Alternative versions of genes (different alleles)
For each gene, an organism inherits…
2 alleles, 1 from each parent ( May be the same, as in true breeding/homozygous individuals; May be different, as in hybrid/heterozygous)
Law of segregation…explain results of identical alleles v hybrid alleles in gametes
The two alleles for each character segregate during
gamete production. If organism has identical alleles, that allele will exist in all gametes; If organisms is hybrid, then
50% of gametes receive dominant allele and 50% receive recessive allele.
test cross explanation
How can we tell if a purple plant is homozygous or
heterozygous??
If we cross the unknown purple-flowered plant with a white-flowered plant, the offspring will tell us:
All offspring are purple–homozygous dominant
offspring are purple and white–> heterozygous
Dihybrid cross
cross that studies the outcome of two different genes
possible hypotheses for dihybrid crosses
If alleles travel together, then only two gametes are made for each parent, resulting in 3 yellow smooth:1green wrinkled
Alternative hypothesis- two pairs of alleles segregate
independently of one another, resulting in four gametes- YR, Yr, yR, and yr, giving 16 possible offspring in
a phenotype 9:3:3:1 ratio (this is correct)
phenotype 9DD:3Dd: 3dD:1dd
- Mendel’s law of independent assortment
therefore states that by the end of meiosis, each pair of homologous chromosomes (and the genes they carry) have been sorted in the gametes independently of how the other pairs were sorted
To find the joint probabilities of independent events-
multiply probabilities of individual events
find the probability that an event can occur in two or more different ways–
the sum of the individual probabilities of those 2 ways
Incomplete Dominance
one allele of a pair is not fully dominant over its partner, so the phenotype of the heterozygous individual is somewhere in between the phenotype of the two homozygous individuals
Complete Dominance
in both heterozygotes and homozygous
dominant individuals, the dominant phenotype occurs
Codominance-
both alleles are at same time in phenotype
multiple allele system
3+ possible alleles coding for a trait
What is polydactyly? Why would one assume that polydactyly is common within the human population? Why isn’t this true?
6 fingers. Bc it’s dominant–but–Just because an allele dominant, does not mean that it is more
common in the population
Type O blood
genotype of ii. No coding for sugars. recessive. antibodies against everything.
Type A blood
genotype of I^Ai or I^A I^A. antibodies against B. dominant.
Type B blood
genotype of I^Bi or I^B I^B. antibodies against A. dominant.
Type AB blood.
genotype of I^A I^B. No antibodies. codominant.
Polygenic inheritance
when a number of genes, in addition to environmental factors, can affect outcome of expression
continuous variation
Polygenic inheritance results in a range of phenotypes called continuous variation- individuals in a population generally exhibit a range of small differences in a trait
exes of continuous variation
Ex- eye color- caused by different genes that affect the production + distribution of melanin in eyes; o Height- variations bell curve–majority have intermediate phenotype and minority has extremes
o Height- variations are expressed in a normal distribution curve, or bell curve -
bell curve phenotypes
majority have intermediate phenotype and minority has extremes
Environmental Effects on phenotype
An individual’s genes provide the potential for developing a particular phenotype but environmental influences may SOMETIMES also shape phenotype
