Mendelian Basics
What is a phenotype?
A trait or characteristic that is physically expressed, such as flower color.
What is the chance of flipping a coin and getting heads?
50%
What is genetic variation?
Differences in DNA among individuals in a population.
What is a population?
A group of individuals of the same species living in the same area.
What is incomplete dominance?
A situation where the heterozygous phenotype is a blend of the two alleles.
What is the difference between dominant and recessive alleles?
Dominant alleles mask recessive alleles when both are present.
What tool is used to predict genetic outcomes in offspring?
Punnett square
Give one source of variation in sexually reproducing organisms.
Crossing over during meiosis, random fertilization, or independent assortment.
What does a bell-shaped curve in trait distribution represent?
Most individuals have average traits, while extremes are less common.
What is codominance?
Both alleles are expressed equally in the phenotype.
A pea plant with genotype Aa is crossed with another Aa. What is the probability of an offspring showing the recessive trait?
25%
In a cross of Aa x aa, what percentage of offspring are expected to be heterozygous?
50%
Why is genetic variation important in populations?
It increases survival chances in changing environments.
In a large population, why might observed ratios differ slightly from expected ratios?
Because of chance/random variation in actual outcomes.
Give an example of a polygenic trait.
Height, skin color, eye color.
In a monohybrid cross, what is the expected ratio of dominant to recessive phenotypes?
3:1
Two heterozygous tall pea plants (Tt) are crossed. What is the probability their offspring will be short (tt)?
25%
If a population has 60% blue-eyed individuals and 40% brown-eyed individuals, what does this tell you about trait distribution?
It shows how traits vary and distribute in a population.
How can probability be applied to explain why traits are not evenly distributed in populations?
Traits follow statistical likelihood, not guarantees, so variation occurs naturally.
Blood type is controlled by multiple alleles. What are the three alleles for human blood type?
IA, IB, i
Explain why heterozygous individuals can act as carriers for genetic disorders.
They carry one recessive allele but do not express the disorder due to the presence of a dominant allele.
A couple are both carriers for cystic fibrosis (Ff). Use probability to explain the chances of their child having the disorder.
25% chance (ff), 50% carrier (Ff), 25% unaffected (FF).
Explain how probability and variation work together to affect population genetics.
Probability predicts outcomes of trait inheritance, while variation explains the range of possible traits.
Explain how natural selection interacts with trait probability in a population.
Favorable traits become more common, altering probability distributions over time.
Explain how statistics and probability help scientists study polygenic traits in populations.
They help predict ranges and distributions of complex traits influenced by many genes.