Group 1
In Mendel's pea plant experiments. What are the two forms of a gene called?
Alleles
What is the molecular basis of dominance?
One allele makes enough protein to hide the other.
What is the difference between an inherited trait and an acquired trait?
Inherited trait: Passed from parents through genes.
Acquired trait: Gained from the environment or experience.
What is a polygenic trait?
A polygenic trait is a trait that is controlled by two or more genes.
In pea plants, yellow seeds (Y) are dominant over green seeds (y).
If two heterozygous plants (Yy × Yy) are crossed, what percentage of the offspring will have green seeds?
25% will have green seeds (yy).
Who studied pea plants and their traits, and formulated an entire law of inheritance?
Gregor mendel
Why do linked genes not follow independent assortment?
Because they’re close together on the same chromosome.
How can environmental factors influence inherited traits?
Environmental factors can affect how inherited traits are expressed.
How is a polygenic trait different from a single-gene trait?
A single-gene trait is controlled by one gene, while a polygenic trait is controlled by many genes working together.
A cross between a red flower (RR) and a white flower (WW) produces pink flowers (RW).
If two pink flowers (RW × RW) are crossed, what is the genotypic ratio?
RR = 25%
RW = 50%
WW = 25%
If a heterozygous pea plant (Tt) is crossed with a homozygous recessive plant (tt), what are the expected genotypes and phenotypes of the offspring?
Genotypes: 50% Tt, 50% tt
Phenotypes: 50% tall, 50% short
What is the purpose of meiosis in inheritance?
To make gametes with half the DNA.
Why do some traits, like human height or skin color, show a wide range of differences among people?
Because they are polygenic traits, meaning they are controlled by many genes.
Why do polygenic traits show a wide range of phenotypes instead of only a few?
Because many genes contribute small effects to the trait, the combined influence creates a continuous range of possible phenotypes
In guinea pigs, black fur (B) is dominant over white fur (b).
If a heterozygous black guinea pig (Bb) is crossed with a white guinea pig (bb), what percent of the offspring will be black?
50% of the offspring will be black.
How can a child show a recessive trait if neither parent shows that trait in their phenotype
Both parents can be carriers — meaning they each have one recessive allele and one dominant allele (heterozygous).
What causes recombination between linked genes?
Crossing over during meiosis.
How can two organisms with the same genotype show different phenotypes?
Even with the same genotype, environmental conditions can change how genes are activated or “turned on,” leading to different phenotypes.
What type of graph is often used to show the distribution of phenotypes for a polygenic trait, and why?
Polygenic traits produce a bell-shaped distribution (bell curve).
A plant has a gene for height: T = tall, t = short.
Even TT or Tt plants stay short if grown in poor soil.
If Tt × Tt produce 4 plants, 2 are in poor soil and 2 in rich soil, how many will grow tall?
About 1–2 plants will grow tall.