Question

mendelian genetics inquiry worksheet

1. look at these genetic makeups:

• tt = homozygous tall
• tt = heterozygous
• tt = homozygous short

why do you think scientists use the word \homozygous\ for tt and tt, but \heterozygous\ for tt?

part 4: genotype vs. phenotype

genotype = the genetic makeup (the alleles an organism has)
phenotype = the observable trait (what the organism looks like)

1. a pea plant has the genotype tt. what is its phenotype? (remember: t is dominant for tall, t is recessive for short.)

1. two pea plants both have the phenotype \tall.\ could they have different genotypes? explain your answer.

part 5: the law of segregation

mendel discovered that when organisms reproduce, alleles separate so that each parent contributes only one allele to each offspring.

scenario: cross a heterozygous tall plant (tt) with a homozygous short plant (tt).

1. the tall plant (tt) can pass either a t or a t allele. the short plant (tt) can only pass a t allele. what are the possible offspring genotypes?

1. what would be the phenotypes of these offspring?

1. what fraction of the offspring would you expect to be tall? what fraction would be short?

Explanation:

Step1: Analyze the cross

We have a cross between \( Tt\) (heterozygous tall) and \( tt\) (homozygous short). Using the law of segregation, the \( Tt\) plant can produce gametes \( T\) and \( t\), and the \( tt\) plant can only produce \( t\) gametes.

Step2: Use Punnett square

The Punnett square for this cross is:

	\( T\)	\( t\)

Answer:

1. The possible offspring genotypes are \( Tt\) and \( tt\).
2. The phenotypes: \( Tt\) is tall (since \( T\) is dominant) and \( tt\) is short.
3. The fraction of tall offspring (\( Tt\)) is \(\frac{1}{2}\), and the fraction of short offspring (\( tt\)) is \(\frac{1}{2}\).