Test Crosses

In African-violet plants, purple flowers are dominant to white flowers. You purchase an African-violet plant with white flowers. It's genotype could be represented as :

• PP

• Pp

• pP

• pp

Tags

NGSS.HS-LS3-1

To discover whether an animal showing the dominant trait is homozygous or heterozygous, it must be crossed with an animal that is:

• homozygous dominant

• homozygous recessive

• heterozygous

• choices B & C

Two tall pea plants are crossed, producing 105 tall plants & 32 short plants. The genotypes of the tall parent plants are:

• Tt & Tt

• TT & Tt

• Tt & tt

• tt & tt

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

A spotted dalmation is mated with a pure-white dalmation (ss) to deteremine whether its genotype is SS or Ss for spots. Three puppies are born, all with spots. We can conclude that the spotted dalmation is SS.

• TRUE

• FALSE

Tags

NGSS.HS-LS3-1

In mice brown (B) is dominant to white (b). A brown mouse is mated with a white mouse. Twelve brown mice are produced. The brown mouse's genotype is:

• BB

• Bb

• bb

• a reliable conclusion can't be reached

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Two brown-eyed parents have a child with blue eyes. The best explanation is:

• a mutation occured before the child was born

• both parents carry the allele for blue eyes

• both parents are pure for brown eyes

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Which scenario best supports the conclusion that a black guinea pig's genotype is homozygous dominant?

• after mating with a white guinea pig, 2 black & 2 white guinea pigs were produced

• after mating with a white guinea pig, 10 black & 8 white guinea pigs were produced

• after mating with a white guinea pig, 12 black guinea pigs were produced

• after mating with a black guinea pig, 4 black guinea pigs were produced

Tags

NGSS.HS-LS3-1

Individuals with the same phenotype have the same genotype

• TRUE

• FALSE

Tags

NGSS.HS-LS3-1

In a test cross to determine whether a fruit fly is homozygous (WW) or heterozygous (Ww) for long wings, 7 long-winged flies & 1 short winged-fly are produced. Which is a valid conclusion?

• the unknown fruit fly is WW

• the unknown fruit fly is Ww

• the unknown fruit fly is ww

• more offspring are needed

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

In hamsters, long tails (L) are dominant to short tails (l). A student wishes to perform a test cross to determine whether a female long-tailed hamster is homozygous or heterozygous for tail length. She mates the hamster with a male long-tailed hamster & studies the offspring, which are 100% long-tailed. She concludes that the female hamster's genotype is "LL". What mistake(s) did the student make?

• she should have mated the female hamster with a male that was known to be hybrid

• she should have mated the female hamster with a short-tailed male hamster

• she should have mated the female hamster with another long-tailed female

• she has to mate members of the litter before she can make a conclusion

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2