Name:
ANSWER KEY
Per.: _____
Genetics and Heredity Quiz Study Guide
Directions: Complete the following
1. What was Gregor Mendel's contribution to the science of genetics?
Gregor Mendel's principles of inheritance form the basis of modern genetics. By
experimenting with pea plant breeding, Mendel developed three principles of inheritance that
described the transfer of genetic traits, before anyone knew genes existed. Mendel's
experiments greatly expanded the understanding of genetic inheritance, and led to the
development of new experimental methods.
2. What organism did Gregor Mendel study?
Gregor Mendel studied pea plants.
3. List at least 5 traits that Mendel observed in his experiments?
Plant Height
Flower Color
Pod Color
Pod Shape
Seed Color
Seed Shape
4. What is a trait?
In biology, a trait or character is a feature of an organism. Traits can be inherited or
acquired.
5. How are traits passed from parent to offspring?
A trait is passed from parent to offspring through DNA. Segments of DNA, called genes,
are the instructions for trait development. Offspring receive 50% of their DNA from each
parent in sexual reproduction.
6. What is meant by the following statement: "Some of the characteristics of an organism are
inherited and some result from interactions with the environment."?
While inherited traits are controlled by genes, interactions with the environment can
influence the development of traits. For example, exercising can increase strength, exposure
to UV rays can cause skin disorders, and exposure to certain chemicals can cause illness
that would not ordinarily develop.
7. What is the difference between a phenotype and a genotype?
Genotype is the genetic makeup of an organism that is based upon the combination of
alleles. The phenotype is the physical expression (appearance) of the trait that is controlled
by alleles.
8. What are the differences between dominant traits and recessive traits?
A dominant trait will always appear if the dominant allele is present. A recessive allele will
only appear if two recessive alleles are present. A recessive trait will be masked (hidden) by
a dominant trait.
9. What is the difference between a purebred trait (homozygous) and hybrid trait (heterozygous)?
A purebreed is a homozygous allele combination. This means that the alleles that control the
trait are the same. A hybrid, heterozygous trait is due to alleles for the trait that are different.
10. What is the difference between a gene and an allele?
A gene is a segment of DNA that is a set of instructions for a trait, while an allele is one of the
alternative forms of a gene
11. How do we indicate dominant and recessive alleles?
A dominant allele is represented by a capitol letter while a recessive allele is represented by
a lower case letter.
12. How is it possible for offspring to display a recessive phenotype? What type of parental
genotypes are necessary for a recessive trait to appear in the offspring?
A recessive trait can develop if the offspring inherits two recessive alleles for that trait. For a
recessive trait to be passed on, the parental genotypes must be either heterozygous Pp, or
Pp crossed with pp, or both parents are homozygous recessive pp
13. What is probability?
Probability is a measure or estimate of how likely it is that something will happen. Probabilities are
given a value between 0 (0% chance or will not happen) and 1 (100% chance or will happen). The
higher the degree of probability, the more likely the event is to happen, or the greater the number of
times such event is expected to happen.
14. How do Punnett squares allow us to predict the probability that a trait will appear?
Punnett squares are useful for predicting the probability of a trait appearing because they
show both the genotypes and genotypes of the trait. By including the genotypes of both
parents, we can see the probability for all potential combinations of the offspring.
15. Where is genetic information stored in each cell?
Genetic information is stored in the DNA.
16. Where is DNA located in eukaryotic organisms?
Chromosomes are found in the nucleus of each cell in eukaryotic organisms.
17. What is a chromosome?
A chromosome is a long strand of DNA.
18. How many chromosomes are found in human body cells?
Each human body cell contains 46 chromosomes.
19. Why are all humans NOT identical to their parents?
Humans reproduce through sexual reproduction, which means that each person's DNA is the
result of a combination of their parent's DNA. We each receive 50% of our DNA from each
parent, and the combination of alleles for traits is random.
Use the letters D and d to answer questions 20-26. (B & b)
20. Pure dominant genotypeDD
21. Pure recessive genotype dd
22. Hybrid genotype Dd
23. Heterozygous gene pair (alleles)
Dd
24. Homozygous gene pair (alleles)
Dd or dd
25. Dominant allele D
26. Recessive allele d
27. Create a Punnett square to cross one heterozygous parent with one homozygous recessive
parent: (use the letter E for eyebrows). List the genotypes and phenotypes that result from this
cross.
Ee
ee
Ee
ee
Genotypes: Ee, ee
Phenotypes: eyebrows, no eyebrows
28. Create a Punnett square to cross a purebred dominant trait with a purebred recessive
trait. List the genotypes and phenotypes that result from this cross.
Tt
Tt
Tt
Tt
Genotypes: Tt
Phenotypes: Tall
29. Complete the missing information in the Punnett square. What genotype would you
use for each parent? Parent 1- (top) bb
Parent 2 (side) - Bb
b
Bb
Bb
bb
bb
Complete the Punnett square and list the genotype and phenotype for the
offspring in percentages. R = round & r = wrinkled
30.
R
r
R
RR
Rr
Genotype: RR
Genotype: Rr
Genotype: rr
r
Rr
rr
Phenotype: Round
Phenotype: Round
Phenotype: Wrinkled
Percent: 25%
Percent: 50%
Percent: 25%
31. Why will two heterozygous parents always produce offspring with a 3:1 phenotype ratio?
Explain.
A heterozygous parent contributes both a dominant and a recessive allele. With two
heterozygous parents, there is only one possible combination for homozygous recessive
alleles (rr). There is a 75% chance of either homozygous dominant or heterozygous allele
combination. The result is a 3:1 ratio.
32. What is the probability of rolling a five on one die?
There is a 1 out of 6 (1/6) probability of rolling any number on a single die.
33. Mr. S. has two zorgs. A long tail is a recessive trait and a short tail is the dominant trait.
Create a Punnett square to show the possible genotypes and phenotypes if his homozygous
long-tailed zorg breeds with his short-tailed heterozygous zorg.
Genotype: _______________ Phenotype: _________________ Percent: __________
Genotype: _______________ Phenotype: _________________ Percent: __________
Genotype: _______________ Phenotype: _________________ Percent: __________
34. Mr. S. bought two fleegles. He thought that he bought two female fleegles. It turns
out, however, that he bought a male fleegle and a female fleegle (oops). The female
fleegle is about to have a baby fleegle (oooh- they're sooo cute). The male fleegle is
heterozygous brown and the female is homozygous white. Brown is the dominant color
for fleegles. Create a Punnett squre to show the possible combinations of the new baby
fleegle. Include the genotypes, phenotypes, and percent probabilities.
Genotype: _______________ Phenotype: _________________ Percent: __________
Genotype: _______________ Phenotype: _________________ Percent: __________
Genotype: _______________ Phenotype: _________________ Percent: __________