Study Guide – Genetics & Heredity Test KEY
1. Who was Gregor Mendel and what experiments did he do to test for genetics?
Austrian monk, “father” of genetics, used pea plants to make first discoveries
about genetics.
2. Explain the two laws that Mendel created.
a. Law of segregation: During meiosis, parental gametes contain only half
the genetic information. (half chromosomes from mom, the other half
from dad)
b. Law of independent assortment: Genes or traits separate independently
and do not influence each other.
3. What does it mean if an individual is “true-breeding”?
They are homozygous and only produce offspring with those types of traits.
4. Be able to create, read, analyze and create probability of Punnett squares.
A
a
a
Aa
Aa
A
a
A
AA
Aa
a
Aa
aa
A
Aa
Aa
A
a
a
Aa
Aa
a
aa
aa
5. What is the difference between homozygous and heterozygous?
Homozygous: same allele (AA or aa)
Heterozygous: different alleles (Aa)
6. What is the difference between genotype and phenotype?
Genotype: genetic makeup of an individual (letters)
Phentype: physical characteristics that represent genotype
7. Explain simple dominant and recessive traits. How many possible phenotypes are
there?
Simple dominance is when the dominant trait masks the recessive trait. There
are only 2 phenotypes possible.
8. What happens when there are traits that show incomplete dominance? How many
possible phenotypes are there?
Incomplete dominance is when both traits are dominant and the heterozygous
individual shows a blend or mix of the two traits. There are 3 possible
phenotypes. (ex: CC = curly hair, SS = straight hair, CS = wavy hair)
9. What happens when there are traits that show codominance? How many possible
phenotypes are there?
Codominance is when both traits are dominant and the heterozygous
individual expresses both traits at the same time. There are 3 possible
phenotypes. (ex: RR = red flowers, WW = white flowers, RW = red and white
speckled)
10. What is the difference between a monohybrid and a dihybrid Punnett cross?
Monohybrid: crossing 1 trait (4 possible outcomes)
DihybridL crossing 2 traits (16 possible outcomes)
11. Give an example of each.
a.
Polygenic traits: skin color, height
b. Multiple alleles: blood
c. Sex-influenced traits: pattern baldness
12. What are the names for the chromosomes
a. 1-22: autosomes
b. 23 (X & Y): sex chromosomes
13. Explain what an X-linked trait is.
An X-linked trait is when a disorder or trait is carried on the X chromosome.
Traits would be more common in males, women may be carriers for these
traits.
14. Why can’t men be carriers for an x-linked trait?
Men only have one X chromosome and if their X has the disorder, then they
will express that trait. Females have two X chromosomes, so they can mask the
disorder with their unaffected X.
15. Explain what happens in each type of mutation:
a. Deletion: When part of a chromosome is lost
b. Inversion: When part of chromosome flips upside down
c. Translocation: When part of one chromosome attaches to another
nonhomologus chromosome
d. Nondisjunction: Problem with splitting chromosomes, results in an
unequal # of chromosomes in daughter cells
16. What would be the phenotypes for the following genotypes?
a. IAIA: Type A
b. IAi: Type A
c. IBIB: Type B
d. IBi: Type B
e. ii: Type O
f. IAIB: Type AB
17. What is a karyotype used for? How many chromosomes are in a normal karyotype?
A karyotype is a visual representation of an individual’s chromosomes. This
type of diagram can be used to detect genetic chromosomal disorders. There
are 46 total chromosomes in a normal karyotype.
18. Be able to read and analyze a pedigree.
a. What symbol represents female? Circles
b. What symbol represents male? Squares
c. What does it mean if a symbol is colored in? The individual has the trait we
are looking for.
d. What do horizontal lines between symbols represent? The couple is
producing offspring.
e. How many children do parents 5 & 6 have? 3 (2 girls, 1 boy with trait)
19. Mr. Anderson and his wife recently had a baby, but it has not been a happy occasion
for them. Mrs. Anderson noticed her new baby has attached earlobes. She claims
that the hospital mixed up her baby with someone else’s. Both Mr. and Mrs.
Anderson are heterozygous for detached his earlobes (Ee). Some members of her
family have attached earlobes, which is the recessive trait. Create a Punnett square
to see if it is possible Mr. and Mrs. Anderson have the correct baby!
E
e
E
e
EE
Ee
Ee
ee
a. List the possible genotypes for their baby. EE, Ee, ee
b. Did the hospital make a mistake? Explain.
No, the hospital did not make a mistake because there is a 25% chance
that their child would have had attached earlobes.