Genetics, DNA, and Heredity
.
1. Given an example of selective breeding? ( selecting two horses and having them mate in order to produce a stronger
offspring)
2. In pea plants, round peas (R) are dominant to wrinkled peas (r). Show five possible crosses for round and wrinkled
peas. Combinations of Crosses for Round and Wrinkled Peas
Two pea plants produce an offspring with a genotype of Rr. Complete the Punnett Square for this cross
R
r
R
RR
Rr
r
Rr
rr
r
3.The following Punnett square, in which (Y) are yellow flowers and (y) are purple flowers, is incomplete.
Which genotype should replace the question mark? ( yy)
4. Genes determine whether you have dimples, what color eyes you have, even if you can roll your tongue. What
statement best describes the role of a gene in inheritance? The gene is a section of DNA that controls a trait that the
organism inherits.
5. What does the notation TT mean to geneticists? ( two dominant alleles)
6. A clone is an organism that is (genetically identical to the organism from which it was produced.)
7. The sex cells produced by meiosis have _____ (the) number of chromosomes as the parent cells. (half)
8. What is the probability of producing a tall pea plant from a genetic cross between two hybrid tall pea plants? (three in
four)
b
9. An example of genetic variation in an organism would be (fruit without seed, presence of dimples, or albinism).
10. A heterozygous organism has (two different alleles for a trait)
11. Scientists call an organism that has two different alleles for a trait (heterozygous).
12. A black guinea pig has the genotype (BB) for fur color. A white guinea pig has the genotype (bb) for fur color. What
is the probability that these two Guinea pigs will produce a guinea pig with white fur? (0%)
13. In pea plants, green pod color is controlled by a dominant allele. Yellow is controlled by a recessive allele. Explain
why a plant with yellow pods can never be a hybrid. (because the allele for yellow is recessive, plants with yellow
pods must have tow recessive alleles. A hybrid would have one dominant allele and one recessive allele, and would
therefore be green)
14. When a purebred plant with red flowers is crossed with a purebred plant that has white flowers, what will be the
expected result, assuming that flower color in this plant shows incomplete dominance? (all will have pink flowers)
15. Identical twins Jenna and Joanna are separated at birth. Jenna is raised by a family whose diet includes a variety of
foods, including many fresh fruits and vegetables. Joanna’s family has a diet that lacks variety; it includes very few
vegetables and many kinds of junk food. When the twins are reunited 25 years later, what physical difference may be
present in the twins? (Jenna will be taller and more fit than Joanna)
16.
A couple has three brown-eyed children the parents are brown-eyed (Bb) The allele for brown eyes is dominant over the
allele for blue eyes. They believe the fourth child they have will be blue-eyed. Explain what actually will happen. (
they have a 25% chance of having a blue-eyed child)
17.An organism’s physical appearance is its (phenotype).
18.In humans, earlobes can be considered attached or unattached. The following list describes earlobe type:
·
Attached earlobe: bottom portion of earlobe is attached directly to head
·
Unattached earlobe: bottom portion of earlobe slopes upward before attaching to head
Unattached earlobes (E) are dominant to attached earlobes (e). The following family pedigree shows which
individuals have unattached or attached earlobes.
Family members 4 and 5 in Generation II are expecting identical twins.
Summarize the gender and earlobe appearance of these two offspring. (the gender is unknown, and both will have
attached earlobes)
19. Alleles are (different forms of genes).
Use this information given below to answer the following questions.
A dog breeder has begun to raise Labrador retrievers. So far, she hasn’t been able to predict the color of the
puppies that she breeds. She does not know the dark fur (D) is dominant over yellow fur (d).
When the breeder crossed a yellow female Lab with a male that had dark fur, she expected half of the puppies
to be yellow and half he puppies to be dark. However, in a litter of 8 puppies, all had dark fur. The breeder next
crossed the same yellow female with a different dark male. This time half of the puppies were yellow and half were
dark.
20. Which letters represent the most probable genotype of the second male? (Dd)
21. How can the woman breed a litter of all yellow puppies?(by making sure that both mother and father are yellow)
22. The breeder is going to cross two dark Labradors. One is homozygous and the other is heterozygous for the trait.
Predict what percentage of the puppies will be yellow. (0%)
23. Use the diagram to answer the following question
Which individuals have the trait that is being traced by the pedigree?
Use the diagram to answer the following questions
The Punnett square below shows a cross between two pea plants, each with green seed pods. Use the square to answer
these questions.
G
G
G
GG
g
Gg
Gg
24. The missing genotype in the empty square is correctly written as (GG)
25. What is the genotype for each of the parents? Tell whether they are homozygous or heterozygous.(One parent is
heterozygous and the other is homozygous for the trait)
26. What percentage of the offspring of this cross will produce green seed pods? (100%)
27. Jeremiah has been studying the experiments performed by Gregor Mendel in his study of inheritance patterns. Jeremiah
decides that he would like to test the inheritance patterns of tall and short pea plants. What statement would likely be
his hypothesis? (If a purebred tall plant is crossed with a purebred short pea plant, all the offspring will be tall)
Use the information below to answer the following questions
The Sickle Cell Mutation and Malaria
Sickle cell anemia is a hereditary disorder caused by a mutation in the shape of red blood cells. Red blood cells are
normally disk-shaped. Sickle red blood cells are shaped like a crescent moon, or sickle. The sickle-shaped cells cannot
travel easily through the blood vessels of the circulatory system. Therefore, people with sickle cell anemia have
problems with oxygen circulation.
Malaria is a disease caused by a parasite. The parasite is transmitted to humans through mosquito bites. Malaria is
common in the warm, wet, tropical and subtropical regions shown in the following map.
Distribution of Malaria
Doctors found that patients with sickle cell anemia seemed to be immune to malaria. Research found that the sickle
cell mutation disabled the effects of the parasite. People with one sickle cell gene did not develop sickle cell anemia
and often survived exposure to malaria. People with two sickle cell genes had very high rates of surviving malaria, but
these people developed sickle cell anemia.
28. In the early 1900s, scientists concluded that a mutated sickle cell gene was harmful and presented no benefits. What is
a logical justification why this conclusion needs revision? (Having one Sickle Cell gene is harmless and provides some
protection from malaria)
29. Some scientists concluded that the sickle cell mutation is beneficial to some people. What is logical evidence that
supports this conclusion? (people with only one mutated gene for sickle cell are not affected by sickle cell anemia and
have some protection against malaria)
30. The following cross shows two people who are not affected by sickle cell anemia but who carry one mutated gene for
the disorder. In this cross, R is the gene for a normal red blood cell, while r is the sickle cell mutated gene.
R
r
R
RR
Rr
r
Rr
rr
What is the chance that an offspring from this cross will be affected with sickle cell anemia?
(25%)