Apolgia Biology Module 8 Study Guide

Front 1

Three pea plants have the following alleles for yellow ("Y") and green ("Y") peas. What is the genotype and phenotype of each? Note whether they are homzygous or heterozygous. a. YY b. Yy c. yy

Back 1

a. this HOMOZYGOUS genotype is "YY" resulting in a phenotype of yellow peas.
b. This heterozygous genotype is "Yy" resulting in a phenotype of yellow peas.
c. This homozygous genotype is "yy" resulting in a phenotype of green peas.

Front 2

What process causes gametes to have only one allele since other human cells have two of each allele?

Back 2

MEIOSIS separates the two alleles.

Front 3

A pea plant which is homozygous in the dominant, axial flower allele ("A") is crossed with a pea plant that is heterozygous in that allele. What are the possible genotypes and phenotypes, along iwth their percentage chances for the offspring?

Back 3

One parent is homzygous dominat, so its genotype is "AA". The other is heterozygous, so its genotype is "Aa". ****Draw Punnett square**** Thus 50% have the "AA" genotype and 50% have the "Aa" genotype. 100% have the axial flower phenotype.

Front 4

A woman is heterozygous in the ability to roll her tongue when extended. If she marries a man who cannot roll his tongue, what percentage of their children will be able to roll their tongues? Remember, the allele for being able to roll your tongue is dominant.

Back 4

50% of the children will be able to roll their tongues. Since the woman is heterozygous, her genotype is "Rr". The man cannot roll his tongue. Since the ability to roll your tongue is recessive, his genotype must be "rr". Since even one dominant allele allows you to roll your tongue...50% will be able to roll their tongues. **DRAW Punnett square.***

Front 5

Recall that in guinea pig coat color, black (filled circles & squares) is dominant and white (hollow circles & squares) is recessive. What is the genotype of the male parent in the cross below? **DRAWING***

Back 5

Since the square that represents the male aprent is filled, it means that he has a black coat. This means he has at least one dominant allele. One of hte offspring is white-coated. The only way that can happen is for each parent to have at least one recessive allele. Thus, the GENOTYPE IS Bb.

Front 6

The following pedigree is for the presence or absence of wings on a certain insect. The hollow circles and squares represent insects without wings, while the filled circles and squares represent insects with wings. Which is the dominant allele? What are the genotypes of individuals 1-4? **DRAWING**

Back 6

This means NO WINGS ("N") is the dominant allele. Since they each must also have the recessive allele, 1 & 2 MUST HAVE THE "Nn" GENOTYPE. Since some of the offspring between 3 & 4 also have recessive traits, they both must have the recessive allele. However, they do not express the recessive trait, so 3 & 4 MUST ALSO HAVE THE "Nn" GENOTYPE. (Explanation - Individuals 1 & 2 can tell us which allele is dominant. After all the offspring have both phenotypes. This means that at least one of htem is homozygous recessive. Thus, each parent mst have the recessive allele. They both have no wings, but they must also carry the allele for wings, since one of their offspring has no wings.)

Front 7

Give the possible phenotypes and the percentage chance for each in the dihybrid cross between a pea plant that is homozygous in producing smooth, yellow peas and a pea plant that produces wrinkled, green peas. The smooth and yellow alleles arre dominant.

Back 7

100% OF THE OFFSPRING HAVE THE "SsYy" GENOTYPE AND THE SMOOTH, YELLOW PHENOTYPE. (Explanation - Since the parent with smooth, yellow peas is homozygous, it genotype is "SSYY". Since the other expresses both recessive alleles, it must be homozygous in the recessive alleles. Thus, its genotype is "ssyy". Both of these parents can only produce one type of gamete each. The one parent can only produce a SY allele and the other can only produce a sy. This gives us a 1 x 1 Punnett square. **DRAWING**

Front 8

Give the possible phenotypes and the percentage chance for each in the dihybrid cross between a pea plant that is heterozygous in producing smooth, yellow peas and another with the same genotype.

Back 8

***smooth, yellow peas (genotypes SSYY, SsYy, SSYy, SsYY) 9 of 16 or 56.25%
***smooth, green peas (genotypes SSyy, Ssyy) 3 of 16 or 18.75%
***wrinkled, yellow peas (genotypes ssYY, ssYy) 3 of 16 or 18.75%
***wrinkled, green peas (genotype ssyy) 1 of 16 or 6.25%
***DRAW PUNNETT SQUARE
--Explanation - Since the parents are both heterozygous in each allele, their genotypes are "SsYy". There are 4 possible gametes: SY, Sy, sY, sy

Front 9

***************
In fruit flies, the color of the eye is a genetic trait that is sex-linked. What is the percentage of males that will have white eyes when a heterozygous, red-eyed female is crossed with a white-eyed male? What is the percentage of females that will have white eyes from the same cross?

Back 9

50% OF THE FEMALES (REMEMBER, ONLY XX's ARE FEMALES) will be white-eyed and 50% of the males (only XY's are males) will be white-eyes. Explanation - If the female is heterozygous, then her genotype is X(R)X(r). Since the male is white-eyed, his genotype is X(r)Y. **DRAW PUNNETT SQUARE***

Front 10

In the case of fruit fly eye color again, what must be the genotype of a male fly if, when crossed with a heterozygous female, there is no possibility of having a female with white eyes?

Back 10

X(R)Y
Explanation - If the male were white-eyed, then the Punnett square would look like the one in the ? w/ the **************, resulting in 50% of the females having white eyes. If the male were red-eyed, however, the resulting Punnett square looks like this: ****DRAW PUNNETT SQUARE

Front 11

If a gamete has two alleles for the same genetic trait, what type of genetic disorder will result in a zygote formed with this gamete?

Back 11

A GENETIC DISORDER FROM A CHANGE IN CHROMOSOME NUMBER will result. If a gamete has two alleles fro the same trait, it must have two of hte same chromosome. In the fertilization process, then, there will be three chromosomes.

Front 12

A person carries a genetic disorder but does not have the disorder. How is that possible?

Back 12

THE GENETIC DISORDER MUST BE RECESSIVE. Thus, the person can carry the trait, but as long as he has the dominant allele, the person will not have the disease.

Front 13

Do sex-linked genetic disorders affect men and women the same? If not, which sex is affected more and why?

Back 13

SEX-LINKED DISORDERS AFFECT MEN MORE FREQUENTLY THAN WOMEN. THIS IS BECAUSE MEN HAVE ONLY ONE ALLELE IN SEX-LINKED TRAITS.

Front 14

A woman with type O blood marries a man with type AB blood. What blood types are possible for their children? What is the percentage chance for each blood type?

Back 14

A - 50%
B - 50%
Explanation - Since the woman is type O, her genotype must be OO, as that would be the only way the recessive allele could be expressed. The man is type AB, so his genotype is "AB". DRAW THE PUNNETT SQUARE***

Front 15

If a person has type B-blood, what are the possible genotypes for that person? Include the possible genotypes related both to the type of blood as well as the Rh-factor.

Back 15

Since the person is type B, the genotype must be either BB of BO. For the Rh-factor, the person expresses the recessive allele. Thus, her genotype must be homozygous in the recessive allele, which we called "pp" in "On Your Own problem 8.10

Front 16

What term do we use to refer to gentic traits that are governed by more than one set of genes?

Back 16

POLYGENETIC INHERITANCE

Front 17

Two individuals have the exact same genotype for a certain trait, but they are not identical when it comes to that trait. How is this possible?

Back 17

While the genetics are the same, the environmental and spiritual factors were probably different. Not all traits are determined by genetics. Most are also determined by environmental factors and (in the case of humans) spiritual factors.