Question

Here are some biology questions pls help ASAP. 15Pts question

Sickle cell anemia is a disease where red blood cells become thin and elongated. If a person has one copy of the sickle cell allele, half of their red blood cells will be misshapen. In this way, the allele is codominant, since both normal and sickled shapes are seen in the blood.

If two parents present the heterozygous phenotype for sickle cell have an offspring, what is the probability of their child having sickle cell?





















A. Their offspring will have a 0% chance of having sickle cell.
B. Their offspring will have a 25% of having the homozygous dominant genotype, resulting in sickle cell.
C. Their offspring will have a 75% chance of having sickle cell.
D. Their offspring will have a 25% chance of having the heterozygous genotype, resulting in sickle cell.



One parent is heterozygous for the sickle cell trait, and the other is homozygous recessive. What is the probability of each offspring displaying each genotype - expressed as a ratio?





















A. 1 homozygous recessive : 0 homozygous dominant: 1 heterozygous
B. 3 homozygous recessive : 1 homozygous dominant: 0 heterozygous
C. 1 homozygous recessive : 1 homozygous dominant: 2 heterozygous
D. 0 homozygous recessive : 1 homozygous dominant: 1 heterozygous


3. In some cattle the genes for brown hair and for white hair are codominant. Cattle with alleles for both brown and white hair, have both brown and white hairs. This condition gives the cattle a reddish color, and is referred to as Roan. What is the probability, expressed as a fraction, of a red cow and a roan bull having a roan offspring?




















A. 1/4
B. 1/2
C. 3/4
D. 4/4












4. In Andalusian fowls, black individuals (BB) and white individuals (bb) are homozygous. A homozygous black bird is crossed with a homozygous white bird. The offspring are all bluish-gray. What is the probability of each phenotype, expressed as a ratio, of two heterozygous individuals?



B
b
B
BB
Bb
b
Bb
bb

A. 1 black : 1 white : 2 bluish-gray
B. 3 black : 1 white : 0 bluish-gray
C. 3 black : 0 white : 1 bluish-gray
D. 2 black : 1 white : 1 bluish-gray

5. In snapdragon flowers the color of the flower is determined by an incompletely dominant gene. If you cross a purebred white snapdragon with a pink snapdragon, what is the likelihood, expressed as a fraction, of an offspring with the heterozygous genotype?




















A.1/4
B. 1/2
C. 0/4
D. 3/4

6. A genus of shrimp Neocaridina can be any color from mottled brown to red. The color of the shrimp is determined by the genes at three loci A,B, and C, each loci has two alleles A or a; B or b; and C or c. The color of the shrimp is determined by the total number of dominant genes, the more dominant genes the darker the shrimp. What genotype below would display the darkest phenotype?

A. AAbbCC
B. AaBbCc
C. aaBBCC
D. AABbCC



7. Skin color for a species of lizards is polygenic with individuals with a fully recessive genotype being green and those with a fully dominant genotype being brown. In an environment the selective pressures favor individuals with a green phenotype, which genotype below would be best fit to the given environment?

A. RRssTT
B. rrSSTt
C. rrSstt
D. RRSSTT

Answer 1

1. B - Aa x Aa = 25% chance AA, which is the only genotype that results in sickle-cell. Aa is called "sickle-cell trait'; it isn't the full disease.

2. A - Aa x aa = we know will produce no homozygous dominant

3. B - RR x Rr = 1/2 chance of Rr (same problem as #5)

4. A - Bb x Bb = 1:2:1 ratio

5. B - WW x Ww = 1/2 chance of Ww

6. D - AABbCC has 5 dominant alleles, which is the most out of the four options

7. C - the one with the fewest dominant alleles will be the most green and the most successful in the environment