Punnett square In a certain plant, red flowers are dominant over white flowers. A plant heterozygous for red flowers and a plant with white flowers are crossed. Which of the following is the expected proportion of phenotypes in the next generation?
A. 4 red, 0 white
B. 2 red, 2 white
C. 1 red, 3 white
D. 3 red, 1 white
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We use the Punnet square to find the population of the resulting offspring from the crossing of a plant heterozygous for red flowers with a plant with white flowers.
Let R be the dominant allele for red while r is the recessive allele color for red. Therefore, the phenotype for parent 1 which is heterozygous for red flower will be Rr and the second parent with white flowers will be rr.
We cross the two phenotypes in a Punnet square as follows
|
|
r |
r |
|
R |
Rr |
Rr |
|
r |
rr |
rr |
Thus, there are 2 heterozygous offspring with red flowers and 2 offspring with white flowers.
Therefore, the Correct Answer is B.
More Questions on Custom TEAS Science Practice Test 1
Question 1:
Metabolism of proteins
Which of the following substances is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia?
A. Sebum
B. Urea
C. Lysozymes
D. Water
The Correct Answer is B.Proteins are nitrogen-based compounds, which when broken down release ammonia. Ammonia is a toxic substance to the body, and sebaceous glands coverts it to urea.
Question 2:
Which of Mendel's laws or principles states that gametes carry one allele for each trait?
A. law of segregation
B. independent assortment
C. gene segregation
D. phenotype assortment
The Correct Answer is A.Question 3:
Pathogens
Which of the following microorganisms lack their own metabolic pathways and can only reproduce inside of a host cell?
A. Bacteria
B. Viruses
C. Helminths
D. Protozoa
The Correct Answer is B.The disease-causing microorganisms are known as pathogens, which include bacteria, fungi, protozoa, worms, viruses and prions. These organisms have distinguishing cell structures from each other. The most notable difference between viruses and other pathogens is that viruses lack a metabolism mechanism of their own and ability to produce proteins encoded by their DNA or RNA. However, they viruses rely on machinery of the host cell to produce their proteins and replicate their genomes.
Question 4:
Punnett squares are used by geneticists to determine the probability of different offspring genotypes. In the one shown below, what letter(s) belong in the lower right box?
A. AA
B. Aa
C. aA
D. aa
The Correct Answer is D.From the given Punnett square, we can cross the genotypes of the two parents and established the phenotypes the offspring will have. The Punnett square is filled as:
|
|
A |
a |
|
a |
Aa |
aa |
|
a |
Aa |
aa |
The requested answer is aa.
Question 5:
Which of the following sequences on a DNA molecule would be complementary to GCTTATAT?
A. TAGGCGCG
B. ATCCGCGC
C. CGAATATA
D. TGCCTCTC
The Correct Answer is C.Question 6:
The Life Cycle of HIV
Which of the following allows the AIDS virus, which contains RNA, to insert viral DNA into the DNA of a host T-cell after the AIDS virus enters the cell?
A. Receptor proteins located on the surface of the virus
B. The protein that makes up the capsid of the virus
C. Reverse transcriptase, an enzyme encoded by the virus
D. The phospholipids found on the envelope of the virus
The Correct Answer is C.The AIDS virus (HIV virus) is Class VI or Group VI in the Baltimore Classification. Based on the Baltimore Classification, this specifically involves the reverse transcriptase enzyme and it is encoded by the virus.
This is the enzyme that will produce DNA molecules from the viral RNA. This is the mechanism involved where it will use the reverse transcriptase enzyme to insert viral DNA into the genetic material of the host cell.
Question 7:
Nitrogen gas is an extremely stable molecule because its structure contains which of the following?
A. Resonance bonds
B. Ionic bonds
C. Triple covalent bonds
D. Hydrogen bonds
The Correct Answer is C.The Lewis structure of nitrogen gas is shown below. Triple bonds are stronger than double or single bonds. Therefore, we can infer that the triple bond between the two nitrogen atoms makes nitrogen gas more stable.
Question 8:
In a plant in which fuzzy leaves (F) are dominant over smooth leaves (f), which of the following crosses will produce only offspring with smooth leaves?
A. Ff x ff
B. Ff x Ff
C. FF x FF
D. ff x ff
The Correct Answer is D.Crossing is the breeding of parents to produce an offspring. Given that f is a recessive allele of smooth leaves while F is the dominant allele of fuzzy leaves. Therefore, where there is F crossing with f, the offspring will have fuzzy leaves over smooth one.
Therefore, for an offspring to have smooth leaves, ff and ff must cross to produce an offspring with smooth leaves.
Question 9:
Gel electrophoresis
To separate genomic DNA fragments by size, which of these laboratory methods is most useful?
A. Filtration
B. Titration
C. Electrophoresis
D. Spectrophotometry
The Correct Answer is C.Electrophoresis is a lab method that is commonly used to separate charge molecules based on their size. Some of the charged molecules include DNA, RNA, and proteins.
Question 10:
Punnett square
In a certain plant, red flowers are dominant over white flowers. A plant heterozygous for red flowers and a plant with white flowers are crossed. Which of the following is the expected proportion of phenotypes in the next generation?
A. 4 red, 0 white
B. 2 red, 2 white
C. 1 red, 3 white
D. 3 red, 1 white
The Correct Answer is B.We use the Punnet square to find the population of the resulting offspring from the crossing of a plant heterozygous for red flowers with a plant with white flowers.
Let R be the dominant allele for red while r is the recessive allele color for red. Therefore, the phenotype for parent 1 which is heterozygous for red flower will be Rr and the second parent with white flowers will be rr.
We cross the two phenotypes in a Punnet square as follows
|
|
r |
r |
|
R |
Rr |
Rr |
|
r |
rr |
rr |
Thus, there are 2 heterozygous offspring with red flowers and 2 offspring with white flowers.