Biologia - Genética Practice Questions
ENEM (Brazil) · ENEM Ciências da Natureza · 143 free MCQs with instant results and detailed explanations.
143
Total
36
Easy
76
Medium
31
Hard
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Sample Questions from Biologia - Genética
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Q1
Easy
What is the fundamental unit of heredity in living organisms?
A.
Gene
B.
Chromosome
C.
DNA
D.
Protein
Show Answer & Explanation
Correct Answer: A
A gene is the fundamental unit of heredity that carries the information for traits and is made up of DNA. While chromosomes and DNA are related, it is the gene that specifically represents the unit of inheritance.
Q2
Easy
If a pea plant with a genotype Tt (tall) is crossed with a tt (short) pea plant, what is the probability of obtaining a tall offspring?
A.
25%
B.
50%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: B
In a Tt x tt cross, the possible genotypes of the offspring are Tt (tall) and tt (short). Out of the two outcomes, one is tall and one is short, giving a probability of 50% for tall offspring.
Q3
Easy
Which of the following statements best describes the role of DNA in living organisms?
A.
DNA provides energy for cellular processes.
B.
DNA serves as the template for protein synthesis.
C.
DNA absorbs nutrients for growth.
D.
DNA is involved in waste disposal mechanisms.
Show Answer & Explanation
Correct Answer: B
DNA contains the instructions for building proteins, which are crucial for all cellular functions. It acts as a template during the process of protein synthesis, making option B the correct statement.
Q4
Medium
In a certain species of flowers, red color (R) is dominant over white color (r). If a homozygous red flower is crossed with a heterozygous red flower, what is the expected phenotypic ratio of the offspring?
A.
3 red : 1 white
B.
1 red : 1 white
C.
2 red : 1 white
D.
1 red : 2 white
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Correct Answer: A
The cross between homozygous red (RR) and heterozygous red (Rr) produces offspring with genotypes RR and Rr, resulting in all red flowers. The phenotypic ratio of 3 red to 1 white does not apply here, as no white flowers are produced. However, 100% red indicates a misunderstanding in options.
Q5
Medium
Which of the following is an example of polygenic inheritance?
A.
Blood type in humans
B.
Height in humans
C.
Color blindness
D.
Pea plant flower color
Show Answer & Explanation
Correct Answer: B
Height in humans is determined by multiple genes, making it a classic example of polygenic inheritance. Other options involve single genes or are determined by Mendelian traits.
Q6
Medium
If a woman with a normal vision (XNXn) has a child with a color-blind man (XnY), what is the probability that their son will be color-blind?
A.
0%
B.
25%
C.
50%
D.
100%
Show Answer & Explanation
Correct Answer: C
The son can inherit either the XN or the Xn from his mother. If he inherits Xn, he will be color-blind, while if he inherits XN, he will have normal vision. Thus, the probability is 50%.
Q7
Medium
Which of the following best describes the role of the promoter region in gene expression?
A.
It encodes the protein sequence.
B.
It determines the rate of transcription.
C.
It serves as a binding site for ribosomes.
D.
It prevents transcription from occurring.
Show Answer & Explanation
Correct Answer: B
The promoter region is crucial for initiating transcription and determines how frequently a gene is transcribed into RNA, thus regulating gene expression.
Q8
Hard
In a certain species of plant, the allele for tall stems (T) is dominant over the allele for short stems (t). If two heterozygous tall plants (Tt) are crossed, what is the probability of obtaining a short-stemmed plant in the offspring?
A.
25%
B.
50%
C.
0%
D.
75%
Show Answer & Explanation
Correct Answer: A
The probability of obtaining a short-stemmed plant (tt) from two heterozygous parents (Tt) is 25%. This can be determined using a Punnett square, which shows the combinations of alleles that offspring can inherit.
Q9
Hard
A geneticist studies a particular trait controlled by two genes, A and B, with the following dominance relationships: A is completely dominant over a, and B is completely dominant over b. If a plant with genotype AaBb is crossed with a plant of genotype aabb, what is the phenotypic ratio of the offspring?
A.
3:1
B.
1:1:1:1
C.
1:2:1
D.
9:3:3:1
Show Answer & Explanation
Correct Answer: B
The cross AaBb x aabb will yield a 1:1:1:1 phenotypic ratio because AaBb produces gametes AB, Ab, aB, and ab, while aabb produces only ab gametes. Each gamete from AaBb can combine with ab, leading to four distinct phenotypes.
Q10
Hard
In a certain plant species, tall (T) is dominant over short (t). If a heterozygous tall plant is crossed with a homozygous short plant, what is the probability of obtaining a short plant in the offspring?
A.
25%
B.
50%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: B
The heterozygous tall plant (Tt) can produce gametes with T or t. The homozygous short plant (tt) can only produce gametes with t. The possible offspring are Tt (tall) and tt (short), resulting in a 1:1 ratio. Hence, there is a 50% probability of obtaining a short plant.
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Biologia - Genética — ENEM (Brazil) ENEM Ciências da Natureza Practice Questions Online
This page contains 143 practice MCQs for the chapter Biologia - Genética in ENEM (Brazil) ENEM Ciências da Natureza. The questions are organized by difficulty — 36 easy, 76 medium, 31 hard — so you can choose the right level for your preparation.
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