Genetics Unit Pre-Assessment (Grade 7)

2.

Rate, on a scale of 1 – 4, 1 being the lowest and 4 being the highest, how interested are you in genetics.

Explanation
The answer to this question is 1,2,3,4 because it allows the respondent to rate their level of interest in genetics on a scale of 1 to 4. This scale provides a range of options for the respondent to choose from, allowing them to accurately express their level of interest.

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3.

A(n) is a segment of DNA that carries the instructions for producing a specific trait (Intermediate Core Curriculum 2.2a)

Chromosome
Karyotype
Enzyme
Gamete
Gene

Correct Answer

A. Gene

Explanation

A gene is a segment of DNA that carries the instructions for producing a specific trait. Genes are responsible for the inheritance of traits from parents to offspring and determine the characteristics of an organism. They provide the instructions for the synthesis of proteins, which play a crucial role in the development and functioning of cells and tissues. Genes can be passed on through generations and can undergo mutations, leading to genetic variations and diversity in populations.

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4.

Breeders have developed a variety of chicken that has no feathers. Which methods were most likely used to produce this variety (Standard 2.2a)?

Artificial selection and inbreeding
Grafting and hybridization
Regeneration and incubation
Vegetative propagation and binary fission
Test cross and polyploidy

Correct Answer

A. Artificial selection and inbreeding

Explanation

Breeders most likely used artificial selection and inbreeding to produce a variety of chicken with no feathers. Artificial selection involves selecting and breeding individuals with desired traits, in this case, the absence of feathers. Inbreeding refers to breeding closely related individuals to maintain the desired traits and create a purebred population. These methods allow breeders to selectively breed chickens with no feathers over multiple generations, resulting in the development of this variety.

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5.

Pea plants come in two sizes – tall plants and dwarf plants. The dominant allele (T) produces tall pea plants, and the recessive allele (t) produces dwarf pea plants. The Punnett Square below shows a cross between tall and dwarf pea plants. What is the probability that the offspring of this cross are homozygous recessive (Intermediate Core Curriculum 2.2c).

0%
25%
50%
75%
100%

Correct Answer

A. 50%

Explanation

The Punnett Square shows that there is a 50% chance of the offspring being homozygous recessive. This is because when crossing a tall plant (heterozygous) with a dwarf plant (homozygous recessive), there is a 50% chance of the offspring inheriting the recessive allele from both parents, resulting in a homozygous recessive genotype.

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6.

Below is a pedigree for an inherited disease. What is the probability that the child labeled III 1 has inherited a gene for this disease (Intermediate Core Curriculum 2.2c)?

0%
25%
50%
75%
100%

Correct Answer

A. 50%

Explanation

The child labeled III 1 has one affected parent (II 2) and one unaffected parent (II 3). If the disease is inherited in an autosomal dominant manner, the affected parent must have at least one copy of the disease-causing gene. Therefore, there is a 50% chance that the affected parent has passed on the gene to the child.

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7.

Chromosomes normally occur as homologous pairs in (Standard 2.1c):

A sperm cell
An egg cell
A zygote
A gamete
A haploid cell

Correct Answer

A. A zygote

Explanation

Chromosomes normally occur as homologous pairs in a zygote. A zygote is formed when a sperm cell fertilizes an egg cell, resulting in the fusion of their genetic material. Each homologous pair of chromosomes consists of one chromosome from the sperm cell and one from the egg cell. This pairing is important for genetic recombination and ensures that the zygote inherits a complete set of chromosomes, with half coming from each parent. Sperm cells, egg cells, and gametes are all haploid cells, meaning they only contain one set of chromosomes, while a zygote is diploid, containing two sets of chromosomes.

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8.

Kernel corn is a trait determined by two alleles. The dominant allele (P) produces a purple color, and the recessive allele (p) produces a yellow color. The photograph below shows an ear of corn produced by crossing two corn plants. The shaded kernels are purple, and the unshaded ones are yellow. The yellow corn kernels can best be described as (Intermediate Core Curriculum 2.2b).

Homozygous dominant
Hybrid
Heterozygous
Homozygous recessive
Codominant

Correct Answer

A. Homozygous recessive

Explanation

The yellow corn kernels can be best described as homozygous recessive because the yellow color is produced by the recessive allele (p). Homozygous recessive means that both alleles for a trait are the same and in this case, both alleles are the recessive allele (p), resulting in the yellow color.

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9.

Which of the following statements is true (Standard 2.1c)?

Chromosome map percentages are not actual chromosome distances, but represent the relative position of genes.
Gene linkage is an exception to Mendel’s Law of Dominance
Genetic recombination involves both gene linkage and chromosome mapping.
Polyploid plants are avoided by plant growers because they are almost always lethal.
Each somatic cell in the human body has a different number of chromosomes depending on the function of the cell.

Correct Answer

A. Chromosome map percentages are not actual chromosome distances, but represent the relative position of genes.

Explanation

Chromosome map percentages represent the relative position of genes rather than actual chromosome distances. This means that the percentage values on a chromosome map do not directly correspond to the physical distance between genes on the chromosome. Instead, they indicate the likelihood of two genes being inherited together, with a higher percentage indicating a higher likelihood of linkage. This concept is important in genetic mapping and understanding the arrangement of genes on chromosomes.

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10.

Which statement describes the work of Gregor Mendel (Standard 2.1a)?

He developed some basic principles of heredity without having knowledge of chromosomes.
He developed the microscope for the study of genes in pea plants.
He explained the principle of dominance on the basis of the gene-chromosome theory.
He used his knowledge of gene mutations to help explain the appearance of new traits in organisms.
He studied the beaks of finches which helped him to develop the theory of evolution by natural selection.

Correct Answer

A. He developed some basic principles of heredity without having knowledge of chromosomes.

Explanation

Gregor Mendel developed some basic principles of heredity without having knowledge of chromosomes. This means that he made significant contributions to the understanding of how traits are inherited from one generation to the next, even though he did not have the knowledge of chromosomes that we have today. Mendel's experiments with pea plants allowed him to discover principles such as the law of segregation and the law of independent assortment, which laid the foundation for modern genetics. His work was groundbreaking and paved the way for future research in the field of genetics.

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11.

Which of the following is an example of how genes can be modified by the environment (Standard 2.1a)?

Pleiotropy (You may inherit a gene for the complex of symptoms that are collectively called sickle-cell anemia).
Incomplete Penetrance (You may inherit the gene for diabetes but never get the disease unless you become overweight)
Epistasis (Your dog inherits a dominant allele that determines whether the fur will have dark pigment and a different allele that determines how dark the pigment will be)
Polygenic Traits (You inherit many different genes which combined effects determines your skin color).
Codominance (A cow inherits two alleles that make a positive contribution to the phenotype resulting in a black and white coat).

Correct Answer

A. Incomplete Penetrance (You may inherit the gene for diabetes but never get the disease unless you become overweight)

Explanation

Incomplete penetrance is an example of how genes can be modified by the environment because it involves inheriting a gene for a disease (diabetes), but the disease only manifests if a specific environmental factor (becoming overweight) is present. This shows that the expression of the gene is influenced by the environment, in this case, the individual's weight.

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12.

Some individuals with blood group A may inherit the genes for dimples, while other individuals with blood group A may inherit the genes for no dimples. This can best be explained by the principle of (Standard 2.1b)?

Dominance
Multiple alleles
Independent assortment
Incomplete dominance
Segregation

Correct Answer

A. Independent assortment

Explanation

The principle of independent assortment states that genes for different traits segregate independently during the formation of gametes. In this case, the presence or absence of dimples is not directly linked to the blood group A. The genes for dimples and blood group A are located on different chromosomes and therefore segregate independently during gamete formation. This means that individuals with blood group A can inherit the genes for dimples or no dimples in a random manner, which is best explained by the principle of independent assortment.

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Genetics Unit Pre-assessment (Grade 7)

Rate, on a scale of 1 – 4, 1 being the lowest and 4 being the highest, how much you already know about genetics.

Quiz Preview

Rate, on a scale of 1 – 4, 1 being the lowest and 4 being the highest, how interested are you in genetics.

A(n) is a segment of DNA that carries the instructions for producing a specific trait (Intermediate Core Curriculum 2.2a)

Breeders have developed a variety of chicken that has no feathers. Which methods were most likely used to produce this variety (Standard 2.2a)?

Below is a pedigree for an inherited disease. What is the probability that the child labeled III 1 has inherited a gene for this disease (Intermediate Core Curriculum 2.2c)?

Chromosomes normally occur as homologous pairs in (Standard 2.1c):

Which of the following statements is true (Standard 2.1c)?

Which statement describes the work of Gregor Mendel (Standard 2.1a)?

Which of the following is an example of how genes can be modified by the environment (Standard 2.1a)?

Some individuals with blood group A may inherit the genes for dimples, while other individuals with blood group A may inherit the genes for no dimples. This can best be explained by the principle of (Standard 2.1b)?