Heredity and Genetics (BIO 3105)

Correct Answer D. Heterozygous

Explanation

Heterozygous refers to having two different alleles for a particular gene, one inherited from each parent. This is in contrast to homozygous, where both alleles for a gene are the same.

Why other options are wrong

A. Recessive

This is incorrect because "recessive" refers to an allele that is only expressed when two copies are present (homozygous recessive). It doesn't describe the relationship between alleles.

B. Homozygous

This is incorrect because homozygous refers to having two identical alleles for a particular gene, either both dominant or both recessive, not different alleles.

C. Allopathic

This is incorrect because "allopathic" refers to a form of medical treatment that involves using drugs or surgery, not a genetic concept. It is unrelated to genetics or allelic pairs.

Correct Answer A. An individual who is a known carrier of a disease

Explanation

In a pedigree chart, a half-filled-in symbol typically represents an individual who is a carrier of a recessive genetic disorder. This means the individual has one copy of the disease-causing allele but does not express the disease since the dominant allele masks the recessive one.

Why other options are wrong

B. An individual with an unknown genotype

A half-filled-in symbol does not represent an unknown genotype. It specifically indicates a carrier, with one normal allele and one disease allele.

C. An affected who is a known carrier of a disease

An affected individual typically has a fully filled-in symbol, not half-filled. A half-filled symbol indicates a carrier, not someone who is affected.

D. An unaffected individual without any disease-causing allele

An unaffected individual without any disease-causing allele is typically represented by an empty symbol, not half-filled.

Correct Answer D. goodness-of-fit

Explanation

The chi-square test is used to assess how well observed data fit expected data. This is commonly known as a "goodness-of-fit" test. It is used to determine if there is a significant difference between the expected frequencies and the observed frequencies in categorical data, such as when testing genetic inheritance patterns.

Why other options are wrong

A. to compare means when population variance is considered to be same

This is not the correct application of the chi-square test. The chi-square test is used for categorical data, not for comparing means or variances.

B. to compare means when population variance is considered to be different

This option describes situations where tests like the t-test or ANOVA would be more appropriate, especially when dealing with comparisons between means in different populations. The chi-square test is not used for comparing means.

C. to compare means when population standard deviation is considered to be different

Like options A and B, this is not the use of the chi-square test. The chi-square test is focused on categorical data, while comparing means with different standard deviations would require different statistical tests.

Correct Answer A. The accumulation of fat in white blood cells

Explanation

Gaucher disease is caused by a deficiency in the enzyme glucocerebrosidase, which leads to the accumulation of fatty substances in various organs, including the liver, spleen, and bone marrow. This accumulation is particularly notable in macrophages, which are a type of white blood cell.

Why other options are wrong

B. The spontaneous breakdown of red blood cells

While Gaucher disease can affect blood cells, it is not primarily caused by the breakdown of red blood cells. The condition is linked to the accumulation of fat in certain types of white blood cells, particularly macrophages.

C. The breakdown of the myelin sheath around nerves

The breakdown of the myelin sheath is associated with diseases like multiple sclerosis, not Gaucher disease. Gaucher disease mainly affects organs like the liver and spleen, and the nervous system may be involved in some cases, but the primary issue is the accumulation of lipids, not nerve damage due to myelin loss.

D. The lack of critical liver enzymes

The problem in Gaucher disease is not specifically the lack of liver enzymes, but rather the lack of glucocerebrosidase, an enzyme that is needed to break down certain lipids. This enzyme deficiency leads to the buildup of fatty materials in various organs, including the liver, but it is not the liver enzymes themselves that are deficient.

Correct Answer C. rrYY and Rryy

Explanation

The F1 generation had round, yellow seeds, which indicates that the round seed (R) and yellow seed (Y) alleles are dominant over their respective recessive traits. The round and yellow phenotype can only result from one parent contributing a dominant allele for both traits. The other parent must contribute the recessive alleles, as shown in the genotypes rrYY (homozygous recessive for seed shape and homozygous dominant for seed color) and Rryy (heterozygous for shape and homozygous recessive for color).

Why other options are wrong

A. rrYy and RRyy

This combination would lead to offspring with both round and wrinkled seeds, but the offspring in the F1 generation had only round seeds. Therefore, these parental genotypes would not produce the observed results.

B. rrYy and Rryy

This combination would lead to some offspring with wrinkled seeds, but the F1 generation had only round seeds. Hence, this genotype pair would not produce all round seeds.

D. rrYY and RRyy

This pair would produce offspring with only yellow seeds (from rrYY) and only round seeds (from RRyy), but the F1 generation had round, yellow seeds, which requires different combinations of dominant and recessive alleles than those listed here.

Correct Answer A. It suggests that traits acquired during an individual's lifetime can be inherited by their offspring.

Explanation

The concept of 'soft' inheritance, also known as Lamarckian inheritance, proposes that traits acquired or modified during an individual's lifetime due to environmental influences or personal experiences can be passed down to offspring. This idea contrasts with the more widely accepted concept of 'hard' inheritance, where genetic traits are inherited strictly according to DNA passed from parent to offspring.

Why other options are wrong

B. It emphasizes the role of genetic information passed from one generation to the next.

This is incorrect because this describes the concept of Mendelian inheritance, not soft inheritance. 'Soft' inheritance suggests the inheritance of acquired traits, not the genetic transmission of traits.

C. It asserts that all traits are determined solely by genetics.

This is incorrect because 'soft' inheritance does not focus solely on genetics. It includes the inheritance of traits that have been altered by environmental factors during an individual's life, such as changes in behavior or physical characteristics due to environmental influences.

D. It is a modern and widely accepted theory in the field of biology.

This is incorrect because 'soft' inheritance is not widely accepted in modern biology. The prevailing theory is that inheritance is largely based on genetic information passed through DNA, and the idea of inheriting acquired characteristics has largely been discredited in favor of genetic inheritance mechanisms.

Correct Answer D. Alleles for different traits were inherited independently.

Explanation

In Mendel’s dihybrid crosses, which examined two traits at the same time, he discovered the principle of independent assortment. This principle states that alleles for different traits are inherited independently of one another, leading to the formation of a variety of genetic combinations in the offspring.

Why other options are wrong

A. Some genes were linked together.

This is not what Mendel observed. While later genetic studies showed that some genes are linked, Mendel's experiments with dihybrid crosses did not indicate gene linkage. Mendel’s independent assortment rule only applies to genes located on different chromosomes or far apart on the same chromosome.

B. One of the pair of alleles is dominant to the other.

This is true for Mendel's monohybrid crosses, but it is not the key finding in his dihybrid crosses. His dihybrid experiments primarily demonstrated independent assortment, not dominance between alleles of different traits.

C. The two alleles controlling a trait were divided equally among the gametes.

This describes Mendel's principle of segregation, which was derived from his monohybrid crosses, not his dihybrid crosses. It states that each allele of a gene pair is segregated into different gametes, but this is not the main observation from his dihybrid crosses.

Correct Answer A. Homozygous

Explanation

Pure-breeding individuals are homozygous for a particular trait, meaning they carry two identical alleles for that gene. This allows them to consistently pass on the same allele to their offspring, ensuring that the offspring will inherit the same genotype and phenotype.

Why other options are wrong

B. Heterozygous

Heterozygous individuals have two different alleles for a particular gene, which does not align with the concept of pure-breeding, where both alleles are identical.

C. Heterozygous dominant

A heterozygous dominant genotype means an individual has one dominant and one recessive allele, but pure-breeding individuals cannot have this genotype as they need identical alleles.

D. Codominant

Codominance refers to the scenario where both alleles in a heterozygous individual contribute equally and visibly to the organism's phenotype, which is unrelated to pure-breeding individuals that must have identical alleles.

Correct Answer A. The phenotype refers to traits in an organism that can be observed

Explanation

The phenotype is the observable physical or behavioral traits of an organism, which are determined by its genetic makeup (genotype) and environmental factors. These traits can include characteristics like eye color, height, and hair texture. The phenotype represents what is visible or measurable in an organism, distinguishing it from the genotype, which refers to the underlying genetic code.

Why other options are wrong

B. The phenotype is the set of genes in an organism.

This is incorrect because the phenotype refers to the observable traits, not the set of genes. The set of genes in an organism is called the genotype. The genotype influences the phenotype but is not the same as it.

C. A gene consisting of a single allele is said to be polymorphic.

Polymorphism refers to the occurrence of two or more different alleles at a particular locus within a population, not a gene consisting of a single allele. A gene with only one allele would not be considered polymorphic.

D. Genotype is a synonym of locus.

This is incorrect. The genotype refers to the genetic makeup of an organism, while the locus refers to the specific location of a gene on a chromosome. They are not synonymous; the locus is a location, while the genotype refers to the actual genetic information present at that location.