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Chapter 3: Problem 11

Distinguish between homozygosity and heterozygosity.

Short Answer

Expert verified
Answer: The main differences between homozygosity and heterozygosity in genetics are: 1. Homozygosity involves inheriting two identical alleles of a given gene, while heterozygosity involves inheriting two different alleles of a given gene. 2. Homozygous individuals can be either dominant or recessive, whereas heterozygous individuals have one dominant and one recessive allele. 3. In a homozygous individual, the phenotype (physical appearance) is determined by the nature of the alleles (dominant or recessive), while in a heterozygous individual, the phenotype is determined by the dominant allele.

Step by step solution

01

Define Homozygosity

Homozygosity occurs when an individual inherits the same allele for a specific gene from both of their parents. In other words, homozygosity is when both homologous chromosomes carry the same allele of a given gene. These individuals are called homozygous for that particular gene, and the alleles can either be dominant or recessive.
02

Define Heterozygosity

Heterozygosity occurs when an individual inherits different alleles for a specific gene from each of their parents. These individuals are called heterozygous for that particular gene. Heterozygosity reflects the presence of two different alleles of a given gene on a pair of homologous chromosomes.
03

Examples

In order to better understand homozygosity and heterozygosity, consider the gene responsible for eye color. Using the simplified example where the gene has only two alleles, the dominant allele B (brown eyes) and the recessive allele b (blue eyes). A homozygous individual would have either two dominant alleles (BB) or two recessive alleles (bb). In the first case, the individual would have brown eyes, while in the second case, the individual would have blue eyes. A heterozygous individual would have one dominant allele and one recessive allele (Bb). In this case, since the dominant allele masks the effect of the recessive allele, the person would have brown eyes.
04

Differences between Homozygosity and Heterozygosity

1. Homozygosity involves two identical alleles of a given gene, while heterozygosity involves two different alleles of a given gene. 2. Homozygous individuals can be either dominant or recessive, whereas heterozygous individuals have one dominant and one recessive allele. 3. In a homozygous individual, the phenotype (physical appearance) is determined by the nature of the alleles (dominant or recessive), while in a heterozygous individual, the phenotype is determined by the dominant allele.

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Most popular questions from this chapter

Two true-breeding pea plants are crossed. One parent is round, terminal, violet, constricted, while the other expresses the contrasting phenotypes of wrinkled, axial, white, full. The four pairs of contrasting traits are controlled by four genes, each located on a separate chromosome. In the \(F_{1}\) generation, only round, axial, violet, and full are expressed. In the \(\mathrm{F}_{2}\) generation, all possible combinations of these traits are expressed in ratios consistent with Mendelian inheritance. (a) What conclusion can you draw about the inheritance of these traits based on the \(\mathrm{F}_{1}\) results? (b) Which phenotype appears most frequently in the \(\mathrm{F}_{2}\) results? Write a mathematical expression that predicts the frequency of occurrence of this phenotype. (c) Which \(\mathrm{F}_{2}\) phenotype is expected to occur least frequently? Write a mathematical expression that predicts this frequency. (d) How often is either \(P_{1}\), phenotype likely to occur in the \(F_{2}\) generation? (e) If the \(F_{1}\) plant is testcrossed, how many different phenotypes will be produced?

The basis for rejecting any null hypothesis is arbitrary. The researcher can set more or less stringent standards by deciding to raise or lower the critical \(p\) value. Would the use of a standard of \(p=0.10\) be more or less stringent in failing to reject the null hypothesis? Explain.

In a cross between a black and a white guinea pig, all members of the \(F_{1}\) generation are black. The \(F_{2}\) generation is made up of approximately $3 / 4\( black and \)1 / 4$ white guinea pigs. Diagram this cross, and show the genotypes and phenotypes.

Consider three independently assorting gene pairs, \(A / a, B / b,\) and $C / c,\( where each demonstrates typical dominance \)(A-, B-, C-)$ and recessiveness \((a a, b b, c c) .\) What is the probability of obtain ing an offspring that is \(A A B b C c\) from parents that are \(A a B b C C\) and \(A A B b C c ?\)

Albinism in humans is inherited as a simple recessive trait. Determine the genotypes of the parents and offspring for the following families. When two alternative genotypes are possible, list both. (a) Two parents without albinism have five children, four without albinism and one with albinism. (b) A male without albinism and a female with albinism have six children, all without albinism.
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