Genetics Meiosis and Mendel's Experiments

Questions and Answers

What process is responsible for the independent assortment of alleles?

Meiosis

How do cells acquire homologous chromosome pairs that carry the alleles that are independently assorted?

Fusion of gametes

Which of the following statements most accurately describes the process of independent assortment?

Alleles of different genes segregate from one another in a random manner.

The principle of independent assortment is best illustrated by events that take place during metaphase II, during which sister chromatids segregate independently of each other.

False Signup and view all the answers

How many genetically unique types of gametes could be produced by an individual with the genotype RrYY?

Two Signup and view all the answers

Which of the following parental genotypes would yield a 1:1:1:1 phenotypic ratio in the offspring?

AaBb, aabb Signup and view all the answers

In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations?

P, F1, F2 Signup and view all the answers

Which of the following is true about a plant with the genotype AABbcc?

It is homozygous at two loci. Signup and view all the answers

What is an allele?

An alternative version of a gene Signup and view all the answers

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

Traits are inherited in discrete units, and are not the results of 'blending.' Signup and view all the answers

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?

Different possible assortment of chromosomes into gametes Signup and view all the answers

Why did Mendel continue some of his experiments to the F2 or F3 generation?

To observe whether or not a recessive trait would reappear. Signup and view all the answers

Which of the following differentiates between independent assortment and segregation?

The law of independent assortment requires describing two or more genes relative to one another. Signup and view all the answers

A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

HT Signup and view all the answers

Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that

Traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1. Signup and view all the answers

Which of the boxes marked 1-4 correspond to plants with dark leaves?

1, 2, and 3 Signup and view all the answers

Which of the boxes correspond to plants with a heterozygous genotype?

2 and 3 Signup and view all the answers

Which of the plants will be true-breeding?

1 and 4 only Signup and view all the answers

Mendel worked

In a monastery Signup and view all the answers

You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?

Red shows incomplete dominance over white Signup and view all the answers

Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height?

A combination of polygenic inheritance and environmental factors Signup and view all the answers

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

Roan × roan Signup and view all the answers

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?

Pleiotropy Signup and view all the answers

Which of the following is an example of polygenic inheritance?

Skin pigmentation in humans Signup and view all the answers

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. The flower color trait in radishes is an example of which of the following?

Incomplete dominance Signup and view all the answers

Skin color in a certain species of fish is inherited via a single gene with four different alleles. How many different types of gametes would be possible in this system?

4 Signup and view all the answers

Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is incompletely dominant to white (r). The heterozygous condition results in pink (Rr) flower color. If snapdragons are heterozygous for height as well as for flower color, a mating between them will result in what ratio?

6:3:3:2:1:1 Signup and view all the answers

Which of the following provides an example of epistasis?

In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing. Signup and view all the answers

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce

All sharp-spined progeny. Signup and view all the answers

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N. Which of the following is a possible partial genotype for the son?

IBi Signup and view all the answers

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N. Which of the following is a possible genotype for the mother?

IAi Signup and view all the answers

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N. Which of the following is a possible phenotype for the father?

B positive Signup and view all the answers

Folk singer Woody Guthrie died of Huntington's disease, an autosomal dominant disorder. Which statement below must be true?

It is very likely that at least one of Woody Guthrie's parents also have had the allele for Huntington's disease. Signup and view all the answers

Various procedures can be used to detect genetic disorders before birth. Among the tests discussed in this chapter, which is the least invasive (list first), and which two allow the chromosomes of the fetus to be examined?

Ultrasound imaging, chorionic villus sampling, amniocentesis Signup and view all the answers

Which of the following do you expect if an individual is heterozygous for the sickle-cell trait?

He or she will show some symptoms of the disease. Signup and view all the answers

An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder that is detectable biochemically in fetal cells. The obstetrician would most reasonably offer which of the following procedures to her patient?

Amniocentesis or CVS Signup and view all the answers

The frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?

Darwin's explanation of natural selection Signup and view all the answers

Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize the amino acid phenylalanine. This amino acid is not naturally produced by humans. Therefore, the most efficient and effective treatment is which of the following?

Regulate the diet of the affected persons to severely limit the uptake of the amino acid. Signup and view all the answers

One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant gene, although it may range from mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?

One of the parents has very mild expression of the gene. Signup and view all the answers

In each generation of this family after generation I, the age at diagnosis is significantly lower than would be found in nonfamilial (sporadic) cases of this cancer (~ 63 years). What is the most likely reason?

Hereditary (or familial) cases of this cancer typically occur at earlier ages than do nonfamilial forms. Signup and view all the answers

Quantitative characters vary in a population along a continuum. How do such characters differ from the characters investigated by Mendel in his experiments on peas?

Quantitative characters are due to polygenic inheritance, the additive effects of two or more genes on a single phenotypic character. A single gene affected all but one of the pea characters studied by Mendel. Signup and view all the answers

Look at the Punnett square, which shows the predicted offspring of the F2 generation from a cross between a plant with yellow-round seeds (YYRR) and a plant with green-wrinkled seeds (yyrr). Select the correct statement about wrinkled yellow seeds in the F2 generation.

The chance that an individual taken at random from the F2 generation produces wrinkled seeds is 25% and the chance that the same individual produces yellow seeds is 75%. Signup and view all the answers

Each chromosome in this homologous pair possesses a different allele for flower color. Which statement about this homologous pair of chromosomes is correct?

These homologous chromosomes represent a maternal and a paternal chromosome. Signup and view all the answers

The pattern of inheritance (monohybrid, dihybrid, sex-linked, and genes linked on the same chromosomes) can be predicted from data if one is given the parent or offspring genotypes or phenotypes. Two organisms, with genotypes BbDD and BBDd, are mated. Assuming independent assortment of the B/b and D/d genes, determine the genotypic ratios in offspring that would occur.

1/4 BBDD, 1/4 BbDD, 1/4 BBDd, 1/4 BbDd Signup and view all the answers

Study Notes

Meiosis and Independent Assortment

Meiosis is the process responsible for the independent assortment of alleles.
Homologous chromosome pairs are acquired through the fusion of gametes.

Mendel's Experiments

The principle of independent assortment states that alleles of different genes segregate randomly.
Mendel's experiments involved true-breeding plants labeled as P (parental), F1 (first generation), and F2 (second generation).
Traits are inherited in discrete units, not through blending.
A plant with genotype AABbcc is homozygous at two loci.

Gametes and Genetic Variation

An individual with genotype RrYY can produce two genetically unique types of gametes.
Parental genotypes AaBb and aabb yield a 1:1:1:1 phenotypic ratio in offspring.
Genotype AaBbCCDdEE allows for numerous gametes due to different chromosome assortments.

Dominance and Recessive Traits

Recessive traits can reappear in F2 generation due to their obscured presence in the F1 generation.
Incomplete dominance exemplified by red and white snapdragons resulting in pink flowers.

Polygenic Inheritance and Pleiotropy

Height in humans is influenced by polygenic inheritance and environmental factors.
Cystic fibrosis is an example of pleiotropy, affecting multiple organs and exhibiting varied symptoms.

Genetic Concepts

Alleles are alternative versions of a gene.
Polygenic inheritance is seen in traits like skin pigmentation.
Incomplete dominance occurs when red and white radish flowers cross to yield purple offspring.

Genetic Crosses and Ratios

Heterozygous snapdragons produce a phenotypic ratio of 6:3:3:2:1.
The cross of roan cattle produces offspring in the ratio of 1 red:2 roan:1 white.
Epistasis is illustrated when one genotype prevents the expression of another.

Blood Types and Inheritance

Blood type inheritance involves multiple alleles and genes with dominance relationships.
Possible genotypes for a mother with blood type A could include IAi.
The father of a type B son could be B positive.

Genetic Disorders and Inheritance Patterns

Huntington's disease is autosomal dominant, suggesting a parent likely carried the allele.
Phenylketonuria (PKU) requires dietary regulation as an effective treatment.
Sickle-cell trait may cause some symptoms, and heterozygosity can provide malaria resistance.

Prenatal Genetic Testing

Ultrasound imaging is a non-invasive technique, while chorionic villus sampling (CVS) and amniocentesis allow chromosome examination.
Genetic disorders can often be detected before birth.

Quantitative Traits

Quantitative characters differ from Mendelian traits due to polygenic inheritance, affecting traits along a continuum.
F2 generation results, derived from specific crosses, can be predicted using Punnett squares.

Homologous Chromosomes

Each chromosome in a homologous pair contains different alleles, representing maternal and paternal contributions.
Homologous chromosomes are essential for understanding inheritance patterns and genetic variation.

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Description

Explore the fundamentals of meiosis, independent assortment, and Mendel's genetic experiments. This quiz covers key concepts such as gamete formation, genotype analysis, and the principles of inheritance. Test your understanding of dominant and recessive traits in genetic variations.