Genetics Chapter 2 Quiz

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Questions and Answers

What is the primary focus of transmission genetics?

The manner in which genetic differences are inherited (correct)

The mechanisms of gene expression in cells

Variations in genetic sequences within a single organism

Evolutionary changes in the genetic material over time

In Mendel's pea plant experiments, what ensured that only specific crosses occurred?

Using plants with identical traits

Removing sperm-producing structures from the plants (correct)

Allowing both self-fertilization and cross-fertilization

Introducing external pollen from unrelated plants

In Mendel's experiments, what trait did the F1 generation exhibit when crossing yellow and green seeds?

Hybrid seeds displaying mixed traits

Both yellow and green traits expressed equally

Only green seeds as dominant traits

Only yellow seeds due to dominance (correct)

What is the term used to describe the different forms of a gene that influence a trait?

Alleles Signup and view all the answers

How does an individual's genotype relate to its phenotype?

Genotype refers to the alleles present, while phenotype is the expressed trait Signup and view all the answers

What defines a true-breeding strain in Mendel's experiments?

A strain that consistently produces the same traits in offspring Signup and view all the answers

What term describes the combination of alleles in an individual organism?

Genotype Signup and view all the answers

What was the result of Mendel's reciprocal crosses?

The same outcome regardless of which parent exhibited each trait Signup and view all the answers

What characterizes the phenotypes of plants exhibiting incomplete dominance?

The offspring show an intermediate phenotype between both parents. Signup and view all the answers

What is the expected phenotypic ratio of seeds in the F2 generation from the genotype Aa Bb?

9 yellow, round; 3 green, round; 3 yellow, wrinkled; 1 green, wrinkled Signup and view all the answers

Which of the following statements is true regarding the principle of independent assortment?

It describes how alleles segregate independently during gamete formation. Signup and view all the answers

What is the expected phenotypic ratio from a cross between two heterozygous plants exhibiting incomplete dominance?

1:2:1 Signup and view all the answers

In codominance, how are the phenotypes represented in heterozygous individuals?

Both phenotypes are distinctly visible. Signup and view all the answers

How is the yellow, wrinkled seed phenotype calculated in the F2 generation?

By multiplying the probability of yellow seeds and wrinkled seeds together. Signup and view all the answers

Which rule would be applied when calculating the probability of two independent genetic events occurring together?

Multiplication rule Signup and view all the answers

In the context of Mendel's laws, what does the principle of segregation state?

Offspring inherit one allele from each parent. Signup and view all the answers

What does a probability value of 0 indicate for a specific genotype in a genetic cross?

The genotype cannot possibly occur. Signup and view all the answers

Which of the following statements is incorrect about independent assortment?

It is observed only in dominant gene interactions. Signup and view all the answers

If a cross is performed between an individual genotype AA and aa, what is the probability of obtaining genotype Aa?

1 Signup and view all the answers

What describes the segregation of alleles during Meiosis I?

Homologous chromosomes are separated, leading to segregation. Signup and view all the answers

In a genetic cross that demonstrates incomplete dominance, which of the following genotypes will produce a pink flower phenotype?

CRCW Signup and view all the answers

What is the probability of rolling a double four?

1/36 Signup and view all the answers

Using the addition rule, what is the probability of rolling a seven in any combination with a pair of dice?

1/6 Signup and view all the answers

Which of the following calculations illustrates the multiplication rule for determining the probability of a specific outcome in genetics?

(1/4) (3/4) (3/4) (3/4) Signup and view all the answers

In a scenario with seeds where 3/4 are yellow and 1/4 are green, what is the probability that one of the four seeds is green while the others are yellow?

27/256 Signup and view all the answers

What is the total probability of having four seeds where any one seed can be green with the others being yellow?

108/256 Signup and view all the answers

What does independent assortment refer to in genetics?

One allele does not affect the segregation of another allele. Signup and view all the answers

What phenotype results from a cross between true-breeding yellow and wrinkled seeds and true-breeding green and round seeds?

Yellow and round Signup and view all the answers

How is the F1 generation phenotype affected by dominance in the provided cross?

It will display only yellow seeds. Signup and view all the answers

What is the result of two genes interacting to affect the same trait?

Epistasis Signup and view all the answers

What inheritance ratio results from the interaction of alleles for feather color in the described case?

13:3 Signup and view all the answers

What does the horizontal line between two individuals in a pedigree represent?

Mating Signup and view all the answers

What do the open symbols in a pedigree diagram signify?

Unaffected individuals Signup and view all the answers

Which genotype results in colored feathers according to the information provided?

CC ii Signup and view all the answers

What do linked genes fail to do?

Assort independently during meiosis Signup and view all the answers

What does a double line in a pedigree represent?

Mating between relatives Signup and view all the answers

Which of the following statements about epistasis is false?

It always involves three or more genes. Signup and view all the answers

What is the expected ratio of female to male progeny from random fertilization?

1/2:1/2 Signup and view all the answers

What phenotype appears only in males among the progeny of the F2 generation?

White eyes Signup and view all the answers

Which genotype results in homozygous female progeny?

XX Signup and view all the answers

What is indicated by the term 'crisscross' in relation to X-linked inheritance?

Inheritance pattern of traits passed alternately between genders Signup and view all the answers

What is true about the relationship between the X and Y chromosomes?

Most genes in the X chromosome have no counterparts in the Y chromosome. Signup and view all the answers

What describes the appearance of white-eyed progeny in the F2 generation?

They only appear in males. Signup and view all the answers

Which generation displays a 1:1 ratio of red to white-eyed males?

F2 generation Signup and view all the answers

What is the significance of a recessive mutation in an X-linked gene?

It is only expressed in males. Signup and view all the answers

Study Notes

Transmission Genetics

Each individual has a unique genome, distinct from those before and after them.
Transmission genetics describes how genetic differences are passed between generations.

Pea Plant Traits

Pea plants exhibit various traits including seed color (yellow/green), seed shape (round/wrinkled), pod color (green/yellow), pod shape (smooth/indented), flower color (purple/white), flower position (stem/tip), and plant height (tall/dwarf).

Pea Plant Crossing

Pea flowers possess sperm and egg-producing structures allowing self-fertilization.
Mendel's controlled crosses involved removing sperm-producing structures to prevent self-fertilization and ensure specific crosses.
Mature pollen collected from a flower on the male parent is deposited on the stigma of the female parent to achieve cross-pollination.
After fertilization, a cloth bag is tied around the fertilized flower to prevent pollen from other plants entering and contaminating the cross.

Yellow vs. Green Seed Traits

True-breeding strains with yellow seeds and true-breeding strains with green seeds were crossed to produce the first filial (F1) generation, which displayed only yellow seeds
The trait that appeared in the F1 generation (yellow seeds) is dominant
The other trait is recessive (in this case, green seeds)

Genotype → Phenotype

Mendel proposed that a hereditary factor (gene) determines traits.
Contemporary understanding attributes contrasting traits to different forms of a gene, called alleles.
Allele combinations constitute an individual's genotype.
The expressed trait or physical characteristic is the phenotype.

F2 Generation

The F2 generation (second filial) showed the reappearance of the recessive trait, with a dominant to recessive ratio of 3:1.
The cross of first generation peas resulted in a second generation (F2) in which there was a reappearance of the recessive trait.

The Principle of Segregation

Each reproductive cell (gamete) possesses only one allele for each gene.
Fertilized egg cells (zygotes) are formed via the random combination of gametes from both parents.

The Principle of Independent Assortment

Segregation of one set of alleles of a gene pair is independent of another set of alleles in a different gene pair, meaning that traits are inherited independently.
The F2 generation from independent crosses results in a 9:3:3:1 ratio for different seed characteristics.

Segregation of Alleles in Meiosis

Segregation is the observed separation of homologous chromosomes during meiosis I, ensuring that each gamete receives only one allele for each gene during the process of gamete formation.

Incomplete Dominance

Neither allele is completely dominant over the other.
The heterozygous phenotype is intermediate between the two homozygous phenotypes – an example of incomplete dominance.

Codominance

Both alleles are expressed fully and distinctly in the heterozygous individual.

Probability

Possible outcomes of a cross are expressed as probabilities ranging between 0 and 1.
Multiplication rule: probabilities of independent events multiply.
Addition rule: Probabilities of mutually exclusive events add.

Multiplication Rule

Probabilities of simultaneous occurrences are products of their individual probabilities if the occurrences are independent.

Addition Rule

Probabilities of mutually exclusive occurrences are summed.

Addition/Multiplication Rules

To determine the probability of a particular combination of traits, the multiplication rule can be used for simultaneous, independent events. The addition rule can be used to find the likelihood of any one of several possible mutually exclusive events.

Independent Assortment

Traits are inherited independently.
Expected progeny ratio for a dihybrid cross is 9:3:3:1. The possible genotypes can be determined, but there are four phenotypes.

Mendel's Laws

Mendel's laws of Segregation and Independent Assortment explain inheritance patterns for traits.
Not all genes display independent assortment, some genes are "linked" together on the same chromosome and do not assort independently.

Epistasis

Two or more genes interact to affect the same trait.
The expression/presence of one trait can mask the expression of another.

Patterns of Inheritance in Humans

Pedigree analysis is used to study inheritance patterns in humans.
A pedigree chart shows family history of a particular trait to help understand inheritance patterns like whether it's dominant or recessive.

Pedigree of a Dominant Allele

Affected individuals appear in each generation.
Affected individuals are equally likely to be male or female.
Most matings with affected offspring have one affected parent.

Pedigree of a Recessive Allele

Affected individuals may skip generations.
Affected individuals are equally likely to be male or female.

Genetic Testing

Genetic testing identifies genotypes and helps predict trait risk.
Benefits include personalized healthcare decisions and risk understanding for reduction in anxiety, which impacts quality of life.
Risks include limited answers, psychological and emotional impact, and concerns regarding privacy and implications on health and life insurance.

Uncommon Inheritance Patterns

Inheritance can involve genetic material from the mitochondria only passed down through the female parent.

Human Sex Chromosomes

Very few genes on the Y chromosome have counterparts on the X chromosome, with roughly 1000 genes on the X chromosome and approximately 50 genes on the Y.

Segregation of Sex Chromosomes

Meiosis in females only produces X-bearing eggs.
Meiosis in males produces a 1:1 ratio of X-bearing and Y-bearing sperm.
Random fertilization leads to a 1:1 ratio of male and female offspring.

X-linked Genes

Traits associated with the X chromosome can be observed in crosses of fruit flies showing recessive mutations; only in males, the ratio of red to white eyes is 1:1 for the F2 generation.

X-linkage

"Crisscross" inheritance refers to X-chromosome inheritance patterns.
Males with X-linked recessive traits will have heterozygous carrier daughters and unaffected sons. All F1 offspring will have red eyes.

Heterozygous Cross

Among progeny from a heterozygous carrier female, half the daughters will be heterozygous carriers, and half of the sons are expected to be affected.

Morgan's Fruit Fly Crosses

The inheritance pattern of the white-eyed mutation is similar to the pattern of X-chromosome inheritance in fruit flies.

Normal Chromosome Separation

In normal chromosome separation for X-linked genes in fruit fly crosses, white-eyed females and red-eyed males result in female progeny with red eyes and male progeny with white eyes.

Abnormal Chromosome Separation: Nondisjunction

Non-disjunction occurs during meiosis resulting in eggs or sperm possessing abnormal numbers of chromosomes.
Nondisjunction in females produces offspring with XXY females and XO males.

Nondisjunction of Sex Chromosomes in Humans

Nondisjunction in females can produce eggs with either two X chromosomes or no X chromosome.

Nondisjunction of Autosomes in Humans

In humans, nondisjunction can occur in autosomes resulting in individuals with extra or missing chromosomes.
Aneuploidy, such as Trisomy 21 or Down syndrome, can result.

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Description

Test your understanding of transmission genetics and Mendelian principles with this quiz. Explore key concepts such as genotype, phenotype, and the ratios from genetic crosses. Answer questions related to Mendel's experiments and principles of inheritance.