Biology Chapter 12 Flashcards

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Questions and Answers

What describes the behavior of chromosomes during meiosis that explains Mendel's Law of Segregation?

The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

What observable cellular process explains Mendel's Law of Segregation?

Homologous chromosomes separating during meiosis I.

What name is given to the most common phenotype in a natural population?

Wild type.

How does the frequency of a dominant, X-linked disorder vary between males and females?

Females would display this disorder with greater frequency than males. Signup and view all the answers

What can be said about sex determination in animals?

The mechanism of sex determination varies with different animal species. Signup and view all the answers

What is the outcome when a white-eyed female Drosophila is crossed with a red-eyed male Drosophila?

None of the females will have white eyes. Signup and view all the answers

What determines the sex of offspring in humans, and why?

The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome. Signup and view all the answers

Which of the following is true of an X-linked gene but not of a Y-linked gene?

The gene is present in both males and females. Signup and view all the answers

How does the arrangement of homologous chromosomes relate to Mendel's Law of Independent Assortment?

The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random. Signup and view all the answers

What would happen if pea shape and pea color were linked genes in a dihybrid cross?

The F2 generation would have included a higher percentage of pea plants producing round, yellow peas. Signup and view all the answers

In general, the frequency with which crossing over occurs between two linked genes depends on __________.

how far apart they are on the chromosome. Signup and view all the answers

What recombinant frequency would you expect if two genes follow Mendel's Law of Independent Assortment?

50% recombinant frequency. Signup and view all the answers

How many sets of chromosomes are found in each human gamete?

<ol> <li></li> </ol> Signup and view all the answers

How many chromosomes are found in each human gamete?

<ol start="23"> <li></li> </ol> Signup and view all the answers

_____ is the process by which haploid gametes form a diploid zygote.

Fertilization. Signup and view all the answers

If self-fertilization occurs in a diploid plant species with 48 chromosomes, the zygote will have _____ set(s) of chromosomes.

<ol start="4"> <li></li> </ol> Signup and view all the answers

What term applies to an organism with extra sets of chromosomes?

Polyploid. Signup and view all the answers

What happens if mutant tetraploid plants are involved?

Are unable to interbreed with a diploid plant. Signup and view all the answers

How do most polyploid plants arise?

Hybridization. Signup and view all the answers

What is a nondisjunction?

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell. Signup and view all the answers

When can nondisjunction occur?

All three answers are correct. Signup and view all the answers

What kind of cell results when a diploid and a haploid gamete fuse during fertilization?

A triploid cell. Signup and view all the answers

Of the following chromosomal abnormalities, which type is most likely to be viable in humans?

Trisomy. Signup and view all the answers

What error occurs when a diploid cell undergoes meiosis and produces two normal gametes and one with n − 1 and one with n + 1 chromosomes?

A nondisjunction error occurred in meiosis II. Signup and view all the answers

What error occurs when a diploid cell produces two gametes with n + 1 and two with n − 1 chromosomes?

A nondisjunction error occurred in meiosis I. Signup and view all the answers

Which situation describes the chromosome number being either 2n + 1 or 2n − 1?

Aneuploidy. Signup and view all the answers

What results from a fragment of a chromosome breaking off and reattaching in reverse?

An inversion. Signup and view all the answers

Which condition is not the result of a chromosomal alteration?

Mosaicism. Signup and view all the answers

Based on Bob and Eleanor's family history, what inheritance pattern does the skin condition most likely follow?

X-linked dominant. Signup and view all the answers

What hypothesis is tested using the χ2 value to find the probability of random fluctuations?

The two genes are unlinked and are assorting independently, leading to a 1:1:1:1 ratio of phenotypes in the offspring. Signup and view all the answers

Between which values on the df = 3 line does the calculated χ2 value lie?

Between 1.42 and 2.37. Signup and view all the answers

What is the probability range that the data fit the expected 1:1:1:1 ratio of phenotypes?

0.50 Signup and view all the answers

Do the results support the hypothesis regarding the unlinked genes?

The hypothesis is supported. Because 0.50 Signup and view all the answers

Study Notes

Chromosome Behavior and Mendel's Laws

During meiosis I, homologous chromosomes separate, supporting Mendel's Law of Segregation.
Observable cellular process explaining this law is the separation of homologous chromosomes.

Phenotypes and Inheritance Patterns

The most common phenotype in a natural population is termed "wild type."
For a dominant, X-linked trait, females are more likely to display the disorder than males.

Sex Determination

Sex determination mechanisms differ across animal species.
In humans, the male gamete (sperm) determines the sex of offspring by contributing either an X or Y chromosome.
An X-linked gene exists in both males and females, while Y-linked genes are not present in females.

Genetic Crosses and Mendel's Findings

A dihybrid cross in pea plants shows different phenotypic ratios if genes are unlinked. Linked genes would produce higher percentages of parental types in the offspring.

Gamete Formation and Chromosome Numbers

Humans are diploid (2n) with 46 chromosomes; each gamete has 1 set (n=23).
Fertilization combines haploid gametes to form a diploid zygote.
In cases of mutations, gametes can have abnormal chromosome counts, leading to polyploidy if additional sets result.

Nondisjunction and Chromosomal Abnormalities

Nondisjunction is an error in cell division where chromosomes fail to separate properly.
This can occur in both meiosis I and II, leading to aneuploidy (2n + 1 or 2n - 1).
The viability of trisomy is greater in humans compared to other chromosomal abnormalities.

Chromosomal Structures and Alterations

Chromosome fragments can reattach incorrectly, causing inversions.
Mosaicism is a condition not directly caused by chromosomal alterations.

Statistics in Genetic Research

The chi-square (χ²) test evaluates hypotheses about the independence of two genes.
A low probability indicates the observed data differs significantly from expected ratios, supporting hypotheses regarding genetic linkage or independence.

Summary of Findings

The data suggest that stem color and petal length genes assort independently, supported by statistical analyses showing no significant differences from expected phenotypic ratios.

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Test your knowledge with these flashcards on Chapter 12 of biology, focusing on meiosis and Mendel's laws. Each card dives into essential terms and concepts related to chromosome behavior during sexual reproduction. Perfect for reinforcing your understanding of genetics!