Biology Chapter 9: Sexual Reproduction

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Questions and Answers

During which phase of meiosis does the diploid cell become haploid?

Telophase I

Prophase I

Anaphase I (correct)

Metaphase I

What structure lines up at the spindle equator during metaphase II?

Dyads (correct)

Tetrads

Homologous chromosomes

Sister chromatids

How many haploid gametes are produced from a single diploid cell after meiosis?

Eight

Two

Six

Four (correct)

How does the chromosome number of daughter cells compare to the parent cell after mitosis?

The same chromosome number (A) Signup and view all the answers

Which of the following describes the genetic relationship between daughter cells and the parent cell after meiosis?

Genetically dissimilar (A) Signup and view all the answers

Where does meiosis occur in humans?

In the testes and ovaries (B) Signup and view all the answers

What is a key event that occurs during prophase I of meiosis but not during mitosis?

Formation of tetrads and crossing-over (A) Signup and view all the answers

What separates during anaphase I of meiosis?

Homologous chromosomes (B) Signup and view all the answers

What is the term for the pairs of chromosomes that are identical in size, shape, and the genes they contain?

Homologues (A) Signup and view all the answers

What is the haploid number in humans?

23 (D) Signup and view all the answers

Which type of cell division is associated with sexual reproduction and the creation of variation in offspring?

Meiosis (D) Signup and view all the answers

How many autosomes do human cells contain?

22 pairs (D) Signup and view all the answers

Which of the following best describes the function of mitosis?

Growth of an organism and tissue repair (D) Signup and view all the answers

What does the process of meiosis produce?

Gametes (C) Signup and view all the answers

What is the diploid number of chromosomes in humans?

46 (D) Signup and view all the answers

What event restores the diploid chromosome number in a sexually reproducing organism?

Fertilization (D) Signup and view all the answers

Which event is NOT associated with meiosis II?

Pairing of homologous chromosomes (B) Signup and view all the answers

What term describes the event where members of a homologous pair move into the same daughter cell during meiosis I?

Nondisjunction (B) Signup and view all the answers

A zygote with three copies of chromosome 13 exhibits:

Trisomy (C) Signup and view all the answers

Which of the following is not a typical characteristic of Down Syndrome?

Tall Stature (C) Signup and view all the answers

A woman is 42 years old. What is the approximate probability of her having a child with Down Syndrome?

1 in 80 births (B) Signup and view all the answers

What is the status of the X chromosome in normal human females?

One X chromosome is functional, and the other becomes a Barr body. (D) Signup and view all the answers

Which set of characteristics is associated with Turner Syndrome?

Short stature, broad chest, and underdeveloped reproductive organs in females. (C) Signup and view all the answers

What is the chromosomal makeup of a person with Klinefelter syndrome?

XXY (D) Signup and view all the answers

What is the outcome of the two cellular divisions in meiosis?

Four haploid daughter cells, each with one chromosome of each pair. (B) Signup and view all the answers

During what process do homologous chromosomes pair up in synapsis to form a tetrad?

Meiosis I (C) Signup and view all the answers

What is the significance of crossing-over during meiosis?

It increases genetic variability by recombining alleles on homologous chromosomes. (A) Signup and view all the answers

Why is maintaining the correct number of chromosomes in new generations a crucial role of meiosis?

To prevent the doubling of chromosome number during fertilization. (A) Signup and view all the answers

During which stage of meiosis do tetrads align at the spindle equator?

Metaphase I (C) Signup and view all the answers

What is a 'dyad' in the context of meiosis?

A newly replicated chromosome composed of of two sister chromatids. (D) Signup and view all the answers

What is the result of the separation of sister chromatids?

The creation of four haploid daughter cells with single chromosome copies (A) Signup and view all the answers

During the first division of meiosis (meiosis I), what event specifically occurs in prophase I?

Synapsis and possible crossing-over. (D) Signup and view all the answers

Study Notes

Chapter 9: Lecture Outline

Sexual Reproduction: Animals and plants reproduce sexually, passing chromosomes to offspring.
Offspring Variation: Each child receives unique chromosome combinations from parents, resulting in differences from parents.
Meiosis: Meiosis is a type of cell division crucial for sexual reproduction and creating variation among offspring.
Homologous Chromosomes: Chromosomes of each parent exist in pairs called homologues; they are identical in size, shape, construction, and the genes they hold, although versions of those genes (alleles) might differ.
Human Chromosomes: Humans have 23 pairs of homologous chromosomes, a total of 46 chromosomes.
- 22 pairs of autosomes
- 1 pair of sex chromosomes (XY in males, XX in females)
Diploid/Haploid Numbers:
- Diploid number is the total chromosome count (46 in humans).
- Haploid number is the number of chromosome pairs (23 in humans).
Human Life Cycle: The human life cycle involves mitosis and meiosis.
- Mitosis is crucial for growth and tissue repair.
- Meiosis leads to gamete production (sperm and egg).
- Gametes have only one chromosome from each pair (23 in humans).
Sperm/Egg Production: In males, meiosis is part of spermatogenesis (sperm production); in females, oogenesis (egg production).
Fertilization: The egg and sperm unite during fertilization, restoring the diploid number in the zygote.
Meiosis Overview: Meiosis involves two cellular divisions, resulting in four daughter cells with one chromosome from each original pair.
- Meiosis I: Homologous chromosomes pair and exchange genetic material (crossing over); then the pairs separate to produce two haploid cells.
- Meiosis II: Sister chromatids separate into new cells, producing a total of four haploid cells.
Crossing-Over: During meiosis' prophase I, homologous chromosomes exchange genetic material, creating new combination of genes in the resulting gametes
Importance of Meiosis: Meiosis maintains chromosome number in each new generation and creates new allele combinations for each new generation. The process also increases genetic variability.
Abnormal Chromosome Inheritance: Errors in meiosis (nondisjunction) can lead to abnormal chromosome numbers in offspring. This can result in various conditions like Down syndrome (trisomy 21).
Nondisjunction: Nondisjunction can occur during meiosis I or meiosis II, where chromosomes or chromatids fail to separate properly, resulting in gametes with too many or too few chromosomes.
Down Syndrome (Trisomy 21): Trisomy 21 is a common example of an abnormal chromosome number caused by nondisjunction, leading to unique physical attributes and mild to moderate intellectual disability.
Sex Chromosome Abnormalities:
- Turner syndrome (XO): Female with monosomy. Physical characteristics of short stature and webbed neck, underdeveloped sexual characteristics.
- Klinefelter syndrome (XXY): Male with trisomy. Physical characteristics such as breast development, underdeveloped testes, long limbs, and reduced facial hair.

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Description

This quiz focuses on key concepts from Chapter 9, including sexual reproduction, meiosis, and homologous chromosomes. Explore how variations among offspring arise and the specifics of human chromosome composition. Test your knowledge of these fundamental biological principles.