Biology: Meiosis and Sexual Reproduction

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Questions and Answers

What is the advantage of sexual reproduction over asexual reproduction?

Ensuring the survival of a single species

Faster adaptation to environmental changes

Greater variation in heritable traits in populations (correct)

Passing on all genes to the offspring

What is the diploid number in humans?

46 (correct)

100

What is the function of a gene?

To provide energy to the cell

To provide structural support to the cell

To regulate cell division

To encode proteins and influence specific traits (correct)

What is the result of asexual reproduction in terms of genetics?

Offspring have identical genes to the parent Signup and view all the answers

What is the purpose of meiosis?

To maintain the current chromosome number Signup and view all the answers

What is the term for different forms of the same gene?

Alleles Signup and view all the answers

What happens to homologous chromosomes during meiosis?

They pair up Signup and view all the answers

Why is sexual reproduction beneficial in a changing environment?

Because it leads to faster adaptation to environmental changes Signup and view all the answers

What is the result of meiosis?

4 haploid daughter cells Signup and view all the answers

What happens during prophase I of meiosis?

Homologous chromosomes pair up and crossing-over occurs Signup and view all the answers

What is the purpose of crossing-over?

To exchange genetic material between homologous chromosomes Signup and view all the answers

What is the result of anaphase I?

Homologous chromosomes separate Signup and view all the answers

What happens during telophase I?

Nuclear envelope and nucleolus start to reappear Signup and view all the answers

What is the purpose of meiosis II?

To separate sister chromatids Signup and view all the answers

What happens during anaphase II?

Sister chromatids separate Signup and view all the answers

What is the result of telophase II?

Nuclear envelopes reform and nucleoli reappear Signup and view all the answers

What is the purpose of prophase II?

To prepare the nucleus for division Signup and view all the answers

What is the result of metaphase II?

Chromosomes line up on the metaphase plate Signup and view all the answers

Study Notes

Meiosis and Sexual Reproduction

Sexual reproduction provides greater variation in heritable traits in populations, allowing for adaptation to changing environments (abiotic or biotic).
This leads to some forms being more adaptive, and adaptive traits spreading faster.

Chromosome Number

Diploid number (2n) is the number of chromosomes in a diploid cell, with two sets of each type (e.g., humans have 46 chromosomes).
Haploid number (n) is the number of chromosomes in a haploid cell, with a single set of each type (e.g., humans have 23 chromosomes).

Alleles and Genes

Alleles are different forms of the same gene, influencing specific traits.
In asexual reproduction, genes are identical to the parent (clones), except for mutations.
In sexual reproduction, pairs of genes (maternal and paternal) are combined, resulting in new combinations of alleles in offspring.

Meiosis

Meiosis involves the production of reproductive cells (gametes) with a haploid number of chromosomes.
Meiosis maintains the chromosome number, producing four haploid daughter cells.
The process of meiosis involves two nuclear divisions, with no S phase between them.

Meiosis I

Prophase I is the most complex stage of meiosis, involving the condensation of chromosomes, nuclear membrane breakdown, and the formation of a spindle.
Prophase I has five stages: leptotene, zygotene, pachytene, diplotene, and diakinesis.
During prophase I, homologous chromosomes pair up and exchange genetic material through crossing-over.

Meiosis II

Metaphase II involves the alignment of chromosomes on the metaphase plate.
Anaphase II involves the separation of sister chromatids, moving to opposite poles of the cell.
Telophase II involves the uncoiling of chromosomes, reformation of nuclear envelopes, and the reappearance of nucleoli.

Cytokinesis

Cytokinesis occurs after both meiosis I and II, resulting in four haploid cells.
In some cases, nuclei may degenerate or be ejected as polar bodies, resulting in a single uninucleate ovum.

Variation in Traits

Crossing over during meiosis I results in the exchange of genetic material between paternal and maternal chromosomes, leading to increased variation in traits.
The separation of chromosome pairs during meiosis I is independent and random, resulting in a huge number of possible combinations (e.g., 8,388,608 in humans).
The combination of these unique sets of genes at fertilization results in an even greater variation in traits.

Life Cycles

Meiosis and cytoplasmic division result in haploid gametes, which fuse to form a diploid zygote.
Many variations exist in life cycles, including the production of gametes, size, and shape, as well as different types of life cycles (unicellular, multicellular, diploid, haploid generations).

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Description

Explore the benefits of sexual reproduction over asexual reproduction, including increased variation in heritable traits and adaptation to environmental changes.