Meiosis Flashcards

Questions and Answers

What is meiosis?

A type of cell division that results in four daughter cells, each with half the number of chromosomes of the parent cell.

What are the two main purposes of meiosis?

To generate haploid cells from a diploid cell and to create genetic diversity.

How is a diploid zygote formed?

Opposite gametes fuse together in fertilisation to produce a diploid zygote.

What are the two types of cell division in meiosis?

Meiosis I and Meiosis II. Signup and view all the answers

What happens during prophase I?

Chromosome condensation and pairing, and spindle formation. Signup and view all the answers

What happens during prometaphase I?

Nuclear envelope breaks down and spindle attaches to the chromosomes. Signup and view all the answers

What happens during metaphase I?

Lining up of homologs. Signup and view all the answers

What happens during anaphase I?

Separation of chromosome homologs. Signup and view all the answers

What happens during telophase and cytokinesis I?

Completion of cell division generating two diploid cells. Signup and view all the answers

What happens during prophase II?

Spindle formation. Signup and view all the answers

What happens during pro/metaphase II?

Nuclear envelope breakdown, spindle attachment and alignment of chromosomes. Signup and view all the answers

What happens during anaphase II?

Separation of sister chromatids. Signup and view all the answers

What happens during telophase and cytokinesis II?

Completion of cell division, generating non-identical haploid cells. Signup and view all the answers

What process makes meiosis distinct from mitosis?

Homologous chromosomes pair to form a bivalent during early prophase I. Signup and view all the answers

What process happens at chiasmata?

Crossing over/recombination between homologous chromosomes occurs. Signup and view all the answers

What are the 5 phases of meiotic prophase I?

Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis. Signup and view all the answers

What happens during Leptotene?

Homologs coalesce or pair up (synapsis) and recombination begins. Signup and view all the answers

What happens during Zygotene?

Synaptonemal complex assembles at closely associated sites where recombination is occurring. Signup and view all the answers

What happens during Pachytene?

Assembly process is complete and homologs are synapsed along their entire lengths. Signup and view all the answers

What happens during Diplotene?

Disassembly of the synaptonemal complex (desynapsis). Signup and view all the answers

What happens during Diakinesis?

When the chromosomes condense and shorten. Signup and view all the answers

How does meiosis generate genetic diversity?

Independent assortment of maternal and paternal homologs and crossing over. Signup and view all the answers

What are the similarities and differences between meiosis and mitosis?

Meiosis II is similar to mitosis but produces 4 haploid gametes. Signup and view all the answers

What can errors in chromosome segregation during meiosis lead to?

Gametes with an incorrect number of chromosomes. Signup and view all the answers

Study Notes

Meiosis Overview

Meiosis is a specialized cell division resulting in four daughter cells, each with half the chromosomes of the parent cell, crucial for gamete and spore production.

Purposes of Meiosis

Generates haploid gametes from diploid germline cells.
Creates genetic diversity in the resulting cells.

Formation of Diploid Zygote

Occurs when two opposite gametes fuse during fertilization, leading to a diploid zygote that undergoes mitosis to form a diploid organism.

Stages of Meiosis

Two main stages: Meiosis I and Meiosis II.

Key Events in Meiosis I

Prophase I: Chromosomes condense, pair up, and spindle apparatus forms.
Prometaphase I: Breakdown of nuclear envelope; spindle fibers attach to chromosomes.
Metaphase I: Homologous chromosomes align at the cell equator.
Anaphase I: Separation of homologous chromosomes occurs.
Telophase I and Cytokinesis: Creation of two diploid cells.

Key Events in Meiosis II

Prophase II: Spindle apparatus re-forms.
Prometaphase II: Nuclear envelope breaks down; chromosomes align.
Anaphase II: Sister chromatids are separated.
Telophase II and Cytokinesis: Four non-identical haploid cells are produced.

Distinctions from Mitosis

In mitosis, chromosomes operate independently, whereas homologous chromosomes pair in meiosis.
Chiasmata form in meiosis, facilitating homologous chromosome pairing.
Sister chromatids are held together by cohesin in mitosis, while bivalents are held by chiasmata in meiosis.

Crossing Over

Chiasmata are the sites where crossing over occurs, allowing genetic recombination between homologous chromosomes.

Phases of Meiotic Prophase I

Five phases: Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis:
- Leptotene: Homologs begin to pair.
- Zygotene: Synaptonemal complex forms to stabilize homologs.
- Pachytene: Complete synapsis occurs along chromosome lengths.
- Diplotene: Synaptonemal complex disassembles.
- Diakinesis: Chromosomes further condense.

Genetic Diversity Mechanisms

Independent assortment of maternal and paternal chromosomes leads to 2^n different gamete combinations.
Crossing over exchanges genetic material, enhancing diversity.

Meiosis vs. Mitosis

Meiosis II resembles mitosis but includes chromosome pairing.
DNA synthesis precedes both processes, and both complete cell division.
Meiosis produces four genetically diverse haploid cells; mitosis yields two identical diploid cells.
Meiosis involves two rounds of division without recombination in mitosis; meiosis maintains cohesion in meiosis I but not in mitosis.

Errors in Meiosis

Improper chromosome segregation can result in gametes with abnormal chromosome numbers.
Errors in recombination may lead to structural chromosome abnormalities.

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Description

Test your knowledge on meiosis with these flashcards. Covering key concepts, such as the definition of meiosis and its main purposes, this quiz will help reinforce your understanding of this crucial cell division process.