Meiosis

Flashcards for studying key concepts related to meiosis, genetic variation, and reproductive processes.

What is meiosis?

Meiosis is nuclear division that leads to halving of chromosome number to produce gametes.

What are the two types of gametes in animals?

Sperm and eggs.

What is the result of meiosis?

Meiosis produces four haploid daughter cells that are genetically distinct.

How does meiosis promote genetic diversity?

Through crossing over, independent assortment, and random fertilization.

What occurs during crossing over?

Exchange or swapping of genetic material between homologous non-sister chromatids.

What defines homologous chromosomes?

Chromosomes that have the same genes in the same position but may carry different alleles.

What is the haploid number (n) for humans?

23 distinct types of chromosomes.

What is the diploid number (2n) for humans?

46 chromosomes, consisting of pairs of homologous chromosomes.

What is the main difference between mitosis and meiosis?

Meiosis includes two rounds of cell division, resulting in four haploid cells, while mitosis results in two diploid cells.

What happens during anaphase I of meiosis?

Homologous chromosomes separate and migrate to opposite ends of the cell.

What are the effects of errors in meiosis?

Errors can lead to conditions like Down syndrome, due to nondisjunction.

What is 'purifying selection'?

Natural selection against deleterious alleles inherited by all offspring in asexual reproduction.

What is the 'changing-environment hypothesis'?

It suggests that offspring produced sexually are more likely to survive in changing environments due to genetic diversity.

Why do some organisms exhibit sexual reproduction despite its costs?

Sexual reproduction increases genetic variation, enhancing survival in changing environments.

What are polyploid organisms?

Organisms with more than two sets of chromosomes, which can occur in plants.

What leads to the formation of a zygote?

The fertilization of a haploid sperm and haploid egg.

Why does meiosis happen?

It exists for the benefits of sexual reproduction, promoting genetic diversity and adaptation.

What is the outcome of meiosis II?

Meiosis II results in four haploid daughter cells, each containing one unreplicated chromosome.

What characterizes the genetic composition of offspring from sexual reproduction?

They are genetically different from their parents due to crossing over and random assortment.

What happens when nondisjunction occurs?

Homologues or sister chromatids fail to separate, leading to gametes with abnormal chromosome numbers.