Meiosis Fundamentals
What is the main purpose of Meiosis?
Producing Gametes (Egg and Sperm cells) for Sexual Reproduction
During which phase does the cell grow and duplicate its DNA before Meiosis begins?
Interphase
During which phase of Meiosis II do chromosomes line up individually in the center of each cell?
Metaphase II
What are Homologous Chromosomes?
Matching pairs of chromosomes, with one inherited from each parent
What is the term for chromosomes failing to separate correctly during Meiosis?
Nondisjunction
Humans have 46 chromosomes in their body cells. How many chromosomes are found in a normal human Egg or Sperm cell?
23 chromosomes
During which phase do Homologous Chromosomes pair up and Crossing Over can occur?
Prophase I
During which phase do sister chromatids separate and move toward opposite ends of each cell?
Anaphase II
What are Sister Chromatids?
Identical copies of a duplicated chromosome that remain attached
What is a Karyotype?
An image of all the chromosomes in a cell, arranged in homologous pairs and ordered by size
What are the two types of Human Gametes?
Egg and Sperm
During which phase do Homologous Chromosome pairs line up next to each other in the center of the cell?
Metaphase I
During which phase do new nuclei form around the chromosomes, preparing the cells for division?
Telophase II
A body cell divides to produce two genetically identical daughter cells for growth and tissue repair. Is this Mitosis or Meiosis? Explain two pieces of evidence that support your answer.
Mitosis. It produces two genetically identical cells, occurs in somatic (body) cells, and involves one cell division.
What is the difference between Monosomy and Trisomy?
Monosomy having one missing copy of a chromosome and Trisomy having an extra copy
What is the difference between a Haploid cell and a Diploid cell?
A haploid cell has one set of chromosomes (n), while a diploid cell has two sets (2n)
During which phase do Homologous Chromosomes separate and move toward opposite ends of the cell, while Sister Chromatids remain attached?
Anaphase I
At the end of Meiosis I, two new cells are formed. What are these two cells called as they enter Meiosis II?
The two haploid cells produced during Meiosis I
What is the name of the process in which Homologous Chromosomes exchange segments of genetic material during Prophase I?
Crossing over
A Karyotype shows three copies of chromosome 21 instead of two. What chromosomal abnormality is present, and what condition is associated with it?
Trisomy 21, also known as Down syndrome
During fertilization, an Egg cell and a Sperm cell join together. Each has 23 chromosomes. How many chromosomes will the new cell have, and will it have one set of chromosomes (Haploid) or two sets (Diploid)?
46 chromosomes and diploid (2n)
At the end of Meiosis I, two new cells form. Do these cells have the original number of chromosomes, or half the original number? What is special about the chromosomes they contain?
Half the original number. Each cell is haploid, but its chromosomes still consist of two attached sister chromatids.
A student says that Meiosis II is unnecessary because the chromosome number was already cut in half during Meiosis I. Explain why Meiosis II is still needed.
Separating the sister chromatids so that four haploid cells can ultimately form
Unlike Mitosis, Meiosis produces genetically different cells. Name two processes that contribute to genetic variation during Meiosis.
Crossing over and chromosome Independent Assortment
Identify the chromosomal abnormality associated with each condition: Turner syndrome, Patau syndrome, Edwards syndrome, and Klinefelter syndrome.
Remember: if it is missing one, its monosomy, and if it has one extra, its trisomy.
Monosomy X (Turner), Trisomy 13 (Patau), Trisomy 18 (Edwards), and an extra X chromosome (usually 47,XXY) in Klinefelter syndrome?