Mitosis and Meiosis

Meiosis I is often referred to as the?

Reduction Division

Given 2n = 46 how many chromosomes and DNA are in Prophase I?

Chromosomes = 46

DNA = 92

Given 2n = 46 how many chromosomes and DNA are in Metaphase I?

Chromosomes = 46

DNA = 92

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Given 2n = 46, how many chromosomes and DNA are in Anaphase I?

Chromosomes = 46

DNA = 92

Given 2n = 46, how many chromosomes and DNA are in Telophase I?

Chromosomes = 46

DNA = 92

Given 2n = 46, how many chromosomes and how much DNA are in Cytokinesis I?

Chromosomes = 23

DNA = 46

Meiosis 2 is called the?

Equal Division

Given 2n = 46, how many chromosomes and how much DNA are in Prophase II?

Chromosomes = 23

DNA = 46

Given 2n = 46, how many chromosomes and how much DNA are in Metaphase II?

Chromosomes = 23

DNA = 46

Given 2n = 46, how many chromosomes and how much DNA are in Anaphase II?

Chromosomes = 46

DNA = 46

Given 2n = 46, how many chromosomes and how much DNA are in Anaphase II?

Chromosomes = 46

DNA = 46

Given 2n = 46, how many chromosomes and how much DNA are in Cytokinesis II?

Chromosomes = 23

DNA = 23

Why don’t cells go through interphase again before Meiosis II?

In Meiosis I, DNA has been copied 1x. If interphase happened again, we’d replicate the DNA again, ending up with extra copies of DNA in our gametes

What is the goal of Meiosis?

The goal oof meiosis is to make 4 genetically different gametes [sex cells]

What’s the acronym for remembering the stages of Meiosis?

PMAT x2

What happens in Interphase [Meiosis]?

DNA replicates

What happens in Prophase I?

• Nuclear envelope disappears

• Chromatin condenses into chromosomes

• Homologous pairs of chromosomes pair and line up next to each other

• Crossing over occurs

What is crossover, and when does it occur?

• Prophase I

• Paired chromosomes exchange segments of DNA, creating genetic diversity

What is Metaphase I?

• Homologous pairs of chromosomes line up in the middle

What is Anaphase I

Homologous pairs separate moving towards opposite spindle poles

What is telophase I?

• Chromosomes arrive at the spindle poles

• Nucleus regrows

• Chromosomes unwind back into chromatin

What is cytokinesis I

Cytoplasm divides the cell into 2

What is the result of Meiosis I?

• Cell divides into 2 haploid cells

• The 2 cells each contain ½ the original number of chromosomes and DNA

What happens in Prophase II?

• Chromosomes condense

• The nuclear envelope dissolves

What happens in Metaphase II?

• Chromosomes line up in the middle

What happens in Anaphase II?

• Sister chromatids separate on opposite sides

What happens to the number of Chromosomes and DNA in anaphase? 2n = 4

• Chromosomes are doubled and equal to DNA

• Chromosomes = DNA = 4

What happens in Telophase II?

• The chromosomes arrive at the spindle poles

• The nuclear envelope reforms

What happens to the number of Chromosomes and DNA in anaphase? 2n = 4

• Chromosomes = DNA = 4

What happens during Cytokinesis II?

• Cytoplasm divides

• 4 genetically unique haploid gametes are produced

• Each cell contains ½ original amount of chromosomes

After cytokinesis, when the cytoplasm divides into 4 cells, how many chromosomes and how much DNA are contained in each cell? 2n = 4

Each cell contains 2 chromosomes and 2 DNA molecules

What if homologous chromosomes don’t pair in PROPHASE I and continue through meiosis?

At the end of M1, one cell will have an extra chromosome while the other will be missing one chromosome

What if separation during anaphase I fails?

• At the end of M1, each cell will contain a different number of chromosomes

• One cell will have 1 chromosome, while another has 3

• Cells proceed through M2, resulting in each cell having an incorrect number of chromosomes

Mitosis makes new ____ cells?

Body cells for growth, replacement and repair

Each cell in Mitosis is genetically ____?

Identical

What happens during the G1 Phase of Mitosis?

• Cell grows back to full size

• copies many of its organelles

What happens in the S phase of Mitosis

• Cell replicates entire DNA now having 2 copies

What happens in the G2 Phase of Mitosis?

• Growth Phase

• Cell checks for and repairs errors from DNA replication

• Synthesizes proteins needed for mitosis

What happens in Prophase

• Chromatin condenses into chromosomes

• Nuclear envelope dissolves

• Centrosomes move toward opposite ends

What happends in Metaphasse

• Chromosomes line up in the middle

• Spindle fibers attach to centromeres

What happens in Anaphase

• Spindle fibers pull chromosomes apart into sister chromatids

• Sister chromatids separate to opposite sides

What happens in Telophase

• Nuclear envelope reforms

• Chromosomes decondense back into chromatin

• Cytokinesis divides the cell into 2

If n = 4, how many chromosomes and how much DNA are in Prophase?

DNA = 8

Chromosomes = 8

If n = 4, how many chromosomes and how much DNA are in Metaphase?

DNA = 8

Chromosomes = 8

If n = 4, how many chromosomes and how much DNA are in Anaphase?

DNA = 8

Chromosomes = 16

If n = 4, how many chromosomes and how much DNA are in Telophase?

DNA = 8

Chromosomes = 4