BIO110 Chp 5 Cell Division

Cell Reproduction

Chapter 5

Cell Division Purposes

Cells divide for 3 reasons. Growth, Repair, and Reproduction.

Types of Reproduction

• Sexual- Two parents produce genetically unique offspring. Gametes are formed and used for reproduction.

• Asexual- One parent produces genetically identical offspring. No gametes involved.

Multiple Select

Why do cells divide? (select all that apply)

• Growth

• Repair

• Respiration

• Reproduction

Multiple Choice

Requires only 1 parent, no gametes

• Sexual Reproduction

• Asexual Reproduction

Multiple Choice

Sexual reproduction yields ______ offspring

• Unique

• Identical

Genetic Material

• All life on Earth uses DNA as their genetic material.

• •The nucleus of every eukaryotic cell contains long strands of DNA called chromosomes.

• Each chromosome contains genetic information in genes.

• A gene contains the information needed to build proteins.

DNA

• Inside the nucleus, the chromosomal DNA is wound around proteins; together they form chromatin. Chromatin is loosely packed

• Most of the time chromosomes are unraveled as loose chromatin.

  
  

Chromosomes

• Every human body cell has 46 chromosomes

• At cell division, chromosomes

  1.Become tightly packed

  2.Duplicate

• Pairs of duplicated chromosomes are called sister chromatids.

• Sister chromatids (duplicated chromosome pair) are joined at the centromere.

Multiple Choice

DNA is in condensed strands called ___________, which have pieces on them called _____ which code for ________.

• Proteins, Chromosomes, Genes

• Genes, Chromosomes, Proteins

• Proteins, Genes, Chromosomes

• Chromosomes, Genes, Proteins

The Cell Cycle

• The cell cycle is an ordered sequence of events in the “lifetime” of a cell.

• There are two broad phases:

• 1. Interphase

• 2. Mitotic Phase

Interphase

• During interphase, the cell

  •Performs its normal functions

  •Grows

  •Prepares for division by duplicating its chromosomes

Mitotic Phase

• During the mitotic phase, the cell undergoes active cell division

• Mitosis (the splitting of the nucleus) occurs in 4 stages (PMAT)

• Cytokinesis is the splitting of the cytoplasm.

• The end result of the mitotic phase is 2 identical daughter cells which both re-enter Interphase of the cell cycle.

Multiple Choice

Which phase of the Cell Cycle do cells spend most of their lifetime in?

• Prophase

• Mitosis

• Interphase

• Cytokinesis

Multiple Choice

Which phase of the Cell Cycle involves the"splitting of the nucleus"

• Mitosis

• Interphase

• Cytokinesis

Prophase

• First step of Mitosis

• Chromosomes condense from chromatin

• Nuclear membrane dissolves. Cell lays down mitotic spindle.

Metaphase

• 2nd Step of Mitosis

• Chromosomes align on the metaphase plate

• Sister chromatids line up and attach to mitotic spindle.

Anaphase

• 3rd step of mitosis

• Chromosomes pull apart

• Sister chromatids are pulled apart from their centromeres as mitotic spindle retracts

Telophase

• Nuclear Envelope reforms

• Two duplicated nuclei are formed

Cytokinesis

• Cytokinesis is the division of the cytoplasm and is the final step in the cell cycle

• The process of cytokinesis is different for plant and animal cells.

• Animal cells have a cleavage furrow and plant cells form a cell plate.

Multiple Choice

Which phase involves the chromosomes lining up in the middle?

• Prophase

• Metaphase

• Anaphase

• Telophase

• Cytokinesis

Multiple Choice

Which phase pulls sister chromatids apart at their centromeres?

• Prophase

• Metaphase

• Anaphase

• Telophase

• Cytokinesis

Multiple Choice

What is formed during animal cell cytokinesis?

• Cleavage furrow

• Cell plate

Multiple Choice

What is formed during plant cell cytokinesis?

• Cleavage furrow

• Cell plate

Cloning

• Cloning can be done through the process of nuclear transplantation

• The surrogate has an egg removed and the haploid nucleus is removed.

• The egg's nucleus is replaced with the already diploid nucleus of the organism that will be cloned (no need for fertilization because the nucleus is already diploid).

Sexual Reproduction- How do you get 1 from 2?

• Most of the cells in your body are diploid; they have two copies of each chromosome.

• Gametes, or sex cells, are haploid: They contain only one copy of each chromosome.

• How does your body make Gametes? Meiosis!

Meiosis

• Gametes (sperm and egg) are formed by a special type of cell division, meiosis.

• Cells produced from meiosis are haploid.

• Like mitosis, meiosis occurs in stages

Meiosis Overview

• In meiosis, there are two rounds of cell division

• Meiosis (like mitosis) starts with chromosome duplication before cell division.

• The result of meiosis is four haploid NON identical offspring cells, all with one-half the number of chromosomes.

Meiosis I: The homologous pairs line up and separate

• Prophase I: Chromosomes condense, crossing over. Homologous chromosome pairs pair up.

• Metaphase I: Independent assortment. Homologous pairs line up on the metaphase plate

• Anaphase I: Homologous pairs separate

• Telophase/Cytokinesis I: end of meiosis I is 2 haploid cells with sister chromatids.

Meiosis II: Separation of the Sister Chromatids

• Prophase & Metaphase II: Chromosomes condense and line up

• Anaphase II: Sister chromatids separate

• Telophase/Cytokinesis II: Result is 4 NON identical Haploid cells (Gametes)

Multiple Choice

There are _____ rounds of cell division in meiosis

• 1

• 2

• 3

• 4

Multiple Choice

There are ____ _______ cells created in meiosis

• 2; haploid

• 4, diploid

• 2; diploid

• 4; haploid

Multiple Choice

Meiosis I involves the separation of what?

• Cytoplasm

• Sister chromatids

• Homologous pairs

Multiple Choice

Meiosis II involves the separation of what?

• Cytoplasm

• Sister Chromatids

• Homologous pairs

Meiosis and Mitosis in Humans

In sexually reproducing organisms, mitosis and meiosis both play important roles

Sexual Reproduction leads to Variation!

• 1. Crossing Over (Prophase I of meiosis)

• 2. Independent Assortment (Metaphase I of meiosis)

• 3. Random Fertilization (random sperm with random egg= nearly endless possibilities)

Multiple Choice

When does independent assortment occur?

• Prophase I

• Prophase II

• Metaphase I

• Metaphase II

Multiple Choice

When does crossing over occur?

• Prophase I

• Prophase II

• Metaphase I

• Metaphase II

Nondisjunction

• Nondisjunction is when chromosomes fail to separate properly.

• Resulting gametes will have too few or too many chromosomes

• One example if nondisjunction is Trisomy 21 (Down's Syndrome) which comes from an individual getting an extra copy of the 21st chromosome.

Summary/ Study Topics

Types of Reproduction, Genetic Material Terms, The Cell Cycle, Mitosis, Meiosis, Nondisjunction