Grade 8 Module 5 5b1q1q

5 MODULES IN 4TH QUARTER MODULE 1:

BIODIVERSITY

MODULE 2:

INTERACTIONS

MODULE 3:

THE DIGESTIVE SYSTEM

MODULE 4:

NUTRITION & WELLNESS

MODULE 5:

CELLULAR REPRODUCTION & GENETICS

BIOLOGY Module 5

STORY LINE • GRADE 3 Pupils learned that living things reproduce and certain traits are ed on to their offspring

GRADE 4 • Pupils learned that humans, animals, and plants go through life cycles. • Some inherited traits may be affected by the environment at certain stages in

STORY LINE • GRADE 5 • Pupils learned how flowering plants and some nonflowering plants reproduce. • They were also introduced to the sexual and asexual modes of reproduction.

GRADE 6 • Pupils learned how non-flowering plants (sporebearing and conebearing plants, ferns, and mosses) reproduce.

STORY LINE • GRADE 7 • After learning how flowering and nonflowering plants reproduce, Grade 7 students learned that asexual reproduction results in genetically identical offspring whereas sexual reproduction gives rise to variation

GRADE 8  Students will learn the process of cell division by mitosis and meiosis.  They will understand that meiosis is an early step in sexual reproduction that leads to variation.

Suggested Time allotment: 4 to 5 hours

KEY QUESTIONS:

•What are the different types of cell division? •How are traits ed on to the next generation?

TOPICS INCLUDED: Review on the Cell Function Review on the Location of Chromosomes in the CELL Cell Cycle: Interphase (G1, S phase, G2) Mitotic Phase Meiotic Phase Nondisjunction (Chromosomal Aberrations) CLASSICAL GENETICS -Mendelian Genetics -Non-Mendelian Pattern of Inheritance Sex-Linked Traits Sex Chromosomes and Sex Determination

Cell Cycle Makes up the entire life of the cell

• Consists of 2 major stages: – Interphase – Mitotic Phase

• Interphase G0 -zero growth (Gap O) G1- initial growth(Gap 1) • S - synthesis

Cell Cycle Part 1: Interphase = normal phase of the cell.  Chromosomes NOT visible. – DNA in form called chromatin ▪ Looks like spaghetti

 The nuclear envelope/membran e present  DNA replication  Cell growth

Mitosis - Review

Cell Cycle Part 2: Cell Division • Also known as Mitotic Phase • Where Mitosis and Cytokinesis occur • A continuous process divided into 4 main stages • Daughter Cells – 2 new cells produced by cell division.

Mitosis = division of 1 diploid nucleus into 2 identical diploid nuclei

• Diploid cell (2n). – cells with 2 sets of chromosomes. 1 set-comes from male parent 1 set-comes from female parent

• All somatic/body cells undergo mitosis for growth, repair or replacement of old cells

Mitosis in an actual cell

Prophase – 1st phase of mitosis.

• Chromatin materials becomes thicker and shorter because of repeated coiling • Chromosomes are now visible • Centrioles form spindle • Nuclear envelope/membrane and nucleoli breaks apart.

Metaphase – 2nd phase

 Chromosomes meet and align in middle or equator.  Spindle fibers attach to centromere  Nuclear envelope/membrane is gone.

Anaphase – 3rd phase

 Centromere splits at the center of the chromosomes.  Chromatids move away from each other.  Spindles pull chromatids apart  The nuclear envelope/membrane still absent

Telophase – 4 phase th

• Chromosomes begin to disappear. • Spindle fibers disappear • Two new nuclear envelopes/membrane s begin to form • Nucleoli reappear. • “reverse prophase”

Cytokinesis • Division of the cell membrane and cytoplasm. • Forms two new Daughter cells

Mitosis - Overview

Interphase

Early Prophase

Late Prophase

Metaphase

Early Anaphase

Telophase - Cytokinesis

Telophase - Cytokinesis

Check for understanding! • 11. Why are the onion root tip and the whitefish blastula useful tissues for the study of cell division? . Why are the onion root tip and the whitefish blastultissues for the study of cell division? • These two tissues were actively dividing, so we could find cells under going mitosis at different phases.

• 2. Distinguish between mitosis and cytokinesis.

Mitosis is the division of the nucleus (nuclear division) produces 2 identical nuclei. Cytokinesis is the division of the cytoplasm – produces 2 cells.

• 3. If a cell has 16 chromosomes when it is

in G1, how many chromosomes will there be in each daughter cell following a mitotic cell division?

• 16

• 4.

What are the genetic consequences of mitotic cell division for the resulting daughter cells?

Every cell is genetically identical to each other. Produces 2 identical nuclei, each with the same number and types of chromsomes as the parent cell.

• 6.

How do plant and animal cells differ in the execution of cytokinesis? Why don’t plant cells undergo cytokinesis in the same manner as animal cells?

During cytokinesis plant cells form a cell plate while animal cells form a cleavage furrow. • Plant cell has a rigid cell wall •

Moving On… • 7. List several important values or attributes that mitotic cell division provides to multicellular life. In other words, in what ways is mitotic cell division useful for life?

• 8. List the 4 stages of the cell cycle and describe the primary cellular activity in each stage.

Cell Division A singlecelled eukaryote (amoeba) reproduces

• Reproduction – Equal distribution of genetic material to two daughter cells

• Growth – Sexually reproducing organisms develop from a single cell (zygote)

• Repair – Replace cells that die from normal wear and tear or accidents

Sand dollar embryo after the egg divided to form 2 cells

Dividing bone marrow cells produce new blood cells

More…. 1. How many daughter cells are produced by mitosis? 2. How does the number of chromosomes in each daughter cell compare with the number of chromosomes in the original parent cell after mitosis? 3. When are chromosomes replicated?   4. During cytokinesis plant cells form a

ANSWERS: 1. How many daughter cells are produced by mitosis? 2 2.How does the number of chromosomes in each daughter cell compare with the number of chromosomes in the original parent cell after mitosis? Same number and type of chromosomes. 3. When are chromosomes replicated? Interphase, specifically S-phase   4.During cytokinesis plant cells form a cell

Meiosis Two rounds of cell division In humans, each daughter cell has 23 chromosomes

Many possible combinations of chromosomes are possible

Random assortment Crossing over

Not identical in human males and females Feature

Males

Females

When does meiosis begin?

Begins at puberty Each step takes about the same time (~64 days total)

Begins during embryonic development May remain in meiosis I for decades (may never complete meiosis)

How is meiosis completed?

Spermatocytes will complete meiosis

Meiosis II happens only with fertilization

How many gametes are formed?

4 spermatids are formed

One ovum is formed

How long does each step take?

ANIMATION OF MEIOSIS

Classical Genetics MENDELIAN PRINCIPLES OF INHERITANCE

Mendel’s Genetics Experime nt with Peas

Pea Characters Investigated

Pea Characters Investigated

MENDEL’S RULE OF HEREDITY

PUNNETT SQUARE: Monohybrid Cross- single trait factor EXAMPLE : seed shape round (RR) is dominant over wrinkled (rr) Problem: Predict the outcome of a cross when a homozygous dominant round pea is cross with a homozygous wrinkled pea plant R R r

r

PR: 100 % ROUND

Rr

Rr

Rr

Rr

GR: 100 % Rr

Dihybrid Cross: two factor cross Seed Shape: Round (RR). Wrinkled Seed Color: yellow (YY) and green (yy) Parents’ genotype: RrYy x RrYy

Gametes RY Ry

RY

Ry

rY

ry

RRYy

RrYY

RrYy

RRYy

RRyy

RrYy

Rryy

RrYY

RrYy

rrYY

rrYy

RrYy

Rryy

rrYy

rryy

RRYY

rY ry

A or O A or AB

“Tell me and I will forget, Show me and I might , Involve me and I will understand.”

Thank You

Chinese Proverb