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 3Pupils learned that living things reproduce and certain traits are passed 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 their life cycles.

STORY LINE

• GRADE 5• Pupils learned how

flowering plants and some non-flowering plants reproduce.

• They were also introduced to the sexual and asexual modes of reproduction.

GRADE 6• Pupils learned how non-

flowering plants (spore-bearing and cone-bearing plants, ferns, and mosses) reproduce.

STORY LINE• GRADE 7• After learning how

flowering and non-flowering 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 passed on to the next generation?

TOPICS INCLUDED:Review on the Cell Function Review on the Location of Chromosomes in

the CELLCell Cycle: Interphase (G1, S phase, G2)

Mitotic Phase Meiotic Phase

Nondisjunction (Chromosomal Aberrations)CLASSICAL GENETICS

-Mendelian Genetics-Non-Mendelian Pattern of Inheritance

Sex-Linked TraitsSex 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• G2 - growth 2 (Gap2)

Cell Cycle Part 1:Interphase = normal phase of the cell.

Chromosomes NOT visible. – DNA in form called chromatin

▪ Looks like spaghetti The nuclear

envelope/membrane 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

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

• Diploid cell (2n). – cells with 2 sets of chromosomes.

1 set-comes from male parent

1 set-comes from female parent

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.• The longest time to occur.

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 – 4th phase

• Chromosomes begin to disappear.

• Spindle fibers disappear• Two new nuclear

envelopes/membranes 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

• 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

A single-celled

eukaryote (amoeba)

reproduces

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 eachdaughter cell compare with the number ofchromosomes in the original parent cell after mitosis? 3. When are chromosomes replicated? 4. During cytokinesis plant cells form a _________while animal cells form a ____________.

ANSWERS:1. How many daughter cells are produced by mitosis? 2

2. How does the number of chromosomes in eachdaughter cell compare with the number of chromosomesin the original parent cell after mitosis? Same numberand type of chromosomes.

3. When are chromosomes replicated? Interphase, specifically S-phase

4. During cytokinesis plant cells form a cell plate whileanimal cells form a cleavage furrow.

Meiosis

Two rounds of cell division

In humans, each daughtercell has 23 chromosomes

Many possible combinations of chromosomes are possible

Random assortmentCrossing over

Not identical in human males and females

Feature Males Females

When does meiosis begin?

How long does each step take?

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

ANIMATION OF MEIOSIS

Classical Genetics

MENDELIAN PRINCIPLES OF INHERITANCE

Mendel’s Genetics

Experiment with Peas

Pea Characters Investigated

Pea Characters Investigated

MENDEL’S RULE OF HEREDITY

PUNNETT SQUARE: Monohybrid Cross- single trait factorEXAMPLE : 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

RR

r

r

Rr Rr

Rr Rr

PR: 100 % ROUND

GR: 100 % Rr

Gametes RY Ry rY ry

RY

Ry

rY

ry

Dihybrid Cross: two factor crossSeed Shape: Round (RR). WrinkledSeed Color: yellow (YY) and green (yy)

Parents’ genotype: RrYy x RrYy

RRYy

RRYY RRYy

RrYY RrYy

RrYy

RrYy

RrYy

RRyy

RrYY

rryy

rrYY

Rryy

Rryy

rrYy

rrYy

A or O

A or AB

“Tell me and I will forget, Show me and I might

remember, Involve me and I will

understand.” Chinese Proverb

Thank You