CHAPTER 6Meiosis is the basis of Sexual Reproduction

SECTION 6.1 PAGE 170

Meiosis

SEXUAL REPRODUCTIONForm of reproduction which

requires two parents, egg and sperm

Produces offspring that are genetically different from each other and any other member of the species

Can occur in plants and animals

MEIOSIS

The process that produces gametes ``sex cells`` – egg in female and sperm in male with half the number of chromosomes as body cells.

HAPLOID VS. DIPLOID

Haploid = half the genetic content (n)

Diploid = genetic equal to the parent. Full genetic content (2n)

Haploid Diploid

46 HUMAN CHROMOSOMES

8 STAGES OF MEIOSIS

Prophase IMetaphase I

Anaphase ITelophase I

Prophase IIMetaphase II

Anaphase IITelophase II

MEIOSIS I MEIOSIS II

Meiosis

MEIOSIS I –RESULTS IN 2 DAUGHTER CELLS

+ Telophase I

MEIOSIS II –RESULTS IN 4 HAPLOID CELLS EACH WITH HALF THE NUMBER OF CHROMOSOMES

+ Telophase II

FORMATION OF EGG AND SPERM

Only 1 egg survives

www.cellsalive.com

Question?

Mitosis Meiosis

Where does it take place?

How many cells are produced?

What happens to the number of Chromosomes?

Type of Reproduction?

Question?

Mitosis Meiosis

Where does it take place? In Body Cells

In Sex organs

How many cells are produced?

2 daughter cells

4 daughter cells

What happens to the number of Chromosomes?

Same Number of

Chromosomes as Parent

½ the number of

Chromosomes as Parent

Type of Reproduction?

Asexual Reproductio

n

Sexual Reproductio

n

CORE LAB ACTIVITY 6-1B PAGE 176-7

“Comparing Mitosis & Meiosis”

SECTION 6.2 PAGE 180

Sexual Reproduction

FERTILIZATION (THE UNION OF EGG AND SPERM TO CREATE A ZYGOTE) MAY OCCUR:

Outside the bodies of the parents – External Fertilization

OR

Inside the mothers body where the developing embryo is nourished for a period of time –

Internal Fertilization

SEXUAL REPRODUCTION IN:

1. Mosses

External fertilizationWater allows the egg

and sperm cells to meet

Has both sexual and asexual stages in its life cycle

SEXUAL REPRODUCTION IN

A MOSS PLANT

SEXUAL REPRODUCTION IN:

2. Flowering PlantsExternal fertilizationPollination - Transfer of

male gametes in structures called pollenPollen adheres to the “sticky” female part

of the plant and male gametes fertilize the eggs

seeds contain the embryo and are usually protected in fruit or cone

SEXUAL REPRODUCTION IN FLOWERING PLANTS

Pollen

Video Clip

SEXUAL REPRODUCTION IN:

3. InsectsIn many insects, the male deposits a package of sperm inside the female.

Insects often change a great deal between hatching and adulthood - METAMORPHOSIS

2 TYPES OF METAMORPHOSIS

Four 4 stagesEgg-Larva-Pupa-Adult

The adult and the larva look completely different

Ex. Butterfly

Three 3 stagesEgg-Nymph-Adult

The adult and the nymph resemble one another

Ex. Grasshopper

Complete Metamorphosis

Incomplete Metamorphosis

COMPLETE METAMORPHOSIS IN A BUTTERFLY

Video Clip

INCOMPLETE METAMORPHOSIS IN A GRASSHOPPER

Video Clip

LARVA AND PUPA STAGES OF A LADY BUG

LARVA AND PUPA STAGES OF A

HOUSEFLY

SECTION 6.3 PAGE 196

Human Reproductive System

MALE REPRODUCTIVE SYSTEM

See Text page 196

FEMALE REPRODUCTIVE SYSTEM

See Text page 197

MAJOR STAGES OF HUMAN

DEVELOPMENTFertilizationFirst Trimester

(weeks 1-12)Second Trimester

(weeks 13-24)Third Trimester

(weeks 25-38)

FERTILIZATIONOccurs in fallopian tubeEgg and sperm unite to produce a zygote

FIRST TRIMESTER (WEEKS 1-12)Movement from fallopian tube to

uterus occursZygote now called an embryo,

attaches to the uterine wallPlacenta and amniotic sac formEmbryo becomes a fetus at about 8

weeksBy the end of this trimester all

major organs have begun to develop

SECOND TRIMESTER (WEEKS 13-24)

Skeleton formsNervous system

begins to functionMother begins to

feel movementOrgans continue to develop

THIRD TRIMESTER (WEEKS 25-38)

Rapid increase in sizeImmune system developsIncreased movement

VISIBLE SIGNS OF PREGNANCY

SECTION 6.4 PAGE 204

Studying Genetic Changes

IMPORTANT DEVELOPMENTS IN GENETICS

GREGOR MENDEL Mid-1800s, Austrian

priestExperimented with

pea plantsConcluded traits

were tiny units of inheritance received in pairs, one from each parent

TRAITS STUDIED BY GREGOR

FRANCIS WATSON AND JAMES CRICK

1953Described the

“double helix” structure of DNA and how it replicates

Won a Noble Prize

THE HUMAN GENOME PROJECT

1986-2003Genome: consists of the full

set of genetic material that makes up an organism.

Scientist around the world collaborated to make a map to identify genes

Used to identify genetic diseases

ALLDERDICE SYNDROME Identified in an isolated community of

Sandy Point where a high incidence of birth defects were noted, believed to be due to a lack of genetic diversity

Symptoms included abnormalities resulting in mental and physical challenges

Dr. Allderdice of Memorial University determined that it was caused by part of one chromosomes being reversed.

DOWN’S SYNDROME•Frequently occurring chromosome Mutation•Individual has an extra 21st chromosome•Generally results in shorter stature, characteristic facial features and may be prone to developing other diseases

CYSTIC FIBROSIS

•Caused by Gene Mutations

•Results in the build up of mucus on the Lungs

GEN

ETIC

EN

GIN

EER

ING

CORE STSE

GENETIC ENGINEERINGBiotechnology

that deals with manipulation of the genome