chapter 6: “ meiosis is the basis of sexual - st. paul's ... show... · pg. 176-7. 1....

Chapter 6: “ Meiosis is the basis of sexual reproduction”

Haploid= half the genetic content (n)

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

The process that produces gametes with half the number of chromosomes as body cells occurs in the sexcells.

DNA replication occurs only once in the process.Meiosis I: the result is two daughter cells.Meiosis II: the result is four haploid cells, each with half the number of chromosomes.

Prophase I: homologous chromosomes pair up.

Metaphase I: homologous chromosomes line up in the middle of the cell.

Anaphase I: homologous chromosomes separate and are pulled to opposite sides.Telophase I: one chromosome from each pair is at each pole of the cell.

Prophase II: one chromosomes of the homologous pair in each cell.Metaphase II: the x-shaped chromosomes form a single line across the middle.

Anaphase II: sister chromatids move to opposite poles of the cell.

Telophase II: a nuclear membrane forms around the chromosomes.

Mitosis Meiosis

In body cells In sex organs to produce sex cells

Two daughter cells Four daughter cells

Same number of chromosomes as parent cell

Half the number of chromosomes as the parent cell

Asexual reproduction Sexual reproduction

“Comparing Mitosis & Meiosis”

Core Lab Activity 6-1B pg. 176-7

1. Mosses: External fertilization Water allows the egg

and sperm cells to meet

Reproduces both sexually and asexually

The Moss

2. Flowering plants

Pollination

Transfer of male gametes in structures called pollenfrom the male structure to the female structure of the plant.

FlowerReproduction

Pollen can be transported by:

1. Pollinators such as bees and other insects, fruit bats

2. Wind

3. Water

After fertilization, seeds are often protected in fruit or cones.

Seeds contain the plant embryos.

In many insects, the male deposits a package of sperm inside the female.Insects often change a great deal between hatching and adulthood.

This change in form is called metamorphosis.

Metamorphosis can be incomplete or complete.

Incomplete

Three stagesThe adult and the nymph resemble one another

Ex. grasshopper

Egg

NymphAdult

Complete

Four stages

The adult and the larva look completely different

Ex. Butterfly

Egg

Larvae

Pupa

Adult

Asexual Sexual

1 parent cells Two parent cells

No gametes; cell divides

2 sex cells unite to form a zygote

Little variation in offspring

Greater variation in offspring

Little energy required Greater energy requited

Less parental care Greater parental care

Male Reproductive SystemTestesScrotumVas deferensUrethraPenis

Female Reproductive System

Ovaries

Oviducts/ fallopian tubes

Uterus

Cervix

Vagina

1. Fertilization

2. First trimester

3. Second trimester

4. Third trimester

Fertilization

Occurs the fallopian tubes

Egg and sperm unite to form a zygote

First trimester

All organ systems begin to develop.

Zygote is called an embryo

Placenta and amniotic sac

form

At 8 weeks, the embryo is now called a fetus.

All major organs are formed

Second trimester

Rapid growth

Skelton forms

Mother will feel movement by 20 weeks.

Growth slows between 20 and 24 weeks.

Third trimester

Growth in preparation for birth; significant in the brain.

Immune system develops

Fat is deposited under the skin.

Menstruation stopsHips will become slightly largerBreast become largerWeight gain and abdomen will bulgeNausea and dizziness?cravings

Gregor Mendel

Mid-1800s

Experimented with inherited traits in

pea plants.

Francis Crick & James Watson

1953

Described the structure of DNA and

how it replicates.

The Human Genome Project1986-2003Genome: consists of the full set of genetic material that makes up an organism.Made a map to identify

genes

This information may be used to check for particular diseases.◦Ex. Allderdice syndrome where part of one chromosome is reversed. Identified in Sandy Point NL.

A special “picture” of a person showing all their chromosomes arranged in a particular order called a karyotype is studied.

Kary

oty

pe

Can help to determine if there is any abnormalities in the chromosomes.

Can identify syndromessuch as Down’s Syndrome (extra 21st

chromosome)

Cystic fibrosis

Can be used to save the genetic information from endangered plants and animals or to mass-produce an organism with a desired trait.

Reproductive cloning:

Also called DNA cloning

Purpose is to produce a genetic duplicate of an existing organism

with desirable

qualities.

Therapeutic cloningUsed to correct health problems.Stem cells and embryonic stem cells are able to become many different types of cells.