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

- requires 2 parents- produces off spring that are genetically different from one another, the parents, and any other

member of their species

Haploid vs DiploidHaploid= half the genetic content (n) gametes or sex cells (egg and sperm) These are the only cells in your body that are haploidDiploid = genetic equal to the parent. Full genetic content (2n) body cells are diploid.

MeiosisThe process that produces gametes with half the number of chromosomes (haploid) as body cells (diploid) occurs in the sex cells.

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.

Meiosis lProphase 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.Interkinesis: phase between cell division; cell will grow and make proteins but will not replicate DNA

Meiosis llProphase II: one chromosomes of the homologous pair in each cell.Metaphase II: the x-shaped chromosomes form a single line across the middleAnaphase II: sister chromatids move to opposite poles of the cell.Telophase II: a nuclear membrane forms around the chromosomes.Cytokinesis – the two daughter cells are separated

Core Lab page 176-177Mitosis vs Meiosis

Mitosis Meiosis

Where it occurs In body cells In sex organs to produce sex cells

# of daughter cells produced Two daughter cells Four daughter cells

# of chromosomes Same number as parent cell

Half the number of one parent cell

Type of reproduction Asexual reproduction Sexual reproduction

Intercourse is not required for sexual reproduction to occur, only in animals that have internal fertilization.“mating” refers to the process by which the gametes arrive at the same place at the same time.

Sexual Reproduction 1. Mosses: (fig 6.14 page 185)Water allows the egg and sperm cells to meet / Reproduces both sexually (specific male and female parts) and asexually (spores)

2. Flowering plants (fig 6.20 page 188)Pollen (male gamete) is formed in the male part of the flower and the egg in the femaleThe fertilized egg will become a seedPollination is the transfer of pollen from the male structure to the female structure of the plant.Identify the male and female structures.

Pollen can be transported by:Pollinators such as bees and other insects, fruit bats / Wind / Water

3. Insects…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 metamorphosis The adult and the nymph resemble one another Ex. Grasshopper (fig 6.25 page 192)

Complete metamorphosis The adult and the larva look completely differentEX. Butterfly (fig 6.26 page 193)

Internal Sexual Reproduction vs External Sexual ReproductionExternal Internal

Egg and sperm unite outside the parents bodies Sperm is deposited inside the female body to meet the egg

Large numbers of offspring produced at one time yet only a few survive to adulthood

More off spring survive even though less are produced

Fertilized eggs are not protected from predators or weather

Embryo is protected from predators

Very little energy required to find a mate More energy required to find a mate

Gametes may not connect so not every egg will be fertilized

Gametes may not connect so not every egg will be fertilized

Asexual Reproduction vs Sexual Reproduction

Asexual Reproduction

1 parent cells

No gametes; cell divides

Little variation in offspring

Little energy required

Less parental care

Sexual Reproduction

Two parent cells

2 sex cells unite to form a zygote

Greater variation in offspring

Greater energy requited

Greater parental care

Studying Genetic ChangesGregor MendelMid-1800s - Experimented with inherited traits in pea plants. Suggested involvement of a dominant and recessive factor in the transmission of traits.

Francis Crick & James Watson1953 - Described the structure of DNA and how it replicates. This paved the way for why and how mutations occur.

Genetic Engineering To the food we eat and health related issues.Lead to fears inside and outside the scientific community

The Human Genome Project1986-2003 Genome: consists of the full set of genetic material that makes up an organism.Made a map to identify genesThis information may be used to check for particular diseases.Ex. Allderdice syndrome where part of one chromosome is reversed. Identified in Sandy Point NL.

Diagnosing a Genetic DisorderA special “picture” of a person showing all their chromosomes arranged in a particular order called a karyotypes studied. Can help to determine if there is any abnormalities in the chromosomes.

Can identify syndromes such as Down’s Syndrome (extra 21st chromosome)

We have no cure for genetic conditions such as Allderdice Syndrome, Down’s Syndrome and Cystic Fibrosis