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.