science 9 unit 4: reproduction -...

Science 9 Unit 4: Reproduction

Unit 4: Reproduction

Chapter 4: Cells & DNA

Heredity Trait: a feature that can vary in size or form between individual within a species (ex. Eye color, hair color, height etc.)

Heredity Trait: a feature that can vary in size or form between individual within a species (ex. Eye color, hair color, height etc.) Heredity: the process through which patterns of traits are passed on from an individual to its offspring

Cells Remember: Cells are the smallest unit of a living thing

•There may be as many as 37.2 trillion cells in the human body

Cells Remember: Cells are the smallest unit of a living thing

•There may be as many as 37.2 trillion cells in the human body Cells are made up of smaller parts called organelles

Cells

The organelle in the center of the cell is called the nucleus

• The nucleus is the “control center” for the cell

• DNA is stored in the nucleus

DNA

DNA stands for deoxyribonucleic acid

• Carries instructions for the cell

• Is responsible for traits and heredity

DNA

DNA Structure

• Long double stranded chain of molecules

• Forms a “helix” – like a twisted ladder

DNA

DNA Structure

• Long double stranded chain of molecules

• Forms a “helix” – like a twisted ladder

• The sides are made up of phosphates and sugars

• The “steps” are made of 4 different base

DNA

Chromosome: tightly coiled, compact section of DNA

• Chromosomes in the nucleus are in pairs

• Most humans have 23 pairs

DNA

Gene: small segments of DNA located at specific places on a chromosome

• May be different sizes (100s- 1000s of bases)

• Each chromosome has 1000s of genes

• Some genes have been shown to code for different traits

• Nucleus contains chromosomes • Chromosomes are made up of genes • Genes are made up of DNA

If all our cells contain the same DNA, how do we have different cells with different functions (retinal ells to see, muscle cells-to move, etc)?

Specialized Cells • Only certain genes in each cell are active or “read” by the cell • Cells read the specific parts of DNA or genes that they need to in

order to produce proteins

Ex. Proteins needed to make muscles work are only produced in muscle cells

Cell Cycle

• Throughout your life your cells divide and new cells replace old cells

• Different types of cells are

replaced at different rates

Cell Cycle • The 3 stages of a cells life (Interphase, mitosis, &cytokinesis)

Cell Cycle

Interphase:

• Longest stage in the cycle

• Cell carries out its function depending on the type of cell (ex. Stomach cell digests food)

• Cell grows

Cytokinesis

Mitosis

Cell Cycle

Interphase:

• Longest stage in the cycle

• Cell carries out its function depending on the type of cell (ex. Stomach cell digests food)

• Cell grows

• DNA replicates (makes a copy of itself)

• Cell continues to grow

Cytokinesis

Mitosis

Cell Cycle

Mitosis:

• Shortest stage in the cycle

• Nucleus divides into 2

• Each nucleus has 1 full copy of each chromosome

Cytokinesis

Mitosis

Cell Cycle

Mitosis:

• Shortest stage in the cycle

• Nucleus divides into 2

• Each nucleus has 1 full copy of each chromosome

• Has 4 steps

• Prophase

• Metaphase

• Anaphase

• Telophase

Cytokinesis

Mitosis

Cell Cycle

Cytokinesis:

• Final stage in the cycle

• Cell is divided into 2 “daughter” cells each with 1 nucleus

Cytokinesis

Mitosis

Mitosis

• The process of the nucleus dividing • There are 4 stages:

• Prophase •Metaphase • Anaphase • Telophase

We can use the acronym P-MAT to remember the order

1. Prophase

• Nuclear membrane breaks down

• Proteins called “spindle fibers” attach to the chromosomes

Spindle fibers Nuclear membrane breaking down Chromosomes

2. Metaphase

• Spindle fibers pull the chromosomes into a straight line along the

center of the cell

Spindle fibers Chromosomes

3. Anaphase

• Spindle fibers contract and pull apart the chromosomes

• Each chromatid (duplicate part of the chromosome) moves to

opposite sides of the cell

Spindle fibers Chromatids

4. Telophase

• 1 complete set of chromosomes is now at each end of the cell

• Spindle fibers break down

• Nuclear membrane forms around each new set of chromosomes

• There are now 2 nuclei in the cell

Nuclear membrane

4. Telophase

• 1 complete set of chromosomes is now at each end of the cell

• Spindle fibers break down

• Nuclear membrane forms around each new set of chromosomes

• There are now 2 nuclei in the cell

Nuclear membrane

**Note: In telophase there are 2 nuclei but it is still 1 single cell

Stages of Mitosis in Onion Cells

Prophase Metaphase Anaphase Telophase


Chapter 5:

Asexual vs. Sexual Reproduction

Asexual Reproduction

Asexual Reproduction:

• Reproduction involving only 1 parent

• Offspring typically have identical genetic information

Clone:

• Individuals that share identical genetic information (DNA)

Types of Asexual Reproduction

1. Binary Fission

• A single parent replicates its DNA and splits into 2 equal parts

• Reproduction can happen very quickly

• Used by amoeba, many types of bacteria, some algae


2. Budding

• Part of a cell pushes outward and forms an overgrowth or bud

• The bud pinches off to become its own cell

• Used by yeast, some sea sponges


3. Fragmentation

• Organism breaks apart as a result of injury

• Each fragment develops into a clone

• Used by sea stars, some plants


4. Vegetative Reproduction

• Special cells in plant stem or roots divide and form new plants

• Used by tulips, strawberries, and potatoes

• Advantageous for farming because can be used to make exact copies of plants

with desired traits (size, taste, etc. )


5. Spore Formation

Spores: Reproductive cells that grow into a new individual by mitosis

• Organism produce spores

• Spores are spread around the environment by wind and water

• Used by bread mold, fungi, ferns etc.

Advantages/ Disadvantages of Asexual Reproduction

Advantages Disadvantages

• Large #s of offspring

reproduced quickly

• Large #s help compete with

other organisms

• Large #s mean species is

more likely survive harsh

conditions and predators

• Offspring are clones,

mutations will be passed on

• Offspring produced close

together will compete for

resources

Meiosis & Sexual Reproduction

Meiosis: The process of producing special cells called gametes

• Meiosis is the basis for sexual reproduction

Meiosis & Sexual Reproduction

Meiosis: The process of producing special cells called gametes

• Meiosis is the basis for sexual reproduction

Sexual Reproduction: Reproduction which requires two parents and produces

offspring that are genetically different from the parents

• Sometimes the genetic differences are visible, sometimes

they are not

Meiosis

Recall:

We said that humans have 23 pairs of chromosomes (46 total)

We receive 1 set from our mother and one set from our father

Therefore each parent is only passing on 23 chromosomes (or half of the number they have)

Meiosis

Diploid: a cell that has 2 complete sets of chromosomes

• For humans this is 23 pairs/ 46 total

Haploid: a cell that has only 1 set of chromosomes

• For humans this would be 23

Meiosis

Diploid: a cell that has 2 complete sets of chromosomes

• For humans this is 23 pairs/ 46 total

Haploid: a cell that has only 1 set of chromosomes

• For humans this would be 23

Gametes: Haploid cells used in sexual reproduction

• Male gametes are call sperm and female gametes are eggs

Meiosis

Meiosis produces gametes with half of the number of chromosomes as the parent (haploid)

• Meiosis occurs only in sex cells

• Meiosis occurs in 2 parts- Meiosis 1 and meiosis 2

Meiosis

Meiosis 1: The original cell divides into 2

Meiosis 2: The 2 cells from stage 1 each divided- there are a total of 4 cells produced

Meiosis 1 Meiosis 2

Stages of Meiosis

Like mitosis, meiosis has several steps

Many of the terms are similar

Meiosis 1: Meiosis 2:

Stages of Meiosis

Meiosis 1: Meiosis 2:

Gamete Formation

Sperm

• Each cell divides evenly

• Produces 4 sperm cells

Egg

• Cells divide unevenly

• Results in 3 smaller cells and 1 large cell

• Smaller cells dissolve and 1 egg cell is produced


Chapter 6:

Mutations and Genetic

Technology

Mutations

Gene Mutation: A change in the order of bases on a gene • Can be positive, negative, or have no effect • Mutations can be passed on to offspring

Mutations

Positive Negative Neutral - A mutated gene that - mutated genes cause - mutations that prevents individuals sickle cell anemia, change an animal’s from contracting HIV cystic fibroses, & coat colour allderdice syndrome

Mutations

Cancer:

A disease caused by uncontrolled cell growth

• A mutation occurs in the part of the DNA that tells the cell to reproduce

• Cells do not divide correctly and begin reproducing uncontrollably

Mutations

Cancer:

• Build up of cells results in a tumor

• Cancer can spread throughout the body as parts of the tumor break off

Mutations Mutagen: A substance or factor that can cause a mutation in DNA • Some mutagens occur in nature others are caused by humans Examples: • Viruses • Cigarette smoke • Pollutants such as mercury • Radiation

Genetic Technology

Karyotype:

Diagnostic technology that allows geneticists to look at the

chromosomes of an individual

• They compare number, size and shapes

• Used to diagnose genetic disorders

Example: Down Syndrome can be diagnosed by a karyotype that shows 3

copies of the 21st chromosome

Cloning

Reproductive Cloning

A technology used to produce a genetic duplicate of an existing or

previously existing individual

• The nucleus from a cell on the donor is transferred into an egg cell

which has had its nucleus removed

• The egg transplanted into a uterus to develop into an embryo and

eventually the intended organism

Cloning

Reproductive Cloning

• 1st cloned animal was a tadpole (1952)

• Dolly the sheep was cloned in 1996

• This polo player has had 6 clones of his horse created

Cloning

Therapeutic Cloning

Cloning used to correct health problems

• Patient’s nucleus is transferred into an egg cell which develops into an

embryo

• Stem cells are collected form the embryo

• Stem cell have the potential to become many different types of cells

• They are transplanted into the patient to replace damaged cells

Cloning

Therapeutic Cloning

Cloning used to correct health problems

Cloning Gene Therapy Mutated genes are replaced with healthy copies of the gene

• Healthy gene is inserted into a virus which delivers the healthy cell to the desired cells

• More research is needed

science 9 unit 4: reproduction -...

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