Unit 3: Genetics

3.0 DNA (deoxyribonucleic acid): A molecule that contains information for an organism’s growth and functions.

3.1 DNA is made of two strands joined like a twisted ladder called a double helix.

3.2 Watson and Crick discovered the double helix structure in 1953.

3.3 Chromosomes: Thread-like structures found in the nucleus made of tightly packed DNA.

3.4 Each species of organism has a constant number of chromosomes.

Ex: Humans have 46 chromosomes

Fruit flies have 8 chromosomes

Ferns (plant) have 100 chromosomes.

Cell Division3.5 Cell Division: A process when a

single cell becomes two cells.

3.6 Cell Division is needed for growth, development, and repair.

3.7 Cell Cycle: The normal pattern of development and division of a cell.

3.8 Two main parts of the cell cycle: Interphase and Mitosis

3.9 Interphase: The part of the cell cycle when the cell grows and carries out normal functions. A cell spends most of its life in this phase. This is the phase when the DNA is replicated.

3.10 Mitosis: The process that divides the nucleus in cells, therefore the genetic material (DNA) divides too.

3.11 Cytokinesis: The division of the cytoplasm.

3.12 When mitosis and cytokinesis are done there are two new identical cells that are genetically the same. (meaning they have the same DNA)

3.13 The cell that divides is called a parent cell. The two cells that result are called daughter cells.

Parent Cell

Daughter Cell

Daughter Cell

Steps of Mitosis1. Prophase- Chromosomes appear

2. Metaphase- Chromosomes line up

3. Anaphase- Chromosomes separate

4. Telophase- New cells form

3.14 Meiosis: Cell division producing 4 “reproductive cells” (sperm or egg cells) that contain half the number of chromosomes of the parent cell.

4646

46

23

23

23

23

Mitosis vs Meiosis

3.15 Gene: is a segment of DNA that explains a particular trait, such as hair color or eye color.

3.16 Humans have 30,000 genes. Some traits are not determined by just one gene.

What are these?

3.17 Gene Splicing: The process of cutting out a particular gene and placing it into a new DNA strand.

3.18 Benefits of Gene Splicing: – 1. Genetically engineered medicine

(Examples: Insulin and Hepatitis B vaccine)

– 2. Genetically modified foods (GMOs) To produce more and better food.

Process of Gene Splicing

1. Identify trait that is desired. (Glowing Jellyfish)2. Take 1 cell.3. Take 1 chromosome from the nucleus.4. Slice 1 gene from the DNA.5. Place gene in another chromosome.6. Put chromosome in the nucleus of a cell.7. Place cell in desired organism.8. New organism has brand NEW TRAIT.

(Glowing Goldfish)

3.19 Heredity: The passing of genes from parents to child.

3.20 Children get half their genes from mom and half their genes from dad.

3.21 Alleles: are 2 different forms of the same gene (one from each parent)

Example: B = the allele for brown eyes

b = the allele for blue eyes

3.22 Dominant vs Recessive:

B (brown eyes) is the dominant allele.

b (blue eyes) is the recessive allele.

3.23 Homozygous = BB or bb

3.24 Heterozygous = Bb

3.25 Punnett Square: Shows how two parents’ alleles might combine in child.

Practice Punnett Square

3.26 Phenotype: (what you see) the appearance of a trait. Example: blue or brown eyes.

3.27 Genotype: The actual gene make-up. Example: BB, Bb, bb

3.28 Probability: is the likelihood, or chance, something will happen.

Example: 100%, 75%, 50%, 25%, 0%

3.29 DNA (deoxyribonucleic acid)- The long ladder shaped molecule that contains the coded information of the genes.

3.30 DNA Replication: To produce 2 news cells the DNA molecule unzips and replicates into 2 new DNA molecules.

3.31 DNA Mutation: When a mistake occurs during replication and one of the rungs of the DNA ladder is substituted with another rung.