Quiz For homeostasis and Cell divison

Lesson 70: DNA Replication

When, Why, and How DNA Replication Occurs

• When? DNA replication occurs in the S-phase of interphase before cell division.

• Why? To ensure genetic information is accurately passed to daughter cells.

• How?

  1. Unwinding: Helicase unzips the DNA double helix.

  2. Base Pairing: Complementary nucleotides match up (A-T, C-G).

  3. Strand Synthesis: DNA polymerase builds new strands using original strands as templates.

  4. Ligase: Seals Okazaki fragments on the lagging strand.

Lesson 71: Enzymes in DNA Replication

Key Enzymes and Their Functions

Mitosis is a cell division that produces new genetically identical daughter cells from a parent cell (2 identical diploids and has no genetic variations). It is vital in the repair and replacement of damaged cells 

Stages of Mitosis

Prophase – Chromosomes condense, spindle fibers form, nuclear envelope breaks down.

Metaphase – Chromosomes align at the metaphase plate.

Anaphase – Sister chromatids separate and move to opposite poles.

Telophase – Nuclear envelope reforms, chromosomes decondense.

Cytokinesis – Cytoplasm divides, forming two identical daughter cells.

Meiosis is a 2 cell division creating 4 genetically unique parent cell (4 different haploid cells) there are genetic variations and there are crossing overs. 

 Meiosis I (Reduction Division)

1. Prophase I – Homologous chromosomes pair up (synapsis) and exchange genetic material (crossing over).
   
   

2. Metaphase I – Homologous chromosome pairs align in the middle (independent assortment).
   
   

3. Anaphase I – Homologous chromosomes (not sister chromatids) separate.
   
   

4. Telophase I & Cytokinesis – Two haploid (n) cells form, each with half the chromosome number.
   
   

Meiosis II (Similar to Mitosis)

5. Prophase II – Chromosomes condense, spindle fibers form.
   
   

6. Metaphase II – Chromosomes align at the equator.
   
   

7. Anaphase II – Sister chromatids separate.
   
   

8. Telophase II & Cytokinesis – Four haploid (n) gametes are formed.

End Result of Meiosis

• Four genetically unique haploid gametes.

• Each gamete has half the number of chromosomes as the original cell.

1. Helicase - Unwinds and separates DNA strands.

2. Primase - Lays down RNA primers for DNA polymerase to begin process

3. Polymerase - adds new matching daughter diploids and connects them 

4. Ligase - sticks the lagging strands together to make one continuous strand.

Lesson 54: The Cell Cycle and Mitosis

Cell Cycle Phases and Checkpoints

1. G1 Phase: Cell grows, prepares for DNA replication.

   • G1 Checkpoint: Ensures the cell is large enough and DNA is undamaged.

2. S Phase: DNA replication occurs.

3. G2 Phase: Prepares for mitosis, checks for replication errors.

   • G2 Checkpoint: Ensures DNA replication is complete.

4. M Phase: Mitosis (division of the nucleus) and cytokinesis (division of the cytoplasm).

   • M Checkpoint: Ensures chromosomes are correctly attached to spindle fibers.

Lesson 72: Meiosis and Genetic Variation

Diploid vs. Haploid

• Diploid (2n): Two sets of chromosomes (e.g., human somatic cells have 46 chromosomes).

• Haploid (n): One set of chromosomes (e.g., gametes have 23 chromosomes in humans).

How Meiosis Increases Genetic Diversity

1. Crossing Over (Prophase I): Homologous chromosomes exchange genetic material, creating recombinant chromosomes.

2. Independent Assortment (Metaphase I): Random orientation of homologous pairs leads to different chromosome combinations in gametes.

Nondisjunction and Chromosomal Disorders

• Nondisjunction: Failure of homologous chromosomes (Meiosis I) or sister chromatids (Meiosis II) to separate properly.

• Leads to aneuploidy (abnormal chromosome numbers), e.g., Down syndrome (trisomy 21).

Lesson 73: Homeostasis and Body Temperature Regulation

Homeostasis and Feedback Mechanisms

• Homeostasis: Maintaining a stable internal environment.

• Negative Feedback: Restores balance (e.g., sweating to lower body temperature).

• Positive Feedback: Amplifies change (e.g., contractions in childbirth).

Endotherms vs. Ectotherms

• Endotherms (warm-blooded): Regulate body temperature internally (e.g., humans, birds).

• Ectotherms (cold-blooded): Depend on external temperatures (e.g., reptiles, amphibians).

Human Temperature Regulation

• Too Hot:

  • Vasodilation: Blood vessels widen, increasing heat loss.

  • Sweating: Evaporation cools the body.

• Too Cold:

  • Vasoconstriction: Blood vessels constrict, reducing heat loss.

  • Shivering: Muscle contractions generate heat.

  • Goosebumps: Hair stands up to trap heat.

Modeling and CER (Claim, Evidence, Reasoning) Best Practices

Modeling Best Practices

• Clearly labeled diagrams.

• Step-by-step representation.

• Arrows to indicate movement (e.g., DNA replication, mitosis, meiosis).

• Different colors to highlight key structures.

CER Best Practices

1. Claim: Clearly state the answer to a question.

2. Evidence: Provide data, experimental results, or factual information.

3. Reasoning: Explain how the evidence supports the claim using scientific concepts.