exam 3

Cell Growth and Division Concepts

1. Questioning Cell Size and P-protein

  • True or False: A scientist studying the effect of P-protein on cell size during S phase would place Cell size on the X axis.

    • Answer: [Not Provided in Transcript]

2. Discovery of P-protein

  • A researcher in human genetics discovers a new regulatory protein involved in the G₁/S checkpoint, referred to as 'prepper protein' or P-protein.

  • Functions of P-protein:

    • Ensures sufficient cytoplasm and nutrients are available to support two daughter cells after cell division.

    • If operational, a small cell will not enter S phase; it will grow larger.

    • A cell only proceeds to S phase if large enough AND if other growth triggers are present.

    • Presence of P-protein alone does NOT initiate DNA replication.

Questions Regarding P-protein Impact

  • True or False: A chemotherapy drug targeting and inhibiting P-proteins would effectively reduce cancer risk.

    • Answer: False

  • True or False: A cell that produces dysfunctional P-proteins, preventing large cells from entering S phase, is at increased cancer risk.

    • Answer: True

3. Cell Cycle Phases and Chromatid Counts

  • Go Phase Consideration:

    • True or False: A cell remaining in Go phase is almost always unhealthy or damaged.

    • Answer: False

  • Chromosome and Chromatid Counting:

    • In diploid (2n) cells with 32 chromosomes (16 homologous pairs) about to enter meiosis, the number of sister chromatids present is:

    • Answer: 64 (since each chromosome duplicates before meiosis).

    • True or False: The main objective of Meiosis I is to separate sister chromatids.

    • Answer: False. (Meiosis I separates homologous chromosomes, whereas Meiosis II separates sister chromatids.)

4. Ploidy and Offspring Outcomes

  • Ploidy Levels in Plants:

    • Humans are diploid (2n), while many plants and animals exhibit varying ploidy levels.

    • If crossing a tetraploid (4n) with an octoploid (8n), the resulting offspring would be dodecaploid (12n).

    • If starting from an octoploid (8n) plant, the most likely ploidy of its gametes will be hexaploid (6n).

5. Genetic Breeding and Outcomes

  • A breeding program involving initial generation (F₀) plants with various traits was initiated.

  • Traits observed:

    • Red stripes vs. Brown stripes in leaves.

    • Frilled vs. Smooth flower petals.

    • Pink vs. Purple flower petals.

Mendelian Trait Analysis

  • Frilled Petals Crossing: Crossing a frilled petal plant with a smooth petal plant, leading all offspring to frilled petals indicates that they are likely homozygous dominant (since smooth petal plants do not exhibit frilled petals).

  • Offspring Probability of Pink Frilled Petals: Given two heterozygous pink frilled plants (with traits represented as Ff), the probability that future offspring will also have pink frilled petals is 3/4 (75%), derived from a dihybrid cross.

  • Pink Petals Allele: If crossing two pink petal plants leads to all pink pets, the allele for pink petals is likely recessive.

6. Genetic Carrier Analysis

  • Jacinta has a genetic condition; her child Marco, doesn't possess the condition, thus should be assessed as a potential carrier for the recessive allele.

    • True or False: Marco can be a carrier of the allele.

    • Answer: True

    • Condition Analysis: Since Jacinta's mother had the condition, it's possible for her to pass recessive alleles; thus the condition likely has 0% inheritance chance for a child when one parent is unaffected.

7. Blood Types and Genetic Conditions

  • Analysis of blood types indicates H-antigen deficiency with hh individuals failing to produce the H-connector, resulting in type hh blood.

    • Probability Inquiry: If both parents are hh, the question arises regarding the probability their first two children exhibit H-antigen deficiency.

8. Seasonal Variation in Traits

  • In a garden setting, various morphs of beets were observed:

    • Red in spring, yellow in summer, and orange in fall. Traits change based on environment, indicative of possible epistasis.

Environmental Impact Testing

  • If conducting testing, temperature would represent a viable independent variable examining these phenotypic changes based on seasonal growth.

9. Summarizing Genetic Inheritance and Probability

  • Parents with a recessive condition need to evaluate genetic distribution among children and advocate for genetic counseling, especially in scenarios involving traits that may not manifest in all offspring.