IB Bio Unit 6 Flashcards-C ancer, Repro, Inheritance, including Cell division, Plant Reproduction, and Human Repro

What is the role of cyclins in the cell cycle?

Proteins that regulate the progression of the cell cycle by activating cyclin-dependent kinases (CDKs). These complexes control key transitions, ensuring proper timing and order of cell division.

Describe the process of cytokinesis in plant cells.

Involves the formation of a cell plate that develops into a new cell wall, dividing the cytoplasm into two distinct daughter cells.

Explain how the mitotic index is used in cancer diagnosis.

The ratio of cells undergoing mitosis to the total number of cells. A higher mitotic index indicates increased cell division, which is often associated with tumor growth and can aid in cancer diagnosis

What is the significance of the G0 phase in the cell cycle?

• resting state where cells exit the cell cycle and cease division.

• temporary or permanent, depending on the organism's needs and cell type

Outline the process of double fertilization in angiosperms.

Involves two sperm cells: one fertilizes the egg cell, forming a diploid zygote, while the other fuses with two polar nuclei to create a triploid endosperm, which nourishes the developing embryo.​

What adaptations do wind-pollinated flowers have?

• Small, inconspicuous petals

• Produce large quantities of lightweight pollen

• Long stamens and pistils to facilitate pollen dispersal by wind.​

Describe the hormonal changes that trigger ovulation.

A surge in luteinizing hormone (LH) levels, prompted by rising estrogen concentrations, triggers ovulation (the release of an egg from the ovary)

What is the role of human chorionic gonadotropin (hCG) during early pregnancy?

hCG maintains the corpus luteum, ensuring continued production of progesterone and estrogen to sustain the uterine lining and support early pregnancy.​

Explain the principle of independent assortment.

Independent assortment states that alleles of different genes segregate independently during gamete formation, leading to genetic variation

What is a test cross, and why is it used?

A test cross involves breeding an individual with a dominant phenotype (but unknown genotype) with a homozygous recessive individual to determine the genotype of the dominant individual based on offspring phenotypes

Explain the role of the following hormones in the menstrual cycle: follicle-stimulating hormone (FSH), luteinizing hormone (LH), and human chorionic gonadotropin (hCG). 

• FSH stimulates the growth of follicles in the ovary

• LH triggers ovulation and the formation of the corpus luteum

• hCG maintains the corpus luteum during early pregnancy

Compare and contrast the processes of spermatogenesis and oogenesis.

Key Differences

• Spermatogenesis is continuous and produces many sperm, while oogenesis is discontinuous and produces a limited number of eggs.

• Sperm formation results in four equal-sized gametes, whereas oogenesis results in one large ovum and discarded polar bodies.

• The egg stops in meiosis II and only completes division if fertilization occurs, while sperm complete meiosis before they leave the testes.

Key Similarities

• Both processes involve mitosis, meiosis, and differentiation.

• Both result in haploid gametes that contribute to genetic variation.

• Both are regulated by hormones (e.g., FSH and LH).

Describe the role of the placenta in pregnancy. 

The placenta is an organ that develops in the uterus during pregnancy, providing oxygen and nutrients to the fetus and removing waste products. It also produces hormones like hCG and progesterone

What is self-incompatibility in plants?

A mechanism that prevents self-pollination, ensuring that cross-pollination occurs, which increases genetic diversity.

Such as:

• S-Alleles and Genetic Recognition

• Pollen-Recognition Mechanism

• Enzyme Inhibition

Compare and contrast sexual and asexual reproduction

• Genetic Diversity: Sexual reproduction creates genetic diversity, while asexual reproduction results in genetically identical offspring.

• Reproduction Rate: Asexual reproduction is typically faster and more energy-efficient, whereas sexual reproduction requires more time and resources.

• Adaptability: Sexual reproduction helps populations adapt to changing environments due to genetic variation, while asexual reproduction lacks this advantage but is more efficient in stable environments.

Compare and contrast mitosis and meiosis

• Purpose: Mitosis is for growth, repair, and asexual reproduction, while meiosis is for sexual reproduction and producing genetic diversity in offspring.

• Number of Divisions: Mitosis involves one division, while meiosis involves two divisions.

• Chromosome Number: Mitosis produces diploid daughter cells (same as parent), while meiosis produces haploidgametes (half the chromosome number).

• Genetic Variation: Mitosis produces genetically identical cells, while meiosis produces genetically diverse cells due to processes like crossing over and independent assortment.

• Daughter Cells: Mitosis results in two identical daughter cells, while meiosis results in four non-identical daughter cells.

Explain the process of mitosis [7 marks]

1. Interphase: cell prepares for mitosis. It consists of G1 (cell grows and carries out normal functions) S (DNA replication), and G2 phases (continues to grow)

2. Prophase: chromosomes condense, form 2 sister chromatids held together by a centromere. Nuclear envelope starts to break down, spindle fibers form extending from the centrosomes.

3. Metaphase: chromosomes align in middle, attaches to a spindle fiber via its centromere, connected to opposite poles of the cell.

4. Anaphase: sister chromatids are pulled by the spindle fibers to opposite poles. Centromere splits, chromatids are moved to separate sides of the cell.

5. Telophase: chromosomes begin to de-condense. Nuclear envelope re-forms around each set of chromosomes, creating two separate nuclei.

6. Cytokinesis: division of the cytoplasm, creates two distinct daughter cells.

   1. Animal cell: cleavage furrow causes cell membrane to separate the cells

   2. Plant cells: cell plate forms to divide the cell.

7. Result: two genetically identical daughter cells, each with the same number of chromosomes as the parent cell. Crucial for growth, repair, and asexual reproduction.

Explain the process of meiosis [8]

Meiosis is the process by which gametes (sperm and eggs) are produced, reducing the chromosome number by half to ensure that the resulting offspring has the correct number of chromosomes after fertilization. It involves two rounds of division: meiosis I and meiosis II. In meiosis I, homologous chromosomes are separated. The process begins with prophase I, where chromosomes condense, homologous chromosomes pair up, and crossing over occurs, leading to genetic variation. In metaphase I, the tetrads align at the metaphase plate, and in anaphase I, the homologous chromosomes are pulled to opposite poles. The cell then undergoes telophase I, forming two haploid daughter cells, each with half the chromosome number of the original.

In meiosis II, which is similar to mitosis, the two haploid cells undergo division again without DNA replication. During prophase II, the chromosomes condense, and spindle fibers form. In metaphase II, chromosomes align at the metaphase plate, and in anaphase II, the sister chromatids of each chromosome are separated. Finally, in telophase II and cytokinesis, four genetically diverse haploid gametes are produced. These gametes have half the chromosome number of the original cell, ensuring genetic variation and proper chromosome number in the offspring upon fertilization.

How does meiosis reduce chromosome number?

Meiosis reduces chromosome number by dividing the chromosome number in half during the formation of gametes (haploid cells), so that when gametes fuse during fertilization, the diploid state is restored.

What are the key differences between male and female reproductive systems?

• The male reproductive system produces sperm continuously, while the female reproductive system produces eggs that are released periodically.

• Males have testes for sperm production, while females have ovaries for egg production.

How do gametes differ between males and females?

• Male gametes (sperm) are small, mobile, and produced in large numbers.

• Female gametes (eggs) are larger, immobile, and produced in fewer numbers.

What are the main organs in the male reproductive system?

SEVEn UP:

• S: eminiferous tubules (where sperm are produced in the testes)

• E: pididymis:(where sperm are stored and matured).

• V: as deferens: (tube that carries sperm from the epididymis to the ejaculatory duct)

• E: jaculatory duct: (the duct that carries sperm from the vas deferens to the urethra)

• N: one:

• U: rethra: (the tube that carries urine and semen out of the body)

• P: enile urethra: (final part of the urethra that passes through the penis)

What are the main organs in the female reproductive system?

The ovaries, fallopian tubes, uterus, cervix, and vagina.

Mnemonic for female sexual development

Ëstrogen Ëstablishes and Progesterone Protects the endometrium.

What are the stages of the ovarian cycle and what hormones regulate it?

The ovarian cycle has three stages: the follicular phase (FSH stimulates follicle growth), ovulation (LH triggers egg release), and the luteal phase (progesterone maintains the uterine lining).

How does the uterine cycle correspond with the ovarian cycle?

The uterine cycle involves the thickening of the endometrium during the follicular phase, ovulation triggering its breakdown, and menstruation if pregnancy does not occur

What hormones are involved in the menstrual cycle and what do they do?

• FSH stimulates follicle growth

• LH triggers ovuLation

• estrogen thickens the endometrium

• progesterone maintains the endometrial lining for pregnancy

How does the sperm penetrate the egg?

It releases enzymes from the acrosome to break down the outer layer of the egg, allowing the sperm to enter.

What role does human chorionic gonadotropin (hCG) play in IVF?

It triggers ovulation, ensuring that eggs are ready for fertilization after being stimulated by FSH.

What are the male and female reproductive organs in a flower?

• The male reproductive organ is the stamen (anther and filament)

• The female reproductive organ is the carpel (stigma, style, and ovary)

How does pollination lead to fertilization in plants?

Pollen from the anther is transferred to the stigma, where it travels down the style to fertilize the ovule in the ovary.

Alphabetical order: anther —> stigma —> style —→ ovule (in ovary)

What is double fertilization in flowering plants?

One sperm fuses with the egg to form a zygote, while another sperm fuses with two polar nuclei to form the triploid endosperm, which nourishes the developing embryo.

What features attract insects to pollinate flowers?

Brightly colored, have a pleasant scent, and produce nectar to attract pollinators.

How do insect-pollinated flowers differ from wind-pollinated flowers?

Insect-pollinated flowers: typically larger, colorful, and have sticky pollen

Wind-pollinated flowers: often smaller, less conspicuous, and have lightweight, non-sticky pollen.

What are some methods to promote cross-pollination?

• Having separate male and female plants

• Using different blooming times

• Promoting the activity of pollinators like insects and wind.

Why is cell division essential for living organisms?

• Growth – increasing the number of cells in multicellular organisms

• Tissue repair – replacing damaged or dead cells

• Asexual reproduction – producing genetically identical offspring

• Gamete production – in sexually reproducing organisms (meiosis)

What is the difference between cytokinesis and mitosis?

• Mitosis is nuclear division, separating replicated chromosomes into two nuclei.

• Cytokinesis is the division of the cytoplasm to form two separate daughter cells.

What is the difference between equal and unequal cytokinesis?

• Equal cytokinesis produces two identical daughter cells (e.g., in mitosis).

• Unequal cytokinesis results in cells of different sizes, such as in oogenesis, where one large egg and three small polar bodies are formed.

identify which of the following are reasons why cells might undergo cell division
I. to produce gametes for sexual reproduction
II. to allow a population of cells to grow while reducing their surface area-to-volume ratio
III. to replace cells that have been lost or damaged

I and II