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Questions and Answers

How does the embryonic development of marsupials differ significantly from that of placental mammals after birth?

Marsupial offspring continue a significant portion of their development in a pouch, whereas placental mammals are more developed at birth.

Describe the role of the scrotum in the male reproductive system and explain why its location is important for sperm production?

The scrotum houses the testicles and regulates their temperature. Its external location is crucial because sperm production requires a temperature slightly lower than the body's core temperature.

Explain why internal fertilization is essential for mammals living in terrestrial environments?

Internal fertilization protects the gametes and developing embryo from desiccation and environmental hazards, increasing the chances of successful reproduction on land.

How do monotremes differ from marsupials and placental mammals in terms of their reproductive strategy?

Monotremes lay eggs (oviparous), while marsupials and placental mammals both give birth to live young (viviparous). Signup and view all the answers

In mammals, what is the primary function of the seminiferous tubules, and where are they located?

The seminiferous tubules are the site of sperm production (spermatogenesis). They are located within the testicles. Signup and view all the answers

What is the function of the Cowper's gland, prostate, and seminal vesicle in the male reproductive system?

These glands produce secretions that contribute to the seminal fluid (semen), which nourishes and protects sperm cells and facilitates their transport. Signup and view all the answers

An animal has internal fertilization and its offspring are relatively undeveloped at birth. They continue their development in a pouch. To which group does this animal MOST likely belong?

Marsupials Signup and view all the answers

How does an erection facilitate internal fertilization in mammals?

An erection allows the penis to become rigid, enabling it to penetrate the female reproductive tract and deposit sperm closer to the egg, increasing the chances of fertilization. Signup and view all the answers

What is the role of oestrogen in preparing the uterus for potential pregnancy, and how do its levels change throughout a full-term pregnancy?

Oestrogen thickens and repairs the uterine lining for zygote implementation. Oestrogen levels increase for the first month, then consistently increase until they dramatically decrease to zero at month 9. Signup and view all the answers

Explain how progesterone supports pregnancy and what happens if its levels are insufficient.

Progesterone maintains the endometrium lining during pregnancy. If progesterone levels are too low, the pregnancy may be lost. Signup and view all the answers

Describe the roles of both follicle-stimulating hormone (FSH) and luteinising hormone (LH) in the ovarian cycle, but NOT during pregnancy.

FSH stimulates follicle growth and egg maturation in the ovary, while LH triggers ovulation and the formation of the corpus luteum, which induces oestrogen production. Signup and view all the answers

How long is the egg viable for fertilization after ovulation, and what occurs if fertilization does not happen within this timeframe?

The egg is viable for 12-24 hours. If fertilization does not occur, the egg dissolves and is shed along with the uterine lining during menstruation. Signup and view all the answers

What is human chorionic gonadotropin (hCG), and where is it produced? Briefly explain its significance in early pregnancy.

hCG is an embryonic hormone produced by cells in the blastocyst/embryo after it implants in the endometrium. Its presence confirms pregnancy. Signup and view all the answers

Explain the function of gonadotropin-releasing hormone(GnRH) and its role in the menstrual cycle.

It triggers the anterior pituitary gland to release FSH and LH which are responsible for stimulating the growth of follicles for ovulation. Signup and view all the answers

Explain why oestrogen and progesterone levels dramatically drop to zero at month 9 of pregnancy.

They are no longer produced due to the endometrium no longer requiring the maintenance of the thick uterine lining, for an easier delivery. Signup and view all the answers

If a drug was administered that blocked the effects of LH, what specific event in the ovarian cycle would be prevented?

Ovulation would be prevented. LH is responsible for triggering the release of the egg from the mature follicle. Signup and view all the answers

During DNA replication, what specific enzyme is responsible for sealing the gaps between Okazaki fragments on the lagging strand, and why is this necessary for the integrity of the newly synthesized DNA?

DNA ligase seals the gaps between Okazaki fragments. This is crucial because it ensures the newly synthesized DNA strand is continuous and stable, preventing fragmentation and maintaining genetic integrity. Signup and view all the answers

Explain how DNA replication contributes to the continuity of a species, and what would happen if DNA were not accurately replicated before cell division?

DNA replication ensures genetic information is passed down accurately through generations, maintaining species characteristics. If DNA replication were inaccurate or absent before cell division, daughter cells would have incomplete or mutated genetic information, likely leading to cell death or dysfunction. Signup and view all the answers

Describe two key mechanisms in meiosis that generate genetic variation, and explain how this variation contributes to a species' ability to adapt and evolve over time.

Crossing over and independent assortment are two key mechanisms. They create new combinations of alleles, increasing genetic diversity. This diversity is crucial for a species to adapt to changing environments and evolve through natural selection. Signup and view all the answers

Explain the role of mitosis in both the development of a multicellular organism and the maintenance of its tissues. How does mitosis contribute to the overall health and function of an organism?

Mitosis is essential for growth and development by increasing cell number. Also, mitosis allows for the replacement of old or damaged cells, maintaining tissue integrity and function. This ensures the organism can maintain homeostasis and overall health. Signup and view all the answers

Outline the central dogma of molecular biology. Briefly describe the roles of transcription and translation in polypeptide synthesis.

The central dogma is DNA → RNA → Protein. Transcription creates an mRNA copy of DNA in the nucleus, while translation uses mRNA to assemble amino acids into a polypeptide chain in the ribosome. Signup and view all the answers

In transcription, RNA polymerase plays a crucial role. Describe its primary function and explain what would happen if RNA polymerase was absent or non-functional.

RNA polymerase binds to DNA, separates the strands, and synthesizes a complementary mRNA copy. Without functional RNA polymerase, transcription would not occur, preventing the production of mRNA and subsequent protein synthesis. Signup and view all the answers

What is the final product of polypeptide synthesis, and why are polypeptides important for cell function?

The final product is a polypeptide, which folds into a protein. Proteins are crucial for cell function as they perform various roles, including enzymatic catalysis, structural support, and cell signaling. Signup and view all the answers

Describe the significance of genetic diversity resulting from meiosis for the continuity of species, linking it to the concepts of mutation and evolution.

The more diversity created contributes more to the continuity of species, due to the likelihood of variation and survival. As mutation creates variation, genetic diversity introduced by meiosis allows mutation and is essential for species' survival and evolution. This combination allows for diversity and species evolution. Signup and view all the answers

How does internal fertilisation contribute to a higher chance of successful offspring development compared to external fertilisation?

Internal fertilisation provides a protected environment within the female’s body, shielding the developing zygote from external threats such as predators and harsh environmental conditions, which increases the chances of survival. Signup and view all the answers

Differentiate between the genetic outcomes of sexual and asexual reproduction, and explain how this impacts the adaptability of a population to changing environmental conditions?

Sexual reproduction results in genetically diverse offspring due to the combination of genetic material from two parents. Asexual reproduction produces genetically identical clones. Genetic diversity enhances a population’s ability to adapt to changes. Signup and view all the answers

Many aquatic animals use external fertilisation. What are the trade offs of this strategy compared to internal fertilisation?

External fertilisation producing more offspring, without parental energy expenditure. Internal fertilisation produces fewer offspring with increased survival rate. Signup and view all the answers

How does the process of fertilisation ensure that the offspring receives the correct number of chromosomes, and what terms describe the number of chromosomes at each stage?

Fertilisation involves the fusion of two haploid gametes (each containing half the number of chromosomes) to form a diploid zygote (containing the full number of chromosomes). Signup and view all the answers

During Metaphase II, where do the chromosomes align within the cell?

The chromosomes line up along the equator of the cell. Signup and view all the answers

What key event occurs during Anaphase II, and what cellular structures facilitate this process?

The sister chromatids separate and are pulled towards opposite ends of the cell by the spindle fibres. Signup and view all the answers

In terms of energy investment by the parents, contrast the typical strategies employed in organisms that utilize external versus internal fertilisation?

External fertilisation typically involves less energy investment per offspring, with parents releasing large numbers of gametes and providing no further care. Internal fertilisation generally involves a higher energy investment per offspring, including gestation and parental care. Signup and view all the answers

Describe a scenario where asexual reproduction would be more advantageous than sexual reproduction for a plant species?

In a stable environment, asexual reproduction allows for the rapid colonisation by producing genetically identical offspring. Sexual reproduction is more beneficial in changing environments where genetic variation is favoured. Signup and view all the answers

Describe the two main events that occur during Telophase II.

The nuclear membrane forms around each set of chromosomes and they begin to uncoil. Cytokinesis then splits the chromosome sets into new cells. Signup and view all the answers

Explain how the mobility of gametes (e.g., sperm) and the presence (or absence) of water influence the mode of fertilisation (internal vs. external) in different animal species?

Mobile sperm and the presence of water favour external fertilisation, as sperm can swim to eggs released into the environment. Lack of water and/or less mobile gametes necessitate internal fertilisation to ensure gamete proximity. Signup and view all the answers

What is the end result of meiosis? And why are these cells important?

Four haploid gametes. They are important because these gametes can fuse with its opposite kind to form a diploid cell so that the zygote will have two alleles for a given gene. Signup and view all the answers

Briefly describe the structure of DNA, mentioning its key components and how they are arranged.

DNA is a double-stranded helix with a sugar-phosphate backbone. It contains nitrogenous bases (A, T, C, G) that pair specifically (A with T, and C with G). Signup and view all the answers

Compare dispersal of offspring in external vs internal fertilisation.

External fertilisation often leads to more widespread dispersal of offspring due to the release of gametes into the environment, increasing the range of distribution. Internal fertilisation can limit dispersal as offspring develop within the parent, though mobility after birth can vary. Signup and view all the answers

Outline the role and mechanism of action of the enzyme `helicase` during DNA replication.

<code>Helicase</code> unwinds the double-stranded DNA molecule by breaking the hydrogen bonds between complementary base pairs. Signup and view all the answers

Describe the function of `DNA polymerase` during the elongation phase of DNA replication.

<code>DNA polymerase</code> adds free-floating DNA nucleotides to the exposed strand and inserts them with their complementary base. It also corrects base pairing errors by splicing out the incorrect base and replacing it with the correct one. Signup and view all the answers

Why is DNA replication essential prior to cell division?

DNA replication is essential because each daughter cell needs a complete and identical copy of the organism's genetic material. Without replication, cell division would result in cells with missing or incomplete genetic information. Signup and view all the answers

During transcription, RNA polymerase moves along the DNA. Does it move along the coding stand or the template strand, and in which direction (3' to 5' or 5' to 3')?

RNA polymerase moves along the template strand in the 3' to 5' direction. Signup and view all the answers

Explain how the sequence of the mRNA strand produced during transcription relates to both the template strand and the coding strand of the DNA.

The mRNA sequence is complementary to the template strand (except uracil replaces thymine) and virtually identical to the coding strand (again, with uracil instead of thymine). Signup and view all the answers

What is the role of tRNA in the process of translation, and how does the anticodon sequence contribute to this role?

tRNA carries specific amino acids to the ribosome. The anticodon on tRNA is complementary to the mRNA codon, ensuring the correct amino acid is added to the polypeptide chain. Signup and view all the answers

Describe what happens when the ribosome encounters a stop codon on the mRNA molecule during translation.

When the ribosome encounters a stop codon, translation terminates. The polypeptide chain is released, and the ribosome complex disassembles. Signup and view all the answers

If a DNA template strand has the sequence `3'-TTCAGG-5'`, what would be the corresponding mRNA sequence produced during transcription?

<code>5'-AAGUCC-3'</code> Signup and view all the answers

Explain the significance of the rough endoplasmic reticulum (RER) in the context of translation and protein synthesis.

The RER is studded with ribosomes, which are the sites of translation. This allows for the synthesis of proteins that are destined for secretion or insertion into membranes. Signup and view all the answers

During translation, what is the specific role of the small and large ribosomal subunits?

The small subunit initially attaches to the mRNA. The large subunit then joins, enclosing the mRNA and facilitating tRNA binding and polypeptide formation. Signup and view all the answers

Describe the 'transfer' process that occurs between tRNA molecules during the elongation stage of translation.

As a new tRNA molecule binds to the next mRNA codon, the prior tRNA molecule detaches and transfers its amino acid to the amino acid on the newly arrived tRNA, forming a peptide bond. This adds another amino acid to growing polypeptide chain. Signup and view all the answers

Flashcards

Fertilisation

Fusion of gametes (sex cells) to form a zygote.

Haploid

Half the normal number of chromosomes in a cell.