2C2 Cell Division and Genetic Diversity

Question 1

What is gametogenesis?

Answer 1

The process of making sex cells, involving mitosis and meiosis to produce haploid daughter cells from a diploid parent cell.

Gametogenesis includes spermatogenesis in males and oogenesis in females.

Question 2

Where are eggs made in female humans?

Answer 2

In the ovaries, while the female fetus is still developing.

The process begins with the formation of primary oocytes during fetal development.

Question 3

When and where does spermatogenesis occur in male humans?

Answer 3

• When: Continuously in the male reproductive system throughout a male’s life after puberty.
• Where: In the Seminiferous tubules of the testes.

The process starts at puberty and involves the testes producing millions of sperm daily.

Question 4

What are the stages of oogenesis?

Answer 4

1. Pre-natal stage
2. Antral stage
3. Pre-ovulation stage

Oogenesis involves the maturation of oocytes, culminating in ovulation during the menstrual cycle.

Question 5

What happens to primary oocytes during the pre-natal stage of oogenesis?

Answer 5

They arrest in the middle of meiosis I during the pre-natal stage.

This arrest occurs in prophase I and remains until puberty when hormonal changes resume their development.

Question 6

What triggers the antral stage of oogenesis?

Answer 6

Puberty and the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH).

These hormones stimulate the growth of ovarian follicles, each containing an oocyte.

Question 7

What is the fate of the polar body in oogenesis?

Answer 7

It will eventually degenerate and is not used for sexual reproduction.

Polar bodies are byproducts of meiosis that contain minimal cytoplasm and are not viable gametes.

Question 8

When does the secondary oocyte complete meiosis II?

Answer 8

Only upon fertilization, becoming a true ovum.

Fertilization by a sperm triggers the completion of meiosis II and the formation of a zygote.

Question 9

What are the main stages of spermatogenesis?

Answer 9

1. Spermatocytogenesis
2. Spermatidogenesis
3. Spermiogenesis

Question 10

How does mitosis differ from meiosis in terms of reproduction?

Answer 10

• Mitosis is asexual reproduction producing identical diploid cells.
• Meiosis is for sexual reproduction producing haploid gametes.

Question 11

How does sexual reproduction differ from asexual reproduction?

Answer 11

• Sexual reproduction: Involves two parents and genetic variation in offspring.
• Asexual reproduction: Involves one parent and produces genetically identical offspring.

Sexual reproduction - e.g. human reproduction.

Asexual reproduction - e.g. yeast reproduction.

Question 12

Give an example of a plant that reproduces asexually.

Answer 12

Strawberry plants shoot out runners along the soil that grow into new strawberry plants.

These are exact copies of the parent plant.

Question 13

List one advantage and one disadvantage of asexual reproduction.

Answer 13

• Advantage: Lots of offspring can be produced very quickly.
• Disadvantage: Lack of genetic variation makes populations vulnerable to diseases.

Question 14

List one advantage and one disadvantage of sexual reproduction.

Answer 14

• Advantage: Fusion of two gametes increases genetic variation in offspring, enhancing survival.
• Disadvantage: Takes time and energy to find mates.

Question 15

What are the two main types of reproduction?

Answer 15

1. Sexual
2. Asexual

Question 16

How do unicellular organisms like yeast reproduce?

Answer 16

Through mitosis, where one cell divides into two identical daughter cells.

This process is called budding in yeast, where a new cell grows out of the body of a parent cell.

Question 17

What is mitosis?

Answer 17

The process where a cell duplicates its DNA and divides into two identical cells.

Mitosis consists of the following stages:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
5. Cytokinesis

Question 18

What is meiosis?

Answer 18

The process of making sex cells (gametes) with half the DNA of the parent for sexual reproduction.

Meiosis consists of two divisions: meiosis I and meiosis II, resulting in four haploid cells.

Question 19

What is vegetative propagation?

Answer 19

A type of asexual reproduction where new plants grow from runners, like in strawberries.

Other forms include grafting, layering, and the use of plant cuttings.

Question 20

How do sea sponges reproduce asexually?

Answer 20

By budding, where a part of the organism pinches off and grows into a new individual.

Question 21

What are gametes?

Answer 21

Sex cells, usually called eggs in females and sperm in males, involved in sexual reproduction.

Gametes are haploid, containing half the number of chromosomes compared to somatic cells.

Question 22

What is the difference between haploid and diploid cells?

Answer 22

• Haploid cells have half the genetic information (like gametes).
• Diploid cells have a full set of DNA (like somatic cells).

Diploid cells have two sets of chromosomes, one from each parent, while haploid cells have one set.

Question 23

Is mitosis classified as asexual or sexual reproduction?

Answer 23

Asexual reproduction.

Mitosis produces cells that are genetically identical to the parent cell.

Question 24

What type of cells result from mitosis?

Answer 24

Diploid cells.

These cells are involved in growth, repair, and maintenance of tissues.

Question 25

Can mitosis lead to the creation of new organisms?

Answer 25

Yes, but it does not always. ## Footnote In single-celled organisms like bacteria, mitosis (binary fission) results in new individuals.

Question 26

Which human body cells undergo mitosis?

Answer 26

Most human body cells, such as skin cells and taste buds. ## Footnote Red blood cells are an exception, as they do not undergo mitosis.

Question 27

What is the primary purpose of **meiosis**?

Answer 27

To produce gametes for sexual reproduction.

Question 28

Why does meiosis involve halving the genetic material?

Answer 28

To bring it back to full at some point during fertilization. ## Footnote This reduction is crucial for maintaining a stable chromosome number across generations.

Question 29

Is meiosis ever used for asexual reproduction?

Answer 29

No.

Question 30

What type of cells are produced by meiosis?

Answer 30

Haploid gametes. ## Footnote These include sperm in males and eggs in females.

Question 31

What is an exception to the usual process of meiosis?

Answer 31

An ova can sometimes grow without being fertilized, having not gone through the correct stages of meiosis but still containing all necessary genetic information. ## Footnote This process is called parthenogenesis, observed in some insects, reptiles, and fish.

Question 32

What is the chromosome number in daughter cells after mitosis?

Answer 32

Diploid (2n). ## Footnote For humans, this means each daughter cell has 46 chromosomes.

Question 33

How many gametes are produced from one cell through meiosis?

Answer 33

Four. ## Footnote For humans, this means each gamete has 23 chromosomes.

Question 34

How do the genetic contents of parent and daughter cells compare in mitosis?

Answer 34

Parent and daughter cells have identical diploid (2n) DNA in mitosis.

Question 35

Where can mitosis occur?

Answer 35

In any somatic cell that needs to replicate.

Question 36

Which organisms often use mitosis to reproduce quickly?

Answer 36

Many single-celled organisms. ## Footnote e.g. bacteria and protozoa.

Question 37

Does asexual reproduction require fertilization or incubation?

Answer 37

No, it doesn't require either. ## Footnote Asexual reproduction can occur without the presence of another organism.

Question 38

What are some methods of **asexual** reproduction?

Answer 38

1. Budding 2. Fission 3. Vegetative propagation ## Footnote Each method varies by organism and environment.

Question 39

Why are populations of asexually created organisms vulnerable to environmental changes?

Answer 39

Due to their genetic uniformity. ## Footnote A single change in the environment can affect all individuals equally.

Question 40

What are **mutations**?

Answer 40

DNA errors that result in changes to the genetic code, leading to population variation and influencing physical traits, behavior, and physiology. ## Footnote Mutations can be spontaneous or induced by external factors like radiation.

Question 41

How do mutations contribute to evolution?

Answer 41

They create genetic variation, which is essential for evolution. ## Footnote Variations that improve survival and reproduction are passed on, while those that hinder these processes are eliminated through natural selection.

Question 42

What is a **somatic** mutation?

Answer 42

Occur in non-reproductive cells and are usually not passed on to offspring. These can affect cell division and may lead to conditions like cancer. ## Footnote Somatic mutations can accumulate over an organism's lifetime.

Question 43

What is a **germ-line** mutation?

Answer 43

Occur in reproductive cells and can be passed on to offspring, affecting traits in future generations. ## Footnote These mutations can influence the genetic makeup of populations over time.

Question 44

What are **gene-level** mutations?

Answer 44

Involve changes to short lengths of nucleotides. They can affect physical characteristics and play a significant role in evolution. ## Footnote An example is insect resistance to pesticides.

Question 45

What are **chromosomal** mutations?

Answer 45

Involve changes to long lengths of nucleotides and often have severe consequences. ## Footnote An example is Down syndrome, caused by an extra copy of chromosome 21.

Question 46

What causes mutations?

Answer 46

* Spontaneous errors during DNA replication. * Exposure to mutagens like chemicals and UV radiation. ## Footnote Mutagens can cause direct damage to the DNA structure.

Question 47

What is a **substitution** mutation?

Answer 47

A type of mutation where one codon is replaced by another, potentially altering the amino acid sequence of a protein. ## Footnote Substitution mutations can be silent, missense, or nonsense.

Question 48

What is an **insertion** mutation?

Answer 48

Occurs when extra base pairs are added into the DNA sequence, which can disrupt the gene's function. ## Footnote Insertions can cause frameshift mutations, altering the entire downstream amino acid sequence.

Question 49

What is a **deletion** mutation?

Answer 49

It's when a section of DNA is lost or removed, which can result in the loss of essential genetic information. ## Footnote Deletions can also cause frameshift mutations, with significant impacts on protein function.

Question 50

How do variations caused by mutations affect a population?

Answer 50

These variations make individuals within a population unique, influencing traits like hair color, skin color, height, shape, and behavior. ## Footnote These variations are crucial for natural selection and adaptation.

Question 51

Can mutations be beneficial?

Answer 51

Yes, if they result in traits that enhance an organism's ability to survive and reproduce in its environment. ## Footnote Beneficial mutations can spread through a population by natural selection.

Question 52

What role do **codons** play in mutations?

Answer 52

* These are sets of three nucleotides that specify amino acids or signal the end of a protein. * Mutations in codons can alter protein synthesis and function. ## Footnote The genetic code is redundant, meaning multiple codons can code for the same amino acid.

Question 53

What are **mutagens**?

Answer 53

These are environmental factors, such as chemicals and UV radiation, that can induce mutations in DNA. ## Footnote Common mutagens include tobacco smoke, asbestos, and certain viruses.