Topic 2 - Life Cycles & Eukaryotic Chromosomes

Question 1

Fertilization

Answer 1

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

Question 2

Gamete

Answer 2

A gamete is a reproductive cell that fuses with another gamete during fertilization to form a zygote, which will develop into a new organism. In animals, male gametes are called sperm, while female gametes are called eggs or ova.

Question 3

Zygote

Answer 3

A zygote is the initial cell formed when two gametes (reproductive cells) fuse during fertilization. It contains all the genetic information from both parents and is the first step in the development of a new organism. The zygote undergoes several cell divisions to form an embryo, which eventually grows into a mature organism.

Question 4

Karyotype

Answer 4

The complete set of chromosomes possessed by an organism; is usually presented as a picture of a complete set of its metaphase chromosomes.

Question 5

Heterogametic sex

Answer 5

The sex (male or female) produces two types of gametes with respect to sex chromosomes. For example, in the XX-XY sex-determining system, the male produces both X-bearing and Y-bearing gametes.

Heterogametic refers to a condition in which the two types of gametes produced by an organism have different sexes or sexes chromosomes. In other words, one type of gamete has a different combination of sex chromosomes than the other.

The consequences of heterogamety can vary depending on the species, but generally, it results in sexual dimorphism (differences between male and female individuals), and increased genetic diversity. This diversity can help populations adapt to changing environments and resist diseases. Additionally, heterogamety allows for the separation of sexual selection pressures between the sexes, which can drive the evolution of distinct male and female traits and behaviours.

Question 6

Homogametic Sex

Answer 6

The sex (male or female) produces gametes that are all alike with respect to sex chromosomes. For example, in the XX-XY sex-determining system, the female produces only X-bearing gametes.

Homogametic sex refers to a condition in which an organism produces gametes that have the same type of sex chromosomes. In other words, both types of gametes have the same combination of sex chromosomes. This is in contrast to heterogametic sex, in which the two types of gametes have different combinations of sex chromosomes.

Question 7

P arm

Answer 7

The petite arm of the chromosome.

Question 8

Q arm

Answer 8

The long arm of the chromosome.

Question 9

Metacentric (chromosome)

Answer 9

Chromosome in which the two chromosome arms are approx. the same length.

Question 10

Telocentric (chromosome)

Answer 10

Chromosome in which the centromere is at or very near one end.

Question 11

Acrocentric (chromosome)

Answer 11

Chromosome in which the centromere is near one end. producing a long arm at one end and a knob, or satellite at the other end.

Question 12

Cohesins

Answer 12

A protein that holds the two sister chromosomes together. The breakdown of cohesin at the centromeres enables the chromatids to separate in anaphase of mitosis and anaphase II of meiosis.

One major consequence of impaired cohesin function is chromosomal segregation errors. This occurs when sister chromatids do not separate correctly during cell division, resulting in unequal distribution of chromosomes to the daughter cells

Question 13

Spermatogenesis

Answer 13

Production of gametes in a male animal; takes place is the testes.

Question 14

Spermatogium (2n)

Answer 14

Spermatogonia are the type of germ cells that give rise to sperm in male mammals. They are the earliest cells in the process of sperm production and are found in the testes.

They are diploid cells in the testes; capable of undergoing meiosis to produce sperm.

Question 15

How many primary spermatocytes, secondary spermatocytes, and sperm are made in one rendition of sperm production?

Answer 15

In one round of sperm production, a single primary spermatocyte gives rise to two secondary spermatocytes. Each secondary spermatocyte then divides to produce two sperm cells.

So, in total, one primary spermatocyte produces four sperm cells. This process of division and differentiation of spermatogonia to form sperm is known as spermatogenesis, and it occurs continuously in the testes of sexually mature males to maintain the supply of sperm.

Question 16

Primary Spermatocyte (2n)

Answer 16

A primary spermatocyte is a spermatogonium that has entered prophase I.

Primary spermatocytes are formed from the division of spermatogonia, which are the earliest cells in the process of sperm production. Primary spermatocytes are diploid cells, meaning they have two sets of chromosomes. They undergo meiosis, which is a type of cell division that reduces the number of chromosomes to half, to form secondary spermatocytes.

Question 17

Secondary Spermatocyte (1n)

Answer 17

Product of Meiosis I in male animals.

Secondary spermatocytes, are haploid cells, meaning they have only one set of chromosomes. They undergo Meiosis II to produce two haploid spermatids each.

Question 18

Spermatids (1n)

Answer 18

The immediate product of Meiosis II in spermatogenesis; matures into sperm.

Question 19

Oogenesis

Answer 19

The production of gametes in a female animal. Oogenesis reduces the number of chromosomes through Meiosis I, resulting in haploid secondary oocytes. The ploidy returns to diploid if the egg is fertilized.

The secondary oocyte then undergoes Meiosis II, which is completed only if the egg is fertilized.

Question 20

Oogonium (2n)

Answer 20

Diploid cell in the ovary; capable of undergoing meiosis to produce an egg cell.

Question 21

Primary Oocytes (2n)

Answer 21

Oogonium that has entered prophase I.

Question 22

Secondary Ooocyte (1n)

Answer 22

One of the products of meiosis I in oogenesis; receives most of the cytoplasm.

Question 23

First Polar Body

Answer 23

One of the products of meiosis I is oogenesis; which is the smaller cell, which contains half the chromosomes but only a small part of the cytoplasm.

Question 24

Ovum

Answer 24

The mature female gamete; is the larger cell, which acquires most of the cytoplasm during oogenesis.

Question 25

Secondary Polar Body

Answer 25

One of the products of meiosis I in oogenesis; receives most of the cytoplasm.

Question 26

Microsporocytes (2n)

Answer 26

Diploid reproductive cell in the stamen of a plant; undergoes meiosis to produce four haploid microspores.

Question 27

Microspores (n)

Answer 27

Haploid product of meiosis in plants.

Question 28

Megasporocytes

Answer 28

Diploid reproductive cell in the ovary of a plant that undergoes meiosis to produce haploid megaspores.

Question 29

Megaspores

Answer 29

One of the four products of meiosis in plants.

Question 30

Summarize Oogenesis & How the ploidy changes throughout the process

Answer 30

In oogenesis, a single diploid oogonium (the earliest cell in the process of egg production) divides to form multiple primary oocytes. The primary oocytes then enter a dormant phase and do not divide again until later in life, when they are stimulated to do so in response to hormonal signals.

When a primary oocyte is stimulated to divide, it undergoes Meiosis I to form a secondary oocyte and a smaller polar body. The secondary oocyte then undergoes Meiosis II, which is completed only if the egg is fertilized. If the egg is fertilized, the resulting zygote is diploid with two sets of chromosomes. If the egg is not fertilized, the secondary oocyte undergoes cytolysis and is not used.

The ploidy changes as follows:

Oogonia are diploid with two sets of chromosomes.
Primary oocytes are also diploid with two sets of chromosomes.
Secondary oocytes are haploid with one set of chromosomes.
If fertilized, the zygote formed is diploid with two sets of chromosomes.

Question 31

Fertilization in Animals

Answer 31

So to summarize, ovulation is the release of an egg from the ovary, fertilization is the merging of sperm and egg genetic material, and implantation is the attachment of the fertilized egg to the uterus.

Ovulation:
- Each month, one of the ovaries releases a mature egg into the fallopian tube.
- The egg is surrounded by fluid and moves along the fallopian tube towards the uterus.
- This release of the egg from the ovary is called ovulation.

Fertilization:
- If sperm are present in the fallopian tube, one of them may fertilize the egg by merging its genetic material with the egg’s genetic material.
- This creates a fertilized egg, also called a zygote.
- The zygote then travels down the fallopian tube and into the uterus.

Implantation:
- The zygote may then implant itself into the lining of the uterus.
- This is the beginning of pregnancy.
- If the egg is not fertilized or if implantation does not occur, the egg and any remaining tissue are shed from the body during menstruation.

Question 31

Fertilization in Animals

Answer 31

So to summarize, ovulation is the release of an egg from the ovary, fertilization is the merging of sperm and egg genetic material, and implantation is the attachment of the fertilized egg to the uterus.

Ovulation:
- Each month, one of the ovaries releases a mature egg into the fallopian tube.
- The egg is surrounded by fluid and moves along the fallopian tube towards the uterus.
- This release of the egg from the ovary is called ovulation.

Fertilization:
- If sperm are present in the fallopian tube, one of them may fertilize the egg by merging its genetic material with the egg’s genetic material.
- This creates a fertilized egg, also called a zygote.
- The zygote then travels down the fallopian tube and into the uterus.

Implantation:
- The zygote may then implant itself into the lining of the uterus.
- This is the beginning of pregnancy.
- If the egg is not fertilized or if implantation does not occur, the egg and any remaining tissue are shed from the body during menstruation.

Question 31

Fertilization in Animals

Answer 31

So to summarize, ovulation is the release of an egg from the ovary, fertilization is the merging of sperm and egg genetic material, and implantation is the attachment of the fertilized egg to the uterus.

Ovulation:
- Each month, one of the ovaries releases a mature egg into the fallopian tube.
- The egg is surrounded by fluid and moves along the fallopian tube towards the uterus.
- This release of the egg from the ovary is called ovulation.

Fertilization:
- If sperm are present in the fallopian tube, one of them may fertilize the egg by merging its genetic material with the egg’s genetic material.
- This creates a fertilized egg, also called a zygote.
- The zygote then travels down the fallopian tube and into the uterus.

Implantation:
- The zygote may then implant itself into the lining of the uterus.
- This is the beginning of pregnancy.
- If the egg is not fertilized or if implantation does not occur, the egg and any remaining tissue are shed from the body during menstruation.

Question 32

Oogonium (2n) are arrested in _______ of meiosis.

Answer 32

Prophase I.

In the female reproductive system, most cells in the ovary are oogonia, which have a diploid number of chromosomes (2n). As the oogonia undergo mitosis, they differentiate into primary oocytes. The primary oocytes remain arrested in prophase I of meiosis until they receive the proper signals to continue.

Question 33

Alternation of Generations

Answer 33

Complex life cycle in plants that alternates between the diploid sporophyte stage and the haploid gametophyte stage. The alternation of generations in plants involves the following steps:

Haploid phase: The first phase of the alternation of generations is the haploid phase, also known as the gametophyte phase. In this phase, the plant produces haploid gametes, such as sperm and egg cells, through meiosis.

Fertilization: The haploid gametes then fuse during fertilization to form a diploid zygote.

Diploid phase: The diploid zygote grows and develops into the diploid phase, also known as the sporophyte phase. In this phase, the plant produces diploid spores, such as spores and seeds, through meiosis.

Spore production: The diploid sporophyte produces haploid spores, known as spores or spores, which can grow into new gametophytes.

Repeat: The process then repeats, with the haploid spores growing into new gametophytes, producing new gametes, and so on.

Question 34

Which of the following best describes the alternation of generations in plants:

A) The cycle in which the sporophyte phase produces spores, which grow into gametophytes, which produce gametes that fertilize to form a new sporophyte phase.

B) The cycle in which the sporophyte phase produces spores, which grow into gametophytes, which produce gametes that fertilize to form a new gametophyte phase.

C) The cycle in which the gametophyte phase produces gametes, which fertilize to form a new sporophyte phase, which produces spores that grow into a new gametophyte phase.

D) None of the above.

Answer 34

Option A is correct.

Option C is not correct because it describes a cycle in which the gametophyte phase produces gametes, which fertilize to form a new sporophyte phase, but then the cycle repeats by producing fragments that grow into a new gametophyte phase. However, in alternation of generations, the gametophyte phase is dependent on the sporophyte phase, not the other way around. The sporophyte phase produces gametes that fertilize to form a new sporophyte phase, which then produces fragments that grow into a new gametophyte phase.

In the alternation of generations, the sporophyte phase is the dominant phase, and it produces gametes that fertilize to form a new sporophyte phase. Without the sporophyte phase, the alternation of generations would stop, and there would be no continuation of the cycle. The gametophyte phase, although important for producing gametes, is dependent on the sporophyte phase for its continuation.

Question 35

what does the dominant phase mean?

Answer 35

The dominant phase refers to the stage in the alternation of generations in which the majority of the organism’s characteristics and functions are expressed. The dominant phase is the phase that is most visible and prominent, and it is the phase that plays the most important role in the continuation of the life cycle. In most cases of alternation of generations, the sporophyte phase is the dominant phase, while the gametophyte phase is the less dominant phase. This means that the majority of the organism’s characteristics and functions are expressed during the sporophyte phase, and the gametophyte phase is only present for a limited time and is used for the production of gametes.

Question 36

Micro refers to ____

Answer 36

Male; they are supplying the smaller gamete with less materials.

Question 37

Mega refers to ______

Answer 37

Females; are contributing more to the gametes.

Question 38

Double fertilization

Answer 38

Double fertilization occurs in flowering plants as a unique feature of their reproductive process. It involves the fusion of two sperm cells with two different cells within the ovules of the female reproductive structure, the pistil.

The first sperm cell fuses with the egg cell to form a zygote (2n), which will develop into the embryo of the seed. The second sperm cell fuses with the secondary nucleus, which is also within the ovule, to form the endosperm. The endosperm is a tissue that provides nourishment to the developing embryo and helps to support the growth of the seedling.

Question 39

Mating Types in the Life Cycle of Yeast

Answer 39

In yeast, the asexual haploid part of the life cycle is characterized by the presence of two different mating types, labelled “a” and “α”.

Question 40

Fusion

Answer 40

Fusion refers to the process of two yeast cells, one with the mating type “a” and the other with the mating type “α”, coming together and forming a diploid cell. During this process, the two haploid nuclei from the “a” and “α” cells combine to form a single diploid nucleus, effectively “fusing” the genetic material of the two cells. This is a key step in the sexual reproduction of yeast, and it results in the creation of new genetic combinations that can drive evolutionary changes over time.

Question 41

After fusing, how do they become ascospores?

Answer 41

After the “a” and “α” yeast cells fuse and form a diploid cell, the diploid cell undergoes meiosis, which is a type of cell division that results in the formation of haploid daughter cells. During meiosis, the diploid nucleus splits into four haploid nuclei, which are then packaged into four ascospores. These ascospores are the result of the sexual reproduction of yeast, and they contain unique combinations of the genetic material from the original “a” and “α” cells. After the ascospores are formed, they can grow into new yeast cells that can repeat the process of mating and sexual reproduction.

Question 42

What is the difference between DNA and RNA?

Answer 42

DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid) are both biomolecules that play a crucial role in the storage and transfer of genetic information. The main difference between them is the sugar molecule that is part of their chemical structure. DNA is composed of deoxyribose sugar, while RNA is composed of ribose sugar. Additionally, DNA is double-stranded and RNA is usually single-stranded. DNA is the long-term storage of genetic information in cells, while RNA is involved in the expression of that information by serving as a template for the production of proteins.