B2- Cell division

Question 1

how many chromosomes do gametes (reproductive cells) have?

Answer 1

23

Question 2

How many chromosomes does the human body have?

Answer 2

46 (23 pairs)

Question 3

What is mitosis?

Answer 3

a stage of the cell cycle where a parent cell divides to produce two identical daughter cells

Question 4

what are chromosomes?

Answer 4

thread-like structures made of around 1 molecule of DNA and proteins, located within the nucleus of a cell. They carry the genetic information of an organism
(they come in pairs)

Question 5

What is a gamete?

Answer 5

A reproductive cell of an animal or plant. In animals, female gametes are called ova or egg cells, and male gametes are called sperm. Ova and sperm are haploid cells, with each cell carrying only one copy of each chromosome

Question 6

What are genes?

Answer 6

A gene is a section of DNA found on a chromosome which controls part of a cell’s chemistry - particularly protein production.

Question 7

Why do chromosomes found in body cells come in pairs?

Answer 7

Chromosomes in body cells come in pairs because each parent contributes one copy of each chromosome to their offspring. This ensures that offspring inherit a complete set of genetic information from both parents, creating a diploid cell

Question 8

Where does mitosis occur?

Answer 8

Mitosis occurs in several key situations: growth, development, cell replacement, repair of damaged tissues, and asexual reproduction ( where a single parent cell divides to produce two identical daughter cells )

Question 9

Where (in the body) does mitosis take place?

Answer 9

in all somatic cells (cells that are not responsible for the production of gametes) in the nucleus.

Question 10

can you describe the 5 stages of mitosis?

Answer 10

-Prophase: The DNA in chromosomes and their copies condenses to become more visible. The membrane around the nucleus disappears.

-Metaphase: Chromosomes and their copies line up in the middle of the cell.

-Anaphase: Chromosomes and their copies are pulled to different ends of the cell.

-Telophase: New membranes form around the chromosomes at each end of the cell.

Question 11

Why must genetic material be doubled during mitosis?

Answer 11

to ensure that each daughter cell receives a complete and identical copy of the original cell’s genetic information.

Question 12

What is the first stage of the cell cycle, can you explain it?

Answer 12

interphase:
- Growth: The cell increases in size and synthesizes new proteins and organelles.
- DNA Replication: The cell duplicates its DNA, creating two identical copies of each chromosome
- Organelle Duplication: Organelles like mitochondria and ribosomes are also duplicated.

Question 13

what is the second stage of the cell cycle, can you elaborate?

Answer 13

Mitosis:
- Nuclear Division: The nuclear membrane breaks down, and the duplicated chromosomes condense and line up in the middle of the cell.
- Chromosome Separation: The duplicated chromosomes are separated, with one copy of each chromosome moving to opposite ends of the cell.
- New Nuclei Formation: A new nuclear membrane forms around each set of chromosomes at the poles of the cell.

Question 14

what is the third stage of the cell cycle and can you describe it?

Answer 14

Cytokinesis:
- Cytoplasm Division: The cytoplasm and cell membrane divide, creating two separate daughter cells.
- Daughter Cell Formation: Each new cell receives a complete set of DNA and its own organelles.

Question 15

Why is mitosis important in living things?

Answer 15

• Mitosis is essential for the growth of multicellular organisms, as it increases the number of cells, which in turn increases the size of the organism.
• It plays a vital role in embryonic development, where cells divide rapidly to form the various tissues and organs of an organism.
• Mitosis continues throughout life, contributing to the overall growth of organism
• Mitosis allows the body to repair damaged tissues and replace worn-out cells.

Question 16

How are characteristics inherited?

Answer 16

Characteristics are inherited through genes, which are segments of DNA located on chromosomes that contain instructions for building and operating the body. Parents pass on these genes to their children during reproduction.

Question 17

What happens when an ova is fertilised?

Answer 17

-sperm cell fuses with egg cell to form a zygote
- zygote contains the full diploid set of chromosomes

Question 18

What is meant by the term ‘growth’?

Answer 18

growth refers to an increase in size, often due to an increase in the number of cells or the size of existing cells.

Question 19

what is meant by the term ‘differentiation’?

Answer 19

Differentiation is the process where unspecialized cells develop into specialized cells with specific structures and functions

Question 20

Why are plant clones genetically identical?

Answer 20

Plant clones are genetically identical because they are produced through asexual reproduction, a process that involves only one parent and doesn’t involve the mixing of genetic material from different parents

Question 21

What is one method of cloning a plant cell?

Answer 21

Cuttings:
A branch from the parent plant is cut off, its lower leaves are removed, and the stem is planted in damp compost. Plant hormones are often used to encourage new roots to develop. The cutting is usually covered in a clear plastic bag to keep it moist and warm. After a few weeks, new roots develop and a new plant grows.

Question 22

What are meristems?

Answer 22

regions of unspecialised cells in which cell division occurs, found at the tips of roots and shoots

Question 23

What is the other method of plant cloning?

Answer 23

Tissue culture:
Stem cells from meristems can be
cloned
.Meristematic cells are removed from a plant and grown in tissue culture
.The cells are grown in a culture medium
that contains agar- to provide support and water for the growing cells – along with nutrients and plant hormones (which manipulate the differentiation of cells) to stimulate growth and cell division ultimately producing genetically identical plants

Question 24

Why is differentiation important in multicellular organisms?

Answer 24

it allows cells to specialize and perform specific functions, enabling the development of complex tissues and organs

Question 25

How do unspecialised cells become specialised?

Answer 25

Unspecialized cells become specialized through a process called differentiation, where specific genes are turned on or off, leading to the production of different proteins and ultimately, changes in cell structure and function

Question 26

What is the difference between differentiation in plants and animals?

Answer 26

-Plant cells retain their ability to differentiate (specialise) throughout their life, whereas Animal cells are mainly restricted to repair and replacement in later life. -stem cells in animals are found in embryos and various adult tissues like bone marrow whereas stem cells are found in the meristems of plants (roots and shoots)

Question 27

Why is it easier to clone a plant rather than an animal?

Answer 27

- natural regenerative capacity makes cloning a relatively straightforward process in plants. -plants can reproduce asexually whereas animals can't therefore the cloning process is easier -there are less ethical issues associated with plant cloning

Question 28

What is a stem cell?

Answer 28

an undifferentiated cell that can divide to produce more stem cells, or differentiate into different specialized cell types

Question 29

How can stem cells be used to help medical issues?

Answer 29

-Stem cells can be used to replenish cells damaged by diseases or treatments like chemotherapy. For example, bone marrow transplants use stem cells to restore blood cell production in leukemia and lymphoma patients -therapeutic cloning: egg cell donated, nucleus is removed from skin cell of patient, egg cell develops into embryo, embryonic stem cells removed an cultured to differentiate into (e.g pancreatic cells that produce insulin for type 1 diabetes patient)- DNA is the same so patient doesn't reject cells and doesn't need immunosuppressants

Question 30

what are the differences between embryonic and adult stem cells?

Answer 30

- embryonic stem cells can pluripotent- can differentiate into any cell type whereas adult stem cells are multipotent so they are restricted to a specific range of cell types from their tissue of origin -embryonic stem cells have a greater capacity to create new tissue compared to adult stem cells, which are generally limited to rebuilding existing tissues -embryonic stem cells can replicate themselves indefinitely which allows them to be cultured and maintained in the lab for long periods however whilst adult stem cells possess this quality, they are susceptible to damage and can be affected by environmental factors, potentially leading to a loss of their regenerative potential.

Question 31

Why are plant clones produced in the agricultural industry?

Answer 31

-to provide crop plants for large-scale cultivation that have desirable characteristics such as disease resistance -Producing new plants by cloning is quicker than allowing plants to reproduce then collecting and sowing seeds. It's therefore an effective way of producing new individuals from rare and endangered plants, helping to preserve the species.

Question 32

Why are embryonic stem cells more useful in the medicine industry?

Answer 32

they have the ability to grow indefinitely in a laboratory environment and can differentiate into almost all types of bodily tissue. This makes embryonic stem cells a prospect for cellular therapies to treat a wide range of diseases

Question 33

what are the pros of using stem cells?

Answer 33

- autologous transplant: using one's own- they can be stored during treatments such as chemotherapy and used to replace cells that are damaged in the process -Stem cells have the potential to regenerate damaged tissues and organs, potentially offering alternatives to organ transplantation

Question 34

What are the costs of using stem cells in medicine?

Answer 34

-The use of embryonic stem cells raises ethical issues due to the consequential destruction of an embryo due to the possibility of its development into a foetus -limited availability: not enough donors -there can be mutations in adult stem cells that have cultured for a long time - risk of rejection -costly procedure that, due to the early stage in which medicine is with knowledge around stem cells, has the possibility of failure