B2 Cell Division

Question 1

In what form does the DNA contain genetic information?

Answer 1

Chromosomes

Question 2

How many pairs of chromosomes are there in a human body?

Answer 2

23

Question 3

How many chromosomes are there in reproductive cells?

Answer 3

23

Question 4

Why do organisms need new cells?

Answer 4

New cell are needed for an organism to grow and to replace cells that have become worn out and to repair damage tissue. The new cells must have rhe same genetic information so they can do the same job.

Question 5

What is a gene and how do genes control characteristics?

Answer 5

A gene is a small packet of information that controls a characteristic or part pf a charecteristic of your body. It is a section of DNA. Most characteristics are made through many different genes rather than a singular one.

Question 6

What is the cell cycle?

Answer 6

The stages of cell division in eukaryotic cells (mitosis)

Question 7

State and explain the 1st stage of the cell cycle (mitosis)

Answer 7

• Stage 1- Interphase: It is the longest stage of the cell cycle. The cells grow bigger, increase in mass and continue with cell activities. They also replicate sub-cellular structures and replicate the DNA, ready for cell division.

Question 8

State and explain the stage 2 of the cell cycle (mitosis)

Answer 8

Stage 2- Mitosis: In this process one set of chromosomes is pulled to each end of the dividing cell and the nucleus divides

Question 9

State and explain stage 3 of the cell cycle (mitosis)

Answer 9

Cytokinesis: The cytoplasm and cell membrane also divide, forming two seperate, identical daughter cells

Question 10

What is mitosis and why is it important?

Answer 10

Mitosis is how eukaryotic cells divide to create two identical cells. This is important as it means that all the cells within a multi-cellular organism carry the same genetic information. Furthermore, it produces cells for growth and development and for the replacement of damaged cells. They are further used in childhood and puberty and continues to be used for adults for continued growth/ replacement of hair follicles, skin, blood snd digestuve system.

Question 11

Name the 4 stages of the creation of a human

Answer 11

• Fertilisation (when the nucleus of the sperm and egg fuse) The fertilised egg is called a zygote
• Early stage embryo
• Late stage embryo
  Cell division (mitosis) and differentiation
• Fetus

Question 12

What is differentiation?

Answer 12

Differentiation is the name of the process by which cells become ‘specialised’ for specific jobs

Question 13

What is an embryonic stem cell and what do they do?

Answer 13

Embryonic stem cells are cells at the early stages of development of the embryo that have not yet undergone differntiation when they become specialised for different jobs. They can divide through mitosis.

Question 14

What is an adult stem cell?

Answer 14

An adult stem cell is a stem cell that remains in the body/ tissues of an adult. They can be found in areas such as: bone marrow, brain, eyes, blood, heart, liver, skin and muscle. Adult stem cells can differentiate into related cell types only.

Question 15

What are some potential risks of stem cell research?

Answer 15

There is a risk rhat adult stem cells might be infected with viruses and could transfer the infections to patients. If stem cells from an adult are used to treat an unreleated oerson, rhey may trugger and immune response. Stem cell research is also slow, diffucukt, expensive and very hard to control. It is also difficult to persuade embryonic stem cells to differentiate inti the needed type of cells.

Question 16

What are the ethical objections to stem cell research?

Answer 16

Some people question the use of a potential human being beung used a source of cell from an embryo, even to cure others, seeing it as abortive. Many religious beliefs also goes against any with the natural process of human reproduction and believe they are a human with a consiounce the moment the egg is fertilised.

Question 17

What happens at the apical maristem?

Answer 17

Apical Maristem cells is the area of cell division (mitosis) and produces undifferenciated cells. It also produces the root cap, which consists of cells that are removed as the meristem is pushed through the soil by cell division and elongation in more proximal cells. They are also responsible for the extension of the roots and shoots.

Question 18

What is the job of phloem cells?

Answer 18

Phloem cells: The cell walls between the cells break down to form sieve plates. These allow water to move freely up the tubes to where it is needed - transpiration stream

Question 19

What is the job of xylem cells?

Answer 19

Xylem cells: A chemical called lignin that builds up in spirals in the cell walls. The cells die and form long hollow tubes that allow water and mineral ions to move easily through them, from one end of the plant to the other. They also help support the stem- translocation

Question 20

What are the two types of cells found in the vascular cylindee within a plant?

Answer 20

Phloem and xylem cells