Biology B2

Question 1

What is a gene

Answer 1

a gene is a small packet of information that controls a characteristic or part of a characteristic. It is a section of a chromsome, which is made by DNA

Question 2

how many chromosomes do you have in the nucleus of your body cells

Answer 2

46 chromosomes, arranged in 23 pairs

Question 3

how do body cells divide

Answer 3

body cells divide in a series of stages called the cell cycle

Question 4

What are the steps of the cell cycle?

Answer 4

stage 1:
the longest stage of the cell cycle. the cells grow bigger, increase their mass and they replicate their DNA to form two copies of each chromosome ready for cell division . They also increase the numbers of subcellular structures

Stage 2:
mitosis - one set of chromosomes is pulled to either end of the dividing cell and the nucleus divides

Stage 3:
this is the stage during which the cytoplasm and the cell membranes also divide to form two identical daughter cells. (The cell membrane grows down the middle and then splits)

Question 5

why is mitotic cell division important?

Answer 5

it is important in the growth and repair and development of multicellular organisms

Question 6

what are chromosomes?

Answer 6

chromosomes carry the genes that contain the instructions for making both new cells and all the tissues and organs.

Question 7

what are stem cells

Answer 7

cells that are unspecialised

Question 8

how long does mitosis take place in plants?

Answer 8

in plants, mitosis takes place throughout their lives

Question 9

what is the difference between differentiation in plants and animals?

Answer 9

in animals, differentiation happens at an early stage in development but many types of plant cells have the ability to differentiate throughout life

Question 10

where are undifferentiated cells formed in plants?

Answer 10

active regions of the stems and roots , known as the meristems

Question 11

where can we source stem cells for us animals?

Answer 11

from embyros (embryonic stem cells) and bone marrow. there are also some embryonic stem cells in the umbilical cord of newborn babies

Question 12

what do an egg and sperm cell fuse to form

Answer 12

a zygote

Question 13

what is a zygote

Answer 13

a fused egg and sperm cell

Question 14

why might stem cells be useful

Answer 14

treatment with stem cells may be able to help conditions such as paralysis and diabetes.

Furthermore, stem cells from plant meristems can be used to produce plant clones quickly and economically to reduce extinction, for research, etc.
You could also make disease resistant plants!!

Question 15

what are some of the problems with embryonic stem cells/adult stem cells?

Answer 15

there are ethical concerns - some believe that it is a violation of human rights as there is no consent given, and the religious beliefs of others suggest that we shouldn’t interfere with the process of human reproduction

process in developing these therapies has been slow and expensive, hard to control.

since they grow and divide rapidly, there are also concerns with whether they may cause cancer

Also, the adult stem cells could contain viruses and transfer infections to patients or trigger immune response.

Question 16

what is therapeutic cloning?

Answer 16

an embryo is produced with the same genes as the patient so the stem cells produced are not rejected and may be used for medical treatment

Question 17

when using stem cells, they need to grow and divide. Name two things the cells may need

Answer 17

glucose and protein/amino acids

Question 18

give advantages of using stem cells to make organs/parts of the body instead of using a dead human donor

Answer 18

it will not be rejected
can be done immediately
no need to wait for a donor

Question 19

evaluate the use of stem cells from a patient’s own bone marrow instead of stem cells from an embryo

Answer 19

embryo advantages:
can create many of them in a lab
painless
can become any type of cell

embryo disadvantages:
ethical concerns
more research is needed

bone marrow cells advantages:
no ethical issues
treats SOME diseases
safe technique

bone marrow cells disadvantages:
can be painful
risk of infection
can only treat few diseases

Question 20

stem cells from human embryos are used to treat some diseases in humans. Explain why.

Answer 20

stem cells are unspecialised, and can differentiate into any type of cell, and can therefore cure lots of diseases. They are also able to divide/multiply