B2 Flashcards
What is a chromosome
Carries the genes
What is a gene
Small packet of information that controls a characteristic - a section of DNA
How many chromosomes and where are they stored
46 in nucleus - 23 pairs. In each paid, one strand is from father and one is from mother
Three sections of cell division in order
Interphase, mitosis, cytokinesis
Why is mitosis needed
For growth and development and to replace damaged/ worm out cells
Stage 1 of cell cycle
Grows bigger, replicates DNA, forms two copies of each chromosome, increases number of sub cellular structures
Stage 2 of cell cycle
Chromosomes line up in centre of cell and one strand is pulled each way, nucleus divides
Stage 3 of cell cycle
Cytoplasm and cell membrane divide to form two identical daughter cells
Products of cell division
Two identical daughter cells
What is differentiation
When human cells turn off some genes to do a particular role
Why do we need stem cells
A specialised cell can only divide by mitosis into the same type of cell. Some can’t divide at all though like blood and skin cells so we use adult stem cells to replace them
What is a stem cell
Undifferentiated cell that can give rise to many different types of cells
How long can plant cells differentiate for
Most of their lives
How do meristems work
Undifferentiated cells are formed at active regions of the stem and roots known as meristems. Mitosis take place here almost continuously. The cells then elongate before differentiating
When do plant cells differentiate
When they are at their final location
Can plant cells re differentiate
Yes, they can move around the plant and change function
Name parts of meristem
Zone of cell division, zone of elongation, zone of differentiation
Cloning plants
Can be cloned from a tiny piece of leaf tissue, cell will unspecialise and then undergo mitosis and form different tissues, the end plant will be identical to the first plant
What do egg and sperm cell form
Zygote
Embryonic stem cells
Inner cells of an embryo which can differentiate into all of the specialised cells in your body
Uses of stem cells in science
Embryonic injected into spinal cord to cure paralysis, embryonic stem cells transplanted into eyes to cure blindness, stem cells to produce cells that produce insulin to help diabetes
Adult stem cells
Undifferentiated cell that can give rise to many more cells of similar types
Why is cloning plants important
Gives a way to produce large numbers of rare plants safely and reliably - stop going extinct and for research
Issues with using embryonic stem cells
Many come from aborted embryos or spare from fertility treatments, slow, difficult, expensive, and hard to control, divide rapidly so may cause cancer,
