B2 - Cell Division Flashcards
What do the nuclei of body cells contain?
23 pairs of chromosomes
What are body cells?
All of our cells other than our gametes (sex cells)
What are chromosomes?
Strands of DNA that have been passed from the mother and father
Why do chromosomes match up into pairs?
They have the same sets of genes
What are genes?
Sections of chromosomes that carry instructions to make proteins
What happens in mitosis?
The pairs of chromosomes double up (replicate)
The cell divides into 2 new daughter cells
What are daughter cells?
The two cells that are identical to each other and to the original parent cell before the mitosis has taken place
What are diploid cells?
Cells that have 23 pairs of chromosomes
What is a zygote?
Fertilised egg
What does meiosis produce?
Gametes (sex cells)
How does meiosis work?
It doubles up the pairs of chromosomes
The cell divides into 2 identical cells with 23 pairs of chromosomes
The cells divide again to form 4 different cells with 23 single chromosomes each
What are haploid cells?
Cells with 23 single chromosomes
What type of cells is haploid
Gametes (sex cells)
All body cells are diploid
What is a stem cell?
A cell that has the ability to become a different type of cell
What are embryonic stem cells?
Cells in an embryo that can become any type of cell because they are unspecialised
What are adult stem cells?
Unspecialised cells that can become multiple types of cell but not any type
What is the main place in the body where adult stem cells be found?
Bone marrow
How does asexual reproduction work?
Using mitosis
What 2 things does mitosis do?
Replaces lost and damaged cells
Grows muscles and bones
What is DNA and where is it found?
A type of acid that contains all of the instructions to put an organism together and make it work
In nucleus of cells in the chromosomes
What is a gene?
A section of DNA that contains all of the instructions to make a specific protein
Describe how cells make proteins
They string together 20 amino acids in a particular order to make a specific protein
What else does DNA do?
Because it tells the cell which proteins to make, that means that it determines what type of cell it is
In what 2 ways is DNA fingerprinting used?
Forensic science
Paternity testing
What are the 3 main uses for stem cells?
Adult stem cells can be used to cure disease (people with blood diseases can be treated by bone marrow transplants which contains stem cells that can turn into new blood cells)
Embryonic stem cells can be used to replace faulty cells in people because of how changeable embryonic stem cells are
To find out more about how cells differentiate and how people develop
What are the 2 arguments against stem cell research?
Embryos shouldn’t be used for research because each one is a potential life
Scientists should concentrate on trying to find other sources of stem cells so that people can be helped without using embryos
What are the 2 arguments for stem cell research?
People think that curing patients that already exist is more important than the rights of embryos
The embryos used in research were usually unwanted ones and would be destroyed anyway
What controls if you are male or female?
If your 23rd pair of chromosome is XX you are female
XY is male
Why are the arrangements XX and XY?
All egg cells come from women so in meiosis, the XX chromosome of the woman is split into 2 X chromosomes meaning the egg is always X
Men have XY so the sperm cell can either get an X chromosome or a Y chromosome at a 50% chance
Describe the Punnett square
You make a table and put the alleles / chromosomes of person 1 as the rows and person 2 as the columns
For each cell of the table, you put the row and column of that row to make a chromosome / allele
Example: If the rows were X and Y (a man) and the columns were X and X, the table would go from left to right as XX, XX, XY, XY
Describe the genetic diagram
You put the 2 original pairs of chromosomes / alleles at the top in circles
You draw lines down from these to the 4 individual chromosomes / alleles
You draw lines from the individual constituents to make all the possible combinations at the bottom
