B2.7 Cell Division Flashcards
How many chromosomes do humans have?
46 (diploid)
Define homologues
Specific number of chromosomes grouped in identical pairs
Define allele
A different form of the same gene
If an allele is recessive, how many are needed?
2
If an allele is dominant, how many are needed?
1
Define heterozygous
Different alleles
Define homozygous
Identical alleles
Define genotype
The genes that we have eg. Yy
Define phenotype
The characteristic shown eg. colour of eyes
What are the differences between mitosis and meiosis?
Mitosis divides once and produces 2 daughter cells
Meiosis divides twice and produces 4 daughter cells
Where are stem cells found?
In early human embryos/ in tissues such as the brain, bone marrow, blood, blood vessels, skeletal muscles, skin and liver
What are the 2 types of stem cell?
Adult and embryonic
What are adult stem cells?
These are unspecialised cells that can develop into many (but not all) types of cells
What are embryonic stem cells?
These are unspecialised cells that can develop into any type of cell
Give an example of how stem cells have the potential to treat illness
Insulin-producing cells are made for patients that suffer from diabetes because they lose the function of their insulin-producing cells within the pancreas. Therefore, the stem cells produce insulin.
What is the controversy regarding stem cells?
The argument for using embryonic stem cells are that the embryos used in research are normally unwanted ones from fertility clinics and that many people will be free from suffering and can be cured of diseases.
The argument against is that it’s immoral to destroy human life.
Define gene
A gene is a section of DNA that codes for a specific protein
Define chromosomes
They are long threads of DNA each made up of many genes that are found in the cell’s nucleus
Define DNA
DNA molecules carry the genetic code that determines the characteristics of a living organism
What are the advantages and disadvantages of genetic screening?
Advantages are that the parents can decide whether to keep or abort the baby and reducing the number of people living with cystic fibrosis reduces health care costs over time.
Disadvantages are that it puts the embryo and mother at risk as well as being very expensive!
Define multicellular
An organism or part of one consisting of many cells
What are gametes?
Sperm and egg that form sex cells
What is the shape of a DNA molecule?
A double helix
What is cystic fibrosis a disorder of?
Cell membranes
What is meant by a ‘carrier’ of a genetic disease?
A carrier is an organism that has inherited a recessive allele for a genetic trait
What are the features of polydactyl?
When an embryo is born with extra fingers or toes
Why is it easier to clone plants than animals?
Most plant cells retain the ability to differentiate throughout life whereas most animal cells become specialised during formation of the embryo
