What are chromosomes made up of?
Large molecules of DNA which has a double helix structure.
Where are chromosomes found?
In the nucleus of cells.
What is a gene?
A section of DNA.
How many chromosomes are there in a body cell?
46 or 23 pairs.
How many chromosomes in a gamete?
23.
What does the fusion of gametes produce?
A zygote which has 46 chromosomes.
How many of the pairs of chromosomes in the human body are sex chromosomes?
1.
What is the female chromosome called?
X chromosomes.
What is the male chromosome called?
Y chromosome.
What is the sex of a child decided by?
The sperm. If it’s X-carrying or Y-carrying (X=girl,Y=boy).
What is mitosis?
The division of body cells to produce new cells.
What is mitosis used for?
Growth and repair, and asexual reproduction.
What happens to the chromosomes in mitosis?
They make a copy so each cell has the same genetic information as the parent.
What is the order of what happens in mitosis?
- Parent cell with 2 pairs of chromosomes.
- Each chromosome replicates itself.
- Copies pulled apart as cell divides.
- Two ‘daughter’ cells with same genetic information.
Where does meiosis occur?
In the testes and ovaries.
What is the order of what happens in meiosis?
- Cell with two pairs of chromosomes.
- Each chromosome replicates itself.
- Copies pulled apart and cell divides.
- Copies separate again as cell divides a second time.
- Four gametes formed each with half the number of chromosomes of parent cell.
What happens during fertilisation?
One chromosome comes from each parent and a single body cell with new pairs of chromosomes are formed. This cell divides repeatedly to form a new individual.
What are alleles?
Different forms of genes.
What are the two types of alleles?
Dominant or recessive.
What will happen if the are two dominant alleles?
The dominant allele will control the characteristic.
What happens if there is a dominant and a recessive allele?
The dominant allele will control the characteristic.
What happens if there are two recessive alleles?
The recessive allele will control the characteristic.
What is monohybrid inheritance?
When a characteristic is controlled by only one pair of alleles. You can do genetic crosses to see how people will inherit.
What is homozygous?
An individual with two of the same alleles.
What is heterozygous?
An individual with two different alleles.
What is the phenotype?
The characteristic that ‘shows’ itself. Eg. Brown eyes.
What is the genotype?
The alleles present. Eg. One brown-eye allele and one blue-eye allele.
What is differentiation?
When cells develop a specialised structure to carry out a specific function.
How do animal cells and plant cells differentiate?
Animal cells-At an early stage so quickly become muscle, nerves, etc.
Plant cells-Differentiate throughout life.
What are stem cells?
Cells that have yet to differentiate.
Where can human stem cells be found?
In human embryos and adult bone marrow.
What is DNA?
Deoxyribonucleic acid.
How do genes code for a particular characteristic?
By providing a code for a combination of amino acids, which make up a protein. Different combinations make different proteins.
What is polydactyly and what type of allele causes it?
It is having extra finger or toes and is caused by a dominant allele.
What is cystic fibrosis and what type of allele causes it?
It is a disorder of cell membranes and is caused by a recessive allele.
Name some pros and cons of stem cell research.
Pros:
*embryos only a few days old, many see them as only microscopic balls of cells
*embryos provide most useful stem cells as adult ones are more limited
*can act as repair kit fir damaged tissue
*could treat many diseases/conditions in the future
Cons:
*many believe it morally wrong
*embryos cultured using nutrients from animal sources, could carry diseases that could be passed to humans
*people who receive cell transplants from stem cell therapy could be infected with viruses
*stem cells may turn cancerous
Name some pros and cons of embryo screening.
Pros:
*doctors can see if a child will have increased risk of getting an illness/disease
*prepares parents for possibility of a child developing a disorder, disease or illness
*carriers of genetic disorders can decide wether or not to have children
Cons:
*could result in abortions if genetic makeup ‘faulty’
*parents may want to choose genetic makeup of child
*potential to be used to decide who can/cannot have children
*could upset people to learn they carry a genetic disorder, disease or illness