B12 Flashcards
Genome
The entire set of genetic material in tan organism
Human genome uses
Allows scientists to identify genes in the genome that are linked to different types of disease, knowing these help us develop effective treatments for them
Can trace the migration of certain populations of people around the world. Different populations of people developed tiny differences in their genomes when they migrated away from Africa, which can be investigated using genomes.
Can make many different proteins from the same gene by using it in different ways , or by switching part of a gene on and off
Where do you inherit your mitochondrial DNA from?
Your mother, because it comes from the mitochondria in the egg
Disadvantages of human genome
Understanding it has taken years of work and billions of pounds
Where does meiosis occur in humans?
Only in the reproductive organs(ovaries in females and testes in males)
Process of meiosis
1) Before the cell begins to divide, it duplicates its genetic information, forming two armed chromosomes which then arrange themselves into pairs.
2) In the first division in meoisis the chromosome pairs line up in the centre of the cell.
3) The pairs are pulled apart so each new cell only has one copy of each chromosome.
4) In the second division, the chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart.
5) You get four gametes, each with only a single set of chromosomes in it. Each of the gametes is genetically different from the others, since chromosomes are shuffled up in meiosis and each gamete only gets half of them, at random.
What happens to the cell produced by gamete fusion?
1) After two gametes have fused during fertilisation, the resulting new cell divides by mitosis to make a copy of itself.
2) Mitosis repeats many times to produce lots of new cells in an embryo.
3) As the embryo develops, these cells start to differentiate into the different types of specialised cell that make up a whole organism.
Which pair of chromosomes decides sex?
The 23rd pair - labelled XY(male) or XX(female)
Which chromosome causes male characteristics?
The Y Chromosome
Which chromosome causes female characteristics?
The X Chromosome
What happens to the X and Y chromosomes when making sperm?
When making sperm, the X and Y chromosomes are drawn apart in the first division in meiosis. There’s a 50% chance each sperm cell gets an X-chromosome and a 50% chance it gets a Y-chromosome.
Characteristics controlled by a single gene
Mouse fur colour
Red-green colour blindness in humans
How many alleles of every gene in your body do you have?
You have two alleles of every gene in your body - one on each chromosome in a pair
Cystic fibrosis
A genetic disorder of the cell membranes. It results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas. Caused by a recessive allele
Polydactyly
A genetic disorder where a baby’s born with extra fingers or toes - but isn’t life-threatening. Is caused by a dominant allele.
