Topic 6, Part 2 - Inheritance, Variation and Evolution Flashcards
what is gamete fusion
when one sperm and one egg meet and they fuse together (fertilisation) to form the full number of chromsomes
what is asexual reproduction
there is only one parent so offspring is genetically identical. there is no fusion of gametes so its identical.
how does asexual reproduction happen
by mitosis, an ordinary cell makes a new one by dividing in two
how does meiosis work (5 steps)
1) duplicates genetic information forming two armed
chromsomes. both copies
2)first division, pairs line up in centre of cell
3)pairs pulled apart, each cell has only one copy of
chromosome
4)second division, chromosomes line up in centre and
pulled apart
5)you get 4 identical gemetes, each genetically different.
what happens when two gemetes have fused together (how an organism is made)
the resulting new cell divides by mitosis to make a copy of itself. repeats many times in embryo. then cells differentiate into cells and specialised cells into an organism
what do x and y chromosomes mean
22 pairs of chromosomes are matched pairs that control characteristics and the 23rd pair decides your sex
which one is a male and female chromosome
XY is male
XX is female
what chromosomes do eggs have
they all have x chromosomes
what chromosomes do spern have
there is a 50% chance of ether getting x or y chromosome in a sperm cell
what is cystic fibrosis
genetic disorder of cell membrane where body produces sticky mucus in air passage ways and in pancreas
what is cystic fibrosis caused by
it is caused by recessive allele (f)
what is a recessive allele
if people only have one copy of the allele wont have disorder. both parents need to be carriers for offspring to have
what is polydactyly
it is a genetic disorder where you have extra fingers or toes
what is polydactyly caused by
cause by dominant allele (D)
what is a dominant allele
can be inherited if only one parent carries it. the parent with it will also have it.
what does it mean to screen a embryo
you can screen an embryo to see if tehy have a genetic disorders then the parents can chose whether they want to keep the child or abort it.
what is vitro fertilastion (IVF)
it is where embryos are fertilised in a laboratory and implanted into mother womb
what is a mutation
where a gene mutates. rare and random change in an organisms dna
what can bacteria do to overcome antibiotics
they can evolve and become antibiotic-resistance.
how do bacteria become antibiotic-resistance
in bacteria, they have a random chance to develop mutations. this can lead to changes in the characteristics of the bacteria making antibiotics less effective
what is meiosis
it produces cell with half the normal number of chromsomes. only happens in reproduction organs
