Biology PAPER2 Inheritance, variation, evolution Flashcards
what is dna
a chemical that genetic material in a cell is made up of
a dna molecule is made up of two stands of DNA coiled together they make a…
double helix
where is the dna found
nucleus
dna is found in really long structures called…
chromosomes
what is a gene
a small section of dna found in a chromosome
what is a genome
fancy term for all genetic material in an organism
what is sexual reproduction
genes from 2 humans (organisms) are mixed
mother and father produce gametes (sex cells) called the…
egg and sperm
mother and fathers gametes (sex cells -sperm and egg) are produced by…
meiosis
each gamete (sex cell) contains…
half the number of a normal cell
when the egg and sperm fuse together this forms a cell with a full number of chromosomes containing…
half from the father and half from the mother
what other type of reproduction happens by meiosis
asexual reproduction
sperm + egg =
fertilised egg (offspring)
how does asexual reproduction work
one parent cell divides into two
what doesn’t happen in asexual reproduction that happens in sexual reproduction
no fusion of gametes
no mixing of genes
to make gametes cells have to divide by…
meiosis
meiosis only happens in the…
reproductive organs
which are the two reproductive organs
ovaries and testes.
how does meiosis happen
1- half of chromosomes come from father and the other half from mother
2- DNA in the parent cell is copied and makes an X-shapoed chromosome
3- the cell divides, each new cell gets half the chromosome
4- each cell divides again, X-shaped chromosomes are pulled apart, you end up with 4 daughter cells -gametes
how many pairs of chromosomes are there in a human body cell
23
females have two..
X chromosomes
what is a punnet square
a genetic diagram
each sperm either has an..
X or Y chromosome
Each egg either has a..
XX
What do genes control
Different characteristics
genes exist in different versions called..
alleles
What is the capital Letter and small letter in an allele called
Dominant or recessive
For an organism to show recessive characteristics both alleles must be..
Recessive
For an organism to show dominant characteristics at least one allele has to be..
Dominant
