genetics Flashcards
What contains the DNA?
chromosomes in nucleus
What is a gene?
A short section of DNA that codes for protein
How many pairs of chromosomes do you have in cells?
23 pairs from both your mum & dad
46 in total.
(sex cells are the exception, they have half so total 23)
describe the first stage of mitosis
Interphase : chromosomes are copied
describe the second phase of mitosis.
Prophase : spindle fibres form in the cell and nuclear membrane starts to disappear
describe the third stage of mitosis
Metaphase: chromosomes line up in the middle
describe the fourth stage of mitosis
Anaphase : chromosomes pulled apart by spindles
describe the 5th stage of mitosis
Telophase: nuclei start to reform
describe the last stage of mitosis
cytokinesis : a cell membrane divides the cells
Describe the structure of DNA
DNA is a polymer made of sub units called nucleotides, with a double helix made of 2 strands of complimentary base pairs. The base pairs are A+T, C+G. These are joined by hydrogen bonds and down the double helix is a sugar phosphate backbone.
what does homozygous mean?
when both alleles for a gene are the same
what does heterozygous mean?
when it’s the alleles for a gene are different
what’s a genotype?
all the alleles in an organism
what’s a phenotype?
the observable physical characteristic
what’s an allele?
A version of a gene
