Topic 11 DNA Flashcards
what is the genome?
entire DNA of an organism
What is a gene?
section of a molecule of DNA that codes for a specific protein
where is DNA located?
in the chromosomes in nucleus of cell
what pair of chromosomes determines the gender of the baby?
23rd
XX= female
XY= male
what is the structure of DNA?
two strands coiled to form a double helix
wraps around histones
each dna molecule is coiled into a chromosome
2 copies of each chromosome (23 pairs, 46 in total, they are homologous inherit one from bio mother and one from bio father)
what is an allele?
different forms of same gene
what does dominant mean?
allele that is always expressed whether partnered by a recessive allele or by itself
what is phenotype
visible characteristics of an organism which occur as a result of its genes
what is a genotype
the alleles that an organism has for a partucilar characteristic
the uprights of the ladder, are two strands of nucleotides, containing:
phosphate group, sugar molecule (deoxyribosesugar) and nitrogeous base
what base does adenine pair with?
thymine
what base does cytosine always pair with?
guanine
how do bases pair?
complementary base pairing
describe the stages of protein synthesis (6 marks)
- DNA unwinds, exposing nucleotide bases
- rna nucleotide bases complentary base pair with one of exposed DNA strands (the template strand) to form mRNA. this is transcription.
- the mRNA, which is single stranded and contains uracil instead of thymine, leaves nucleus and enters cytoplasm.
- mRNA binds to a ribosome
- ribosome reads first three bases (the codon) and complementary base pairs it to an anticodon on tRNA
- TRNA has an amino acid attached. ribosome continues reading along the mRNA codons, and amino acids on tRNA are bonded together(via a peptide bond)
- tRNA is released, having left the amino acid behind to form a peptide chain (which eventually forms a protein) this is translation
