Biology: B3 - DNA, Protein Synthesis

what is the structure of DNA

• double helix

• 2 base pairs, 4 bases

• sugar phosphate back bone

• weak hydrogen bonds

• nucleotide

what is variation

differences in the characteristic of an organism

what is continuous variation

data that can be any value in any range

what is discontinuous variation

data that can only be a limited set of values

what is genetic variation

differences in organisms because of what they inherit from their parents

what is environmental variation

differences caused by the environment e.g. heat, light

what is sexual reproduction

• having 2 parents

• offspring can adapt and evolve

• quite slow

• energy and time is used up

what is asexual reproduction

• having 1 parent

• genetically identical

• fast

• all bad genetic information is passed on

what is meiosis

• not genetically identical cells

• haploid cells (23 chromosomes)

• sexual reproduction

• 2 divisions

why is salt needed

it makes the DNA stick together

why is detergent needed

it breaks down the cell membrane

why is ice cold ethanol needed

creates a precipitate

what is a precipitate

a solid withing the solution e.g. strands of DNA

what are proteins made of

• amino acids

• 1 amino acid = 1 triplet/codon

what is protein synthesis

using amino acids to make proteins

what is the copying process called

transcription

what are the steps of protein synthesis - transcription

• in the nucleus the DNA unzips

• the enzyme (polymerase) attaches and unzips at the start codon, runs along the exposed strand

• the gene is copied and T is replaced with a U

• MRNA

what happens in protein synthesis - translation

• MRNA leaves through a nuclear pore

• MRNA attaches to a ribosome

• this is called TRNA

• TRNA bring the correct amino acid (anti codon) fits to the codon of MRNA and leaves amino acid

• amino acids join together, this is called a peptide bond

• protein folds up

what is a poly peptide

a protein

what is an allele

a version of a gene

what does homozygous mean

2 of the same alleles

what does heterozygous mean

2 different alleles

what does dominant mean

only 1 chromosome with a certain allele is needed for this characteristic

what does recessive mean

you need both alleles to have this characteristic

colourblindness

• recessive

• sex-linked

• carried on the X chromosome