DNA, genes + chromosomes/ proteinsynthesis/ mutations Flashcards
describe DNA in prokaryotes
DNA molecules are short and circular
found in circular plasmids and circular chromosomes
don’t have nuclei, mitochondria and chloroplasts
describe DNA in eukaryotes
DNA molecules are long, linear and found in the nucleus. DNA molecules are associated with proteins (histones)
DNA has a negative charge, histones have a positive charge= DNA winds around the histone and creates an ionic bond
DNA and histone condenses into a chromosome
how many chromosomes are found in one cell
46 (23 pairs)
describe DNA in mitochondria and chloroplasts
DNA is short and circular like plasmids found in eukaryotes
chloroplasts and mitochondria have circular DNA have origins of bacteria
describe the differences between the structure and organisation of DNA in prokaryotes and eukaryotes
prokaryotes have circular and short DNA whereas eukaryotes have long and linear DNA
prokaryote DNA is found in circular chromosomes and circular plasma whereas eukaryotes DNA found in the nucleus
DNA in prokaryotes is associated with histones whereas DNA and prokaryote is not
describe the similarities between the structure and organisation of nuclear DNA in eukaryotes and prokaryotes
both:
contain phosphodiester bonds
made up of DNA nucleotides
have negatively charged DNA
have double stranded DNA
definition of gene
a base sequence of DNA that codes for the amino acid sequence of a polypeptide or a functional RNA
definition of locus
a fixed position of a chromosome where a gene is found
definition of allele
different version of the same gene
definition of genome
the entire genetic material in an organism/ cell
definition of introns
non coding regions of a gene
definition of exons
part of a gene that contain instructions for making many proteins
features of chromosomes
exist in homologous pairs and carry the same genes as eachother
what does. a gene contain
a sequence of DNA bases which determine a specific amino acid sequence
how are bases read in genetic code
triplets which correspond to one amino acid
how do you read a genetic code table
look down side for the first letter in the triplet, then look along the top for the second letter in the triplet and then find the triplet with the correct third letter
what are the 3 properties of genetic code
universal
non- overlapping
degenerate
what does universal mean
genetic code is the same in every living organism
what does non- overlapping mean
each base / triplet is read only once, assigns an amino acid and moves on
what does degenerate mean
multiple triplets code for the same amino acid
why is the feature of genetic code being degenerate helpful
if there is a mutation that he amino acids would usually stay the same and protein isn’t affected
how can a mutation be harmful to the primary structure of a protein
changes the R group of amino acids so the structure can change and for different bonds
charges of amino acids may differ and shape of protein will change
what does TAG mean in genetic coding
stop converting code into amino acids
what is the name for non coding sections of a gene
introns
what is the enzyme that breaks hydrogen bonds to unwind DNA double helix during transcription
RNA polymerase
what is the process of transcription
- hydrogen bonds are broken, unwinding DNA using RNA polymerase and exposes DNA bases
- free floating RNA nucleotides line up against adjacent complimentary base pairs
- RNA polymerase creates phosphodiester bonds between adjacent RNA nucleotides (making pre mRNA)
- eukaryotes remove introns from pre-mRNA to make mature mRNA (through splicing)
how does DNA move to ribosomes
a copy of each gene is sent there as DNA is too large (mRNA)
what happens during transcription
a base sequence in a gene is used to create a short single stranded piece of RNA (mRNA)
what are the differences in structure between DNA and mRNA
DNA- long strand mRNA- short strand
DNA- double stranded mRNA- single stranded
DNA- deoxyribose mRNA- ribose
DNA- thymine mRNA- uracil
DNA- hydrogen bonds mRNA- no hydrogen bonds
how many tRNA molecules are in each cell
64
what is the role of tRNA
transport amino acids to ribosomes
what is the structure of tRNA
single stranded
clover leaf shape
amino acid binding site
anticodon
what is the anticodon complimentary to
codons on mRNA
what are the similarities between mRNA and tRNA
both are:
single stranded
temporary
same bases
ribose sugar
phosphodiester bonds
found in ribosome
what are the differences between mRNA and tRNA
m- linear t- clover leaf
m- codons t- anticodons
m- nucleus t- ribosomes
what is the process of translation
- mRNA binds to ribosome
- 2 tRNAs arrive at ribosome carrying specific amino acids, hydrogen bonds form between codons and complimentary anticodons
- a peptide bond forms between amino acid in a condensation reaction, using ATP
- 1 tRNA leaves, ribosome moves to next codon
- the next tRNA binds to codon, another peptide bond forms between amino acids
- steps repeat until tRNA reaches a stop codon, a long sequence of amino acids form and detaches to form a polypeptide
what is a gene mutation
a random change in t he base sequence of dna in a chromosome that creates a new allele
what occurs when there is a substitution mutation
one or more bases is swapped for another- causing a change in the amino acid sequence
what are the possible impacts of a substitution mutation
different amino acid sequence
early stop triplet
which impact of a substitution mutation is the most damaging
early stop code as it can cause the protein to stop being made
how can a mutation affect an enzyme
changes R group, changed primary structure (base sequence of DNA), changes tertiary structure as charged of amino acids can change (no ionic bonds) and polypeptide chain can’t fold into a 3d shape, the active site changes shape and won’t be complimentary meaning enzyme substrate complexes can form
What is an addition mutation?
insertion of a base into the base sequence
What is a deletion mutation?
removal of a base from base sequence causing a frame shift is all triplets afterwards are changed
