DNA,RNA and protein synthesis A Flashcards
what is the difference between the DNA stored in eukaryotes vs. prokaryotes
-Eukaryotic DNA= long,linear,associated with proteins called histones, tightly coiled into chromosomes
-Prokaryotic DNA= short, circular, not associated with histones
name the protein associated with DNA in a chromosome
histone
compare and contrast DNA in eukaryotic cells with DNA in prokaryotic cells
COMPARISONS
-nucleotide structure is identical
-nucleotides joined by phosphodiester bond
CONTRASTS
-eukaryotic DNA is longer
-eukaryotic DNA is linear and prokaryotic is circular
-eukaryotic DNA is associated with histones
mitochondria and chloroplasts also contain ……… DNA like prokaryotic cells
circular
what is a gene
section of DNA on a chromosome coding for one or more polypeptides
What is the nature of the genetic code
-triplet code= sequence of three bases codes for a specific amino acid
-degenerate= more than one triplet codes for a single amino acid
-universal= same triplets code for the same amino acids in all living organisms
-non-overlapping= each triplet is read in sequence and bases are not shared between triplets
what is an exon
exons are sequences of DNA within a gene that code for amino acids
what are introns
introns are DNA sequences within a gene that don’t code for amino acids
what are non-coding base sequences
-DNA that does not code for sequences of amino acids
-found between genes and at the end of chromosomes
what are non coding repeats
DNA sequences found outside of genes that repeat over and over
name two types of non-coding DNA
introns and repeats
what name is given to a sequence of three DNA bases that codes for an amino acid
a triplet
what is a genome
complete set of genes in a cell
what is a proteome
the full range of different proteins that a cell is able to produce at a given time
what are alleles
different version of the same gene
what is a homologous pair of chromosomes
same size chromosomes with same genes, but different
alleles
describe how a gene is a code for the production of a polypeptide
-because base/nucleotide sequence
-in a triplet
-determines order/sequence of amino acid sequence
describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule
-condensation reaction
-between phosphate and deoxyribose
-catalysed by DNA polymerase
not all mutations in nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why
-triplets code for same amino acid
-occurs in introns/ non-coding sequence
name the type of bond between complementary base pairs
hydrogen
name the type of bond between adjacent nucleotides in a DNA strand
phosphodiester
what does the m in mRNA stand for
messenger
what is an mRNA codon
an mRNA codon is a sequence of three mRNA bases that codes for amino acid
what does t in tRNA stand for
transfer
what are the differences between mRNA and tRNA
mRNA
-single helix/straight
-longer
-contains no hydrogen bonds
tRNA
-folded into clover shape
-shorter
-contains hydrogen bonds
what are the 2 stages of protein synthesis
1.transcription
2.translation
what is transcription
-eukaryotes= transcribing DNA to pre-mRNA in the nucleus
-prokaryotes=transcribing DNA to mRNA in cytoplasm
what is splicing
-happens in eukaryotes only as prokaryotes do not have introns
-introns are removed from pre-mRNA to form a strand of mRNA containing exons
describe how mRNA is formed by transcription in eukaryotes
-hydrogen bonds between DNA bases break
-only one DNA strand acts as a template
-free RNA nucleotides align by complementary base pairing
-uracil is used in place of thymine
-RNA polymerase joins nucleotides
-by phosphodiester bonds
- pre-mRNA is spliced to form mRNA
describe how mRNA is produced from an exposed template strand of DNA
-free RNA nucleotides form complementary base pairing
-phosphodiester bonds form
-by action of RNA polymerase
in eukaryotic cells, the base sequence of mRNA might be different from the sequence of the pre-mRNA. explain why
-introns in pre-mRNA
-removal of sections of pre-mRNA/ splicing
describe the role of DNA helicase in eukaryotic transcription
-breaks hydrogen bonds between the two DNA strands in a gene
-separates strands and allows DNA double helix to uncoil
-allowing one strand to be used as a template
-to produce complementary mRNA
what is translation
-translating mRNA into a polypeptide
-happens at the ribosomes
describe how a polypeptide is formed by translation of mRNA
-mRNA attaches to ribosomes
-tRNA anticodons bind to complementary mRNA codons
-tRNA brings a specific amino acid
-amino acids join by peptide bond
-amino acids join with the use of ATP
-tRNA released
-the ribosome moves along the mRNA to form the polypeptide
describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation
-tRNA brings specific amino acid to ribosome
-anticodon on tRNA binds to codon on mRNA
-amino acids join by condensation reaction using ATP
what is the role of ATP in translation
● Hydrolysis of ATP to ADP + Pi releases energy
● So amino acids join to tRNAs and peptide bonds form between amino acids
what is the role of tRNA in translation
● Attaches to / transports a specific amino acid, in relation to its anticodon
● tRNA anticodon complementary base pairs to mRNA codon, forming hydrogen bonds
● 2 tRNAs bring amino acids together so peptide bond can form
what are anticodons and where are they found
-sequences of three bases found at the end of tRNA molecules
-bind to complementary codons in mRNA
