DNA,RNA and Protein Synthesis-Topic 4A Flashcards
What are chromosomes?
Thread like structures each made up of one long molecule of DNA
Where are chromosomes found?
In the nucleus
How do Prokaryotes differ from Eukaryotes when storing DNA? (2 differences + 1 similarity)
Shorter
Circular
However both carry DNA as chromosomes
What forms the primary structure of a protein?
The sequence of amino acids in a polypeptide
What determines the order of amino acids in a polypeptide?
The order of bases in a gene.
What is a gene?
A sequence of DNA bases that codes for either a polypeptide or functional RNA
Each amino acid is coded for by …….. …….
A sequence of three bases called a triplet.
What is the first stage of protein synthesis?
DNA is copied into messenger RNA
What is functional RNA?
RNA molecules (other than mRNA) which perform special tasks In protein synthesis e.g. tRNA
What is a cell’s genome?
The complete set of genes in the cell.
What is a cell’s proteome?
The full range of proteins that the cell is able to produce.
The genetic code is degenerate. What does this mean?
(some) amino acids have more than one coding triplet
The genetic code is Universal. What does this mean?
The same codons code for the same amino acids in all organisms.
What is a benefit of the genetic code being no-overlapping?
Each base in the sequence is part of only one codon.
What are introns?
Sections of non coding DNA within a gene.
What are exons?
Coding sections of DNA within a gene.
Why are introns removed during protein synthesis?
So they don’t affect the amino acid order.
What are Non-coding repeats?
DNA sequences that repeat over and over but don’t code for amino acids either.
Genes can exist in different forms called…
Alleles.
What do alleles do?
Code for slightly different versions of the same polypeptide. (this is because the order of bases in each allele is slightly different)
Humans have …… pairs of chromosomes
23
Pairs of matching chromosomes are called….
homologous pairs
In a homologous pair both chromosomes are the same size and have the same ……. but may have different …….
In a homologous pair both chromosomes are the same size and have the same genes but may have different alleles.
Alleles coding for the same characteristic will be found at the same ………. …… (…….) on each chromosome in a homologous pair.
Alleles coding for the same characteristic will be found at the same fixed position (locus) on each chromosome in a homologous pair
Mitochondria and chloroplasts have similar DNA to …….. ……
Mitochondria and chloroplasts have similar DNA to prokaryotic DNA.
What is a DNA triplet?
3 bases in a gene coding each amino acid.
Name the two types of RNA
mRNA and tRNA
What stage is mRNA made?
During transcription
What is the role of mRNA?
Carries the genetic code from the DNA to the ribosomes where it’s used to make a protein during translation.
What is mRNA?
A single polynucleotide strand
What are codons?
3 adjacent bases, in mRNA
Name the first stage of protein synthesis?
Transcription
Name the second stage of protein synthesis
Translation
tRNA is involved in…….
Translation
What does tRNA do?
Carries the amino acids that are used to make proteins , to the ribosomes
What is tRNA?
Single nucleotide strand folded into a clover shape
How is a tRNA molecule held in it’s shape?
Hydrogen bonds between specific base pairs hold the molecule in this shape.
What is an anticodon?
A specific sequence of 3 bases on tRNA.
They also have an amino acid binding site on the other end.
Why are DNA strands produced in opposite directions?
(use enzyme action knowledge) [4]
Antiparallel strands
The shapes of nucleotides are different
Enzymes have an active site which is a specific shape.
Only substrates with a complementary shape can bind with the active site of enzyme.
Why can nucleotides only be added in 5’-3’ direction?
DNA Polymerase
is specific
so only complementary on the 5’ end of the strand.
shapes of 5’ end & 3’ end are different so polymerase cannot work on 3’ end.
Describe how the DNA in a eukaryotic cell is arranged so that it can fit into the nucleus?
DNA wound around histone proteins
Tightly coiled into compact chromosomes
Describe the structure of tRNA
Single polynucleotide strand folded into a clover shape. Hydrogen bonds between the specific base pairs hold the molecule in this shape.
Describe the structure of mRNA
Single polynucleotide strand. 3 adjacent bases on strand = codon
mRNA strands contains introns and exons are called….
pre-mRNA
What is splicing?
Introns are removed and the exons joined together forming mRNA strands
Where does splicing occur?
The nucleus
Why does splicing not happen in prokaryotes?
No need for splicing because there aren’t any introns in prokaryotic DNA.
