DNA genes and chromsomes Flashcards
Difference between EUK AND PROK DNA
Eukaryotic is linear, long, wound up around histones, coiled up tightly but prokaryotic is circular, shorter and doesn’t associate with histone proteins and condenses to fit in cell by supercoiling
What is a gene
A sequence of DNA bases that code for a polypeptide
What do genes that don’t code for a polypeptide code for
Functional RNA
What is a cells genome
The complete set of genes in the cell
What are introns
Sections of a gene that don’t code for amino acids
What are exons
Sections of a gene that do code for amino acids
Does Prok dna have introns
No
What is an allele
An alternative form of a gene
What are homologous pairs
Pairs of matching chromosomes
Difference between MRNA AND TRNA
Mrna is made in transcription but TRNA is involved in translation.
MRNA carries the genetic code from DNA to teu domes which is used to make a protein during translation but TRNA Carries the amino acids to the ribosomes
MRNA and TRNA are single polynucleotide strands but TRNA is a clover shape
In MRNA there are triplets but in TRNA there are anti codons
What is transcription
It is when a MRNA copy of a gene is made from DNA
RNA polymerase attaches to DNA double helix at the start of a gene
H bonds between DNA strands break which exposes some bases
One of the strands is used as a template for MRNA copy
RNA polymerase lines up free RNA nucleotides next to the exposed bases and they connect through base pairing
Joined togther by DNA polymerase
The RNA polymerase moves along the DNA which separates the strands and assembles MRNA
H bonds re form
When RNA polymerase reaches a specific sequence called a stop signal MRNA production stops
MRNA moves out the nucleus and attached to a ribosomes in the cytoplasm
What is translation
Amino acids are joined together to form a polypeptide
MRNA attaches to a ribosome
TRNA carries an amino acid to the ribosome by the help of ATP which provides energy for the TRNA and amino acids bond to form
A TRNA molecule has an anticodon that is complementary to the first codon on MRNA which join through base pairing
This happens again for a second TRNA molecule
Then the TRNA molecule moves away and leaves the amino acids behind
The third TRNA molecule binds on the next MRNA codon and it’s amino acid hinds to the first two and the second TRNA molecule moves away
This continues untill a stop single on MRNA
The polypeptide chain moves away from the ribosome
What happens to introns and exons in EUK and PROK
They are both copied into MRNA during trancription. Then splicing occurs introns removed and exons joined together
In prok the MRNA is produced from DNA - no splicing - no introns
