DNA and proteins Flashcards
What is the function of DNA?
Stores and transmits genetic information
Describe the structure of DNA molecules
It is double-stranded helix
Describe the DNA within eukaryotes
The DNA is bound to proteins (histones), in linear chromosomes found in the nucleus
(also circular DNA found in mitochondrion and chloroplast)
Describe DNA is prokaryotes
Unbound and circular. Found in the cytoplasm.
Describe nucleotide composition and bonding
Deoxyribose sugar molecule, phosphate, a nucleotide base
Weak hydrogen bonds between the strands
strong bonds in the backbone
What are the nucleotide (DNA) parings
and what is the purpose of complementary base pairing
A, T, G and C
important for DNA replication. weak bonds important for replication
Describe the importance of DNA replication
DNA must be replicated before mitosis so each daughter cell can be identical to each other and to the parent.
Describe the steps of semi conservative DNA replication.
1.The enzyme helicase unwinds the strands and breaks the weak hydrogen bonds between the strands
2.Free nucleotides bind themselves to the exposed bases through complementary base pairing. The enzyme polymerase assists with binding the bases and the sugar/phosphate backbone of the new strand.
3.The strand elongates until it is complete. The end result is two new molecules of DNA which are identical to the original. They consist of one newly synthesized strand and one existing strand.
Why is it called semi-conservative replication
The end result is two new molecules of DNA which consist of one newly synthesized strand and one existing strand.
Where in the cell cyle does DNA replication occur?
S phase (synthesis phase), which is before mitosis.
What is the function of a gene?
To code for a polypeptide.
- Distinguish between cons and introns as coding and non-coding segments of DNA found in genes in eukaryotes
Introns are non coding section of DNA
Exons are coding sections of DNA
Describe how both exons and introns are transcribed but only the information contained in exons is translated to form a polypeptide in eukaryotes.
Their both transcribed intro RNA intros are removed through intro splicing. so that only the exons make up the mRNA strand.
What is the difference between coding and a template strand?
coding strand and mRNA molecules are both complementary to the template strand (template strand is where the mRNA molecule will bind).
Describe mRNA tRNA rRNA and miRNA
mRNA - messenger RNA (exons)
tRNA - Transferring the amino acids to the ribosomes
rRNA- Ribosomal RNA (protein synthesis)
miRNA (micro regulation of thing like gene expression).
Describe transcription
RNA polymerase binds to the genes and unwinds the DNA strands.
Free RNA nucleotides bind to the template strand. Polymerase assist with complemantary base pairing and forming the mRNA backbone (ribose sugar and phosphate)
this continues till the strand is complete.
the Pre-mRNA strand undergos intron splicing where introns are removed then the mRNA leaves the nucleus through a nuclear pore
Describe the relationship between DNA and RNA codons, anticodons, and amino acids
Codon is three nucleotide that code for an amino acid. each codon is complementary to an anti codon. which is attached to corresponding amino acid via tRNA (jesus cross)
Describe the steps of translation
mRNA binds to a ribosome.
Ribsome helps the amino acid placed in the right spot through the complmentary base paring with the anti-codon which is attached to the tRNA.
A peptide bond is formed between 2 correctly placed amino acids, therefore the first tRNA molecule is no longer needed, and the ribosome can move up the mRNA strand, elongating and repeating this process
