Storing and Using Genetic Information Flashcards
What is a phenotype
A outward, physical manifestation of organism
What is a genotype
The full hereditary information of organism (even if not expressed)
Why are proteins all functionally different
Due to their structure
What is protein structure dependent on
The primary structure and therefore the specific sequence of amino acids
What is the molecular structure of DNA
It is a chain of nucleotide monomers
What does each nucleotide contain
Sugar
Base
Phosphate group
What is the sugar on DNA called
2’ - deoxyribose
What shape do DNA molecules form
Double helix
What is the backbone of DNA
Sugar phosphate
How many bases are there for every full turn of the helix in DNA
10
Do the polynucleotide chains run parallel or anti-parallel to each other
Anti-parallel
One runs 5’ to 3’ while the other runs 3’ to 5’
How does the polynucleotide chains running anti-parallel to each other affect the double helix
It allows it to remain stable
What does the way the double helix is wound result in
Major groove
Minor groove
In which groove are many binding sites found
Major
Why are the grooves formed important in DNA
For the interaction of proteins with the DNA molecule
Is the double helix, right or left handed
Right handed
What are the bases in DNA
Adenine
Cytosine
Guanine
Thymine
How to the bases pair in DNA
A-T
C-G
Which base is switched in RNA
Thymine becomes Uracil
How many bonds are found between A-T
2 hydrogen bonds
How many bonds are found between C-G
3 hydrogen bonds
Describe the nucleus
The largest organelle in the cell
Contains most of the cell’s genetic material (DNA)
Replication of DNA and the first steps in decoding it for protein production take place in the nucleus
How big is the nucleus
5-10 μm in diameter
When are chromosomes visible in a cell
Only when the cell is dividing
What is DNA packaged into in the nucleus
Thread-like structures called chromosomes
What are chromosomes
A single piece of DNA containing many genes, regulatory elements and other nucleotide sequences
How many chromosomes do humans have
46
What is chromatin
The mixture of DNA, proteins and RNA that package DNA within the nucleus
Which two forms of chromatin can be found
Heterochromatin (condensed)
Euchromatin (extended)
What do transcription and replication require
The two strands of DNA to separate temporarily to allow enzymes access to the DNA template
What are barriers to enzymes in transcription and replication
Nucleosomes and folding of chromatin
Name two major reversible mechanisms by which chromatin is made more accessible
Histones can be enzymatically modified
Histones can be displaced by chromatin remodeling complexes
What does it mean when it is said that DNA replication is semi-conservative
One-half of each new molecule of DNA is old; one-half new
What must be broken to split the double helix
Hydrogen bonds
In what direction is DNA replicated
5’ to 3’
Where can DNA polymerase add new nucleotides
Only to the 3’ end of the growing strand
What are formed on the lagging strand
Okazaki fragments
How are okazaki fragments joined to produce one continuous strand
By DNA ligase
How is the 5’ end of the lagging strand replicated
A specialized enzyme, telomerase, replicates the 5’ ends of the lagging strand
How many bases are exactly the same in all people
99.9%
What are exons
Coding regions
What are introns
Non-coding regions
What happens to introns and exons in transcription
Introns - eliminated
Exons - spliced
What does the genetic code describe
How base sequences are converted into amino acids
What is a set of three bases called
Codon
What does each codon specify
A particular amino acid
How many codons can be formed from 4 bases
4^4 = 64 codons
How many amino acids have been found in proteins
20
Which amino acids are only coded for by one codon
Methionine
Tryptophan
What is methionine also termed
Initiation codon as this is the signal for protein synthesis to begin
What is degeneracy
The number of codons is greater than the number of amino acids
What can single point mutations cause
Dysfunctional proteins
Give an example of a single point mutation producing a dysfunctional protein
Mutated haemoglobin gene causes Sickle Cell Anaemia
In the mutant hemoglobin a hydrophilic glutamate (Glu) is substituted by the hydrophobic valine (Val), (GAA or GAG becomes GUA or GUG)
What is the major role of RNA
To participate in protein synthesis
What types of RNA are there
Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA)
What is mRNA
It is transcribed from DNA and carries information for protein synthesis
What is alternative splicing
A process by which the exons of the RNA produced by transcription of a gene (a primary gene transcript or pre-mRNA) are reconnected in multiple ways during RNA splicing
What does alternative splicing result in
The resulting different mRNAs may be translated into different protein isoforms; thus, a single gene may code for multiple proteins
What does alternative splicing increase
Diversity of proteins that can be encoded by the genome
What does the initiation codon determine
The reading frame of the RNA sequence.
What is a open reading frame
A set of codons runs continuously and is bounded by a start/initiation codon and a termination codon
What does the open reading frame identify
DNA which encodes protein sequences in genome sequencing projects
What occurs in the nucleus
Transcription (DNA to mRNA) and alternative splicing
What occurs in the cytoplasm
Post translational modifications
tRNA, rRNA and protein present here
What is the major role of tRNA
To translate mRNA sequence into amino acid sequence
Acts as an adapter molecule between the coded amino acid and the mRNA
What is rRNA
A component of ribosomes
Where are rRNA molecules produced
In the nucleus
Transported to cytoplasm, where they combine with proteins to form a ribosome
What is a polysome
Several ribosomes can translating mRNA at one time
