MMSC 491 EXAM 1 QUESTIONS WITH VERIFIED
ANSWERS
The length of the human genome is: - Answers - 3.2 billion bp
Coding DNA is only ___% of our DNA, remainder is non-coding: - Answers - 1.5%
Length of protein coding genes in bacteria: - Answers - ~1000 bp
Starting intron consists of ______ (splice donor site) and ending intro consists of ____
(splice acceptor site) - Answers - 1. GU
2.AG
What does the untranslated region of mRNA do? - Answers - Regulate Gene
Expression
mRNA stability
Start codon:
Stop Codons: - Answers - Start: AUG
Stop: UAA, UAG, UGA
How do tRNA carry amino acids? - Answers - Amino acids are covalently bonded to the
3' end of tRNA
Untranslated regions have what on the 5' end? And how it is advantageous? - Answers
- 1. 7-methylguanosine linked to first nucleotide by a 5' -5' phosphodiester bond
2.Protects transcript against 5' and 3' exonuclease attack and facilitates transport to
cytoplasm and ribosomal attachment
For untranslated region, what is on the 3' end, what is the length of it, and what does it
do? - Answers - 1. Poly A Tail
2. ~150-200 nucleotides long
3. Transport mRNA to cytoplasm, facilitates binding to ribosomes and stabilizing mRNA
How is folding stabilized? - Answers - Hydrophobic and hydrophilic interactions,
covalent cross-linking at cysteine residues (disulfide bonds)
Explain how protein leaves the cell - Answers - Polypeptide carries N-terminus ladder
sequence (signal peptide) required to cross membrane -> signal peptide cleaved at
membrane, releasing mature protein
*signal peptide contain hydrophobic amino acids (100-300 bp)
,Constitute Polypeptides - Answers - individual amino acid chains, linked by peptide
bond, that combine to form functional proteins
Small nuclear RNA (snRNA): - Answers - -Chemically modify specific bases in rRNA
-Spliceosome: Degrading introns in the pre-mature RNA to make a mature RNA
small Cajal-body RNA (scaRNA) - Answers - Chemically modify spliceosomal snRNA
Ribozymes - Answers - Cleave tRNA and rRNA precursors
"RNA World Hypothesis" - Answers - RNA is the original genetic material before DNA
and protein
-This is possible because ss-RNA has a flexible structure and can form complex shapes
w/ intramolecular H-bonds
RNA Base Pairing: - Answers - G-U , A-U, G-C
In RNA, what does a stem loop in the structure help with: - Answers - stem loop act as
recognition elements for binding regulatory proteins- critical for determining overall RNA
structure
in rRNA, where does catalytic activity occur? - Answers - 28s rRNA
Two Broad Classes of long non-coding RNA:
Intergenic + intragenic
What are these and what are they involved with? - Answers - Intergenic- between genes
(ex: regulate neighboring genes, control expression of genes on other chromosomes)
Intragenic - reside within protein-coding genes (ex: sense and antisense. antisense:
bind to complementary sequence to downregulate gene expression)
Tiny Non-coding RNA:
Micro RNA (miRNA)-
Piwi Protein-Interacting RNAs (piRNA)- - Answers - Micro RNA (miRNA)- recognize and
bind to defend target regulatory sequences present in specific mRNA to downregulate
their expression
Piwi Protein-Interacting RNAs (piRNA)- in germ cells to decrease excess activity of
transposons (mobile DNA elements)
What's seen when a chromosome is stained? - Answers - Alternating Bands and low
resolution
What percent of genome is euchromatin? - Answers - 93%
What percent of genome is heterochromatin? - Answers - 7% (mainly constituitive
heterochormatin)
, Psuedogenes - Answers - Inactive copies of functional genes
What does the BLAST Program aid in?
What other programs are involved? - Answers - Compare human coding DNA to other
related sequences in the genomes of other mammals
Works: translating putative coding DNA in all 6 reading frames (3 per strand) then
compare
BLASTN- nucleotide query / BLASTP- protein sequence / TBLASTN - protein sequence
to nucleotide sequence / BLAT- rapid sequence search across whole genome
Why do RNA genes lack open-reading frames? - Answers - Poorly conserved through
evolution
What does ENCODE (Encyclopedia of DNA Elements) aid in? - Answers - Compare
RNA sequence to genome wide transcription analysis, evolutionary sequence
comparisons, and functional assays (bioinformatics)
What occurred millions of years ago that started the evolution of the human genome?
How did the genome become bigger? - Answers - 1.Aerobic prokaryote was
endocystosed by an anaerobic precursor cell
Mitochondrial genome originated from a from a prokaryote genome excise, causing
large decrease in size
2.Series of mechanisms copied existing DNA sequences and added to the genome
How does duplication of DNA occur? - Answers - Reverse transcriptase
-Make DNA copies into RNA transcripts -> inserted into the genome
Percent of E.coli genome that is coding DNA sequences - Answers - 90%
Percent of Human Genome that is coding sequences: - Answers - 1.2%
What is Purifying Selection?
What percent of human genome goes through this? - Answers - 1. Mutations that
resulted in adverse change to phenotype is effectively removed from populations over
generations (causes lower reproduction success rates)
2. 10%
How many human mitochondrial genes do we have?
What are those genes comprised of? - Answers - 1. 37 mitochondrial genes
2. 24 RNA genes (2 rRNA, 22 tRNA)
13 genes for oxidative phosphorylation
*mtDNA does not have introns*
How many genes do humans have? - Answers - 20,000-25,000 genes
ANSWERS
The length of the human genome is: - Answers - 3.2 billion bp
Coding DNA is only ___% of our DNA, remainder is non-coding: - Answers - 1.5%
Length of protein coding genes in bacteria: - Answers - ~1000 bp
Starting intron consists of ______ (splice donor site) and ending intro consists of ____
(splice acceptor site) - Answers - 1. GU
2.AG
What does the untranslated region of mRNA do? - Answers - Regulate Gene
Expression
mRNA stability
Start codon:
Stop Codons: - Answers - Start: AUG
Stop: UAA, UAG, UGA
How do tRNA carry amino acids? - Answers - Amino acids are covalently bonded to the
3' end of tRNA
Untranslated regions have what on the 5' end? And how it is advantageous? - Answers
- 1. 7-methylguanosine linked to first nucleotide by a 5' -5' phosphodiester bond
2.Protects transcript against 5' and 3' exonuclease attack and facilitates transport to
cytoplasm and ribosomal attachment
For untranslated region, what is on the 3' end, what is the length of it, and what does it
do? - Answers - 1. Poly A Tail
2. ~150-200 nucleotides long
3. Transport mRNA to cytoplasm, facilitates binding to ribosomes and stabilizing mRNA
How is folding stabilized? - Answers - Hydrophobic and hydrophilic interactions,
covalent cross-linking at cysteine residues (disulfide bonds)
Explain how protein leaves the cell - Answers - Polypeptide carries N-terminus ladder
sequence (signal peptide) required to cross membrane -> signal peptide cleaved at
membrane, releasing mature protein
*signal peptide contain hydrophobic amino acids (100-300 bp)
,Constitute Polypeptides - Answers - individual amino acid chains, linked by peptide
bond, that combine to form functional proteins
Small nuclear RNA (snRNA): - Answers - -Chemically modify specific bases in rRNA
-Spliceosome: Degrading introns in the pre-mature RNA to make a mature RNA
small Cajal-body RNA (scaRNA) - Answers - Chemically modify spliceosomal snRNA
Ribozymes - Answers - Cleave tRNA and rRNA precursors
"RNA World Hypothesis" - Answers - RNA is the original genetic material before DNA
and protein
-This is possible because ss-RNA has a flexible structure and can form complex shapes
w/ intramolecular H-bonds
RNA Base Pairing: - Answers - G-U , A-U, G-C
In RNA, what does a stem loop in the structure help with: - Answers - stem loop act as
recognition elements for binding regulatory proteins- critical for determining overall RNA
structure
in rRNA, where does catalytic activity occur? - Answers - 28s rRNA
Two Broad Classes of long non-coding RNA:
Intergenic + intragenic
What are these and what are they involved with? - Answers - Intergenic- between genes
(ex: regulate neighboring genes, control expression of genes on other chromosomes)
Intragenic - reside within protein-coding genes (ex: sense and antisense. antisense:
bind to complementary sequence to downregulate gene expression)
Tiny Non-coding RNA:
Micro RNA (miRNA)-
Piwi Protein-Interacting RNAs (piRNA)- - Answers - Micro RNA (miRNA)- recognize and
bind to defend target regulatory sequences present in specific mRNA to downregulate
their expression
Piwi Protein-Interacting RNAs (piRNA)- in germ cells to decrease excess activity of
transposons (mobile DNA elements)
What's seen when a chromosome is stained? - Answers - Alternating Bands and low
resolution
What percent of genome is euchromatin? - Answers - 93%
What percent of genome is heterochromatin? - Answers - 7% (mainly constituitive
heterochormatin)
, Psuedogenes - Answers - Inactive copies of functional genes
What does the BLAST Program aid in?
What other programs are involved? - Answers - Compare human coding DNA to other
related sequences in the genomes of other mammals
Works: translating putative coding DNA in all 6 reading frames (3 per strand) then
compare
BLASTN- nucleotide query / BLASTP- protein sequence / TBLASTN - protein sequence
to nucleotide sequence / BLAT- rapid sequence search across whole genome
Why do RNA genes lack open-reading frames? - Answers - Poorly conserved through
evolution
What does ENCODE (Encyclopedia of DNA Elements) aid in? - Answers - Compare
RNA sequence to genome wide transcription analysis, evolutionary sequence
comparisons, and functional assays (bioinformatics)
What occurred millions of years ago that started the evolution of the human genome?
How did the genome become bigger? - Answers - 1.Aerobic prokaryote was
endocystosed by an anaerobic precursor cell
Mitochondrial genome originated from a from a prokaryote genome excise, causing
large decrease in size
2.Series of mechanisms copied existing DNA sequences and added to the genome
How does duplication of DNA occur? - Answers - Reverse transcriptase
-Make DNA copies into RNA transcripts -> inserted into the genome
Percent of E.coli genome that is coding DNA sequences - Answers - 90%
Percent of Human Genome that is coding sequences: - Answers - 1.2%
What is Purifying Selection?
What percent of human genome goes through this? - Answers - 1. Mutations that
resulted in adverse change to phenotype is effectively removed from populations over
generations (causes lower reproduction success rates)
2. 10%
How many human mitochondrial genes do we have?
What are those genes comprised of? - Answers - 1. 37 mitochondrial genes
2. 24 RNA genes (2 rRNA, 22 tRNA)
13 genes for oxidative phosphorylation
*mtDNA does not have introns*
How many genes do humans have? - Answers - 20,000-25,000 genes
