MCAT: Biochemistry exam 2024 with
questions and correct answers
DNA topoisomerase II (DNA gyrase) - CORRECT ANSWERremoves positive supercoils
ahead of advancing replication forks
telomerase - CORRECT ANSWERsynthesis of telomers
DNA polymerase - CORRECT ANSWERsynthesizes new DNA strands reading the
template DNA 3' to 5' and synthesizing the new strand 5' to 3'
- leading strand: requires only one primer and can be synthesized continuously
- lagging strand: requires many primers and is synthesized in discrete sections (Okazaki
fragments)
recombinant DNA - CORRECT ANSWERDNA composed of nucleotides from two
different sources
restriction enzyme - CORRECT ANSWERcuts both the plasmid and fragment leaving
them with sticky end which can bind
hybridization - CORRECT ANSWERjoining of complementary base pair sequences
polymerase chain reaction (PCR) - CORRECT ANSWERautomated process which
millions of copies of a DNA sequence can be created from a very small sample by
hybridization.
central dogma - CORRECT ANSWERDNA --> RNA --> proteins
redundancy & wobble - CORRECT ANSWERthird base in the codon, allow mutations to
occur without affecting the protein
point mutations - CORRECT ANSWERsilent: no effect on protein synthesis
missense: produce a codon that coeds for a different aa
frameshit: nucleotide addition/deletion changing the reading frame of subsequent
codons
RNA vs DNA - CORRECT ANSWER- substitution of a ribose sugar for deoxyribose
- substitution of uracil for thymine
, - single stranded vs double stranded
3 major types of RNA in transcription - CORRECT ANSWER- mRNA: carries the
message from DNA in the nucleus via transcription of the gene; travels into the
cytoplasm to be translated
- tRNA: brings in aa. recognizes the codon on the mRNA using its anticodon
- rRNA: makes up much of the ribosome; enzymatically active
transcription - CORRECT ANSWER1. helicase and topoisomerase unwinds DNA
double helix
2. RNA polymerase II binds to TATA box within promoter region of gene (25 base pairs
upstream from first transcribed base)
3. hnRNA synthesized from DNA template (antisense) strand
posttranscriptional modifications - CORRECT ANSWER- cap added to 5' end
- poly-A tail added to 3'end
- splicing done by spliceosomes; introns removed and exons ligated together.
alternative splicing combines different exons to acquire different gene products
translation - CORRECT ANSWERoccurs at the ribosome
1. initiation
2. elongation
3. termination
posttranslational modifications - CORRECT ANSWER- folding by chaperones
- formation of quaternary structure
- cleavage of proteins or signal sequences
- covalent additions of other biomolecules (phosphorylation, carboxylation,
glycosylation, prenylation)
transcription factors - CORRECT ANSWERsearch for promoter and enhancer regions in
DNA
promoter - CORRECT ANSWERwithin 25 base pairs of the transcription start site
enhancers - CORRECT ANSWERmore than 25 base pairs away from the transcription
start site
passive transport - CORRECT ANSWER- simple diffusion: does not require a
transporter. small nonpolar molecules passively move from areas of high concentration
to low.
- osmosis: diffusion of water across a selectively permeable membrane
questions and correct answers
DNA topoisomerase II (DNA gyrase) - CORRECT ANSWERremoves positive supercoils
ahead of advancing replication forks
telomerase - CORRECT ANSWERsynthesis of telomers
DNA polymerase - CORRECT ANSWERsynthesizes new DNA strands reading the
template DNA 3' to 5' and synthesizing the new strand 5' to 3'
- leading strand: requires only one primer and can be synthesized continuously
- lagging strand: requires many primers and is synthesized in discrete sections (Okazaki
fragments)
recombinant DNA - CORRECT ANSWERDNA composed of nucleotides from two
different sources
restriction enzyme - CORRECT ANSWERcuts both the plasmid and fragment leaving
them with sticky end which can bind
hybridization - CORRECT ANSWERjoining of complementary base pair sequences
polymerase chain reaction (PCR) - CORRECT ANSWERautomated process which
millions of copies of a DNA sequence can be created from a very small sample by
hybridization.
central dogma - CORRECT ANSWERDNA --> RNA --> proteins
redundancy & wobble - CORRECT ANSWERthird base in the codon, allow mutations to
occur without affecting the protein
point mutations - CORRECT ANSWERsilent: no effect on protein synthesis
missense: produce a codon that coeds for a different aa
frameshit: nucleotide addition/deletion changing the reading frame of subsequent
codons
RNA vs DNA - CORRECT ANSWER- substitution of a ribose sugar for deoxyribose
- substitution of uracil for thymine
, - single stranded vs double stranded
3 major types of RNA in transcription - CORRECT ANSWER- mRNA: carries the
message from DNA in the nucleus via transcription of the gene; travels into the
cytoplasm to be translated
- tRNA: brings in aa. recognizes the codon on the mRNA using its anticodon
- rRNA: makes up much of the ribosome; enzymatically active
transcription - CORRECT ANSWER1. helicase and topoisomerase unwinds DNA
double helix
2. RNA polymerase II binds to TATA box within promoter region of gene (25 base pairs
upstream from first transcribed base)
3. hnRNA synthesized from DNA template (antisense) strand
posttranscriptional modifications - CORRECT ANSWER- cap added to 5' end
- poly-A tail added to 3'end
- splicing done by spliceosomes; introns removed and exons ligated together.
alternative splicing combines different exons to acquire different gene products
translation - CORRECT ANSWERoccurs at the ribosome
1. initiation
2. elongation
3. termination
posttranslational modifications - CORRECT ANSWER- folding by chaperones
- formation of quaternary structure
- cleavage of proteins or signal sequences
- covalent additions of other biomolecules (phosphorylation, carboxylation,
glycosylation, prenylation)
transcription factors - CORRECT ANSWERsearch for promoter and enhancer regions in
DNA
promoter - CORRECT ANSWERwithin 25 base pairs of the transcription start site
enhancers - CORRECT ANSWERmore than 25 base pairs away from the transcription
start site
passive transport - CORRECT ANSWER- simple diffusion: does not require a
transporter. small nonpolar molecules passively move from areas of high concentration
to low.
- osmosis: diffusion of water across a selectively permeable membrane
