BIO 302 EXAM #3 2025/2026 QUESTIONS
AND ANSWERS 100% PASS
How does 6 feet of DNA fit into the tiny nucleus in each of our cells? - ANS DNA is wrapped
around proteins known as histones to form chromatin. Packing the DNA into nucleosomes
condenses the DNA approximately sevenfold. It can be further organized by winding the
chromatin into more compact structures. Coiling the chromatin around itself decreases the
space it occupies by another sixfold or so. Through a series of similar compacting strategies, the
entire genome can fit inside the nucleus of a single cell.
Identify and correctly label the following in a diagram of DNA nucleotide
a) Nitrogenous base
b) sugar
c) phosphate
d) 5' end
3) 3' end -
ANS http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101
%20lectures/dna/img004.gif
http://www.ib.bioninja.com.au/_Media/nucleotide_med.jpeg
If given a sequence of DNA, be able to state what the complementary sequence would be. Be
sure to
correctly label the 5' and 3' ends. - ANS DNA: A - T & G - C
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,RNA: A - U & G - C
In what direction does DNA polymerase build DNA? How does RNA polymerase know where to
start? How does it know where to stop? - ANS - DNA polymerase moves along the old strand
in the 3'-5' direction, creating a new strand having a 5'-3' direction
- RNA polymerase binds only to promoters (signals in the DNA molecule) which show it exactly
where to start (and stop) making mRNA
- Similar signals in DNA cause transcription to stop when a new mRNA molecule is complete.
Why is DNA synthesis considered to be semi-conservative? - ANS When two strands become
four strands after replication, then each double helix has one new and one old strand. This
means that newly formed double helix is half new and half old.
What biochemical property do histone proteins have that help them to bind DNA? What is their
role in chromatin formation? - ANS Histone is positively charged and can bond to the
negatively charged DNA molecules
- DNA wraps around the histone, forming nucleosomes (chromatin)
- Tails of DNA stick out, allowing for the formation of higher level chromatin.
How is heterochromatin different from euchromatin? Which form would you expect to see
during
metaphase of mitosis? Why? Which form would you expect to see during interphase? Why? -
ANS Heterochromatin: DNA densely packed around histones
- seen during interphase b/c transcriptionally inactive (inaccessible to enzymes & turned off)
Euchromatin: Region of DNA that is uncoiled/loosely coiled around histones
- undergoing active transcription into RNA
- seen during metaphase
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, Nucleotide - ANS A building block of DNA, consisting of a five-carbon sugar covalently
bonded to a nitrogenous base and a phosphate group.
Chromatin - ANS Clusters of DNA and proteins in the nucleus of a cell that make up
chromosomes
Primer - ANS A molecule (a short strand of RNA or DNA) whose presence is required for
formation of another molecule (a longer chain of DNA)
Polymerase Chain Reaction - ANS A method of producing thousands of copies of DNA
segment using the enzyme DNA polymerase
steps: breaking hydrogen bonds, annealing primers, and synthesizing using DNA polymerase.
Histone - ANS Globular protein that assist in DNA packaging in eukaryotes. Histones form
octamers around which DNA is wound to form a nucleosome.
DNA polymerase - ANS Enzyme involved in DNA replication that joins individual nucleotides
to produce a DNA molecule
sugar-phosphate backbone - ANS The alternating chain of sugar and phosphate to which the
DNA and RNA nitrogenous bases are attached
Nucleosome - ANS Bead-like structure in eukaryotic chromatin, composed of a short length
of DNA wrapped around a core of histone proteins
Hydrogen bond - ANS Attraction between a slightly positive hydrogen atom and a slightly
negative atom.
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
AND ANSWERS 100% PASS
How does 6 feet of DNA fit into the tiny nucleus in each of our cells? - ANS DNA is wrapped
around proteins known as histones to form chromatin. Packing the DNA into nucleosomes
condenses the DNA approximately sevenfold. It can be further organized by winding the
chromatin into more compact structures. Coiling the chromatin around itself decreases the
space it occupies by another sixfold or so. Through a series of similar compacting strategies, the
entire genome can fit inside the nucleus of a single cell.
Identify and correctly label the following in a diagram of DNA nucleotide
a) Nitrogenous base
b) sugar
c) phosphate
d) 5' end
3) 3' end -
ANS http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101
%20lectures/dna/img004.gif
http://www.ib.bioninja.com.au/_Media/nucleotide_med.jpeg
If given a sequence of DNA, be able to state what the complementary sequence would be. Be
sure to
correctly label the 5' and 3' ends. - ANS DNA: A - T & G - C
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,RNA: A - U & G - C
In what direction does DNA polymerase build DNA? How does RNA polymerase know where to
start? How does it know where to stop? - ANS - DNA polymerase moves along the old strand
in the 3'-5' direction, creating a new strand having a 5'-3' direction
- RNA polymerase binds only to promoters (signals in the DNA molecule) which show it exactly
where to start (and stop) making mRNA
- Similar signals in DNA cause transcription to stop when a new mRNA molecule is complete.
Why is DNA synthesis considered to be semi-conservative? - ANS When two strands become
four strands after replication, then each double helix has one new and one old strand. This
means that newly formed double helix is half new and half old.
What biochemical property do histone proteins have that help them to bind DNA? What is their
role in chromatin formation? - ANS Histone is positively charged and can bond to the
negatively charged DNA molecules
- DNA wraps around the histone, forming nucleosomes (chromatin)
- Tails of DNA stick out, allowing for the formation of higher level chromatin.
How is heterochromatin different from euchromatin? Which form would you expect to see
during
metaphase of mitosis? Why? Which form would you expect to see during interphase? Why? -
ANS Heterochromatin: DNA densely packed around histones
- seen during interphase b/c transcriptionally inactive (inaccessible to enzymes & turned off)
Euchromatin: Region of DNA that is uncoiled/loosely coiled around histones
- undergoing active transcription into RNA
- seen during metaphase
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, Nucleotide - ANS A building block of DNA, consisting of a five-carbon sugar covalently
bonded to a nitrogenous base and a phosphate group.
Chromatin - ANS Clusters of DNA and proteins in the nucleus of a cell that make up
chromosomes
Primer - ANS A molecule (a short strand of RNA or DNA) whose presence is required for
formation of another molecule (a longer chain of DNA)
Polymerase Chain Reaction - ANS A method of producing thousands of copies of DNA
segment using the enzyme DNA polymerase
steps: breaking hydrogen bonds, annealing primers, and synthesizing using DNA polymerase.
Histone - ANS Globular protein that assist in DNA packaging in eukaryotes. Histones form
octamers around which DNA is wound to form a nucleosome.
DNA polymerase - ANS Enzyme involved in DNA replication that joins individual nucleotides
to produce a DNA molecule
sugar-phosphate backbone - ANS The alternating chain of sugar and phosphate to which the
DNA and RNA nitrogenous bases are attached
Nucleosome - ANS Bead-like structure in eukaryotic chromatin, composed of a short length
of DNA wrapped around a core of histone proteins
Hydrogen bond - ANS Attraction between a slightly positive hydrogen atom and a slightly
negative atom.
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
