REVISION QUESTIONS AND ANSWERS FOR GENETICS
1. Distinguish between DNA, genes and chromosomes.
Chromosomes carry DNA in cells. DNA is responsible for building and maintaining your human structure.
Genes are segments of DNA that contain the code for a specific protein that functions in one or more types
of cells in the body.
Genes - A gene is the basic physical and functional unit of heredity. Genes are made up of DNA.
DNA - double helix carrying genetic instructions for the development, functioning, growth and reproduction
of all known organisms
Chromosomes - a threadlike structure of nucleic acids and protein found in the nucleus of most living cells,
carrying genetic information in the form of genes.
2. What traits do structural, enzymatic and hormonal proteins codes for?
Structural Proteins – Physical Traits
Enzymatic Proteins – Metabolic Traits
Hormonal Proteins - Control of growth and development
3. List some pioneers of DNA research?
Friedrich Miescher (1869) - isolated nucleic acids in pus cell
around 1869
Frederick Griffith (1928) - contributed the first step in
identifying DNA as the genetic material
Joachim Hammering (1930) - determine that nucleus of a
cell controls the development of living things
Oswald Avery, Maclyn McCarty, Colin MacLeod (1944) -
learned the identity of the “transforming substance”.
Alfred Hershey, Martha Chase (1952) - conclusively
showed that DNA, not protein, is the genetic material.
4. Describe the DNA structure and type of bonds that hold the
structure together.
The DNA double helix resembles a twisted ladder.
The twin rails of the ladder, also called the sugar–
phosphate “backbones,” are alternating units of
deoxyribose and phosphate joined with covalent bonds.
The ladder’s rungs are A–T and G–C base pairs joined by
hydrogen bonds.
, ADDITIONAL NOTE: The Structure of DNA
The two strands in DNA are held together by
hydrogen bonding between the bases. DNA bases
always pair in the same way: A with T and C with
G. The double-stranded molecule is twisted into a
double helix shape resembling a twisted ladder.
Opposite strands run antiparallel to each other,
meaning that they run in opposite directions. This
ensures that the strands fit tightly together.
5. Distinguish between purines and pyrimidines.
Adenine and guanine are purines, bases with a double
ring structure.
Cytosine and thymine are pyrimidines, which have a
single ring.
6. What is “Chargraff’s Rule”?
In DNA
PURINES base pair with the PYRIMIDINES
A-T
G-C
3 hydrogen bonds between C and G
2 hydrogen bonds between A and T
7. What are Condons?
Sequence of 3 nucleotide bases coding for one amino acid when it is translated.
And different series of amino acids build polypeptides which ultimately makes proteins
Genetic info in mRNA is used to direct the order of specific amino acids during protein synthesis
A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or
stop signal during protein synthesis.
8. Describe the 5 stages of the cell cycle involved in DNA
replication.
1) Gap 1 (early biosynthesis)- the cell increase in size,
copies organelles and make the molecular building
blocks it will need in later steps.
•Gap 0 (terminally differentiated cells)
2) Synthesis (DNA replication) – a complete copy of
DNA in the nucleus.
3) Gap 2 (late biosynthesis in prep for mitosis) - the cell
grows more, makes proteins and organelles, and begins
to reorganize its contents in preparation for mitosis.
G2 phase ends when mitosis begins.
1. Distinguish between DNA, genes and chromosomes.
Chromosomes carry DNA in cells. DNA is responsible for building and maintaining your human structure.
Genes are segments of DNA that contain the code for a specific protein that functions in one or more types
of cells in the body.
Genes - A gene is the basic physical and functional unit of heredity. Genes are made up of DNA.
DNA - double helix carrying genetic instructions for the development, functioning, growth and reproduction
of all known organisms
Chromosomes - a threadlike structure of nucleic acids and protein found in the nucleus of most living cells,
carrying genetic information in the form of genes.
2. What traits do structural, enzymatic and hormonal proteins codes for?
Structural Proteins – Physical Traits
Enzymatic Proteins – Metabolic Traits
Hormonal Proteins - Control of growth and development
3. List some pioneers of DNA research?
Friedrich Miescher (1869) - isolated nucleic acids in pus cell
around 1869
Frederick Griffith (1928) - contributed the first step in
identifying DNA as the genetic material
Joachim Hammering (1930) - determine that nucleus of a
cell controls the development of living things
Oswald Avery, Maclyn McCarty, Colin MacLeod (1944) -
learned the identity of the “transforming substance”.
Alfred Hershey, Martha Chase (1952) - conclusively
showed that DNA, not protein, is the genetic material.
4. Describe the DNA structure and type of bonds that hold the
structure together.
The DNA double helix resembles a twisted ladder.
The twin rails of the ladder, also called the sugar–
phosphate “backbones,” are alternating units of
deoxyribose and phosphate joined with covalent bonds.
The ladder’s rungs are A–T and G–C base pairs joined by
hydrogen bonds.
, ADDITIONAL NOTE: The Structure of DNA
The two strands in DNA are held together by
hydrogen bonding between the bases. DNA bases
always pair in the same way: A with T and C with
G. The double-stranded molecule is twisted into a
double helix shape resembling a twisted ladder.
Opposite strands run antiparallel to each other,
meaning that they run in opposite directions. This
ensures that the strands fit tightly together.
5. Distinguish between purines and pyrimidines.
Adenine and guanine are purines, bases with a double
ring structure.
Cytosine and thymine are pyrimidines, which have a
single ring.
6. What is “Chargraff’s Rule”?
In DNA
PURINES base pair with the PYRIMIDINES
A-T
G-C
3 hydrogen bonds between C and G
2 hydrogen bonds between A and T
7. What are Condons?
Sequence of 3 nucleotide bases coding for one amino acid when it is translated.
And different series of amino acids build polypeptides which ultimately makes proteins
Genetic info in mRNA is used to direct the order of specific amino acids during protein synthesis
A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or
stop signal during protein synthesis.
8. Describe the 5 stages of the cell cycle involved in DNA
replication.
1) Gap 1 (early biosynthesis)- the cell increase in size,
copies organelles and make the molecular building
blocks it will need in later steps.
•Gap 0 (terminally differentiated cells)
2) Synthesis (DNA replication) – a complete copy of
DNA in the nucleus.
3) Gap 2 (late biosynthesis in prep for mitosis) - the cell
grows more, makes proteins and organelles, and begins
to reorganize its contents in preparation for mitosis.
G2 phase ends when mitosis begins.
