Honors Genetics: FINAL Exam Review
REVIEW ALL OLD QUIZZES/TESTS!
Chapter 1: Introduction to Genetics
Know the differences between PROKARYOTES and EUKARYOTES
Prokaryotes are small and less complex than eukaryotes; prokaryotes have DNA usually as a round
circular plasmid; eukaryotes have a membrane-bound nucleus and organelles.
What is the function of DNA?
Code for the production of proteins that lead to structure and function
What is a MUTATION?
Change in the nucleotide sequence of DNA.
What 3 categories do mutations fall into and provide an example of each.
Positive that leads to natural selection/evolution
Negative that leads to disease or death
Neutral that is often hidden since the same amino acid is still produced
Chapter 2: Mitosis and Meiosis
Describe the appearance of chromosomes based on centromere location.
Chromatin is DNA during interphase, when the cell is not dividing. It is coiled like spaghetti on a plate, not
condense to form chromosomes (X). The centromere holds sister chromatids together and the location of
the centromere is used to assist in identification of chromosome # during karyotyping of an individual.
Describe the cell clock and apply to the type of cell that divides
G1 and G2 are for growth and work
S is for replication of DNA
M is for Mitosis/Meiosis and Cytokinesis
LABILE cells are constantly dividing and do not
exit the cell cycle.
STABILE cells are in the cell cycle during growth
and repair but will QUIESCE and simply work.
PERMANENT cells are made during embryonic
development and will simply work for the
remainder of the life span, never to divide again.
What is the purpose of MITOSIS?
Diploid to Diploid division of the nucleus for the production of somatic/body cells during growth and
repair.
What is the purpose of MEIOSIS?
Diploid to Haploid division of the nucleus for the production of germline/gametic cells for the purpose of
reproduction.
Know the similarities and differences between SPERMATOGENESIS and OOGENSIS.
Spermatogenesis begins during puberty and will last the remainder of life. It produces 4 genetically
different haploid cells.
Oogenesis begins during fetal development, stops and begins again at puberty, stops and begins again at
ovulation and fertilization. It produces 1 mature ova and 3 polar bodies
Chapter 3: Mendelian Inheritance
Be able to analyze an AUTOSOMAL DOMINANT and AUTOSOMAL RECESSIVE pedigree.
Chapter 4: Modification of Mendelian Ratios
Know how to differentiate between different pedigrees
Autosomal Dominant/Autosomal Recessive
X-linked Dominant/X-linked Recessive
Review blood group inheritance
ABO
Describe the issues surrounding sex-linked inheritance in human males
Chapter 9: Evidence Favoring DNA as Genetic Material
Understand the sequence of experiments that proved DNA was the mechanism of inheritance.
Griffith: experiment proved that some factor was being passed from dead pathogenic bacteria to live
bacteria to make it pathogenic.
Avery, McCloud, McCarty: experiment proved that DNA was necessary for transformation to occur.
Hershey-Chase: experiment proved that a nucleic acid was needed for transformation to occur.
Know the nucleotide structures, including sugars and phosphate arrangement.
Describe the Watson-Crick Model of DNA (page 193-194)
2 chains
purine opposite a pyrimidine
chains held together by H-bonds
Guanine is paired with cytosine by three H-bonds
Adenine is paired with thymine by two H-bonds
anti-parallel orientation of the two chains
the molecule is stabilized by: large # of H-bonds and hydrophobic bonding between the stacked bases
Describe electrophoresis
Separation of DNA fragments by size and charge. The DNA has a slight negative charge and will travel
through the gel to the positive electrode. The larger fragments move slowly while the large fragments will
travel fast through the gel matrix and create a banding appearance.
Chapter 10: DNA Replication and Recombination
Why must DNA replicate?
So the cells produced during mitosis and meiosis have the genetic info needed for normal structure and
function (mitosis) OR for inheritance of traits to offspring (meiosis).
Describe the process of DNA replication as a semiconservative replication process.
Understand the difference between conservative and dispersive replication.
How did the Messelson-Stahl experiment prove semiconservative replication?
Meselson and Stahl proved that DNA replication was performed in a semiconservative manner, resulting in
2 new double helices each with one NEW strand and one OLD strand wound together. The experiment is
pictured below. Remember, the tubes showing conservative and dispersive replication are what would be
EXPECTED if DNA replication were performed in that manner. The actual experiment, when carried out,
showed that DNA replication was a SEMICONSERVATIVE process.
The experiment used labeled nitrogen-15 (heavy) and nitrogen-14 (light). When DNA labeled with N-15
was grown in a medium of N-14, the resulting tubes showed a layer of N-14/N-15 band in the middle of the
tube after ONE round of replication. When incubated in N-14 again in the SECOND round, the tubes
showed a band of N-14/N-15 and a band of N-14/N-14 (light). This proved the SEMICONSERVATIVE
nature of DNA replication.
Know why E. coli was used as the organism for experimentation.
Model organism that has a quick reproductive cycle and results can be observed in a short period of time.
List the enzymes involved, including their functions.
helicase – unwinds the double helix by breaking hydrogen bonds that hold base pairs together.
gyrase – relieves strain of unwinding while helicase does its job. Stabilizes.
polymerase – matches complementary strands of DNA while making new strand of DNA; makes a polymer
topoisomerase – relaxes DNA from super-coiled nature to get ready for replication.
Understand the significance of telomeres and telomerase in relation to cell division and cell aging.
telomeres are the caps of repeated nucleotides at the end of chromosomes that are lost each time a cell
replicates its DNA. Telomerase is the enzyme that can add nucleotides at the end of the chromosome to
prevent this shortening. Most somatic cells lack telomerase and therefore when the telomere is gone, cells
age as coding DNA (exons) are lost during DNA replication.
Chapter 12 and 13: The Genetic Code, Transcription, and Translation
Describe the 3 main types of RNA, their function, and their location in the cell.
mRNA is produced in the nucleus as a complimentary strand to DNA; it has the ability to leave the nucleus
and travel to the cytoplasm.
tRNA is found in the nucleus only and will carry the correct amino acid to the ribosome for the
construction of an intact polypeptide sequence; the anticodon on tRNA matches to the codon on mRNA.
rRNA is the component (with proteins) that make up the structure of the ribosome.
Differences between DNA and RNA.
DNA
RNA
Location
Nucleus
Nucleus and cytoplasm
Bases
A,T,G,C
A,U,G,C
Function
Code for construction of a protein
Construction of a protein (carry info and match amino
acids
What is transcription? Can you transcribe a segment of DNA into mRNA?
Transcription is the function of making a complimentary mRNA copy from a section of DNA to use in the
construction of a protein in the cytoplasm.
What is a ribosome? Where are ribosomes located in EUKARYOTIC cells?
Organelle responsible for the production of an amino acid sequence that is coded in the mRNA that travels
from the nucleus.
What is the function of transfer RNA? Where does the amino acid bind to the tRNA molecule?
tRNA has a 3-letter sequence (anticodon) that is complimentary to mRNA. The tRNA has an amino acid
bound to the 3’ end of the nucleotide strand.
Describe the codon dictionary. Can you read a codon chart? How many start codons? Stop codons? What are
they?
What are the 3 main steps of Translation?
#1: Initiation: the mRNA binds to the small ribosomal subunit and “START” is read to begin the
production of a polypeptide sequence. The large subunit then binds to the small to make an intact
ribosome.
#2: Elongation: the mRNA moves through the ribosome at 3 different positions, the P site, the A site, and
the E site. The P and A sites are responsible for the formation of a peptide bond between each amino acid.
This bond is formed through dehydration synthesis with the help of the enzyme peptidyl tranferase. Once
the peptide bond is formed, the uncharged tRNA moves to the E site (E=exit) so the next tRNA’s can move
into the P and A sites.
Be able to TRANSCRIBE and TRANSLATE a DNA sequence into an amino acid sequence.
Provide detailed information about PKU.
Phenylketonuria is an inherited metabolic disorder. This condition results in the lack of an enzyme,
phenylalanine hydroxylase, which is responsible for the transformation of phenylalanine into tyrosine.
This transformation is necessary to prevent the build-up of phenylalanine in the brain. If this condition is
not diagnosed early in life and a strict diet is not adhered to, severe brain damage will result.
Provide detailed information about sickle cell anemia and describe the significance of sickle cell disease that
made it a useful tool in studying genetic mutations and protein structure/function.
Sickle cell anemia is an inherited condition due to the substitution of one amino acid for another in the 6th
position of the beta subunits in hemoglobin. This substitution of glutamic acid for valine results in misfolding of the tertiary structure of the beta subunits and malformed hemoglobin. Sickled red cells do not
have the flexibility of normal RBC’s and lack the same oxygen carrying capacity that normal RBC’s have.
Hemoglobin is a quaternary structured protein made up of 4 subunits – 2 alpha and 2 beta held together by
a central atom of iron.
Identify an amino acid structure, the significance of the R group, and the chemistry of linking amino acids
together.
What 4 categories do all 20 biologically needed amino acids belong? What are the characteristics of each of these
categories? How do they play a role in the formation of a protein?
Hydrophobic side chain want to be as far away from water as possible and while folding, will orient
themselves toward the middle of the tertiary structure.
Hydrophilic side chains want to be close to water and while folding, will orient themselves on the exterior of
the tertiary structure.
Acid side chains have a slight negative change and will form a salt bridge with a basic side chain.
Base side chains have a slight positive charge and will form a salt bridge with an acid side chain.
As the protein folds to form a tertiary structure, the side chains (R-groups) will orient themselves
according to the descriptions provided above.
What are the 4 structures that make a 3-dimensional protein? Describe each arrangement and how it is held
together.
Primary structure is formed through peptide bonds made in the ribosome during translation and produce
a straight chain.
Secondary structure is formed through hydrogen bonds and produce alpha helices or beta pleated sheets.
Tertiary structure is formed through the interaction of the side chains and their chemical behavior and
produce a variety of shapes.
Quaternary structure is formed by the combination of 2+ tertiary structures held together by a central
molecule.
Chapter 14: Mutations and the Human Genome
Identify the difference between point mutations and frameshift mutations.
Recognize insertion, deletion, and substitution mutations when comparing one code to another.
Understand the impact that mutations have on the ability to create a correct Amino Acid sequence
What is the difference between a neutral mutation and a silent mutation?
Vocabulary Review
DIPLOID: 2N; represents the number of chromosomes in a somatic cell.
HAPLOID: N; represents
the number of chromosomes in a germline/gametic cell.
ALLELE: options of a
gene.
GENOTYPE: what is present on the chromosome for each allele; TT, Tt, tt
PHENOTYPE: the physical expression of the genotype
CHROMATIN: DNA during interphase, uncondensed and coiled like “spaghetti on a plate”
CHROMOSOMES: condensed and coiled DNA visible during mitosis and meiosis
SISTER CHROMATIDS:
HOMOLOGOUS CHROMOSOMES:
GENETIC VARIATION
TRAIT
GENE: sequence of nucleotides that produces a single protein.
SEGREGATION: separation of sister chromatids during mitosis and meiosis that produces the correct
number of chromosomes.
HOMOZYGOUS: TT or tt
HETEROZYGOUS: Tt; AKA carrier