Midterms Reviewer Flashcards
Phenotypic expression of a pair of alleles depends on?
Combination and their mode of inheritance?
What is Gene Interaction?
It is where phenotypic expression of a gene or an allele is either MASKED or ALTERED by another gene or allele.
Gene interaction that is particularly involved in suppressing the expression of a gene or allele.
Epistasis
Either dominant from both pairs of alleles will allow the expression of the trait
Duplicate Gene Interaction (15 : 1)
Both dominant alleles from each pair will allow the expression of the trait. Also known as double recessive epistasis because the presence of any pair of recessives will prevent the trait from being expressed.
Complementary Gene Interaction (9 : 7)
Type of gene interaction where the expression of a trait in one gene is masked by the recessive allele of the other gene
Single Recessive Epistasis (9 : 3 : 4)
Type of gene interaction where the expression of one pair of alleles is masked by a dominant allele from the other pair
Dominant Epistasis (12 : 3 : 1)
Type of gene interaction where an allele prevents the expression of the other pair of alleles
Dominant Suppressor Epistasis (13 : 3)
Type of Pedigree Analysis where the abnormal allele is dominant, and the normal allele is recessive.
Autosomal Dominant Pedigree Analysis
Type of Pedigree Analysis where the abnormal allele is recessive, and the normal allele is dominant.
Autosomal Recessive Pedigree Analysis
Type of Pedigree Analysis where the abnormal allele is sex linked recessive, and the normal allele is dominant.
X-linked Recessive Pedigree Analysis
Type of Pedigree Analysis where the abnormal allele is sex linked dominant, and the normal allele is recessive.
X-linked Dominant Pedigree Analysis
Type of Pedigree Analysis where the abnormal allele is on the Y chromosome.
Y-linked Pedigree Analysis
It refers to the physical association of genes on the same chromosome.
Gene linkage
Genes that are located on the same chromosome are called?
Linked Genes
Genes that are located on the same chromosome are called?
Linked Genes
All the genes present in a chromosome are known as what?
linkage group.
How many Linkage and sex-linked groups in humans; in Females? and Males?
Female
23 linkage and 1 sex-linked
Male
24 linkage groups
Genes that are closer to each other have a greater tendency of being inherited together during crossing-over. This is because they are?
genetically linked.
It shows the location (locus) of physically linked genes on a chromosome in a linear arrangement.
Genetic map
It refers to the precise location of the gene on the DNA as well as its size, based on the sequence of complementary base pairs. It also helps determine the exact distance between the linked genes.
Molecular Location
This determines the cross-over data which shows the way of mapping the location of a gene in a chromosome.
Recombination Frequency (Rf)
What is the possibility of recombination if genetically linked genes are so close together that they are never separated, even during crossing-over
zero
Genes that are not genetically linked (farther from each other) have a tendency of?
Being unlinked during crossing-over.
If the genes were separated during crossing over, 50% of the gametes would contain separate copies of the genes and their chromosomes are called?
recombinant chromosomes.
The other 50% of the gametes would contain both copies of the genes because there was no crossing-over involved. Their chromosomes are the same as the chromosome of the parent cell, thus referred to as?
parental chromosomes
This method is used to determine both the location of genes and their distances from each other. It requires three linked genes.
Three-point Cross
Three-point cross; state three possible events that happen to non-sister chromatids during meiosis.
(a) No crossing -over (NCO)
(b) Single crossing -over (SCO)
(c) Double crossing -over (DCO)
In what specific stage of the cell cycle does DNA replication occur?
S-Phase
if crossing over does not occur, how many types of gametes will be formed, based on the alleles present?
2
if crossing over occurs, how many types of gametes will be formed, based on the alleles present?
4
It is the exchange of genetic material between homologous pairs.
Crossing-Over
A DNA molecule found in the nucleus that carries the genetic material.
Chromosomes
The chromosome is made up of what?
two identical sister chromatids
The sister chromatids attached at a point called the what?
centromere
The centromere constricted portion divides the chromosome into two sections called the what?
arms
What are two types of arms?
p arm and q arm
The location of the centromere is the basis for classifying the chromosomes. State four types.
A. Telocentric
B. Acrocentric
C. Submetacentric
D. Metacentric
Chromosome type that has a centromere at the tips of the chromosome.
Telocentric
Do humans possess telocentric chromosomes?
No, but other mammals do.
A chromosome that has centromeres located quite near the tip of the chromosome.
Acrocentric
Chromosomes that have a centromere located near the middle, resulting in a slightly unequal arm.
Submetacentric
A chromosome that has a centrally located centromere with p and q arms of almost the same length.
Metacentric
A single chromosome contains how many DNA molecules?
One
What allows the DNA molecule to be supercoiled?
Histones
Describe DNA by the number of strands, manner or formation, and shape.
A DNA molecule is made up of two DNA strands arranged in an antiparallel manner and twisted into a double helix
The nucleoside is made up of?
a sugar and a nitrogenous base
State the composition of Nucleotides
A. Phosphate Group
B. Sugar Group
C. Nitrogenous Base
What are the types of bonds found within a nucleotide
Nucleotide bases form hydrogen bonds
Glycosidic bond within a nucleoside
Sugars are connected via ester bonds
What forms complementary base pairs?
Purines and Pyrimidines
Group of proteins responsible for DNA packaging
Histones
What do you call pairs of histones,
What are the four types,
these form form a?
Dimers;
H2A, H2B, H3, H4
forming an octamer
Proteins that participate in DNA packaging
Non-histone proteins
The average length of one DNA molecule is approximately how many cm?
5 cm
How many DNA’s per cell
46
The first level of DNA packaging is the formation of what?
Nucleosome
A series of nucleosomes form this structure that looks like “beads on a string”
chromatin
What histones allow the 2 nm diameter DNA to wind around the tetramer once. What is formed from this process?
H3 and H4.
A tetrasome is formed
What are the more reliable packaging histones that allow DNA to form a negative superhelical turn around a histone octamer twice, forming this structure?
2A and 2B
It forms a nucleosome
Between adjacent nucleosomes is a short DNA segment called the what?
linker DNA
What histone is associated with the linker DNA. which promotes further coiling by compacting the nucleosomes into a 30 nm chromatin?
H1
What are the two possible configurations for chromatin?
Solenoid and Zigzag Models
The third level of compaction
Euchromatin
What two structures interact with each other to form the euchromatin?
30 nm fiber and the nuclear matrix
A special feature of the euchromatin
Radial loops
The anchor to the nuclear matrix via internal matrix proteins, forming a loop
matrix attachment regions
Further compaction of the 300 nm euchromatin forms a? (Include measurement)
700nm heterochromatin
T or F: Transcription occurs in heterochromatin segments
False
Permanently inactive heterochromatin. Formed by DNA segments that are no longer used or needed by the cell
Constitutive Heterochromatin
Inactive for sometime then uncoils back to euchromatin if the transcription is required by the cell, then coils again into a heterochromatin
Facultative Heterochromatin
T or F:
During the prophase stage of cell division, the chromatin enters the last level of compaction
True
All euchromatin coils into heterochromatin, then all heterochromatin undergoes supercoiling to form the?
Chromosome
Enzyme that binds sister chromatids together
Cohesin
Enzyme that aid in the coiling of the chromatin until the final metaphase chromosome is formed
condensin
The genetic material of viruses is either composed of?
DNA or RNA
Prokaryotic and eukaryotic genetic material is composed of the
DNA
The sugar component of the genetic material is a?
Pentose
The sugar component of the RNA specifically?
Ribose
What bond is used to bind nitrogen bases with sugar to form a nucleoside?
N-glycosidic bond.
What type of bonds connects adjacent sugar groups?
Phosphodiester bond
Number of Hydrogen bonds between A-T and G-C
A-T have two
G-C have three
What nitrogen base is found in the RNA strand instead of Thymine?
Uracil
What are the three types of RNA?
tRNA, mRNA, and rRNA
Involves a series of events that leads to the production of new cells.
The cell Cycle
What are the two major phases of the cell cycle?
Interphase and Cell Division
Why is the Interphase called the Resting Phase?
It is simply because the cell is not undergoing cell division. Instead, it is synthesizing cellular materials.
This is the phase that occurs immediately after cell division when the daughter cells are half the size of the parent cell.
Gap 1 / G1 / Growth Phase
During this G1, the small daughter cell undergoes synthesis of _________ for growth and normal functioning.
cytoplasmic materials
What ends G1 phase?
Once the small daughter cells have reached the required size.
Synthesis Phase / S Phase focuses on the synthesis of?
synthesis of the DNA
This is the time when the microtubule organizing center of the cell, called centrosomes
are duplicated
S-Phase
What ends the S-phase?
Once the genetic material has been replicated,
T or F: A cell that enters the S phase is committed to completing the cell cycle
True
During this stage, the cell completes its growth
G2
Gap 2 / G2 Phase focuses on the synthesis of?
synthesis of materials for cell division
Gap 2 / G2 Phase focuses on the synthesis of?
synthesis of materials for cell division
Cells that divide slowly or cease dividing enter this stage.
G0 phase
Is the phase that involves the division of the nucleus and the cytoplasm.
M-phase
What do you call the division of the nucleus?
Karyokinesis
What do you call the division of the cytoplasm?
Cytokinesis
Two types of karyokinesis occur during the M-phase: which are?
mitosis and meiosis
Type of cell division that occurs in somatic cells.
Mitosis
Type of cell division that occurs in gametic cells
Meiosis
The function of Mitosis, describe the number and nature of daughter cells.
Growth and Repair of cells; 2 diploid daughter cells.
This is the first stage of the M – phase, immediately after the G2 stage
Prophase
Spindle fibers that attach to the kinetochores of the chromosomes and move the chromosomes towards the equatorial region of the cell
Kinetochore Microtubules
spindle fibers that are not attached to the kinetochore of the chromosomes and are of two types.
Nonkinetochore Microtubules
short microtubules that extend outward from the poles
astral Microtubules
microtubules that extend from the pole towards the equator, meet at the equator, and overlap
polar/interpolar microtubules:
Also known as the cell equator
Metaphase Plate
Enzyme that degrades the cohesins between the centromeres, causing the separation of the sister chromatids
Separase
What causes the cell to elongate?
Interpolar microtubules
A division of the cytoplasm that starts to appear either during late anaphase or early telophase until it finally splits the cell into two identical daughter cells
Cytokinesis
In animal cytokinesis, The plasma membrane forms a depression or cleft called?
cleavage furrow
The cleavage furrow is formed by the constriction of a contractile ring made of?
actin and myosin
In Plant cytokinesis, It is a network of microtubules and microfilaments form a scaffold at the equatorial plane
Phragmoplast
In plant cytokinesis, It is the vesicles from the Golgi apparatus.
Phragmosomes
What is formed by the fusion of phragmosomes?
cell plate
In leptotene, Chromosomes look for their homologous pair to form a?
bivalent
A process where chromosomes align their centromeres.
encounter
The checking process in leptotene.
assessment
What do you call the chromosomes that have the same size, shape, and genes?
Homologous chromosomes
A process where homologs confirm their pairing.
licensing
Meiotic stage where synapsis occurs
Zygotene
a protein complex formed between the homologous chromosomes to make sure that they are bound tightly together
Synaptonemal Complex
What do you call 2 tightly bound chromosomes?
bivalent
What do you call sister chromatids in terms of synapsis formation?
tetrad
What ends zygotene?
When bivalents are bound together
The meiotic stage where crossing over occurs.
Pachytene
Synapsis has bound the homologs so close that the arms of adjacent non-sister chromatids overlap at a point called the?
Chiasma
This initiates the exchange of genetic materials
overlapping of arms
This is responsible for the genetic variations observed between and among members of the same species and between different organisms
Crossing Over
Meiotic stage of synaptonemal complex breakdown
Diplotene
Final step of prophase I
Diakinesis
Chiasma slides towards the terminal region of the chromosome, a process called?
Terminalization
A stage where the cells rest for a bit before beginning meiosis 2
Interkinesis
Protein kinases (enzyme) activated by cyclins
Cyclin-dependent Kinases (CDKs)
Type of cell division cycle (cdc) proteins that bind to CDKs and activate them
Cyclins
binds to CDK3
Cyclin C
binds to CDK4
Cyclin D
binds to CDK2
Cyclin E
binds to CDK2 and CDK1
Cyclin A
binds to CDK1
Cyclin B
Inhibits CDKs to ensure that they are activated only when needed
Cyclin-dependent kinase inhibitors (CKIs)
Inhibits CDK2; when increased, the cell enters GO
P21
Important for separating the chromosomes during anaphase
Anaphase Promoting Complex/Cyclosome (APC/C)
Kinases that phosphorylate molecules to either activate or deactivate them
Other cdc Proteins
Complex that promotes G0/G1 transition
CDK3-C complex
It is a transcription factor that is required for the synthesis of cyclin E,
E2F
E2F is bound to and inactivated by, the tumor repressor protein called?
retinoblastoma protein (Rb)
A cyclin required for G1/S transition
Cyclyn E
: promotes G1/S transition
: promotes the degradation of cyclin D
: promotes synthesis of cyclin A
CDK2-E complex
: promotes DNA replication
: called the S-phase Promoting Factor (SPF)
: promotes degradation of cyclin E
CDK2-A complex
: promotes S/G2 transition
: promotes the synthesis of cyclin B
: promotes the degradation of cyclin E
CDK1-A complex
: promotes G2/M transition
: called the Maturation Promoting Factor (MPF)
: promotes degradation of cyclin A
: promotes activation of APC/C
CDK1-B complex
: promotes degradation of securin to release separase
: promotes anaphase/G1 transition
: promotes degradation of cyclin B
: promotes the synthesis of cyclin D
APC/C
Separase is inactivated by an inhibitor called?
Securin
They are important in verifying that the processes in each phase have been accurately completed before progressing to the next phase.
Cell Cycle Checkpoints
Checkpoint located in the G1 stage just before the G0 and the S stages
G1 or Restriction Checkpoint
Checkpoint located at the end of the G2 stage
G2 or DNA Damage Checkpoint
This checkpoint will have to make sure that there were no damages incurred during DNA synthesis
G2 or DNA Damage Checkpoint
Determines if the cell has met the requirements for growth and if there are no damages in the DNA
G1 or Restriction Checkpoint
Located at the end of the Metaphase stage
Anaphase Checkpoint or Spindle Assembly Checkpoint (SAC)
Checks if the kinetochore microtubules are properly attached to the kinetochores
Anaphase Checkpoint or Spindle Assembly Checkpoint (SAC)
These proteins serve as the “guards” of the cell cycle checkpoints.
Checkpoint Proteins
Checkpoint protein found in G1 checkpoint
P53
A tumor repressor protein and considered as the “guardian of the genome”
P53
Has the ultimate task of cell cycle arrest for repair or apoptosis once it receives a signal that something is wrong in an event in the cell cycle
P53
How does P53 signal cell cycle arrest?
- it arrests growth by signaling P21 synthesis to inhibit CDK2 and CDK1
- inhibiting these molecules prevents cyclin from activating them and effectively preventing the progression of the cell cycle
How does P53 signal apoptosis?
o P53 inhibits Bcl2 (B-cell lymphoma 2) to release Bax (Bcl2-associated X protein)
o Bax signals the release of cytochrome C from the mitochondria
o Cytochrome C binds with Apaf1 (apoptotic protease-activating factor 1), changing its molecular conformation, forming an apoptosome
o Apoptosome binds to Caspase 9 to form an apoptosome-caspase 9 complex
o The complex interacts with caspase 3 and caspase 7 to promote apoptosis
T or F:
Most cancers are due to a P53 gene mutation
True
A checkpoint Protein found in the G2 checkpoint
Ataxia Telangiectasia Mutated (ATM)
A sensor protein that detects double-strand breaks in the DNA that probably occurred in the S-phase
Ataxia Telangiectasia Mutated (ATM)
T or F:
Even if ATM is functional, if P53 is absent or non-functional, there will be no signal for
cell cycle arrest or apoptosis
True
Checkpoint Protein found in the spindle assembly checkpoint
Mitotic Arrest Deficient (MAD)
Spindle assembly checkpoint; if kinetochore microtubules are attached properly to the kinetochores. State the next steps
- If the balanced tension is detected, signaling cdc20 to bind to APC/C to form cdc20-APC/C complex
- this complex promotes securin degradation, the release of separase, and removal of cohesins to separate sister chromatids
Spindle assembly checkpoint if there is no balanced tension due to the failure of a kinetochore-microtubule to attach to a kinetochore, what are the events that will occur?
- Bub1 (budding uninhibited by benzimidazole 1) attaches to the kinetochore and recruits MAD1
- MAD1 activates MAD2, which in turn binds to cdc 20 to form a MAD2-cdc20 complex
- This complex binds to APC/C inhibiting it
- APC/C can no longer perform its function to promote anaphase
An unfertilized egg that undergoes mitosis, but fails to undergo cytokinesis?
The result of mitosis without cytokinesis will be a cell with more than one nucleus. Such a cell is called a multinucleated cell.
A cell with a chromosome that lost its centromere?
An acentric chromosome is fragment of a chromosome that lacks a centromere. Since centromeres are the attachment point for spindle fibers in cell division, acentric fragments are not evenly distributed to daughter cells during cell division.
A cell with a chromosome that contains two centromeres?
A dicentric chromosome is an abnormal chromosome with two centromeres. It is formed through the fusion of two chromosome segments, each with a centromere, resulting in the loss of acentric fragments (lacking a centromere) and the formation of dicentric fragments.
If cell division during gametogenesis were non-meiotic, what would be its consequence for future generations of diploid organisms?
No crossing over happens. the number of chromosome become double after each generation and genetic makeup of species changes.
