Lecture 6-8 Flashcards
Most plants and animals are what configuration of chromosome
diploid
What is monoploidy
only one set of chromosomes (not pairs like humans)
What is polyploidy
more than normal set of chromosomes (ie. triploidy, tetraploidy, etc.)
Why is it beneficial for plants to be polyploidy
more genetic material = larger and stronger
What are autopolyploids
all chromosome sets are identical
What are the observable traits of autopolyploidy
more vegetative growth and less seed production
How does autopolyploidy occur through mitosis
diploid 2n goes through replication but cytokinesis fails and no cell division occurs, resulting in a tetraploid 4n cell
How does autopolyploidy occur in meiosis
cytokinesis of 1 of 2 daughter cells in meiosis 2 fails, creating a 2n and a 1n that combine to form a triploid
What is the problem with polyploidy
many polyploids are sterile due to problems with pairing and separation of homologous chromosomes in meiosis
Does a plant still have reproductive efforts even if its sterile
yes, just unsuccessful efforts
What occurs in meiosis 1 to make it non viable in many polyploids
gametes end up with random variation of talents, making them non viable so they die
If you have a 3n=33 polyploid plant trying to reproduce, what would be observed in metaphase 1 and anaphase 1
sister chromatid pairs are pulled to poles randomly, resulting in univalents, bivalents, or trivalents depending on the separation
If a 3n=33 plant undergoes meiosis attempts and 2 homologous chromosomes pair while the other does not pair at all, what is observed
11 bivalents and 11 univalents (to make 3n=33)
If a 3n=33 plant undergoes meiosis attempts and all homologous chromosomes pair up, what is observed
11 trivalents (to make 3n=33)
If a 3n=33 plant undergoes meiosis attempts and no homologous chromosomes pair up, what is obersved
33 univalents
In a 3n=33 organism, how many segregation options are there
11 options
What are allopolyploids
polyploids as a result of crossing between 2 or more species
What type of reproduction is done to produce allopolyploids
asexual (mitosis)
Why can’t sexual reproduction occur between plant A and plant B
chromosome sets from A and B are not homologous to one another
What occurs spontaneously in plant chromosomes
can double their chromosomes spontaneously
What is an amphidiploid
a plant originating from hybridization between 2 plant species in which the chromosome number is the sum of the 2 parental chromosome numbers
How would a sterile animal be formed
interspecies crosses (polyploidy)
What is an example of polyploidy in animals resulting in a sterile animal
donkey x horse = mule
What is aneuploidy
diploid genome that lacks a chromosome or carries an extra
what is the term for a 2n + 1
triploidy
what is the term for a 2n-1
monoploidy
What is the result of non disjunction in meiosis 1
1 daughter cell gets no chromosomes, one daughter cell gets all chromosomes
- once in meiosis 2 the cell with chromosomes further divides, while the other produces empty daughter cells
(results in 2 trisomic and 2 monosomic cells when fertilized)
What is the result of non disjunction in meiosis 2
normal division occurs in meiosis 1, however in meiosis 2 one of the cells separates incorrectly, creating an empty daughter cell and a daughter cell with an extra chromosome
(results in a trisomic chromosome and monosomic chromosome, and 2 normal diploids)
What happens to autosomal monosomies in humans
lost early in pregnancy (never seen as live births)
What happens to autosomal trisomies in humans
only 1 type of trisomy occurs that results in life into adulthood - Down syndrome
rest usually die by age 2-3 due to genetic defect
What is the only fully viable human trisomy
chromsome 21 - Down syndrome
What is the gamete configuration of Turner syndrome
X0
What is the gamete configuration of Kleinfelter syndrome
XXY
What is the gamete configuration of triple x syndrome
XXX
What is the gamete configuration of double y males
XYY
How are Turner syndrome, Klinefelter syndrome, and triple x syndrome tolerated
x inactivation
How is double y male syndrome tolerated
Y chromosomes are small and usually only carry hormones, so little effect on humans as a whole
If a diploid has a 2n=36 configuration, how many chromosomes would be present in a monosomic member of this species
2n - 1, so 35 chromosomes would be observed in this specific species
How does age of mother impact risk of trisomy and monosomy
as age increases of mother, risk of trisomy or monosomy also increases
Why does age play a role in risk of trisomy or monosomy
exchange of genetic material occurs constantly as eggs are arrested in prophase 1, with more exchange of this material (more time aged) the likelihood of mitotic spindle separation decreases which results in higher risk for non disjunction
What, other than age, has been found to impact trisomy and monosomy risk
chemicals (environment)
What is a deletion/deficiency
missing chromosome segment
What is a duplication
extra chromosome segment
What is hypoploidy
hypo = less
less genetic material as a result of deletion or deficiency
What is hyperploidy
hyper = more
more genetic material as a result of duplication (or gain of an entire chromosome)
What is translocation
when a segment from one chromosome is detached and reattached to a different (non homologous) chromosome
What is reciprocal translocation
pieces of two non-homologous chromosomes are exchanged without any net loss of genetic material
What are compound chromosomes
formed by the fusion of homologous chromosomes, sister chromatids, or homologous chromosome segments
What are Robertsonian translocations
formed by the fusion of 2 non homologous chromosomes at their centromeres
How can a translocation lead to cancer
if moved to a chromosome that cannot regulate it, replication will occur out of hand and cause mutations (cancer)
