Exam 1- My Q's Flashcards
What does each chromosome have that distinguishes them from others?
a characteristic centromere position and unique length and shape
karyotype
display of the chromosome complement of a cell or individual
homologous chromosome pair
same length, shape, centromere position, identical genetic potential, not genetically identical
How many autosomes do humans have
22
why can sex chromosomes interact even though they are different sized and shaped
can behave as homologous because of their pseudoautosomal regions
haploid or diploid?
egg
zygote
adult
egg: n
zygote: 2n
adult: 2n
What are germ cells?
they are cells in the sex organs testis and ovaries that can divide my meiosis to produce gametes
Key words for prophase 1
metaphase 1
anaphase
telophase
prophase: crossing over, condensation, synapsis (pairing of homologous pairs)
metaphase: line up at equator of cell
anaphase: disjunction
telophase: splitting cell into 2, cleavage
What are the results of prophase 1
4 chromatids- tetrad
where and when does crossing over happen?
chiasma during prophase 1
what are chromosomes like in prophase 1
consist of 2 sister chromatids. still attached
what is the main event of phase 1 and 2 of meiosis
phase 1: reduces ploidy of original germ cell from diploid to haploid
phase 2: recombines genetic info further now that chromosomes have crossed over
disjunction, what is it when does it happen
movement to opposite poles in cell, anaphase I and II
What is the difference between telophase 1 and 2
in telophase 2 the chromatids are mosaic, mixed info between mom and dad
What is the final result of meiosis phase 2
4 genetically unique daughter cells
how many cells mature in spermatogenesis vs oogenesis
sperm: 4
ovum: 1
What are mendel’s 3 proposals
1: there are recessive and dominant traits
2: there are unit factors or genes that are passed from parent to offspring. these unit factors exist in alternative forms
3: 2 alleles segregate during gamete formation, there is an equal probability that a gamete receives 1 allele from each gene
What is mendel’s 4th proposal
segregating pairs of alleles assort independently from one another.
Autosomal recessive inheritance
the trait appears in progeny of unaffected parents. appears equally in both sexes
Autosomal dominant inheritance
trait almost always appears in each generation, usually at least 1 affected parent. more common in heterozygotes than homozygotes
wildtype allele
most common phenotype, usually dominant
mutant allele
has a mutation, usually recessive
polymorphic allele
more than 1 wildtype allele of a given gene that coexist
haplosufficiency
when a single functional allele is sufficient to bring about a function
complete dominance
an allele is expressed whenever present
incomplete dominance
neither allele is fully dominant, forms a new intermediate phenotype
codominance
2 alleles are both dominant, forms a new phenotype where both are present, spotted.
Lethal alleles
mutations in genes whose proteins are essential for survival, the organism can die from it
recessive lethal allele
homozygotes don’t survive, 2 copies allele needed to kill
dominant lethal allele
only 1 allele needed to kill, very rare
pleiotropy
expression of an allele that has multiple phenotypic effects. can be expressed at different developmental stages
x linked recessive
more males affected, no sons receive it. affected females pass it to all sons
x linked dominant
affected males pass to all daughters but not sons
dosage compensation
females have the potential to make twice the x linked genes but have gene inactivation randomly. preventing the expression of x linked genes every single time
epistasis
2+ genes influence a trait and one overrides the other
recessive epistasis
the homozygous genotype prevents the expression of another
dominant epistasis
a dominant allele of one gene overrides the expression of another gene
gene interaction
2 or more genes influence a single trait
complementary gene interaction
at least 1 dominant allele of each gene is needed to produce a certain phenotype. 1 allele is stronger than the other
euploidy
having an exact multiple of complete chromosome sets
ex: haploid, diploid
aneuploidy
having an extra or missing individual chromosome
monosomic
loss of a single chromosome
2n-1
trisomy
gain of a single chromosome
2n+1
why are triploids usually sterile?
because they cant be equally distributed into their own cells, they produce aneuploidy gametes.
What are the ways chromosomes numbers can be varied?
nondisjunction, complete nondisjunction, mitotic slippage, hybridization
nondisjunction
during meiosis I or II, chromosomes don’t correctly separate
what are the results of nondisjunction
offspring with one extra or one missing chromosome, anueploidy
complete nondisjunction
no cell separation, one daughter cell empty in meiosis 1, cell separates only in meiosis 2
mitotic slippage
mitosis fails and never happens, cell never separates results in tetraploid cell
1:1
Test cross
3:1
F1xF1 single trait- normal expected results
9:3:3:1
dihybrid normal results, 2 traits
1:2:1
incomplete dominance
1:1:1:1
codominance
2:1
recessive lethal
9:3:4
recessive epistasis (albino scenario)
12:3:1
dominant epistasis
9:7
complementary interaction/ duplicate recessive epistasis (at least 1 capital of each gene to give a certain phenotype)
down syndrome
2n+1 autosomic
patau
2n+1 autosomic
edward
2n+1 autosomic
turner
sex linked 2n-1 (X)
klinefelter
sex linked 2n+1 (XXY)
triplox
sex linked 2n+2 to + 4, extra x
what are the consequences of aneuploidy
can cause abnormal phenotype due to imbalance of gene expression
how does a trisomy express
excessive amounts of gene products
how does a monosomy express
deficient amounts of gene products
what can non disjunction lead to
aneuploidy
what can complete nondisjunction cause
autopolyploidy, like a triploid
what can mitotic slippage lead to
autopolyploidy
what can hybridization lead to
allopolyploidy, sterility
allopolyploidy
more than 2n (polyploidy) with 2 different but similar species
autopolyploidy
more than 2n all chromosomes from the same species.
Which hybrids are sterile and which arent
if there is a nondisjunction, then there are 2 copies of each chromosome (amphidiploid) then those hybrids are viable offspring. If 2 species mate but meiosis performs like normal, the gametes are non viable because there are not even pairs.
What causes deletion and duplication
unequal crossover
What is intercalary and terminal deletion
intercalary- deletion in interior
terminal-deletion at the end
what happens if there is a deletion on a very short chromosome
hypoploidy: under representation of a gene
what happens if there is a duplication
hyperploidy: over representation of a gene
what is paracentric and pericentric inversion
para- does not include centromere
peri-includes centromere
What are some of the possible effects of inversion
could affect fertility, causes loop formation, a fragment is lost
What are the consequences of translocations
reduced fertility
What if translocation happens during meiosis
1 chromosome can be homologous to more than one other, creates cross or diamond type formation gametes are duplicated and deficient
robertsonian translocation
the extreme of short chromosomes attach to longer chromosomes. usually on acrocentric (centrosome near end)
