week 4 Flashcards
how do the genes travel for meiosis
Genes that are on the
same chromosome
travel through meiosis
together
can genes recombined or crossover
- However, alleles of
chromosomally linked
genes can be
recombined by
crossing-over.
do genes segregate randomly
Some genes
do not segregate randomly
when genes are linked
Genes are “linked” if
present on the same
chromosome
what is the gene recombination
The divergence from
linkage is called
recombination
what is the Sturtevant
Sturtevant:
* The frequency of recombination reflects distance
between genes.
is the inheritance pattern of one trait similar to the other trait
The inheritance pattern of one trait does not affect the inheritance
pattern of another trait.
when Homologous recombination happens
Homologous recombination occurs during
prophase I of meiosis
what does tetrad or bivalent means
A tetrad or bivalent (this means
FOUR homologous chromatids) is
formed
what does chiasma means
A chiasma (plural chiasmata, this
is the physical junction between
the homologous chromatids) is
the site where recombination
occurs
what is the affect of the long distance between the chromosomes on the recombination
When genes are more distant from one another on the chromosome, the likelier
they are to crossover independent from the other,
generating recombinant gametes
what are the three Possible Scenarios for Dihybrid Cross AaBb X AaBb There Are
1) Genes A and B are independently assorting -
4 classes of offspring with a 9:3:3:1 ratio
2) Genes A and B are tightly linked so
that crossing over does not happen2 classes of offspring with a 3:1 ratio
3) Genes A and B are linked and crossing-over
occurs (variations in the 3:1 ratio)
ratio of 24:1:1:7 is the variation of which ratio
The ratio 24:1:1:7 is a
variation of 3:1 ratio
when the recombination is caused
Recombination is caused by a physical exchange between paired
homologous chromosomes early in the prophase of the first meiotic
division after chromosomes have duplicated.
how many of the chromotids are involved in the crossing over
At any one point along a chromosome, the process of exchange
(crossing over) involves only two of the four chromatids in a
meiotic tetrad.
when is the crossover became visible as chiasmate
Late in prophase I, crossovers become visible as chiasmata.
what is the chromosome mapping
Chromosome mapping: Linked genes can be mapped on a
chromosome by studying how often their alleles recombine.
what cause the Nail Patella Syndrome
Nail Patella Syndrome is caused by a rare
dominant allele, N, on chromosome 9
how does the NPS1 mutation cause the nail patella syndrome
The NPS1 mutation (causing the
syndrome) is linked to the gene for
the B blood group phenotype
- Recombination frequency between
B and NPS1 is estimated and used for
mapping of the N gene
what are the phynotypes of the Prognatism syndrome
Prognatism: normal variations in the size of the mandible,
could be pathological if extreme
when was the Prognatism had the high frequency
Prognatism was frequent in the Habsburg royal family peaking
at the time of Philip II and Charles I of Spain
