When paternal and maternal chromosomes change their materials with each other in cell division this event is called
synapsis
crossing over
bivalent forming
dyad- forming
B.
crossing over
Crossing over is the mutual exchange of segments of homologous chromatids during first meiotic prophase.
Synapsis is the fusion of chromosome pairs at the start of meiosis.
DNA replication precedes the start of Meiosis I. During Prophase I, homologous chromosomes pair and form synapses. The paired chromosomes are called bivalents and the formation of chiasmata caused by genetic recombination becomes apparent.
Dyad formation is a double chromosome resulting from the splitting of a tetrad during meiosis (germ cell formation).
A person who is trisomic for twenty first pair of chromosome suffers from
Klinefelter's syndrome
Down's syndrome
Turner's syndrome
None of the above
Which one of the following can help in the diagnosis of a genetical disorder?
ELISA
ABO blood group
PCR
NMR
The children of a haemophilic man and a normal woman are
all haemophilic
only daughters are haemophilic
only sons are haemophilic
neither sons nor daughters are haemophilic
A man of blood group 'A', marries a woman of blood group 'B', both of them are heterozygous for blood group, chances of their first child having blood group AB will be
25%
50%
75%
100%
If a plant having yellow or round seeds was crossed with another plant having green and wrinkled seeds then F, progeny are in the ratio
15 : 1
1 : 15
1 : 13
all yellow and round seeds
Which of the following conditions represents a case of codominant genes
A gene expresses itself, suppressing the phenotypic effect of its alleles.
Genes that are similar in phenotypic effect when present separately, but when together interact to produce a different trait.
Alleles, both of which interact to produce a trait, which may or may not resemble either of the parental types.
Alleles, each of which produces an independent effect in a heterozygous condition.
