Question

a monohybrid cross can yield offspring with _____ different genotypes ?

1,2,3,4, or impossible to predict?

a women has an x chromosome with a disease allele, which of he rchildren could inherit the disease allele? can you also show how please

a) only her sons can inherit the allele

b) only the daughters

c) both daughters and sons can inherit

Answer 1

1st question)

A monohybrid ( mono means single )cross is cross based on single charecter inheritence i.e based on sigle pair of alleles . parent differs in single allele of same gene (for example in pea plant the gene is T /t for height and allele pair is either TT or tt or Tt . Here the cross between this allele pair will be known as monohybrid cross .) and monohybrid cross can yield offspring with maximum 3 genotype. -1) dominant homozygous genotype 2) recessive homozygous genotype and 3) heterozygous genotype

As for example in a monohybrid cross of sweet pea plant, heterozygous tall plants (Tt) are self crossed (here the single charecter is plants height) and yeild offsprings with three different genotypes.

Gamets will be T and t

	T	t
T	TT (homozygous dominant genotype )	Tt (heterozygous genotype)
t	Tt (heterozygous genotype)	tt ( recessive homozygous genotype)

So in monohybrid cross maximum 3 types of genotypes can be found in offspring .

In case of homozygous monohybrid cross ( between TT and tt only one genotype (Tt) will be yeild.

	T	T
t	Tt	Tt
t	Tt	Tt

Here in this homozygous monohybrid cross only one genotype is yeild in F1 and yeild 3 genotype in F2 generation

2nd question)

If a female is carring one defected X allele (diseases creating) then she can trnsmit the diseases both to her son and daughter.. (option c is right option both daughter and son can inherit)

As daughter will carry XX chromosome among which one chromosome comes from her mother . Here if the mother has one defected X allele so there is a 50% possibility of transmitting that defected X allele to her daughter . And if the defefected X allele is dominant type in nature then daughter will also express the diseases and if the diseases allele is recessive then the daughter will become carrier of the diseases  

In case of son who has XY chromosome. here this X is inherited to the son from his mother so here also 50% possibility of transmitting the defected allele .

The main thing is mother donates single X Chromosome to both her son and daughter hence both can inherit the disease allele. Thats why option a and b are wrong .

Let assume female has XX ( where X is diseases allele) and the male is XY

	X	Y
X	XX (here daughter inherited the disease allele X)	XY ( here boy inherited the diseases allele X)
X	XX	XY