Unfortunately this interesting case has never been critically investigated, and the statement that the mulatto breeds true rests almost entirely upon {130} information that is general and often vague.
Nevertheless, as breeding tests have amply shown, we are dealing with but two interacting factors which segregate cleanly from one another according to the strict Mendelian rule.
By accepting the "Presence and Absence" hypothesis we are committed to the view that the dominant form possesses an extra factor as compared with the recessive.
The result of the meeting of these two series of gametes is given in Fig.
The character of each individual is represented by the sex signs in brackets, the black being grossulariata in appearance and the light ones lacticolor.
For it is the only form of variation of whose heredity we have any certain knowledge.
Some of these would possess it in a less and some in a greater degree than the parent.
The two were mutually exclusive so far as the gamete was concerned.
These albinos are, as it were, like photographic plates exposed but undeveloped.
Through the continued action of natural selection on each successive generation the useful variation was gradually worked up, until at last it reached the magnitude of a specific {141} distinction.
None of the F2 male birds, however, showed the full deep pigmentation of the Silky.
The intensity of the coupling, however, varies in different cases.
Such is the blue of the Andalusian fowl, and, according to Professor Wilson, the roan of the Shorthorn is similar, being the heterozygous form produced by mating red with white.
Scheme to illustrate the heterozygous nature of the pure Brown Leghorn hen.
An individual may be homozygous for one or more characters, and at the same time may be heterozygous for others.
Breeding tests alone can decide which is the heterozygous and which the homozygous form.
But it may be heterozygous for the purpling factor when it will throw the dilute red (tinged white), or it may be heterozygous for either or both of the two colour factors (cf.
The heterozygous tall pea or the heterozygous rose-combed fowl cannot be distinguished from the homozygous form by mere inspection, however close.
The female is heterozygous for a dominant factor (F) which is lacking in the male.
A {78} hornless ram, therefore, put to a flock of F1 ewes should give rise to equal numbers of zygotes which are heterozygous for the horned character, and of zygotes in which it is completely absent.
Since the female is always heterozygous for F, her gametes must be of two kinds, viz.
The F1 birds produced by crossing were in constitution CcBb, and being heterozygous for two factors produced in equal numbers the four sorts of gametes CB, Cb, cB, cb.
We will suppose that in dioica femaleness is dominant to maleness, and that the female is heterozygous for this additional factor.
If he marries a normal woman (Ffmmxx), the spermatozoa Mfx unite with ova fmx to give normal males, while the spermatozoa mfX unite with ova Fmx to give females which are heterozygous for the colour-blind factor.
Being heterozygous for two factors they will produce four kinds of gametes in equal numbers, viz.
On this last hypothesis the mutation here considered might be a heterozygous specimen, with the dextral condition dominant in the head and the sinistral in the body.
The Mendelians, when the mutations of Oenothera were first described, endeavoured to show that they were merely examples of the segregation of factors from a heterozygous combination.
Or it might be somehow due to what Morgan and his colleagues have called crossing over in the segregation of heterozygous chromosomes, so that a part corresponding to a sinistral body is united with a part corresponding to a dextral head.
On this theory, therefore, there would always be some females heterozygous for the male character.
In this the female is heterozygous for sex as in Abraxas grossulariata, and the barred character is sex-linked.
It is true that in heterozygous individuals characters may develop more fully in the adult stage than in the young.
The normal male is heterozygous for this normal factor.
It is so coupled only in the heterozygous grossulariata [female], and at the same time the grossulariata character is repelled.
There is now no doubt that this proserpina is a heterozygous form, resulting from a combination of the characters of arthemis and astyanax.
It must be remembered that we have no knowledge what the heterozygous form may be, and in the case of red and yellow it is probably a reddish buff.
Similarly we may say that at least garden Petunias are heterozygous in respect of singleness.
Often, perhaps generally, they are nothing but heterozygous forms, and often also they are conditions corresponding with the presence of factors in their reduction-stages.
Some of these normals must be expected therefore to be heterozygousunless some selective fertilisation occurs.
But nothing can be more certain than that these plants are simply heterozygous combinations made by the union of gametes bearing the characters of diurna and vespertina.
It relates to certain Oenotheras heterozygous for dwarfness, in which (p.
Or to use the adjective forms, a pure black guinea-pig is homozygous for black pigment, an albino guinea-pig is homozygous for absence of pigment, while a cross between the two is heterozygous for pigment.
Females heterozygousfor lethal sc were therefore crossed to bar males, and their daughters were tested.
Club females were obtained by breeding F2 club males to their F2 long-winged sisters, half of which should be heterozygous for club.
Females heterozygous for this lethal, lethal sc, were mated to white males and the daughters were back-crossed to white males.
Since both females and males of chrome were on hand, it should have been an easy matter to continue the stock, but many matings failed, and it was necessary to resort to breeding in heterozygous form.
Since no "pinks" appeared the color is recessive, and the brother was not heterozygous for it.
Consequently a femaleheterozygous for notch bred to a wild male gives a 2:1 sex-ratio; half of her daughters are notch and half normal; the sons are only normal.
This heterozygous bar female is always readily distinguishable from the normal, but can not always be separated from the pure bar.
But from the gray sisters heterozygousfor lemon (bred to lemon males) some lemon females were also produced.
As the cultures dry out the abnormal males are the first to change over to normal, then the heterozygous females, and lastly the homozygous females.
Although the mother was fertilized by a normal male, every daughter is heterozygous for one or the other of the lethal factors.
This shows that the mother of the original high sex-ratio was heterozygous for a recessive sex-linked lethal.
Half the daughters of such a pair are expected to be heterozygous for lemon and also for cherry and vermilion, which went in from the father.
Supposing this to be so, all his offspring, of both sexes, must be heterozygous for X.
All males are heterozygous for I, but during the segregation of characters at some stage in the formation of the families only the male-producing sperms come to contain the factor I.
In a population in equilibrium consisting of homozygous dominants, heterozygous dominants and recessives the last named class comprises 2.
With a heterozygous mimetic female (iiXx), which is also producing germ cells with and without X in equal numbers, he may be expected to give the usual result, viz.
There is no difference in appearance between the heterozygous and the homozygous mimetic insects, whether they belong to the A or to the H form.
It must be supposed that the character depending upon the given factor shews complete dominance, so that there is no visible distinction between the homozygous and the heterozygous forms.
The three sets of figures in the left-hand column indicate different positions of equilibrium in a population consisting of homozygous dominants, heterozygous dominants, and recessives.
Either of these factors when present alone, whether in homozygous or heterozygous form, causes about the same degree of low fecundity to be manifested.
An agouti-black (AA BB EE Dd) becomes a pure black when heterozygous for E.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "heterozygous" in a variety of sentences. We hope that you will now be able to make sentences using this word.
