What proportion of all species that ever lived has become extinct?

Data from several papers by chargaff: for example,

jeka94

YES.The distribution of bases in sea urchin DNA and salmon DNA follow Chargaff's rules because the percentage of A bases is approximately equal to the percentage of T bases, and also the percentage of G bases is approximately equals to the percentage of C bases in both species. According to Chargaff's rule the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.

5 0

4 years ago

Considering the drifting of continents, how do you explain the abundance of marsupials and the absence of native placental mamma

garri49 [273]

Answer:

this phenomenon is a natural consequence of evolutionary processes and continental drift

Explanation:

Marsupials are mammals in which newborn offspring are carried in a pouch of the female (mother) body. On the other hand, placentals are mammals that complete embryo development in the mother's body, in the placenta. All the extant marsupials are endemic to Australia and the Americas. It has been shown that marsupials diverged (evolved) in South America, Australia and Antarctica when these landmasses were joined. In Australia, marsupials evolved to fit an ecological niche, which can be attributed to geographic isolation due to continental drift, while placental mammals are relatively recent and more scarce (mainly bats and rodents) within this region.

5 0

3 years ago

Which of these would most likely cause a mutation? A the placement of ribosomes on the endoplasmic reticulum B the insertion of

astra-53 [7]

the insertion of a nucleotide into DNA would most likely cause a mutation.

7 0

3 years ago

How are the modes for reproduction different in unicellular and multicellular organism.

Neporo4naja [7]

The unicellular and multicellular organism are different in asexual and sexual mode of reproduction.

The reproduction is the phenomenon which involves the production of an offspring by particular individuals or individuals to propagate there species. Reproduction are of two types:

1. Asexual reproduction: In asexual reproduction, they does not involve the fusion of gametes. The unicellular organism reproduce mainly by binary fission. In this, a single cell divides into two daughter cell. The daughter cell completely resembles their parent. It involves only one parent.

2. Sexual reproduction: In sexual reproduction, there is a fusion of gametes that brings changes in genetic combination. The germ cell undergoes meiosis that produces haploid gametes that fuse to form new individuals. It involves either one or two parents.

To learn more about Reproduction here

brainly.com/question/14329745

#SPJ4

3 0

2 years ago

An additional gene, gene W, was also examined. A test cross was made between true-breeding EEWW flies and EEWW flies. The result

Debora [2.8K]

This question is incorrect but here is the correct question below;

An additional gene,gene W was also examined. a test cross was made between true breeding EEWW flies and eeww flies. The resulting F₁ generation was then crossed with eeww flies. 100 offspring in the F₂ generation were examined and it was discovered that the E and W genes were not linked.

Which is the correct genotype of the F₂ offspring if the genes were linked and if the genes were not linked?

a) Linked: 50% EeWw and 50% eeww; not linked: 25% EeWw, 25% Eeww, 25% eeWw and 25% eeww.

b) Linked: 25% Eeww, 50% eeWw; not linked:parental genotypes EeWw and eeww.

c) Linked genotypes (EeWw and eeww) and recombinant genotype ( Eeww & eeWw) in the F₂ generation are nearly the same irrespective of their linkage.

d) Linked: mostly with parental genotypes, Eeww and eeWw; unlinked: 25% EeWw and eeww with 75% Eeww and eeWw.

Answer:

a) Linked: 50% EeWw and 50% eeww; not linked: 25% EeWw, 25% Eeww, 25% eeWw and 25% eeww.

Explanation:

a test cross was made between true breeding EEWW flies and eeww flies

If EEWW self crossed, we have the following ( EW, EW, EW, EW)

Also, for eeww, we have ( ew, ew, ew, ew)

EW EW EW EW

ew EWew EWew EWew EWew

All offspring are (EWew)

The question goes further by saying "The resulting F₁ generation was then crossed with eeww flies".

And we are asked to find the correct genotype of the F₂ offspring if the genes were linked and if the genes were not linked

∴

To determine the offsprings of the linked genes we need to go by the definition and understand what linked genes are: Linked genes are genes that are physically close together on the same chromosomes. Effect of recombinantion on linked genes, results in gene swaps which occur in chromosomes that are homologous.

Having said that; If EWew × eeww

we have; EW & ew × ew & ew

EW ew

ew EeWw eeww

offspring that

are linked in ⇒ EeWw EeWw & eeww eeww

F₂ will be

$\frac{1}{2}$ = 50% of EeWw of the total 100 offspring in the F₂ cross

$\frac{1}{2}$ = 50% of eeww of the total 100 offspring in the F₂ cross

∴ Linked genes = 50% EeWw and 50% eeww.

For unlinked genes; If EWew × eeww

if rearrangement occurs in EWew and EWew self crossed, we have ( EW,Ew,eW,ew) as the traits needed for the unlinked gene F₂ crossing.

Also ewew will be (ew, ew, ew, ew).

EW Ew eW ew

ew EeWw Eeww eeWw eeww

We have the following results for the unlinked genes

$\frac{1}{4}$ = EeWw 25% of the total 100 offspring in the F₂ cross

$\frac{1}{4}$ = Eeww 25% of the total 100 offspring in the F₂ cross

$\frac{1}{4}$ = eeWw 25% of the total 100 offspring in the F₂ cross

$\frac{1}{4}$ = eeww 25% of the total 100 offspring in the F₂ cross

∴ not linked: 25% EeWw, 25% Eeww, 25% eeWw and 25% eeww.

3 0

3 years ago