Exam how do we know if a trait is caused by one gene or by two genes that interact? example: dihybrid cross of pure-breeding parents produces three phenotypes in f2 progeny if single gene with incomplete dominance, then f2 progeny should be in 1: 2: 1 ratio if two independently assorting genes and recessive epistasis, then f2 progeny should be in 9: 3: 4 ratio these ratios can appear very similar. further breeding studies can reveal which hypothesis is correct.

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation:

there are 35 white marbles

step-by-step explanation:

y- yellow marbles

4y + 5 = 45

subtract 5 from both sides

4y = 40

divide for from both sides

y = 10

plug in 10 to get 40 yellow marbles then subtract by 5 to get 35 marbles

thus there are only 10 yellow marbles

a bird that nests only in a particular tree species.

i believe the correct answer is the virus gets an envelope that contains host molecules when it leaves the host cell.

explanation:

during the bidding/release stage of a virus, it encapsulates itself with part of the membrane of the host cells in this case the cells of the monkey and is the reason as to why the scientist found the genetic material of the monkey on the viral cell surface.

further explanation

to understand this answer, we have to know the cycle a virus undergoes to replicate. a virus is basically a bunch of genetic material enclosed in a capsule and lacks any machinery or organelles to ensure their survival so they must enter a host cell in order to get the environment needed to survive. some viruses enter and lyse(destroy) the host cell after they have replicated and undergo the lytic cycle while some enter and leave the cell intact after replicating and these undergo a lysogenic cycle. to enter the cell, they undergo the first process called attachment by binding to specific receptors and co-receptors on the surface of the host cell. after attaching to the cell, they start the second phase called penetration where virus enters or is engulfed whole by the host cell through a process called endocytosis. it is the same process that a cell takes up materials it needs or pathogens around it. uncoating of the virus then happens after the virus has been engulfed and is the third stage. the virus then undergoes releasing of its genetic material in the host's matrix.   the materials then enter the nucleus and undergo biosynthesis by adding themselves in strands of rna being translated and then copies of the virus are produced in addition to the host genetic material. the material/newly formed viral material then undergoes assembly inside the host cell and form a capsule around them. the virus undergoes the last release/budding stage by binding to the host membrane and pushing outwards. in doing so when they tear away from the host membrane, they pick up the genetic material from the membrane of the host cell to form their envelope.

learn more:

1.

2.

3.

level: high school