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Virty [35]
2 years ago
11

Remove the roller bearing fastened to the shaft:

Biology
2 answers:
zalisa [80]2 years ago
6 0
The correct answer would be (B) close the ring in the bearing or the ring in the bearing

Hope this helps! Merry Christmas to you all!!!
Alina [70]2 years ago
3 0

Answer:

B-Close the ring in the bearing or the ring in the bearing.

Explanation:

hope it's help

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Suppose that ear length in rabbits is controlled by two additive genes, each of which has two alleles. A true-breeding female (a
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Answer:

The ear length will be 11 cm.

Explanation:

To know about the ear length of F1 generation, we need to know that how much length in centimeters is contributed by each of the alleles. As we know, each allele has the same value for contributing to the effect of ear length, hence we can divide the ear length by 4 to get our results.

As 6 divided by 4 is 1.5 hence, the allele a and b contribute to 1.5 cm of the length of the ear.

6 divided by 4 is 4, hence the alleles And B contribute to 4 cm of the length of the ear.

The F1 generation will have AaBb genotype hence, the lenght will be 4+1.5+4+1.5 = 11 cm.

6 0
3 years ago
A researcher is examining a sample of smooth muscle tissue under a microscope. Which of the following would correctly describe w
iVinArrow [24]
The answer would be B
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2 years ago
Describe the probable effects on gene expression in the lac operon of each mutation: a. Mutation in the lac operator that delete
Stella [2.4K]

Answer:

a. Reduces represor binding.

b. Constitutive expression of the operon.

c. Stronger promoter if it is more similar to the consensus sequence. Weaker promoter if less similar.

Explanation:

The lac operon is an operon required for lactose transport and metabolism in enteric bacteria such as <em>Escherichia coli</em>. <u>It is regulated by glucose and lactose availability</u> and consists of the following structural genes:

  • Lac z gene: encodes the enzyme β-galactosidase, which catalyzes the hydrolysis reaction of lactose into glucose and galactose.
  • Gene lac y: encodes the protein galactoside permease involved in the transport of lactose into the bacterium.
  • Lac a gene: encodes the enzyme thiogalactoside transferase, which catalyzes the transfer of the acetyl group of acetyl coenzyme A to 6-OH of a thiogalactoside acceptor. This gene is not related to lactose metabolism.
  • Promoter: region of DNA recognized by RNA polymerase for transcription.
  • Operator: region of DNA located between the promoter and the beginning of the structural genes, which is recognized by the repressor protein Lac I.
  • Repressor gene (lac I): encodes the Lac I repressor protein, which recognizes the operator region, where it binds. It prevents the transcription of genes under the control of this promoter but stimulates the binding of RNA polymerase. When the repressor is absent (in the presence of inducer which in this case will be lactose or IPTG), RNA polymerase will begin transcription.

The lac operon is under a type of negative regulation, where genes can always be transcribed, except when the Lac I repressor protein is bound to the operon region, for which it has a high affinity. In this case, the promoter of the lac I gene is constitutive, so the Lac I protein is permanently expressed and remains bound in tetramer form to the operon region, preventing the transcription of structural genes.

Since lactose is the inducer of the operon, it is able to bind to the Lac I repressor protein and generate a conformational change that decreases its affinity for the operon region. Thus, the operon region is left free, <u>RNA polymerase can freely transcribe the structural genes and β-galactosidase can degrade lactose to glucose plus galactose</u>. <u>In the absence of lactose, the Lac I repressor protein maintains its high affinity for the operator region, preventing RNA polymerase from transcribing the structural genes</u>. In this way, the system remains closed with consequent energy savings for the bacterium.

As a final clarification, actually the true inducing molecule of the lac operon is called allolactose, an isomer of lactose obtained by a transglycosylation occasionally carried out by β-galactosidase.

a. When there is a mutation in the lac operator that deletes most of the operator, then the repressor Lac I can no longer bind and RNA polymerase will begin transcription.

b. When there is a mutation in the Lac I gene that eliminates the binding of repressor to operator, then this protein can not produce the repression so there would be a constitutive expression of the operon.

c. Since the promoter us a region of DNA recognized by RNA polymerase for transcription, if there is a mutation here it will generate a stronger promoter in the case that this part is similar to a consensus sequence (the most commonly encountered nucleotides found at a certain location). In the case that it is less similar, then it will generate a weaker promoter.

7 0
3 years ago
A model of cell division is shown here. A student evaluates the model and makes the claim that the cell division increases genet
loris [4]

Chromosomes exchange genetic material in step 3.

<h3><u>Explanation</u>:</h3>

The meiosis is the type of cell division that takes place for gametogenesis. The meiosis has two phases - meiosis I and meiosis II.

The meiosis I has the events like crossing over and independent assortment which leads to the mixing of genes between homologous chromosome pairs and separation of homologous chromosome pairs. So the two cells that are produced from the meiosis I are genetically different. The step 3 shows the crossing over of prophase 1 of meiosis I. So, it shows the genetic difference between the offsprings and leads to genetic variation.

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h2o / water molecules

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3 years ago
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