Answer:
- Independent assortment of chromosomes
- Crossing over
Explanation:
Independent assortment of chromosomes
We each have a diploid genome that is used to make haploid gametes. The selection of which combinations of chromosomes (and the particular alleles they hold) that are passed on to the gametes is random. I.e. 1 gamete could have the paternal chromosomes 1, 4, and 6, and maternal 2, 3 and 5. Another gamete could have paternal 2, 4, and 6, and maternal 3 2 and 5.
This produces unique combinations of alleles that are passed onto the next generation after sexual reproduction.
Crossing over
Crossing over occurs when homologous chromosomes pair up and align during meiosis. When this happens, they can exchange genetic material at homologous sites. This means that even <em>within </em>chromosomes, there are new combinations of alleles being created to pass on to the gametes before sexual reproduction. That is, each chromosome will have chunks of maternal and chunks of paternal DNA.
Both of these features increase genetic variation by two mechanisms, and this is occurring in two individuals, producing genetically diverse offspring.
The most important differences between a transmission electron microscope and a scanning electron microscope are: Rather than the broad static beam used in TEM, the SEM beam is focused to a fine point and scans line by line over the sample surface in a rectangular raster pattern
question answered by
(jacemorris04)
Star stuff. All matter heavier than hydrogen in your body was produced in stars.
Answer:
An amino acid activates the repressor so that the repressor binds to the operator and prevents transcription.
Explanation:
In an operon, promoter is followed by operator which is finally followed by the structural genes to be transcribed. RNA Polymerase binds to the promoter and initiates transcription. A repressor can negatively control the transcription process by binding to the operator so that the RNA Polymerase is not able to move forward and transcription is halted.
For example: in trp operon, tryptophan amino acid binds to the repressor molecule which leads to change in repressor's shape. The repressor is now able to bind to the operator and prevent transcription.
