Bio Test 3 Flashcards
What happens in Prophase?
DNA condesnses into chromatids
Centtrioles form and move to the opposite sides of the cell.
What happens in Telophase?
A nucleus forms around each set of chromosomes.
5) Be able to identify and describe what the following components that move chromosomes during M-phase are – centrosome, centriole, microtubules
Centrosomes move to be like the poles on each end of the cell and connect the microtuble “threads” to the centrioles at the middle of the chromosomes.
7) What do checkpoints do, and how do they do this job? (discuss cyclin/cdk’s in your answer)
Checkpoints control when and how the cell moves through the different phases. There are checkpoints at G1, G2 and M. Molecules inside cells, cyclins and cyclin-dependent kinases. Cyclin binds to CDK to move the cell past the checkpoint, if cyclin levels are too low the CDK becomes inactive and the cell cycle is paused.
8) What is a way that cells speed up or slow down the cell cycle?
It can speed up the cycle by activating specific cyclins and cdks so it moves through the checkpoints. It can slow down the cell cycle by stoping the process when it detects DNA damage or errors.
9) What cellular signals control the cell cycle (cell division of a cell)?
In addition to the internal signals from cyclins and cdks, the cell also receives signals from other cells regarding nutrient, growth factors, density-dependent inhibition and anchorage dependance.
5) What are the three things that happen during sexual reproduction that causes genetic variation to occur? State each, then describe them in detail.
Crossing over- where nonsister chromatids exchange chromosome tips.
Independent Assortment where which copy of the chromosome is passed on is random.
Combining chromosomes of genetically different gametes- dna from two distinct parental genomes mixing in new ways.
Incomplete dominance
two traits mixing
-Codominance
two traits present together
Multiple allelic traits
More than 2 possible alleles for a given trait, like blood type.
a. State the three things that happens to RNA during processing
The 5’ end gets a 5’cap, the 3’ end gets a poly-A tail and RNA splicing removes introns and joins exons.
b. What are introns/exons, and which stick around?
Introns are “filler” DNA that aren’t needed and are removed to have a continuous coding sequence, leaving only the exons.
Describe Transcription
Initiation begins with the promoter code (TATA . . .) that tells where to begin transcribing for that gene. RNA polymerase binds to the DNA template strandat the TATA box and unzips the double helix. In elongation the RNA polymerase copies the template strand into an mRNA strand using with the relevant RNA base pair till it reaches the Termination signal and pulls off.
Elongation
Arrange the following structures from smallest to largest
- “Naked” DNA double helix -
-Histone proteins -
-Loops -
-Scaffold -
-Nucleosome-
-30nm fiber -
-300nm fiber -
-“Metaphase chromosome”: Note, this chromosome will be well packed in other stages of mitosis as well. -
- Naked DNA
2 Histone Proteins
Nucleosomes
30 Nm fiber
Loops
Scaffold
300 Nm fiber
Metaphase chromosome
What are two ways we discussed cells preventing mutations from occurring?
DNA polymerase proofreads the DNA while it is copying it. Mismatched or damaged DNA is fixed by multiple enzymes working together.
