No Two Sperm or Eggs are Alike!

chromosomes and sperm cell

Hopefully you figured out possible combinations of chromosomes for this sperm by calculating 2 to the power of the number of chromosome pairs (4).  24 = 16 possible sperm from just these four pairs of chromosomes.  But in reality, Aaron has 23 chromosome pairs.  So 223 = 8,388,608 possible sperm cells just from Aaron's relatively limited amount of DNA!  This is the amazing thing about independent assortment.  It means that each reproductive cell randomly receives one chromosome from each pair, and every time reproductive cells are created, that randomization happens all over again.

Screen Shot 2018-10-04 at 11.49.08 AM.pngAnd this doesn't apply only to Aaron's body!  Each of the four individuals in this scenario is capable of producing over 8 million genetically different egg or sperm cells.  When you add crossing over to the mix, the possibilities go up even further.  Crossing creates brand new combinations of genetic material on chromosomes that might never have existed before on Earth!  After those new chromosomes go through independent assortment, the resulting sperm and eggs are likely 100% unique and never before encountered.  Altogether, this means it is basically impossible for these twins to create identical babies.  Even if the parents' DNA is the same, crossing over and independent assortment create huge amounts of variation in the combinations of DNA they might pass on.  This is why, as much as siblings might share certain traits, they will never actually be genetically identical, except in the case of identical twins.  (Identical twins are formed by a single embryo splitting in two, so they actually come from the exact same sperm and egg.)

Microscopy Prelab-Quiz

 Score for this attempt: 10 out of 10

Submitted Jan 16 at 1am

This attempt took 2 minutes.

 

Question 1

1 / 1 pts

When viewing specimens on both the dissecting microscope and the compound microscope, you place your eyes in front of the...

  

Objective Lenses

 

  

Ocular Lenses

 

  

Stage

 

  

Iris

 

 

Question 2

1 / 1 pts

If you use transmitted light on the dissecting microscope, the light will...

  

shine in from the right side of the object and bounce off the object

 

  

shine down from above the object and bounce off the object

 

  

shine in from the left side of the object and bounce off the object

 

  

shine up from the bottom of the microscope and pass through the object

 

 

Question 3

1 / 1 pts

What kind of microscope is shown in the picture above?

  

Compound Microscope

 

  

X-Ray Microscope

 

  

Dissecting Microscope

 

  

Electron Microscope

 

 

Question 4

1 / 1 pts

What kind of microscope is shown in the picture above??

  

X-Ray Microscope

 

  

Electron Microscope

 

  

Compound Microscope

 

  

Dissecting Microscope

 

 

Question 5

2 / 2 pts

Select the correct description for each labeled structure using the drop down options.

Label A

 

               Objective Lenses             

Label B

 

               Stage             

Label C

 

               Iris Control             

Label D

 

               Course Focus Knob             

 

Question 6

1 / 1 pts

When viewing a new slide on the compound microscope, we would begin with...

  

the high power (40X) lens pointing down

 

  

the stage all the way down

 

  

the iris all the way open

 

  

the low power (4x) lens pointing down

 

 

Question 7

1 / 1 pts

Which letter indicates a knob that we would NOT use at high power (40x).

  

D

 

  

C

 

  

E

 

  

B

 

 

Question 8

1 / 1 pts

Which of the following is true regarding prepared slides?

 

  

They are prepared by students during class using a blank slide

 

  

They sometimes include a dye that students place on the slide

 

  

They include a label saying what is on the slide

 

  

They require a cover slip that student hinge over the top of a specimen

 

 

Question 9

1 / 1 pts

The correct procedures for putting away a compound microscope include...

  

Point the high power lens down and wrap up the cord

 

  

Point the high power lens down and move stage to bottom

 

  

Point the low power lens down and move stage to middle

 

  

Point the low power lens down and detach the cord

 

you run into your old friend, Aaron, who tells you that (strange as it sounds) he and his identical twin brother Jared got married to identical twin sisters! He says it’s going to be really exciting, because both couples just had baby girls, so his and Jared’s kids will also be identical twins!

Using your understanding of meiosis (e.g., including crossing over/recombination & independent assortment), what do you say to Aaron in response?

(Hint: since the important processes here act on pairs of chromosomes, it can be helpful to use "within pairs" or "between pairs" or "from each pair" frequently in your responses!)

In a moment, I'm going to ask you to share your individual thoughts in an application question.  This discussion is an opportunity to share ideas with some colleagues and get clarifications before responding individually!

Meiosis

 Meiosis is a type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes (the sex cells, or egg and sperm). In humans, body (or somatic) cells are diploid, containing two sets of chromosomes (one from each parent).

dip·loid -[ˈdipˌloid] ADJECTIVE

(of a cell or nucleus) containing two complete sets of chromosomes, one from each parent. Compare with haploid

• What is a simple definition of meiosis? Define Meiosis

Meiosis is a type of cell division during which a single cell divides twice and produces four daughter cells. 

These four daughter cells contain half the amount of genetic material and are known as our sex cells (gametes).Apr 15, 2023

What is difference between mitosis and meiosis?

What's the Difference? 

Mitosis produces two genetically identical “daughter” cells from a single “parent” cell, whereas meiosis produces cells that are genetically unique from the parent and contain only half as much DNA. Most cells in the body regularly go through mitosis, but some do so more often than others.Sep 8, 2021

Quizz 4

 Score for this attempt: 5 out of 5

Submitted Feb 3 at 1:45am

This attempt took less than 1 minute.

 

Question 1

1 / 1 pts

It would be most accurate to say crossing over happens...

  

Within a fertilized egg after the sperm DNA meets the egg DNA

 

  

In sperm cells or egg cells after they have been created but before fertilization

 

  

In cells in the reproductive organs before sperm or eggs are created

 

  

Within any cell throughout the body after DNA is replicated and the cell is ready to divide

 

 

Question 2

1 / 1 pts

Sachin & Giselle Question 1:

Sachin (a male) is planning to have a baby with his partner, Giselle (a female).  The DNA that is passed along to their baby will include new combinations of codes due to crossing over.  In the process of crossing over, DNA can be mixed up and recombined between...

  

Any two of Sachin's chromosomes within a pair, including his sex chromosomes

 

  

Any of Sachin's chromosomes mixing with any of Giselle's chromosomes

 

  

Any two chromosomes in Sachin's cells

 

  

Any two of Sachin's chromosomes within a pair, except for his sex chromosomes

 

 

Question 3

1 / 1 pts

Sachin & Giselle: Question 2

Sachin (a male) is planning to have a baby with his partner, Giselle (a female).  The DNA that is passed along to their baby will include new combinations of codes due to crossing over.  In the process of crossing over, DNA can be mixed up and recombined between...

  

Any two of Giselle's chromosomes within a pair, including her sex chromosomes

 

  

Any two of Giselle's chromosomes within a pair, except for her sex chromosomes

 

  

Any of Giselle's chromosomes mixing with any of Sachin's chromosomes

 

  

Any two chromosomes in Giselle's cells

 

 

Question 4

1 / 1 pts

Which of the following best describes what happens in independent assortment when creating a sperm cell?

  

The sperm cell randomly receives one chromosome copy from each pair of chromosomes

 

  

The sperm cell receives any random set of 23 of the 46 chromosomes

 

  

The sperm cell receives one X chromosome, plus a random selection of any of the 44 remaining chromosomes

 

  

The sperm cell receives either an X or Y chromosome, plus a random selection of any of the 44 remaining chromosomes

 

 

Question 5

1 / 1 pts

Considering only independent assortment, how would you figure out the number of possible different egg cells in a species that has 16 pairs of chromosomes?

  

Multiply 2 times 16

 

  

Calculate 2 to the power of 16

 

  

Multiply 16 times 16

 

  

Calculate 16 to the power of 2