ASSIGN #3 Meiosis leads to variation!

ASSIGN #3 Meiosis leads to variation!

This is a lesson. Complete the questions and then get ready to freshen up your notes with the informational picture slides that follow each question.

Multiple Choice

Meiosis is cell division that MAKES

• body cells

• gametes

Meiosis makes gametes (sex cells)

Multiple Choice

If 1 cell goes into meiosis, how many cells come out (are made)?

• 1

• 2

• 3

• 4

Meiosis has 2 divisions (PMAT twice)...so produces 4 cells (gametes)

Multiple Choice

Meiosis produces cells that have ______ # of chromosomes as normal body cells.

• the same

• half of the

• double the

Meiosis produces cells that have 1/2 the number of chromosomes as normal body cells

Multiple Choice

Meiosis produces cells that are _____________ to each other.

• identical

• not identical

Meiosis produces 4 cells that are NOT identical

• Look at this diagram...the end four cells at the right...NONE of them are identical.

Multiple Choice

Homologous chromosomes are pairs of chromosomes that code for the same traits and have a similar length. Where do these chromosomes come from?

• offspring

• biological parents

• great grandparents

Homologous chromosomes are pairs of chromosomes that are

• similar in size and carry the same genes that code for the same traits.

Multiple Choice

A cell that goes into meiosis divides _____ time(s).

• 1

• 2

• 3

• 4

A cell that goes through meiosis divides 2 times.

• goes through PMAT twice!

Multiple Choice

If a fruit fly has 6 chromosomes in their body cells, how many chromosomes do they have in their gametes?

• 1

• 3

• 6

• 12

Meiosis produces cells that have 1/2 the number of chromosomes as normal body cells

• If a species has 10 chromosomes in their body cells, they will have 5 in their gametes

Multiple Choice

Why do gametes have to have 1/2 of the chromosomes of the normal body cells?

• It takes 2 gametes to make another individual. So if the gametes each have half the number of chromosomes, when they come together they make 1 cell with the complete set of chromosomes.

• Gametes are not cells. In order to be a complete cell, they need the full set of chromosomes, so each gamete brings 1/2.

Gametes have to have half the chromosomes, so when they come together they make 1 zygote (cell) with a complete set of chromosomes

• 
  

Multiple Choice

What is crossing over?

• when a sperm crosses the cell membrane of the egg

• when the body dies

• when one homologous chromosome swaps 'legs' with the partner chromosome

In meiosis, crossing over happens in the first division.

• the dad's chromosome crosses with the mom's chromosome

• a portion of mom's chromosome (genes) gets attached to dad's and vice versa

• ONE way variation happens in meiosis

Multiple Choice

What does random (independent) assortment mean for meiosis?

• the sperm are randomly sorted inside the body

• the sperm that fertilizes the egg is random

• the homologous chromosomes are randomly lined up during meiosis (random which side dads chromosome and mom's chromosome ends up on for each pair)

Random assortment of the homologous chromosomes is shown here

• Yellow is the chromosome that came from dad in the pair and blue came from mom

• the random lining up can result in different combinations of chromosomes in the gametes (see the top to boxes compared to the bottom two boxes)

• ONE way variation happens in meiosis

Multiple Choice

TRUE or FALSE: Chromosomal mutations during the division of meiosis can cause variation.

• TRUE

• FALSE

Mutations from the inappropriate division of the chromosomes

• can result in variation in the gametes

• and can create problems for the resulting offspring

• examples of this are trisomy 13, downs syndrome and klinefelter's syndrome

• ONE way variation happens in meiosis

Open Ended

Describe in detail THREE ways variation of traits for offspring can come from MEIOSIS.

Ways variation of traits comes from MEIOSIS

• 1. random assortment of homologous chromosomes allows for the chromosomes from mom and dad (in the homologous pair) to be randomly aligned. This shuffles up the alleles present in the gametes.

• 2. crossing over of the homologous chromosomes allows for some portions of chromosomes to be placed on their homologous pair. This shuffles up the type of alleles present in the gametes.

• 3. mutations of the chromosomes during the two divisions of mitosis. One chromosome may not separate from its pair OR one chromosome may not split. This results in gametes with different numbers of chromosomes

• 4. another kicker - all 4 gametes made during meiosis are DIFFERENT from each other.