Reproduction System (Meiosis and Mitosis)

Question 1

Sister Chromatids

Answer 1

Sister chromatids is the term used to refer to each “component” of a chromosome.

Question 2

Centromere

Answer 2

This is the structure that is used to hold two sister chromatids together in order to form a chromosome.

Question 3

Centrioles

Answer 3

This is the structures located on both sides of the cell that produce spindle fibres.

Question 4

Spindle Fibres

Answer 4

These are the threads that attach to the centromere during cell division.

Question 5

Equatorial Plate

Answer 5

This is the location on the cell where the chromosomes line up just before cell division.

Question 6

Haploid

Answer 6

Haploid, also known as “n” refers to a cell having only half of the typical number of chromosomes.

Question 7

Diploid

Answer 7

Diploid, also known as “2n” refers to a cell that has two copies of each chromosome.

Question 8

Polyploidy

Answer 8

Polyploidy, also known as “3n” refers to have more than two sets of a chromosome.

Question 9

Homologous Chromosomes

Answer 9

This refers to chromosomes that are similar and have the same genes but different alleles.

Question 10

Tetrad

Answer 10

This is the structure that forms when two homologous chromosomes pair up.

Question 11

Synapsis

Answer 11

This term is the process that occurs to form a tetrad.

Question 12

Crossing Over

Answer 12

This refers to the exchange of genetic material during synapsis.

Question 13

Binary Fission

Answer 13

This refers to the asexual reproduction where the cell separates into two cells and the cell duplicates chromosomes and then divides. It would have the same number of chromosomes as the parent cell and thee would be no genetic variability.

Question 14

Mitosis

Answer 14

This is when the daughter cell receives the same number of chromosomes as the parent cell. The chromosomes would be 46, and there would be no genetic variability because the parent and daughter cell would be identical.

Question 15

Meiosis

Answer 15

This refers to the process that has two stages of division where the chromosome number of parent cell is reduced by half (23 chromosomes) and it has lots of genetic variability.

Question 16

Germ Cell

Answer 16

It is important to not e that when referring to germ cell you are referring to a cell that gives rise to a gamete and that has not gone through Meiosis yet. For germ cells there are, “primary spermatocytes - seminiferous tubules (testes)” and “primary oocytes- ovaries (follicle)”. For sperm cells, it is important to note that men are producing this throughout their lifetime, and have 4 equal sperm. For women, their eggs/ova, is something they are born with in a finite amount, and will end up with one egg and 3 polar bodies.

Question 17

Meiosis - Gametogenesis (In Depth)

Answer 17

It is important to note that Meiosis has two stages of cell division. The first stage of cell division is referred to as the “reductional” stage. That is because during this stage, the number of chromosomes of a parent cell, is reduced by half (23 chromosomes) and they are all double stranded [diploid –> haploid]. The second stage of cell division in Meiosis is referred to as the “Equational” stage that is because the double stranded chromosomes become single stranded, because the sister chromatids of the daughter cell are separating.

Question 18

Stages of Meiosis

Answer 18

Stage 1:

• The first stage is Interphase. In this phase, it is diploid with 23 chromosomes and they are all double stranded.
• The next phase is Early Prophase 1. In this phase the nuclear membrane dissolves and the centrioles are at both ends of the poles (cell) and start growing spindle fibres that condense and thicken. The homologous pairs go closer together and start to form tetrads, (2 chromosomes, 4 chromatids). It is diploid, they are double stranded and there are 46 chromosomes.
• The next phase is Late Prophase 1. In this phase the homologous pairs undergo synapsis, and crossing over takes place. It is diploid, they are double stranded and there are 46 chromosomes.
• The next phase is Metaphase 1. In this phase the tetrads line up on the equatorial plate and the spindle fibres then attach to the centromeres. It is diploid, they are double stranded and there are 46 chromosomes.
• The next phase is Anaphase 1. The homologous pairs separate and are moved to opposite ends of the pole where the segregation of each chromosome happens independently. It is diploid, they ate double stranded and there are 46 chromosomes.
• The next phase is Telophase 1. In this phase, a nuclear membrane forms around the double stranded chromosome and they decondense into chromatin. It goes from diploid to haploid, with 23 chromosomes instead of 46 but they are still double stranded.
• The next phase is Cytokinesis 1: They are haploid but still double stranded and the new daughter cells have formed.

Stage 2 (It is important to note that no crossing over takes place in stage 2 of Meiosis, and there is also no Interphase.)

• When the Prophase 2 stage happens, it is still the same. The chromatin condenses and the centrioles move to the poles and the spindle fibres form. It is still haploid with 23 chromosomes, and DS.
• When Metaphase 2 happens, the spindle fibres still attach to the centromeres, and they line up at the equatorial plate. Again, it is still haploid with 23 chromosomes, and DS.
• When Anaphase 2 happens, the spindle fibres contract and they get pulled to each pole and they are still haploid with 23 chromosomes, but they are now and SS.
• Telophase 2, the nuclear membrane begins to form at both poles they are haploid with 23 chromosomes, and SS.
• Cytokinesis 2, it is still haploid with 23 chromosomes, and SS. And 4 daughter cells are created.

Question 19

Stages of Mitosis

Answer 19

• Interphase, it is diploid with 46 chromosomes and they are double stranded. The chromosomes are duplicated.
  Prophase, it is diploid with 46 chromosomes and they are double stranded. The nuclear membrane dissolves and the chromatin condenses into chromosomes and the centrioles move to opposite poles and attach/produce spindle fibres.
• Metaphase, it is diploid with 46 chromosomes and they are double stranded. The chromosomes line up at the equatorial plate and the spindle fibres attach to each centromere.
• Anaphase, it is diploid with 46 chromosomes and they go from double stranded to single stranded. The spindle fibres contract causing the chromosomes to split at each centromere. The sister chromatids move to opposite ends of the cell.
• Telophase it is diploid with 46 chromosomes and they are single stranded. The chromosomes de-condense into two groups of chromatin and a nuclear membrane forms around each group, and the centrioles dissolve their spindle fibres.
• Cytokinesis it is diploid with 46 chromosomes and they are single stranded. The cleavage pinches the cell into two separate daughter cells and it enters its own interphase and the cycle continues.