Meiosis study

Question 1

What is meiosis?

Answer 1

Meiosis helps produce gametes and ensures genetic variation
- meiosis is a type of cell division in which the number of chromosomes is reduced by half (23 chromosomes)

Question 2

Phases of meiosis?

Answer 2

Meiosis begins with a diploid cell and ends with 4 Hapliod cells
- Meiosis 1 begins after dna replication in inter phase (s phase)
- both meiosis 1 and 2 go through the same 4 phases of mitosis
Prophase
Metaphase
Anaphase
Telophase

Question 3

what happens in meiosis 1
prophase 1?

Answer 3

nuclear envlope breaks down, chromosomes condens, and centioles move to opposite poles of the cell, and a spindle begins to form
- chromosomes pair up in homologous chromosomes and crossing over occurs during prophase 1

Question 4

What are homologous chromosomes?

Answer 4

Homologous chromosomes is a pair of chromosomes that are similar in size, shape, and genetic content

Question 5

What is crossing over?

Answer 5

Crossing over is when homologous chromosomes exchange segments of dna and this results in genetic variation

Question 6

What happens in meiosis 1
Metaphase 1?

Answer 6

Metaphase 1= spindle fibers attach to the paired homologous chromosomes, and they line up along the metaphase plate

Question 7

What happens in Meiosis 1
Anaphase 1?

Answer 7

Anaphase 1= spindle fibers shorten and the chromosomes of each homologous pair start to separate and move to opposite poles of the cell

Question 8

What happens in meiosis 1
Telophase 1 and cytokinesis?

Answer 8

Telophase 1 and cytokinesis= spindle breaks sown and new nuclear membrane forms
- the cytoplasm of the cell divides and 2 haploid daughter cells each have a random assortment of chromosomes and 1 from each homoglous pair
- go onto meiosis 2 the dna doesnt replicate between meiosis 1 and 2

Question 9

What happens in meiosis 2
Prophase 2?

Answer 9

Prophase 2= nuclear envelope breaks down, spindle forms in each haploid daughter cell, and the centrioles seperate and move to oppposite poles

Question 10

What happens in meiosis 2
Metaphase 2?

Answer 10

Metaphase 2= spindle fibers line up sister chromatids of each chromosome along the metaphase plate of the cell

Question 11

What happens in meiosis 2
Anaphase 2?

Answer 11

Anaphase 2= sister chromatids seperate and move to opposite poles of the cell

Question 12

What happenes in meiosis 2
Telophase 2 and cytokinesis?

Answer 12

Telophase 2 and cytokinesis= spindle breaks down, new nuclear membrane forms, cytoplasm of the cell divides, and 4 haploid cells result which each has a unique combination of chromosomes
- 4 haploid cells are not identical to the parent cell or to each other because of the different alleles and crossing over

Question 13

What does synapsis mean?

Answer 13

Synapsis is when homologous chromosomes pair up
-when the tetrad pairs up

Question 14

What is the difference between meiosis 1 and 2

Answer 14

meiosis 1 separates pairs of homolgous chromosomes and meiosis 2 makes sure that 1 copy of each chromatid is in each of the 4 haploid cells

Question 15

What happends to homolgous chromosomes after crossing over?

Answer 15

Homolgous chromosomes are not identical after crossing over because they now contain different alleles and genes

Question 16

3 reasons for why we have genetic variation?

Answer 16

Crossing over, random fertilization, and independent assortment
- meiosis produces offspring that are different to protect them against diseases

Question 17

What is independent assortment?

Answer 17

How your chromosomes were sorted independently

Question 18

What is random fertilization?

Answer 18

It’s almost impossible for a sperm and egg cell to create genetically identical people

Question 19

What is a tetrad?

Answer 19

Duplicated homologous chromosomes

Question 20

What is nondisjunction?

Answer 20

The failure of 1 or more pairs of homologous chromosomes or sister chromatids to seperate
- leads to some daughter cells having too much or too little chromosomes

Question 21

What caused Down syndrome?

Answer 21

Due to having 1 extra copy of chromosomes in trisomy 21, and this leads to Down syndrome because there are 3 copies of chromosomes instead of 2

Question 22

What are deletions?

Answer 22

Chromosome segment lost

Question 23

What are translocation?

Answer 23

Segment from chromosome is transfers to another chromosome that doesnt need it

Question 24

What are duplication?

Answer 24

Segment from 1 chromosome is transfers to its homolgous chromosome giving it a duplicate of genes

Question 25

What are inversions?

Answer 25

Segment of chromosome is swapped by the order being flipped

Question 26

What are genes?

Answer 26

Genes contain the instruction for a single protein