Week 11 Meiosis and cell junctions

Question 1

What are the two stages of Meiosis?

Answer 1

Meiosis 1 and Meiosis 2

Question 2

What are the 4 phases of Meiosis 1?

Answer 2

Prophase 1, Metaphase 1, Anaphase 1, and Telophase 1

Question 3

What happens during Prophase 1?

Answer 3

1. Chromosomes condense
2. The spindle forms
3. Nuclear envelope breaks down
4. Homologous chromosomes join together and join at regions called the Chiasmata where regions of the homologous chromosomes are swapped

Question 4

What is crossing over in meiosis?

Answer 4

Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis

Question 5

What is the chiasmata?

Answer 5

In genetics, a chiasma is the point of contact, the physical link, between two chromatids belonging to homologous chromosomes.

Question 6

What happens in Metaphase 1?

Answer 6

1. Chromosomes attatch to kinetochores
2. Chromosomes allign in the middle of the cell
3. Homologous chromosomes align together

Question 7

What happens in Anaphase 1?

Answer 7

1. The chromosomes move to the poles
2. Homologous chromosomes seperate
3. Sister chromatids remain attached at the centromere

Question 8

What is the centromere?

Answer 8

The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids.

Question 9

What happens in telophase 1?

Answer 9

Two haploid cells form, each chromatid is still paired with its sister chromatid

Question 10

What happens during meiosis 2?

Answer 10

Another round of cell division occurs resulting in 4 haploid daughter cells

Question 11

How many haploid daughter cells does meiosis make?

Answer 11

4

Question 12

What does crossing over result in?

Answer 12

Genetic diversity

Question 13

How does crossing over occur in early prophase 1?

Answer 13

The duplicated chromosomes condense, Homologous chromosomes pair in a process called synapsis and are held together by proteins.

Question 14

What is synapsis?

Answer 14

the fusion of chromosome pairs at the start of meiosis.

Question 15

How does crossing over occur in middle prophase 1?

Answer 15

Crossing over occurs which results in new combinations of genes in each chromatid. Sister chromatids are no longer identical.

Question 16

How does crossing over occur in late prophase 1?

Answer 16

Synapsis complex disassembles and the homologuesare held together at the site of crossing over (chiasma). The sister chromatids are held together at the centromere

Question 17

What is independent assortment?

Answer 17

Different genes independently separate from one another when reproductive cells develop.

Question 18

What does independent assortment cause?

Answer 18

Genetic diversity

Question 19

Sexual Organisms generate diversity through what?

Answer 19

Crossing over, independent assortment, and random fertilisation

Question 20

What are diploid organisms?

Answer 20

Diploid is a cell or organism that has paired chromosomes, one from each parent.

Question 21

Fusions of haploid cells produced what offspring?

Answer 21

diploid 2n offspring

Question 22

Cells in multicellular organisms need to be what?

Answer 22

Stably attatched to eachother

Question 23

Both multicelluar and unicellular organisms need to be able to what?

Answer 23

Communicate and coordinate

Question 24

Do plants need junctions to join cells together?

Answer 24

No they dont, as they dont have connectig junctions

Question 25

How can cell walls communicate with one another through the cell wall?

Answer 25

By communication junctions

Question 26

What is plasmodesmata?

Answer 26

a narrow thread of cytoplasm that passes through the cell walls of adjacent plant cells and allows communication between them

Question 27

What are cytoplasmic bridges?

Answer 27

thin strand of cytoplasm linking cells as in higher plants,

Question 28

What is the size exlusion limit of the plasmodesmata?

Answer 28

1.5kDa therefore only small signalling molecules could pass through from cell to cell

Question 29

Gene expression tests have showed proteins up to 30 kDa and pieces of mRNA can move through the plasmodesmata. How?

Answer 29

The plasmodemata can close or open under various conditions.

Question 30

Plant viruses hack what to infect neighbouring cells?

Answer 30

The plasmodesmata

Question 31

What is Dalton Da?

Answer 31

A unit of molecular weight

Question 32

Do animals need junctions to join cells together?

Answer 32

Yes in some cases.

Question 33

In what cases do animals need junctions to join cells together?

Answer 33

For skin cells and muscle cells ect

Question 34

In what cases do not animals need junctions to join cells together?

Answer 34

Red blood cells ect

Question 35

What are tight junctions?

Answer 35

Connecting junctions in animal cells that form a seal to prevent the movement of liquids and material between cells. Specific proteins hold cells together forming a ‘Water Proof’ layer.

Question 36

Tight junctions are important in what type of tissue?

Answer 36

Epithelial tissues

Question 37

How do tight junctions help the blood;brain barrier?

Answer 37

Prevents the passage of molecules between the cells.

Question 38

What are adherens junctions?

Answer 38

Adherens junctions are protein complexes that occur at cell–cell junctions in epithelial and endothelial tissues, usually more basal than tight junctions. Soft connection