Inheritance of DNA 2D part 2 (Textbook) Meiosis

Question 1

homologous pair

Answer 1

have the same genes arranged in the same order in the DNA of the chromosome. Different versions or alleles may be present on either chromosomes

Question 2

Recombination

on a molecular level what happens

Answer 2

invloves the precise breaking of of covalently bonded DNA backbones exchanging the ends with those of the other homologue and reforming the bonds.

Question 3

as a result of recombination

Answer 3

Each chromosome passed on to offspring is composed of a novel miture of both maternal and paternal DNA sequences

Question 4

Meiocytes

Answer 4

cells that are destined to divide by meiosis

Question 5

interkinesis

Answer 5

a brief interphase that separates the two meitotic divisions
no DNA replication

Question 6

Prophase 1

Answer 6

The replicated chromosomsomes each consist of two sister chromatids begin to fold and condense into threadlike structures in the nucleus. The chromosomes of each homologous pair then come togther and line up side by side in a zipperlike way in synapsis. When they are paired, the chromaids undergo genectic recombination.

Question 7

In prophase 1 the line up of two homologous chromosomes is called a

Answer 7

tetrad

Question 8

What holds the homologous chrommosomes pair in prophase?

Answer 8

synaptonemal complex
(Protein framework)

Question 9

In genectic recombination..

How is this done, what happens, what holds it, what happens after done

Answer 9

the homologous chromosomes are held by a protein framework. Regions of the homologous chromatids exchange segments producing new combinations of alleles. This involves the breakage and rejoining of DNA molecules by enzymes. When the exchange is complete towards the end of prophase I, the synaptonemal complex disassembles and disappears.

Question 10

What is exchanged in recombination

*Not just as simple to alles/genes u dummy

Answer 10

All the DNA sequence stretching from the site of recombination to the ends of the participating chromatids

Question 11

As prophase 1 finishes,….

Answer 11

a spindle forms in the cytoplasm

Question 12

Prometaphase I

Answer 12

The nuclear envelope breaks down and the spindle enters the former nuclear area. Microtubules attach to the attach to the fused kinotochore of each homologous chromosome).

Question 13

In prometaphase, where are the two homologous chromosomes held tgt

Answer 13

at the crossover part or chiasmata

Question 14

Metaphase I

Answer 14

Movements of the spindle microtubules align the recombined tetrads on the equatorial plane between the two spindle poles

Question 15

Anaphase 1

Answer 15

The two chromosomes of each homologous pair seperate and move to opposite spindle poles. The movement seperate homologous pairs delievering a haploid set of chromosmes to each pole of the spindle.

Question 16

Aside from genetic recombination, whats the second source of major genectic variability

Answer 16

The random alignment of chromosomes of maternal and paternal origin at metaphase I followed by their segreagation to opposite poles at anaphase I

Question 17

Telophase I (5)

Answer 17

Telophase I is a brief transitory stage in which there is little to no change in the chromosomes.

The microtubules break down, the nuclear membrane reforms, and the chromosomes return to an uncondensed state.

Cytokinesis in telophase I creates halploid cells.

Question 18

Interkinesis

Answer 18

the spindle of the first meiotic division dissaembles and microtubules reassemble into new spindles for the second division

Question 19

prometaphase II

Answer 19

nuclear envelope breaks

spindle enters the former nuclear area

spindle attaches to the two kinetochores of each chromosomes.

Question 20

Metaphase 2

+diversity arised how?

Answer 20

Movements of the chromosomes within the spindle bring them to rest at the metaphase plate

another chance of diversity as recombination in prophase I results in the sister chromatids being different. The orientation would determine which is going to which haploid cell.

Question 21

how is meiosis 2 diff from mitosis (3)

Answer 21

• meiosis 2 produce reproductive cells
• there is no immediate preceding DNA replication phase
• resulting daughter cells are genetically different

Question 22

Anaphase 2

Answer 22

sister chromatids of each chromosome seperate from eachother and move to opposite poles.

Question 23

Telophase 2

Answer 23

chromosomes decondense to interphase state

soindles disassemble
nuclear envelope form around chromatin

cell divides

Question 24

sporadic cancer

Answer 24

cancer not inherited

Question 25

proto oncogene

Answer 25

normal genes that stimulate growth and cell division

Question 26

Alterations that an oncogene cause can include

Answer 26

amplify number of of copies of the gene. A mitation in the genes promoter or other regulatory sequence that increase transcription rate or the gene is under control of a stronger promotor or enhancer.

Question 27

Tumour supressor gene

What is do+ex plus what ust happen for inhibitory activity to be lost

Answer 27

A gene that when inactived by mutation results in a selective growth advanatage to the cell.

For ex: tumour supressor genes can encode growth inhibiting factors that inhibit cell growth and division.

Tumor supressor genes are recessive that is both alleles of a tumour suppresor gene must be inactivated for inhibitory activity fo the gene’s product to be lost un cancer cell.