Term3

Question 1

What kind of division is meiosis

Answer 1

Sexual

Question 2

How many nuclear divisions occur in meiosis

Answer 2

2 nuclear divisions creating four haploid daughter cells from single diploid parent cell

Question 3

What two things occur in meiosis 1

Answer 3

• independent segregation
• crossing over

Question 4

What happens in independent segregation 3m

Answer 4

• homologous pairs of chromosomes line up opposite each other at equator of cell

• random where in equator paternal+ maternal chromosome pair lie ( random assortment )

• pairs are separated so one of each homologous pair ends up in daughter cell

Can use 2^n to work out combinations possivle

Question 5

What happens in crossing over

Answer 5

Also occurs in meiosis 1

• homologous pairs line up opposite eaxhother in equator

• chromatids can get tangeled and twisted

• puts tension on chromatid causing chromatid to snap off and combine w another pair

• results in new combination of alleles

Question 6

What 2 ways introduces genetic variation in meiosis

Answer 6

• independent assortment
• crossing over

Question 7

What kind of cells does mitosis make

Answer 7

2 genetically identical diploid cells ( contains chromosomes in pair )

Question 8

What happens to cells in interphase

Answer 8

Cell replicates organelles and copies DNA

Question 9

What happens in Mitotic phase of cell. Cyyckee

Answer 9

• nucleus divides into two daughter cells
• cells divides into two daughter cells each w a nucleus

Question 10

In interphase why can’t we see chromosomes in the nucleus

Answer 10

Not visible instead we see chromatin

Question 11

Why does chromatin have a loose open structure

Answer 11

• DNA accessible for transcription and replication

Question 12

What is a chromosome

Answer 12

A single long molecule of DNA

Question 13

What happens to chromosomes during interphase

Answer 13

• chromosomes r replicated so we have two identical molecules of DNA which are called sister chromatids

Question 14

What is a centromere

Answer 14

Point where sister chromatids are joined

Question 15

What happens in prophase

Answer 15

• centrioles move to opp poles
• nucleolos and nuclear membrane brake down
• 2 sister chromatids w centromere in middle can be seen clearly

Question 16

Metaphase

Answer 16

• the centrioles form the spindle made from microtubules
• they attach to centromeres
• push + pull so that they line up on equator of cell

Question 17

Anaphase

Answer 17

• microtubules pull this splits centromere
• sister chromatids separate and return to chromosomes
• pulled towards opposite poles of cell using ATP

Question 18

Cytokinesis

Answer 18

• cell membranes pulled inwards via cytoskeleton
• forms furrows which deepen
• eventually membranes fuse to make 2 separate independent cells

Question 19

Might have to lookn over cytokinins in animals + plants

Question 20

Totipotent

Answer 20

Able to become a complete human being

Question 21

Blastocyst

Answer 21

• A hollow ball of cells.

• The outer blastocyst layer becomes the placenta.

• Inner mass of cells goes on to form the tissues for the developing embryo.

Question 22

Pluripotent embryonic stem cells

Answer 22

Has the potential to give rise to most types of cells

Question 23

Differentiated

Answer 23

Lose the ability to develop into a wider range of cells as they have become specialised.

Question 24

Multipotent stem cells

Answer 24

Cells which retain a certain capacity to give rise to a variety of different cell types (adult stem cells)

Question 25

How do stem cells become specialised?

Answer 25

• Totipotent cells contain the same genes • some of these genes are active while some are switched off • To become specialised the DNA containing the active genes is transcribed and translated into proteins • The proteins will determine how the cell functions

Question 26

How can plants be reproduced using tissue culture

Answer 26

• explants are grown on sterile agar plant • grown to form a callus • altering chemicals in growth medium can lead to differentiation of callus to a plant embryo • develops into clone of the plant

Question 27

Advantages of reproducing plants using tissue culture

Answer 27

• quick process producing identical cells • plants are disease free • genetically modified so can use best quality plants

Question 28

Disadvantages of genetically modified plants using tissue culture

Answer 28

• all genetically similar plants so if disease comes they’d all die as there is not genetic variation •

Question 29

What do growing nutrients contribute to in growing plants using tissue culture

Answer 29

• genes are activated or deactivated certain conditions can change these

Question 30

Where can you find totipotent stem cells

Answer 30

• embryo as thy job ability to turn into a human Embryonic stem cells