Cell reproduction

Question 1

Cell Cycle stages - Interphase

Answer 1

G1 Phase - cell growth
S Phase - DNA Replication
G2 Phase - cell prepares for division

Question 2

Cell cycle - M phase & C phase

Answer 2

M phase -mitosis, nucleus divides
C phases - cytokinesis

Question 3

Mitosis stage 1

Answer 3

Prophase - chromatin threads condense becomes visible, cellular membrane disappears, spindle fibers begin to form attach to centromeres of chromosomes, move to opposite poles

Question 4

Mitosis stage 2

Answer 4

Metaphase - chromosomes move to centre of cell equator (metaphase plate), the centrioles are located at opposite sides of the cell

Question 5

Mitosis stage 3

Answer 5

Anaphase - spindle fibers shorten and pull the centromeres of chromosomes to opposite poles, separating the sister chromatids, there is a complete identical set of maternal and parental chromosomes

Question 6

Mitosis stage 4

Answer 6

Telophase - decondenses, two new nuclear membranes form, spindle fibres disappear, cell elongates and cleavage furrow forms ready for cytokinesis

Question 7

Meiosis 1 (Prophase 1)

Answer 7

Prophase 1 - chromatids condense, maternal and parental attached to each other and pair up (CROSSING OVER), consists of two sister chromatids, nuclear membrane & nucleus disappears, spindle fibres begin to form, attachment to centromes of chromosomes and move opposite poles

Question 8

Meiosis 2 (Metaphase 1)

Answer 8

Metaphase 1 - maternal and parental line-up on metaphase plate in a homologous pairs (INDEPENDENT ASSORMENT) - line-up in pairs independently of every other pair, resulting in RANDOM ASSORTMENT in 4 daughter cells

Question 9

Meosis 3 (anaphase 1)

Answer 9

Anaphase 1 - spindle fibres shorten pulling centromere, each member of homologous pairs move to each end of cell resulting in a random combinations of maternal and parent

Question 10

Meiosis 4(telophase 1)

Answer 10

Telophase 1 new cellular membrane spindle fibres disintegrate

Question 11

Meiosis 5(cytokinesis 1)

Answer 11

Cytokinesis 1 - cytoplasm separates = 2 haploid cells, one chromosome from each

Question 12

Meiosis 6 (prophase 2)

Answer 12

Prophase 2 - chromatids condensers you spindle fibres nuclear membrane disintegrates

Question 13

Meiosis 7 (metaphase 2)

Answer 13

Metaphase 2 - Individual chromosomes light up along the metaphase plate in random order spindle fibres attach to centromere

Question 14

Meosis 8 (anaphase 2)

Answer 14

Anaphase 2 - sister chromatids separate at centromeres as spindle fibers shorten and move to opposite poles

Question 15

Meiosis 9 (telophase 2)

Answer 15

Telophase 2 - chromosomes unwind loosen, reform chromatin, 4 nuclear membranes membranes

Question 16

Meiosis 10 (cytokinesis 2)

Answer 16

Cytokinesis 2 - separate cytoplasm full non-identical haploid cells
animal cells - cleavage furrow
plant cell - new cell wall plates

Question 17

Binary Fission

Answer 17

-prokaryotes cells
aesexual reproduction
1Prior - chromosomes tightly coiled
2Replication - genetic material and plasmids replicate and separates 3Elongation - replicated materials attached to cell membrane are pulled opposite side in cell as it elongates 4Cell Wall - New cell wall starts to develop
5Cytokinesis - new cell fully developed
6Final - cell separate form two identical daughter cells and become tightly packed together

Question 18

Apoptosis in multicellular organisms

Answer 18

Apoptosis the orderly programmed self-destruction of cells
- vital for the development and shaping of organs and tissues
- cause cells to die at a specific stage of development
Eg. Tadpoles tail as it becomes a frog Humans loosing webbing between fingers and toes

Question 19

Phenotype

Answer 19

Is an observable trait

Question 20

How does environment influence gene activity

Answer 20

Genes cannot dictate the structure of an organism themselves environment helps.
E.g. twins trait may look different even though they might have the same genre and protein for trait

Due to external factors: pH level, temp, food availability, light/wind exposure
Eg. With plants some flower petal colours determined by the pH in the soil
Internal Factors: action of hormones
Eg. Human hormone realeased triggering puberty - gondotrophin