Cell Division 16.1

Question 1

Homologous chromosomes

Answer 1

Contains the same genes at the same location but could contain different forms of the same gene (blue eyes and brown eyes)

Question 2

Alleles

Answer 2

Different forms of the same gene

Question 3

Ploidy

Answer 3

Number of each copies of chromosome. -> diploid (2N) haploid (N)

Question 4

Human number of chromosomes

Answer 4

2n=46
2n- 2 copies
46- total chromosomes

Question 5

Karyotype

Answer 5

Complete set of an individuals chromosomes. Normal human somatic karyotype-> 22 pairs of autosomes + 2 sex chromosomes

Question 6

Interphase- G1

Answer 6

Gap/growth: replication of organelles (not including dna)
-cell grows in size
-accumulates structures for dna replication

Question 7

Interphase- s phase

Answer 7

DNA replication: single stranded into double stranded.
-at the end of s phase: 46 double stranded chromosomes, each with 2 sister chromatids

Question 8

Interphase- G2

Answer 8

Replenishes energy to prepare for cell division
-produces structures necessary for cell division

Question 9

Cell division: mitosis- prophase

Answer 9

Chromatids condenses into chromosomes (double stranded, 2 sister chromatids held together by centromere)
-necleur membrane and necleous breaks down.
-centrioles move to opposite ends of the cell, spindle fibres form

Question 10

Mitosis- metaphase

Answer 10

Spindle fibres attach to centromere of each chromosome and guides chromosomes to the equator of the cell.
-each sister chromatids faces one end of the cell.

Question 11

Mitosis- anaphase

Answer 11

Spindle fibres shorten, centromere splits, sister chromatids pulled apart to separate ends of the cell.

Question 12

Mitosis-Telophase

Answer 12

Chromatids unwind into chromatin. Necleur membrane and necleolus reforms. Spindle fibres break down

Question 13

Mitosis- cytokinesis

Answer 13

In animals: indentation forms in cell membrane, cell is pinched off in the middle to form 2 daughter cells.
Plants: cell plate forms in the middle of the cell, reinforced by cellulose to form a new cell wall, separating daughter cells.

Question 14

Meiosis: reduction

Answer 14

2n=46 turns into n=23

Question 15

Meiosis interphase

Answer 15

Germ cells (those who produce gametes) goes through growth and synthesis

Question 16

Meiosis 1 prophase

Answer 16

Necleur membrane disappears, spindle fibres form. In the necleus homologous pairs come together and crossover to exchange genetic info. (Synapsis)

Question 17

Meiosis 1 metaphase

Answer 17

Spindle fibres guide homologous pairs to line up at the equator

Question 18

Meiosis 1 anaphase

Answer 18

Spindle fibres shorten, homologous chromosomes separate

Question 19

Meiosis 1 telophase

Answer 19

Necleur membrane reforms, spindle fibres disappear. Results in 2 haploid cells. 2n(ds)-> n(ds)

Question 20

Meiosis 2

Answer 20

No interphase between meiosis 1 and 2. Similar to mitosis: separate sister chromatids. Ends with 4 daughter cells, haploid and single stranded. N(ds) -> n(ss)

Question 21

Independent assortment:

Answer 21

Metaphase 1. Each part of homologous chromosomes separate randomly and independently of other pairs

Question 22

Nondisjunction

Answer 22

Homologous chromosomes or chromatids don’t seperage properly in anaphase.
Anaphase 1: both homologous chromosomes go to one end, 4 gametes affected.
Anaphase 2: both sister chromatids go to one end. 2 gametes affected. Results in trisomy or monosomy