Chap 16

Question 1

Describe the processes of synapsis and crossing over

Question 2

What are the key events during the phases of meiosis?

Question 3

Differences between mitosis and meiosis (key differences)

Question 4

Life cycles of diploid dominant species vs. haploid dominant species vs. species that exhibit an alternation of generations

Question 5

Describe how chromosomes vary in size, centromere location, and number

Question 6

What are the four ways that the structure of a chromosome can be changed via mutation?

Answer 6

• deletions: segment of chromosome is missing
• duplications: doubles a particular region (repeated segment)
• inversions: flips a region to the opposite orientation
• translocation: simple = moves a segment of 1 chromosome to another chromosome; reciprocal = exchanges pieces between 2 different chromosomes

Question 7

Compare + contrast changes in number of sets of chromosomes and changes in the number of individual chromosomes

Question 8

When a cell prepares to divide, the chromosome becomes more _________________ which ___________ the apparent length and __________ their diameter

Answer 8

Tightly compacted, decreases length and increases diameter

Question 9

Diploid

Answer 9

Cells of an organism carry 2 sets of chromosomes (2n) —> one from mother, one from father —> humans = 2n where n = 23

Question 10

haploid

Answer 10

Contain one set of chromosomes (1n)

Question 11

Which humans cells are diploid? Which are haploid?

Answer 11

Most human cells are diploid. Gametes, the sperm and egg cells, are haploid.

Question 12

Gametes

Answer 12

A haploid cell involved with sexual reproduction, such as sperm or egg cell

Question 13

what is a homolog and in what organism does it occur?

Answer 13

a member of a pair of (NON-IDENTICAL) chromosomes = homolog –> appear in diploid organisms
- have same genetic info just different alleles

Question 14

mitotic cell division

Answer 14

a process in which a eukaryotic cell divides to produce two new cells that are genetically identical to the original cell

Question 15

what are autosomes

Answer 15

non-sex chromosomes

Question 16

mitosis

Answer 16

division of one nucleus into 2 nuclei (followed by cytokinesis) in which the mother cell divides into 2 (genetically identical) daughter cells
- each daughter cell receives 1 copy of each chromosome

Question 17

what is a centromere

Answer 17

the region where the two sister chromatids are tightly associated
- also an attachment site for kinetochore proteins

Question 18

what protein holds sister chromatids together

Answer 18

cohesin

Question 19

kinetochore

Answer 19

a group of proteins that bind to a centromere and are necessary for sorting chromosomes

Question 20

what is the spindle apparatus? what is it made of?

Answer 20

the structure responsible for organizing and sorting eukaryotic chromosomes during cell division (mitotic spindle or meiotic spindle)
- composed of microtubules

Question 21

how does the cell cycle work?

Answer 21

• G1 (first gap) phase: cell commits to divide + maybe some molecular changes + cell growth
• S (synthesis of DNA) phase: each chromosome is replicated to form a pair of sister chromatids –> cell will have twice as many chromatids as the number of chromosomes in G1 phase (goes from 46 chromosomes/chromatids to 46 chromosomes but 92 chromatids)
• G2 (second gap) phase: cell synthesizes proteins necessary for chromosome sorting and cell division
• M (mitosis and cytokinesis) phase: first mitosis (division of one nucleus into 2 nuclei) = 92 chromatids of 46 pairs separated so each daughter cell gets 46 chromosomes –> followed by cytokinesis, division of cytoplasm to produce 2 distinct daughter cells

Question 22

mitosis phases

Answer 22

interphase: (G1: cell growth, S: DNA synthesis, G2: cell growth) chromosomes have already replicated
prophase: sister chromatids condense, mitotic spindle begins to form + nuclear envelope begins to dissociate into vesicles + nucleolus no longer visible
prometaphase: nuclear envelope has completely dissociated into vesicles and mitotic spindle = fully formed + sister chromatids attach to spindle via kinetochore microtubules
metaphase: sister chromatids algin along metaphase plate
anaphase: sister chromatids separate and individual chromosomes move toward poles as kinetochore microtubules shorten –> polar microtubules lengthen and push poles apart
telophase: chromosomes decondense and nuclear envelope reforms into 2 separate nuclei
cytokinesis: separates mother cell into 2 daughter cells and begins with cleavage furrow in animal cells or cell plate in plants

end result: 2 genetically identical daughter cells

Question 23

define meiosis

Answer 23

process by which haploid cells are produced from a cell that was originally diploid

Question 24

meiosis I vs meiosis II

Answer 24

meiosis I: the two homologs of each chromosome pair separate into 2 daughter cells
- each daughter cell has 1 set of chromosomes
- result: 2 haploid cells
meiosis II: the sister chromatids of each chromosome separate into 2 daughter cells
- each of the 2 daughter cells from meiosis I divides
- result: 4 haploid cells

Question 25

what are the two key events that happen at the beginning of meiosis that do not occur in mitosis?

Answer 25

1. bivalent: Homologous pairs of sister chromatids that are associated with each other, lying side by side; also called a tetrad - synapsis: process of forming a bivalent - synaptonemal complex: a protein structure that connects homologous chromosomes 2. Crossing over: physical exchange between chromosome pieces of the crossing bivalent = recombination - increases genetic diversity of a species (new combination of alleles on same chromosome) - chiasma: arms of chromosomes tend to separate but remain adhered at a crossover site

Question 26

meiosis phases

Answer 26

prometaphase: in

Question 27

difference in prometaphase in mitosis vs. meiosis

Answer 27

mitosis results in 2 genetically identical diploid daughter cells meiosis results in 4 unique haploid cells mitosis: no synapsis during prophase meiosis (I): (yes synapsis) bivalents are formed mitosis: crossing over = rare meiosis: crossing over = common prometaphase: - in mitosis, each pair of sister chromatids is attached kinetochore microtubules from both poles vs. - in meiosis I, each pair of sister chromatids is attached to just one pole via kinetochore microtubules metaphase: - in mitosis, sister chromatids aligned in a single row - in meiosis I, bivalents align and in meiosis II sister chromatids aligned in a double row

Question 28

meiosis phases

Answer 28

meiosis I: - prophase I: chromosomes condense, bivalents form, crossing over occurs, and nuclear envelope begins to dissociate - prometaphase I: spindle apparatus complete, nuclear envelope completely dissociates into vesicles, bivalents (chromatids) attach to kinetochore microtubules - metaphase I: bivalents randomly align along metaphase plate + each pair of sister chromatids attached to one pole - anaphase I: connection between bivalents break but sister chromatids stay together --> each pair moves towards opposite poles - telophase I: sister chromatids have reached respective poles and decondense + nuclear envelope reforms - cytokinesis: 2 daughter cells separated by cleavage furrow result of meiosis I: 2 haploid cells no DNA replication (S phase) in between meiosis II: - prophase II: sister chromatids condense, spindle starts to form + nuclear envelope begins to dissociate - prometaphase II: nuclear envelope completely dissociates into vesicles + sister chromatids attach to spindle via kinetochore microtubules - metaphase II: sister chromatids align along the metaphase plate + each pair of sister chromatids is attached to both poles - anaphase II: (unlike anaphase I) sister chromatids separate and individual chromosomes move toward the poles as kinetochore microtubules shorten + polar microtubules lengthen and push poles apart - telophase II: chromosomes decondense + nuclear envelope reforms - cytokinesis: cleavage furrow separates the 2 cells into 4 cells result: 4 genetically different haploid cells

Question 29

distinguish between the life cycles of diploid dominant species, haploid dominant species, and species that exhibit an alternation of generations

Question 30

sexual reproduction vs asexual reproduction (definitions)

Answer 30

sexual reproduction: process in which 2 haploid gametes unite in a fertilization event to produce a diploid cell called a zygote - for multicellular species, the zygote then grows and divides by mitotic cell divisions into a multicellular organism with many diploid cells asexual reproduction: process that occurs when offspring are produced from a single parent, without fusion of gametes from 2 parents --> offspring = clones of parent

Question 31

cell reproduction is also known as _____________

Answer 31

cell division

Question 32

homologous pairs are separated into different cells during ___________________

Answer 32

meiosis I

Question 33

sister chromatids are separated during ____________________

Answer 33

mitosis and meiosis II

Question 34

variation in chromosome structure

Question 35

What chromosomal variations have major effects on the characteristics of an organism?

Answer 35

structure and number

Question 36

a heritable change in the genetic is define as ______________

Answer 36

a mutation

Question 37

aneuploidy

Answer 37

abnormal number of particular chromosme (An alteration in the number of particular chromosomes so that the total number of chromosomes is not an exact multiple of a set is referred to as)

Question 38

what type of chromosome number is lethal in mammals

Answer 38

polyploidy

Question 39

polyploidy in plants is ___________ animals

Answer 39

more common than

Question 40

If a homologous pair of chromosomes fails to separate during meiosis I, what will be the result

Answer 40

two gametes will have two of the affected chromosomes and two gametes will have zero of the affected chromosomes