Meiosis

Question 1

heredity

Answer 1

transmission of traits from one generation to the next

Question 2

genetics

Answer 2

the study of heredity and the variation of inherited characteristics

Question 3

genes

Answer 3

a discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA

Question 4

haploid

Answer 4

a cell with only one set of chormosomes

Question 5

homologous chromosomes

Answer 5

pair of chromosomes with same length, centromere position, and staining pattern that possess genes for the same characteristics at corresponding loci

Question 6

karyotype

Answer 6

ordered display of chromosome pairs of a cell arranged by size and shape
-allows identification for chromosomal mutations and gender

Question 7

diploid cells

Answer 7

cells with two sets of chromosomes (2n); one from each parent

Question 8

autosomes

Answer 8

not a sex chromosome

Question 9

sex chromosome

Answer 9

chromosome that determines the sex of an individual

Question 10

locus

Answer 10

a specific place along the length of a chromosome where a given gene is located

Question 11

gamete

Answer 11

a haploid cell, such as an egg or sperm. gametes unite during sexual reproduction to produce a diploid zygote

Question 12

variation

Answer 12

differences between members of the same species

Question 13

asexual reproduction

Answer 13

Asexual
– Single individual passes genes on to offspring
– Creates identical daughter cells (clones)
– Done by binary fission & mitosis

Question 14

sexual reproduction

Answer 14

– Two parents produce
offspring that has a unique combination of parents’ traits
– Gives genetic variation
– Done by meiosis plus fertilization

Question 15

Human Life Cycle

Answer 15

• Begins with the fusion of a sperm & egg (fertilization) which results in a zygote
• Zygote develops into a developed person via mitosis to increase somatic
cells & eventually reaches sexual maturity
• Gametes are then produced in the gonads by meiosis until fertilization occurs again

Question 16

plant and some algae life cycle

Answer 16

alternation of generations
-multicellular diploid sporophyte undergoes meiosis to produce haploid spores. spores divide mitotically, forming multicellular haploid gametophytes. Through mitosis, gametophytes form gametes, in which fertilization results in diploid zygote that will develop into next sporophyte generation.

Question 17

fungi and protists life cycle

Answer 17

diploid zygote undergoes meiosis, forming haploid cells that develop into unicellular descendants or haploid multicellular adult organisms. the haploid organism carries out further mitosis, producing cells that will develop into gametes.

Question 18

Meiosis

Answer 18

• crossing over in prophase results in genetic diversity
• two divisions
• 2n→n
• results in four genetically distinct daughter cells (gametes) that can sexually reproduce

Question 19

Prophase I

Answer 19

homologous pairs line up and cross over at chiasmata

-centrosome movement to opposite poles, spindle microtubule formation, nuclear envelope breakdown, nuclei dispersal

Question 20

Metaphase I

Answer 20

pairs of homologous chromosomes (tetrads) are arranged on metaphase plate and connected to kinetochore microtubules

Question 21

Anaphase I

Answer 21

spindle apparatus separates pairs of homologous chromosomes as they move toward opposite poles

Question 22

Telophase I

Answer 22

each half of cell has complete haploid set of chromosomes (sister chromatids remain intact)

Question 23

Meiosis II

Answer 23

-depending on the cell tpe, the nuclear envelope will reform and DNA will relax in between meiosis I and meiosis II
sister chromatids are separated, resulting in four haploid daughter cells that are all different

Question 24

genetic variation

Answer 24

evolutionary
principles & the continuation of populations around the world
-ensures that populations can withstand environmental changes

Question 25

independent assortment

Answer 25

Homologous pairs line up at the metaphase plate during Metaphase I and metaphase II independent of each other
– Result is a 50% chance that a gamete will end up with maternal or paternal chromosome from the homologous pair
– Each daughter cell from meiosis I represents one option of the possible 8 million combinations of parental chromosomes

Question 26

crossing over

Answer 26

• Occurs during prophase I when homologous pair line up
• Nonsister chromatids are broken at the same place and swap equal amount of DNA to form recombinant
chromosomes
– This creates new combinations of maternal & paternal genes
• Humans average 1 to 3 crossovers per homologous pair
-can only occur with the two inside, non-sister chromatids of tetrads

Question 27

random fertilization

Answer 27

• When sexual reproduction occurs one gamete for each parent will fuse to form a zygote
– This represents one possible outcome from 64 trillion possible gene combinations (this doesn’t even include the changes that result from cross over)!
– Hence, siblings can be very different from each other
-each gamete is equally likely to be fertilized

Question 28

pros and cons of sexual reproduction

Answer 28

pros: more genetic variety so population can survive in changing environment
cons: slower process of reproduction, requires male and female gametes

Question 29

pros and cons of asexual reproduction

Answer 29

pros: fast rate of reproduction and pop. growth, large pop., does not require partners
cons: no genetic variety so pop. is susceptible to extinction