Meiosis

Question 1

What is the purpose of meiosis?

Answer 1

The purpose is to create gametes, or sex cells

Results in a haploid number of chromosomes

Question 2

Interphase 1

Answer 2

Same as mitosis

Question 3

Prohphase 1

Answer 3

Homologous pairs of chromosomes pair up (maternal paternal) - called synapsis
DNA cross over happens via the chiasmatat (alleles switch randomly)
Chromsosomes stay attached as tetrads (2 chromosomes, 4 chromatids)
Creates recombinant chromatids
- same as mitosis, centrioles and spindle fibers appear, nuclear membrane disintegrates

Question 4

Metaphase 1

Answer 4

Tetrads align along the equator, still in connected pairs (independent assortment, the tetrads line up randomly, ensuring random diversity)
Spindle fibers attach to kinetochores

Question 5

Anaphase 1

Answer 5

Tetrads are pulled apart by their kinetochores, splitting the two chromosomes apart
Sister chromarids are still in tact (even though they’re no longer identical)

Question 6

Telephase 1

Answer 6

Nuclear membrane starts to form, cleavage furrow

Still a diploid

Question 7

Cytokenisis 1

Answer 7

Cell splits into two, the two daughter cells become haploids (n= 23)
Nuclear membrane forms etc

Question 8

Interphase 2

Answer 8

No DNA replication, chromosomes are in x shape

Question 9

Prophase 2

Answer 9

No crossing over/synapsis, centrioles and spindle fibers form, move to opposite poles

Question 10

Metaphase 2

Answer 10

Chromosomesign up along the equator/metaphase plate

Spindle fibers attach to centrometers

Question 11

Anaphase 2

Answer 11

Chromatids are separated, pulled apart to opposite poles.

Question 12

Telophase 2

Answer 12

Chromosomes unwind, nuclear membrane forms spindle fibers disintegrate

Question 13

Cytokenesis 2

Answer 13

4 haploid cells

DNA is in chromatids

Question 14

Why did gregor mendel chose pea plants

Answer 14

Fast, easy, easy to organize, self fertilizing, exhibits true breeding (offspring has same phenotype is parent)

Question 15

Pea plant observable traits

Answer 15

Seed shape (R) (r)
Colour (Y) (y)
Pod shape I i
Pod colour G g
Flower colour P p
Flower location A a
Plat size T t

Question 16

Monohybrid cross

Answer 16

Crossing two organisms with only one difference between them
Parent generation (initial crossing organisms)
F1 (First generation)
F2 (second generation)

Question 17

Dominant gene

Answer 17

Stronger, masks recessive Gene’s in heterozygous organisms

Question 18

Recessive gene

Answer 18

Weaker, can not be expressed without two recessive Gene’s, only expressed in homologous pairs

Question 19

How did he use the pea plants

Answer 19

Pea plants are self fertilizing (female and male sex organs)

He cut off stamens that produce pollen, and pollinated another flower with it to mix

Question 20

Mendels laws

Answer 20

Law of segregation

• each trait is a result of 2 alleles
• every gamete only gets a single allele (each offspring contains only 1 allele from each parent)
• expressed gene depends on dominance/recessiveness

Law of independent assortment
Chromosomes mix randomly during meiosis 1
- the allele a gamete receives for one gene, doesn’t influence the allele recieved for another gene

Question 21

Heterozygous

Answer 21

Individual with 2 kinds of alleles

Question 22

Homozygous

Answer 22

Individual with 1 kind of allele

Question 23

Genotype vs phenotype

Answer 23

Genotype is the genetic code

Phenotype is the expresses trait