Lecture 11

Question 1

Is interphase mitosis?

Answer 1

NOOOOO

Question 2

How does mixing occur

Answer 2

Regions of chromosomes get swapped between homologation

Crossovers between homologous chromosome lead to regions being swapped

Crossover sites are called Chiasmata (singular= chiasma)

Question 3

Synapsis

Answer 3

Homologs pair up during meiosis

Held together by synaptonemal complex

Question 4

Meiosis when does crossover and exchange occur

Answer 4

During prophase 1

Starts prior to condensation of chromosomes

Question 5

Sources of genetic variation during sexual reproduction 1-3 are included in meiosis

Answer 5

1- mixing genes between homologous chromosomes

2- random segregation pattern of maternal and paternal homologous chromosomes during anaphase 1

3- transom segregation pattern of sister chromatids during anaphase 2

4- fertilization

Question 6

Mitosis super quick summary

Answer 6

Prophase- chromosomes form

Metaphase- chromosomes in the middle, spindles attach

Anaphase and telophase- spindle rips the chromosomes in half and pulls them back to the pole of the cells. Then they divide

Question 7

What to pay attention to to determine the stage of MEIOSIS

Answer 7

Chromatin: condensed or not?

Nuclear envelope: present or not?

Centrosomes (animals): replicated? Position?

Chromosomes: Position? Attachment to microtubules? Sister chromatids attached?

ONLY FOR MEIOSIS: are homologous chromosomes paired or not

Question 8

How many possibilities in terms of random orientation for humans vs 3 chromosome critter

Answer 8

2^3= 8

2^ 23= 8,388,608 possibilities

Question 9

Fungi and algae (zygotic meiosis)

Answer 9

Spore 1n > (many mitosis) > mature 1n> gametes> zygote 2n > meiosis

Repeat

Question 10

Alternation of generations in plants

Answer 10

• direct product is 4 haploid spores not gametes
• spores germinate and grow into a haploid plant

-When mature, haploid plant produces sperm/ egg which fuse to make a zygote

• the sperm/ egg are formed by mitosis since the plant is already haploid

Question 11

Zygotic meiosis

Answer 11

Spore1n > many mitosis> mature 1n > mitosis> gametes 1n > fertilization> zygote 2n > no mitosis> meiosis

Repeat

Like plants produces 4 spores

Question 12

What if ur cell cycle doesn’t stop

Answer 12

When a single mutated cell keeps dividing it creates a mass of abnormal cells called a tumor