Meiosis

Question 1

Where do homologous chromosomes come from?

Answer 1

one from mother, one from father

Question 2

Homologs have the same ______ but potentially different _______.

Answer 2

genes, alleles

Question 3

Trisomy 21

Answer 3

aka Down Syndrome, extra chromosome 21

Question 4

Mitosis vs meiosis

Answer 4

Mitosis: 2 diploid cells with identical chromosomes (46 each)
Meiosis: 4 haploid cells with a mix of paternal and maternal DNA (23 chromosomes each)

Question 5

Cell Division Cycle (Mitosis)

Answer 5

Interphase and Cell Division

Question 6

Interphase

Answer 6

G1: rapid growth and metabolic activity; centriole replication (8-10 hrs)
S: chromosome replication (DNA synthesis, 6-8 hrs)
G2: growth and final prep for cell division (4-6 hrs)

Question 7

Cell Division

Answer 7

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
5. Cytokinesis
   < 1 hr

Question 8

Human life cycle

Answer 8

1. Meiosis
2. haploid gametes (ovum and sperm cell, 23 chromosomes each)
3. Fertilization
4. Diploid zygote (2n = 46)
5. Mitosis and development
6. Growth/adulthood

Question 9

Meiosis I: Prophase I

Answer 9

Chromatin condenses to chromosomes, crossing-over occurs, centrosomes move, nuclear envelope dissipates

Question 10

Meiosis I: Metaphase I

Answer 10

chromosomes line up on equatorial plate, spindle fibers attach to centromeres

Question 11

Meiosis I: Anaphase I

Answer 11

centromeres contract and pull apart homologous chromosomes away from each other and toward opposite poles

Question 12

Meiosis I: Telophase I

Answer 12

Homologous chromosomes decondense and nuclear envelope reappears

Question 13

Cytokinesis I

Answer 13

Cell splits into two haploid daughter cells (1n, 23 chromosomes)

Question 14

Meiosis II: Prophase II

Answer 14

chromosomes condense, new set of spindle fibers form

Question 15

Meiosis II: Metaphase II

Answer 15

centromeres of paired chromatids align along equatorial plate

Question 16

Meiosis II: Anaphase II

Answer 16

spindle fibers contract and pull apart the chromosomes at the centromeres, moving them toward opposite poles

Question 17

Meiosis II: Telophase II

Answer 17

nuclear envelope reappears, chromosomes decondense into chromatin, cells begin to separate

Question 18

Cytokinesis II

Answer 18

The 2 daughter cells split into 4 haploid cells (1n)

Question 19

Why is Prophase I particularly important?

Answer 19

Crossing-over and recombination happen in this step

Question 20

Cross-over

Answer 20

2 NON-sister chromatids of the homologous chromosomes cross over each other and share DNA, resulting in recombinant chromatids

Question 21

What is a chiasma?

Answer 21

where the non-sister chromatids cross during cross-over/recombination

Question 22

What are cohesins?

Answer 22

protein complexes that hold sister chromatids together

Question 23

What are synaptonemal complex (SC) proteins?

Answer 23

proteins that hold homologous chromosomes together in Synaptonemal Complex

Question 24

What is Mendel’s Law of Segregation?

Answer 24

separation of alleles that are reunited by fertilization

Question 25

What is Mendel’s Law of Independent Assortment?

Answer 25

genes on non-homologous chromosomes assort independently

Question 26

What are the three sources of genetic diversity?

Answer 26

mutation, recombination, and independent assortment