11.5 meiosis leads to the formation of gametes

Question 1

Meiosis Overview

Answer 1

-Two nuclear divisions but DNA is replicated only once.
-Converts diploid cells to haploid cells.
-Generates genetic diversity crucial for evolution.

Question 2

Meiosis 1

Answer 2

-Preceded by DNA replication in S phase.
-Homologous chromosome pairs separate, but individual chromosomes stay together.

Question 3

Prophase 1

Answer 3

-Homologous chromosomes pair via synapsis.
-Forms bivalents with chiasmata where crossing over occurs, increasing genetic variability.

Question 4

Crossing Over

Answer 4

-Exchange of genetic material between nonsister chromatids.
-Results in recombinant chromatids and increased genetic diversity.

Question 5

Metaphase 1

Answer 5

-Independent assortment allows for chance combinations of homologous chromosomes.
-Increases genetic variation due to chance alignment in anaphase 1.

Question 6

Meiosis 2

Answer 6

-Not preceded by DNA replication.
-Sister chromatids are separated, contributing to genetic diversity.

Question 7

Nondisjunction

Answer 7

-Errors in meiosis result in aneuploidy.
-Homologous pairs or sister chromatids may fail to separate, leading to chromosome number abnormalities.

Question 8

Aneuploidy Examples

Answer 8

-Down syndrome results from trisomy 21 (three copies of chromosome 21).
-Monosomy can be lethal, as seen in fetuses lacking a copy of a chromosome.

Question 9

Translocation

Answer 9

-Pieces of chromosomes break away and attach to other chromosomes.
-Can lead to genetic disorders.

Question 10

Karyotyping

Answer 10

-Counting and analyzing chromosomes during metaphase of mitosis.
-Helps diagnose chromosomal abnormalities.

Question 11

Polyploidy Overview

Answer 11

-Organisms with more than two sets of chromosomes.
-Complete extra sets of chromosomes are called polyploid.

Question 12

Types of Polyploidy

Answer 12

-Triploid (3n), tetraploid (4n), and higher levels are possible.
-Autotriploid and autotetraploids are important in forming some species.

Question 13

Polyploidy and Meiosis

Answer 13

-Diploid and even-numbered polyploid cells can undergo meiosis.
-Triploids are usually sterile and cannot undergo meiosis.

Question 14

Autopolyploidy

Answer 14

-Nondisjunction during meiosis 1 leads to autopolyploidy after fertilization.
-Polyploid cells are larger and favored as crop plants.

Question 15

Examples of Polyploid Plants

Answer 15

-Bananas and seedless watermelons are triploid.
-Triploids are seedless and commercially valuable.

Question 16

Genetic Diversity in Meiosis

Answer 16

-Meiosis generates genetic diversity through independent assortment and crossing over.
-Essential for adaptation and evolution.

Question 17

Impact of Polyploidy on Evolution

Answer 17

-Polyploidy can lead to rapid speciation and adaptation.
-Provides genetic material for natural selection to act upon.

Question 18

Significance of Nondisjunction and Translocation

Answer 18

-Nondisjunction and translocation can lead to genetic disorders and chromosomal abnormalities.
-Understanding these processes is crucial for medical genetics and breeding programs.