Sexual Reproduction & Meiosis

Question 1

What is Mitosis?

Answer 1

-First part of M phase in the cell cycle

Mitosis is a process where a single cell divides into two identical daughter cells (

• 1 nuclear division (5 stages) followed by a cytoplasm division (cytokinesis)
• Produce daughter cells with same genetic information (DNA replication)
• Daughter cells are exact copies of the mother cell, same amount of DNA, number of chromosomes, genetic information
• Asexual reproduction in simple single-celled organisms NOT IN HUMANS

Question 2

What are somatic cells?

Answer 2

-Almost all of the cells in an multicellular organism are SOMATIC (’body cells, other than sex cells or gametes)

-Multicellular organisms are produced by rounds of mitosis from a single cell

Question 3

What are diploid cells?

Answer 3

-two copies/sets of each chromosome (2n), one set inherited from each parent

-In humans, diploid cells contain 46 chromosomes (22 pairs of homologous autosomes + 2 sex chromosomes)

Question 4

What are somatic cells?

Answer 4

-Any living organism other than the reproductive cells

Question 5

What are the features of somatic cells?

Answer 5

-Do not contribute to inheritance diploid cells
-Originated by mitosis

Question 6

How many chromosomes do diploid cells have?

Answer 6

-46
-22 pairs
-2 sex cells

Question 7

What are homologous autosomal chromosomes?

Answer 7

-Pairs of chromosomes that are not sex cells

Question 8

What is a locus of a chromosome?

Answer 8

-Location of a gene on a chromosome

Question 9

What are sex chromosomes?

Answer 9

-Pairs of chromosomes that participate in sex determination

Question 10

What sex chromosomes do females have?

Answer 10

XX

Question 11

What sex chromosomes do males have ?

Answer 11

-XY

Question 12

What is the difference between X and Y chromosome?

Answer 12

-The X chromosome is bigger and carries different genes

Question 13

What are gametes ?

Answer 13

-Reproductive cells?

Question 14

What are spermatozoa and egg cells produced from?

Answer 14

-Diploid germ-line cells

Question 15

Where does meiosis occur?

Answer 15

-Specialised germ-line cells that residee in the ovaries or testes

Question 16

What is meiosis ?

Answer 16

-A cell division that produces 4 non-identical daughter cells having half the number of chromosomes of the parent cell

Question 17

What does meiosis involve?

Answer 17

-One round of DNA replication then two rounds of nuclear division

Question 18

What is the first event in meiosis?

Answer 18

-Interphase (G1, S, G2)

Question 19

What is a tetrad?

Answer 19

-4 Chromatids

Question 20

What stage does crossing over occur?

Answer 20

-Prophase 1

Question 21

What is crossing over?

Answer 21

-Genetic exchange between DNA segments of the non-sister chromatids

Question 22

How does crossing over cause genetic diversity?

Answer 22

-Allele reassortment creates unique mixture of maternal and paternal homologs

Question 23

What happens in metaphase 1 ?

Answer 23

-Spindle microtubules from both poles capture each tetrad and move them towards the centre of the meiotic plate

Question 24

What happens in anaphase 1?

Answer 24

-Homologous chromosomes separate and move towards opposite poles

Question 25

What happens in telophase 1?

Answer 25

-Two nuclear envelopes form around each set of chromosomes

Question 26

What happens in cytokinesis 1?

Answer 26

-Daughter cells that have one set of chromosomes but duplicated

Question 27

What is interkinesis?

Answer 27

-A small interphase after meiosis 1 and before meiosis 2 during which chromatin uncoils

Question 28

What happens in meiosis II?

Answer 28

-Meiosis II is like mitosis; sister chromatids separate and four haploid cells are formed. Note that each has half the chromosomes of the parent cell. These cells differ genetically from each other and from the cells of the parents

Question 29

What errors can occur during meiosis?

Answer 29

-Separation of homologous or sister chromosomes may not be achieved which can result in to few or too many copies of a particular chromosome

Question 30

What are the 5 stages of mitosis ?

Answer 30

Prophase
Metaphase
Anaphase
Telophase
Cytokinesis