Lesson 3: G3 - Sexual Reproduction

Question 1

What are the 2 key process of sexual reproduction?

Answer 1

1) formation of haploid cells, or gametes, which contain genetic information from the parents

2) Two sex cells joining to form a zygote, the first cell of a genetically unique individual, through fertilization

Question 2

Types of fertilzation methods

Answer 2

• Gamtes fuse to form zygote
• Insects pollinating

-External fertilzation

-Interal fertilzation

Question 3

sex cells are produced through…

Answer 3

meiosis

-This is the process through which haploid gametes are formed

Question 4

TRUE OF FASLE: in meiosis chromosome # in each generation is cut in half

Answer 4

TRUE

Question 5

How many chromosomes do sex cells contain?

Answer 5

23 Chormosomes

Question 6

combination of two gametes (sperm and egg - both haploid) will result in…

Answer 6

omplete set of chromosomes (diploid, 2n = 46)

Question 7

homologous chromosomes

Answer 7

You receive a complete set of DNA from each parent (one version of each gene)

-ensures the offspring is genetically unique from each parents

Question 8

Meiosis is a process that involves __#__
divisions that produces __#__ haploid gametes from _#__ diploid parent cell

Answer 8

Meiosis is a process that involves two divisions that produces 4 haploid gametes from 1 diploid parent cell

Question 9

gametogenesis

Answer 9

formation of sex cells

Question 10

Formation of sperm

Answer 10

spermatogenesis

Question 11

ormation of egg cells or ova

Answer 11

oogenesis

Question 12

spermatogenesis and oogenesis formed through process called…

Answer 12

meiosis

Question 13

Steps in Meiosis

Answer 13

• Interphase
  -Meiosis I: Prophase I
  -Meiosis I: Metaphase I
  -Meiosis I: Anaphase I
  -Meiosis I: Telophase I
  -Meiosis II: Prophase II
  -Meiosis II: Metaphase II
  -Meiosis II: Anaphase II
  -Meiosis II: Telophase II

Question 14

Interphase

Answer 14

Cell grows to nearly twice in size
Nucleus makes a copy of its DNA
Organelles are also replicated

Question 15

Meiosis I: Prophase I

Answer 15

Chromatin condenses into chromosomes

The nuclear membrane dissolves

Centrioles move to opposite sides of the cell

Spindle fibers begin to grow

Homologous chromosomes come together and intertwine to form a tetrad by a process called synapsis

Each chromosome is made of 2 sister chromatids, and you have 1 chromosome from each parents

These four sister chromatids together is called a tetrad

Crossing over can also occur at this stage:

-This is when intertwined chromatids from different chromosomes break off and reattach at the chiasmata

-This causes an exchange of genetic material at certain sections

-This works to mix or recombine genetic information further increasing genetic variation in the gene pool

Question 16

synapsis

Answer 16

intertwinning of chromosomes

Question 17

Meiosis I: Metaphase I

Answer 17

tetrads migrate towards the center of the cell, called the equatorial plate

This is accomplished through spindle fiber
attachment at the centromeres like in mitosis

The tetrads align their centromeres at the middle of the cell

Question 18

Meiosis I: Anaphase I

Answer 18

Homologous chromosomes move to opposite poles of the cell when the spindle fibers shorten

-means that only one of the two chromosomes from each homologous pair will be in each new daughter cell and therefore are genetically unique

Question 19

Meiosis I: Telophase I

Answer 19

The nuclear membranes reform, spindle fibers dissolve and the cell begins to divide via the first cycle of cytokinesis

Each new cell has only 1 (not two) duplicated copy of a chromosome at this point

Only the maternal or paternal chromosome is in each new cell

Therefore the cells are haploid

Question 20

Meiosis II: Prophase II

Answer 20

Each haploid cell has one chromosome made of two sister chromatids at this point

The sister chromatids are not genetically identical though, due to the crossing over that occurred during prophase I

Once again, the nuclear membrane dissolves, centrioles move to opposite poles and spindle fibers reform

Question 21

Meiosis II: Metaphase II

Answer 21

Again, the one chromosome made of two sister chromatids move to center of the cell, called the equatorial plate

This is accomplished through spindle fiber attachment at the centromeres like in mitosis
The chromosomes align their centromeres at the middle of the cell

Question 22

Meiosis II: Anaphase II

Answer 22

Sister chromatids now separate and move to opposite poles of the cell
Each cell now has a single sister chromatid, not a duplicate copy
These will not be identical due to the genetic exchange that occurred in crossing over

Question 23

Meiosis II: Telophase II

Answer 23

the nuclear membrane reforms around the chromatids, the DNA relaxes into chromatin and the spindle fibers dissolve
The second nuclear division is now completed
Soon after, cytokinesis will occur for the second time
This will result in 4 haploid daughter cells (that are NOT identical)

Question 24

What stages of meosis allow for gentic variation?

Answer 24

In Prophase I, crossing over occurs randomly

In Metaphase I and II, it is random as to which side each chromosome goes to