4. Meiosis And Sexual Life Cycles

Question 1

What is heredity?

Answer 1

Transmission of traits from one generation to the next.

Question 2

What is variation?

Answer 2

The differences in offspring appearance from their parents or siblings.

Question 3

What is Genetics?

Answer 3

The study of heredity and heredity variation

Question 4

How do offspring inherit genes?

Answer 4

Offspring inherit chromosomes from the parents, which is the genetic link to the parents and family resemblances as genes program for specific traits that emerge as we develop from fertilised eggs to adults.

Question 5

How is genetic information passed on?

Answer 5

In the form of Gene’s specific DBA Nucleotide sequence that the cell translates into different features as well as synthesises specific enzymes and proteins.

Question 6

What are the “vehicles” of gene transmission?

Answer 6

Gametes

Question 7

What is the locus?

Answer 7

A gene’s specific location along the length of a chromosome.

Question 8

What is a nucleotide?

Answer 8

The basic building blocks of nucleus acids (DNA & RNA).

A - Adenine
C - Cytosine
G - Guamine
T - Thymine

Question 9

What type of organisms are reproduced asexually?

Answer 9

Clones.

Exact genetic copy offspring are produced from parent as a copy of its genome is inherited without gamete fusion or variation.

Question 10

What type of organisms are reproduced sexually?

Answer 10

Genetically varied offspring.

Due to a unique gene combination inherited from both parents.

Question 11

What is Ploidy?

Answer 11

Number of sets of chromosomes in a cell

Question 12

What is haploid?

Answer 12

One set of chromosomes.

Question 13

What is diploid?

Answer 13

Two sets of chromosomes. Both maternal and paternal.

Question 14

What does homologous mean?

Answer 14

Two structures of the SAME composition as they exist in pairs.

Question 15

What are Autosomes?

Answer 15

Non sex chromosomes

Question 16

What is the life cycle?

Answer 16

The generation to generation sequence of stages in the reproductive history of an organism, from conception to production of its own offspring.

Question 17

What is a karyotype?

Answer 17

An ordered display of the pairs of cellular chromosomes.

Question 18

Another name for Homologous Chromosomes?

Answer 18

Homologs

Question 19

Sets of chromosomes in humans?

Answer 19

23 pairs of chromosomes with half being maternal and the other half being maternal.

Question 20

What are homologous chromosomes?

Answer 20

Two chromosomes of a pair, having the same length, centromere position and staining pattern.

Question 21

What is fertilisation?

Answer 21

The union of gametes

Question 22

What is a zygote?

Answer 22

A fertilised egg

Question 23

How do chromosomes behave in the human life cycle?

Answer 23

Cycle begins when a haploid sperm from the father fuses with a haploid egg from the mother.

The zygote is diploid as it contains two sets of haploid chromosomes, bearing both maternal & paternal genes.

As humans mature, mitosis of the zygote and its descendant cells generate all the somatic cells of the body.

Gametes are the only cells not produced by mitosis. They come from germ cells in the gonads.

Question 24

What are the gonads?

Answer 24

Female and male reproductive organs. The testes and ovaries.

Question 25

What is meiosis?

Answer 25

Process of Gamete formation

Where Cell division reduces the number of sets of chromosomes from two to one in the gametes to counteract the doubling of chromosomes at fertilisation.

As a result both Sperm and Egg cells are haploid.

Fertilisation will restore the diploid condition by combining the two sets of chromosomes, continuing the human life cycle for further generations.

Question 26

Where does meiosis occur?

Answer 26

In germ cells.

Question 27

How many parts does meiosis have?

Answer 27

Meiosis has two parts. Meiosis 1 and meiosis 2.

Question 28

What does meiosis 1 do?

Answer 28

Separates homologous chromosomes

Question 29

What does meiosis 2 do?

Answer 29

Separates paired sister chromatids.

Question 30

Explain the process of Meiosis 1.

Answer 30

• Prophase 1

Chromosomes condense
Nuclear envelope breaks down
Mitotic spindle forms
Synapsid occurs to form tetrads.
Crossing over/ Recombination occurs.

• Metaphase 1

Chromosomes migrate to the metaphase plate where each homolog is attached to a kinetochore microtubule from the opposing pole.

• Anaphase 1

Microtubules shorten and pull chromosomes to opposing poles of the cell, breaking up the tetras but sister chromatids still persist.

• Telophase 1

Each half of the cell has a complete haploid set of chromosomes of two non identical sister chromatids.
The nuclear envelope reappears.

• Cytokinesis

Division of the cytoplasm.

*Meiosis 1 ends with two genetically different haploid daughter cells with 23 chromosomes of paired sister chromatids.

Question 31

Explain the process of meiosis 2.

Answer 31

• Prophase 2

No DNA replication
Chromosomes condense
Nuclear envelope breaks down
Mitotic spindle forms

• Metaphase 2

Chromosomes migrate to the metaphase plate where each chromatid is attached to a kinetochore microtubule from the opposing pole.

• Anaphase 2

Microtubules shorten and pull chromatids to opposing poles of the cell, breaking them up.

• Telophase 2

Each half of the cell has a complete haploid set of chromosomes.
The nuclear envelope reappears.

• Cytokinesis

Division of the cytoplasm.

*Meiosis 2 ends with four genetically different haploid daughter cells

Question 32

What is a tetrad?

Answer 32

A group of four chromatids

Question 33

What is Synapsis?

Answer 33

The pairing of homologous chromosomes

Question 34

What is crossing over/ Recombination?

Answer 34

The exchange of allele segment amongst homologous chromosomes.

Question 35

What is an allele?

Answer 35

Gene that occupies a specific location on a chromosome and controls a trait.

Question 36

What is Chiasmata?

Answer 36

Point of contact between homologous pairs of chromosomes. (It’s like the centromeres)