Mod 5 HEREDITY: Cell replication

Question 1

Define mitosis and its purpose.

Answer 1

Mitosis is the production of two genetically identical daughter cells (somatic) in which they are diploid, containing the same gene code. The purpose of mitosis is for the growth and repair of cells,

Question 2

Define interphase

Answer 2

Duplication of chromosomes, in which the cell crows and repairs for cell division. Occurs in both mitosis and meiosis, however is not a stage in the cycle.

Question 3

List the 4 stages of mitosis

Answer 3

Prophase
Metaphase
Anaphase
Telophase

Question 4

Describe prophase

Answer 4

First stage of mitosis in which the nucleus of the cell breaks down, with chromosomes condensing and centrioles being separated and moving to opposite ends of the cell

Question 5

Describe metaphase

Answer 5

“M” for middle. Second stage of mitosis where chromosomes condense at the middle of the cell, being attached to spindle fibres. Nucleus has been degraded.

Question 6

Describe anaphase

Answer 6

“A” for away. Third stage of mitosis, where sister chromatids are split apart by spindle fibres. This separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells.

Question 7

Describe telophase

Answer 7

“T” for two. Two nuclei are formed (two daughter cells), and chromosomes are at the very end of the cells. Cytokinesis then occurs, creating a cleavage burrow that splits the cytoplasm into two cells.

Question 8

Define meiosis and its purpose.

Answer 8

Meiosis is the production of gametes that produces 4 genetically unique haploid daughter cells. Purpose is to reproduce the normal diploid cells to haploid cells and to make egg and sperm.

Question 9

Describe prophase I

Answer 9

The first stage of meiosis involves DNA being exchanged and causing crossover between homologous pairs of chromosomes within the cell.

Question 10

Describe metaphase I

Answer 10

Second stage of meiosis, where homologous pairs aligned in the middle of the cell, with spindle fibres attached to them.

Question 11

Describe anaphase I

Answer 11

Third stage of meiosis involves the separation of homologous chromosomes via spindle fibres.

Question 12

Describe telophase I

Answer 12

Fourth stage of meiosis, where two nuclei are formed. Cytokinesis then takes places, forming two new daughter cells.

Question 13

Describe prophase II

Answer 13

Fifth stage of meiosis where a new spindle apparatus forms, the nuclear envelope breaks down, and the chromatin condenses into chromosomes again.

Question 14

Describe metaphase II

Answer 14

Sixth stage of meiosis, where chromosomes line up in the middle, with spindle fibres attaching onto chromosomes.

Question 15

Describe anaphase II

Answer 15

Seventh stage of meiosis where separation of the sister chromatids

Question 16

Describe telophase II

Answer 16

Eighth stage of meiosis, where nuclei are reformed. Cytokinesis then follows to produce 4 daughters cells.

Question 17

Outline the Watson and Crick DNA model

Answer 17

The DNA model was discovered in 1953 that DNA is a double-stranded helical molecule that replicates itself during cell division. Watson and Crick’s model incorporated Franklin’s findings and added the specific details of the double helix structure, including the specific pairing of the nitrogenous bases (adenine with thymine, and guanine with cytosine).

Question 18

Define DNA replication

Answer 18

Producing two identical copies of DNA from an original DNA molecule

Question 19

Outline the steps of DNA replication

Answer 19

1. Unzipping: Helicase is an enzyme that goes along the double strand and opens the DNA. It does this by breaking the hydrogen bonds among the two stands.
2. Formation of RNA: Primase enzyme is attacked to one of the strands, and makes a small piece of RNA. This is known as the primer, which is the starting point for DNA replication.
3. Addition of complementary bases: DNA polymerase attaches to the primer, moving along the strand and adding complementary bases onto the leading strand.
4. Creation of primers: As DNA works from the 5’ and 3’ directions, the opposite strand (lagging) will not be made. So alternatively, primers are created and DNA adds bases in a series of okazaki fragments.
5. Removing the primers: Exonuclease enzyme will come and remove all primers, with DNA polymerase filling in the gaps that the primers binded onto the DNA
6. Sealing: DNA ligase seals fragments of DNA in both strands. This creates a continuous chain of DNA.

Question 20

Assess the effect of the cell replication processes on the continuity of species

Answer 20

Cell division results in two genetically identical daughter cells, occurring in somatic cells. The steps to successful mitosis include, excluding interphase: prophase, metaphase, anaphase, and telophase. Chromosomes consist of genes encoding for a specific protein. For instance, haemoglobin is a protein found in red blood cells. This protein is responsible for delivering oxygen throughout the body. Therefore, mitosis plays a crucial role in the continuity of species, ensuring that cell proteins are synthesised successfully. Absence of mitosis would cease life, as organisms cannot grow and would eventually perish due to cellular death.

Meiosis is the production of four genetically unique haploid gametes through PMAT (I) and PMAT (II). Crossing, independent assortment, and random segregation contribute to genetic variation of species. Crossing over refers to the exchange of DNA between paired homologous chromosomes. Independent assortment describes how different genes independently separate from one another when reproductive cells develop. Random segregation involves each gamete receiving just one gene copy, which is selected randomly. Genetic variation plays an important role in natural selection, acting as a distinguishing factor based on favourable traits and characteristics. This allows for them to succeed in the environment. Overall, genetic diversity introduced by meiosis is the key to adaptability of a population to diseases and environmental changes. If meiosis were absent, genetic variation and evolution would not exist, significantly decreasing species’ chances to survive and reproduce to ensure their continued survival.