BIO1101 - Module 4

Question 1

Module 4 - What understanding do genetics provide us with?

Answer 1

How traits are passed down from generation to generation.

Question 2

Module 4 - What are the two critical processes of the cell cycle?

Answer 2

i) Replications of cells genetic material

ii) Cellular division

Question 3

Module 4 - What is the process of cellular replication called?

Answer 3

Mitosis

Question 4

Module 4 - What are the two major classes of cellular reproduction?

Answer 4

i) Asexual reproduction - Results in cells identical to the parent cells
ii) Sexual reproduction - Results in mixing of the genetic material and thus cells that differ from the parent cells

Question 5

Module 4 - The cell cycle allows _____ organisms (e.g. bacteria) to divide and reproduce and allows ______ organisms to grow and develop from fertilized eggs.

Answer 5

The cell cycle allows unicellular organisms (e.g. bacteria) to divide and reproduce and allows multicellular organisms to grow and develop from fertilized eggs.

Question 6

Module 4 - In eukaryotes, which have very large genomes, the genetic material (DNA) is packaged in linear chromosomes which allows easier replication and distribution. Each chromosome is made up of chromatin.

What is chromatin?

Answer 6

DNA + protein

Question 7

Module 4 - What is the difference between somatic cells and gametes?

Answer 7

i) Somatic cells are the normal cells of the body. In humans, somatic cells have 46 chromosomes.
ii) Gametes are the reproductive cells (sperm and egg cells). They have 23 chromosomes.

When sexual reproduction occurs, and two gametes (sperm and egg) fuse, the number of chromosome is restored to 46.

Question 8

Module 4 - The cell cycle incorporates stages for both _____ growth and ______.

Answer 8

The cell cycle incorporates stages for both cellular growth and replication.

Question 9

Module 4 - What are the 5 distinct stages of mitosis?

Answer 9

i) Prophase
ii) Prometaphase
iii) Metaphase
iv) Anaphase
v) Telophase / cytokinesis

Question 10

Module 4 - Explain prophase

Answer 10

Step 1 - In the nucleus, chromatin fibres condense so chromosomes become visible, consisting of identical sister chromatids joined at the centromere.

The mytotic spindle begins to form in the cytoplasm and centrosomes begin to move apart to either end of the cell.

Question 11

Module 4 - Explain Prometaphase

Answer 11

Step 2 - The nuclear envelope begins to disintegrate, allowing microtubules to attach at the kinetochore.

The spindle extend from each polar centrosome towards the cells equator. Not all spindle fibres attach to chromosomes however.

Question 12

Module 4 - Explain metaphase

Answer 12

Step 3 - Chromosomes move towards the centre of the cell and centromeres of all chromosomes line up equidistant from either pole.

Question 13

Module 4 - Explain anaphase

Answer 13

Step 4 - Paired sister chromosomes split apart to allow individual chromosomes to move to opposite ends of the cell, ensuring that each new cell later ends up with one copy of the duplicated chromosome.

Chromosomes dragged apart by kinetochore microtubules. Poles of the cell move further apart, making cell oval shaped.

Question 14

Module 4 - Explain Telophase / cytokinesis

Answer 14

Step 5 - Cell further elongates. Daughter nuclei begin to form at the two poles. Nuclear membranes begin to form around the chromosomes. Nucleoli reappear. Chromosomes become less condensed and harder to see. Cell cleaves into two daughter parts (cytokinesis).

Question 15

Module 4 - What are the 3 important ways that meiosis allows genetic variation to be produced?

Answer 15

i) Independent assortment of chromosomes
ii) Crossing over (homologuous recombination)
iii) Random fertilisation

Question 16

Module 4 - What is the difference between meiosis and mitosis?

Answer 16

i) meiosis: Involves the division of sex cells

ii) mitosis: Involves the division of body cells

Question 17

Module 4 - What is S-phase?

Answer 17

The phase of the cell cycle in which DNA is replicated

Question 18

Module 4 - What is interphase?

Answer 18

Refers to all stages of the cell cycle that is not mitosis (about 90% of the cycle time). It is not accompanied by observable changes under the microscope.

During interphase the cell grows, replicates its DNA and prepares for mitosis, during the 3 sub-components:

G1) Cell growth occurs. DNA synthesis occurs.
G2) Cell growth continues. Cell prepares to divide.
Mitotic phase) Short part of the cycle whereby the cell actually divides.q

Question 19

Module 4 - As a result of mitosis, cells divide and two identical daughter cells are produced, a process that is thought to have evolved from simple bacterial _____ _____

Answer 19

As a result of mitosis, cells divide and two identical daughter cells are produced, a process that is thought to have evolved from simple bacterial binary fission.

Question 20

Module 4 - Meiosis involves one round of _____ _______ followed by two rounds of ______ (meiosis I and meiosis II). This results in the production of four ______cells

Answer 20

Meiosis involves one round of DNA replication followed by two rounds of division (meiosis I and meiosis II). This results in the production of four daughter cells

Question 21

Module 4 - How can cellular reproduction occur?

Answer 21

By asexual or sexual means. 
Asexual process (binary fission in bacteria and mitosis in eukaryotes) allows cells to produce identical daughter cells.
Sexual process (meiosis) allows genes to be mixed both during gamete formation and as a result of random fertilisation.

Question 22

Module 4 - What is the location of a gene on a chromosome called?

Answer 22

Locus

Question 23

Module 4 - What is Mendels 1st Law of Segregation?

Answer 23

When pairs of alleles segregate during the formation of gametes (meiosis) and the pairing is
restored by the fusion of gametes during fertilization.

Question 24

Module 4 - What is the difference between a test cross and a back cross?

Answer 24

Testcross: A cross between an unknown genotype and a true breeding recessive phenotype (e.g P? ×
pp). Although the genotype of one parent is not certain (? could be either P or p), the phenotype is purple. A testcross ‘tests’ what the unknown genotype is.

Backcross: crossing F1 offspring to one or other parent

Question 25

Module 4 - What is a monohybrid cross?

Answer 25

Results in the 3 in 4 result where 2 true breeding parents.

Question 26

Module 4 - What is Mendels 2nd Law of Independent Assortment?

Answer 26

Pairs of alleles at different loci segregate into gametes independently

Question 27

Module 4 - What is incomplete dominance?

Answer 27

Dominant genes may not be fully dominant resulting in heterozygote that is intermediate between the two homozygotes

Question 28

Module 4- Chromosomes of the same type and numbers in both sexes are called:

Answer 28

Autosomes

Question 29

Module 4- Genes on a particular chromosome may be split apart by _______ breaking and rejoining during meiosis I. Thus meiosis may give rise to new combinations of genes in gametes.

Answer 29

Genes on a particular chromosome may be split apart by chromatid breaking and rejoining during meiosis I. Thus meiosis may give rise to new combinations of genes in gametes.

Question 30

Module 4 - The further two genes are apart on a chromosome, the ______ likely they are to split during Meiosis I

Answer 30

more likely

Question 31

Module 4 - What kind of fashion are genes organised in along chromosomes?

Answer 31

Linear

Question 32

Module 4 - What does DNA consist of?

Answer 32

Deoxyribose (sugar), a phosphate and one of four bases (A, T, G or C).