THE CELL

Question 1

Structure of the Nucleus

Answer 1

Appears as a large rounded or oval structure near the cell center.

Question 2

What is the function of the Nuclear Envelope?

Answer 2

Forms a selectively permeable barrier between the nuclear and cytoplasmic compartments.

Question 3

What is the structure of the Nuclear Envelope

Answer 3

Composed of two concentric membranes separated by a perinuclear space.

Question 4

The outer nuclear membrane is continous with the?

Answer 4

Continuous with the Rough Endoplasmic Reticulum (RER).

Question 5

The inner nuclear membrane is associated with?

Answer 5

Associated with a meshwork of proteins called the nuclear lamina.

Question 6

What are Nuclear Pore Complexes?

Answer 6

They bridge the inner and outer nuclear membranes.

Question 7

The Chromatin consists of?

Answer 7

Consists of DNA and associated proteins in an uncoiled state.

Question 8

2 TYPES OF CHROMATINS

Answer 8

1. HETEROCHROMATIN
2. EUCHROMATIN

Question 9

What is a Heterochromatin?

Answer 9

Electron-dense material, basophilic clumps

Question 10

What is a Euchromatin made up of?

Answer 10

Finely dispersed granular material

Question 11

What Chromatin is Present in females yet absent in males?

Answer 11

Barr Body (Sex Chromatin)

Question 12

DNA in chromatin is extensively packaged by associating with basic proteins called?

Answer 12

histones

Question 13

What do histones provide for a chromosome?

Answer 13

Histones provides structural support for a chromosome

Question 14

What is a chromatid?

Answer 14

Each long DNA double helix with its associated proteins

Question 15

After DNA replication, two chromatids held together by complexes of cohesin proteins make up each ____?

Answer 15

chromosome

Question 16

Fill in the blanks: X and Y chromosomes determine _____, while autosomes are _____ pairs.

Answer 16

X and Y chromosomes: sex
Autosomes: homologous pairs

Question 17

Difference Between Chromosome and Chromatid:

Answer 17

Chromosome: a DNA molecule with part or all of the genetic material (genome) of an organism

Chromatid: one copy of a newly copied chromosome which is still joined to the original chromosome by a single centromere

Question 18

Traits of a Euchromatin: (11)

Answer 18

• Transcriptionally active
• DNA is loosely packed
• Actively present in prokaryotic and eukaryotic genome
• Genetically active
• Present at the inner side of the nucleus
• Stained lighter
• Early replicative
• Aren’t sticky
• Allow genes to form proteins
• Low genetic density
• Consists of 2 to 3% of the genome

Question 19

Traits of a Heterochromatin: (11)

Answer 19

• Transcriptionally inactive
• DNA is highly packed
• Only present in eukaryotic genome
• Genetically inactive
• Present at nucleus periphery
• Stained dark
• Late replicative
• Are usually sticky
• Regulates genetic integrity and controls gene expression
• High genetic density
• Consists of 97 to 98% of the genome

Question 20

X and Y sex chromosomes contain genes that determine what?

Answer 20

whether an individual will develop as a female or a male.

Question 21

In addition to the pair of sex chromosomes, cells contain pairs of _____?

Answer 21

autosomes

Question 22

Each of these pairs of chromosomes contains one chromosome originally derived from the mother and one derived from the father. The members of each chromosomal pair are called _____?

Answer 22

Homologous

Question 23

Why are cells of most tissues (somatic cells) considered diploid?

Answer 23

because they contain pairs of chromosomes.

Question 24

Sperm cells and mature oocytes are haploids because?

Answer 24

they contain half the diploid number of chromosomes, each pair having been separated during meiosis

Question 25

Characteristics of a Haploid (n) [2]

Answer 25

• One copy of each chromosome • Three non-homologous chromosomes

Question 26

What are two characteristics of a Diploid (2n)?

Answer 26

• Two copies of each chromosome • Three pairs of homologous chromosomes (of maternal and paternal origin)

Question 27

What is the function of the nucleolus?

Answer 27

Involved in the synthesis of ribosomal RNA (rRNA) and the assembly of ribosome subunits.

Question 28

Describe the structure of a nucleolus

Answer 28

Spherical, highly basophilic subdomain of nuclei.

Question 29

In the Nucleolus, Intense basophilia of nucleoli is due not to heterochromatin but to the presence of?

Answer 29

densely concentrated ribosomal RNA

Question 30

What is it called when there is a regular sequence of events that result in new cells?

Answer 30

The Cell Cycle

Question 31

Before differentiation, most cells undergo repeated cycles of two processes:

Answer 31

macromolecular synthesis (growth) and division (mitosis)

Question 32

Four distinct phases of the cell cycle:

Answer 32

▫ Mitosis ▫ G1 (the time gap between mitosis and DNA replication) ▫ S (the period of DNA synthesis) ▫ G2 (the gap between DNA duplication and the next mitosis)

Question 33

Describe what is the Interphase:

Answer 33

It is considerably longer than the M phase and is the period during which the cell doubles in size and DNA content.

Question 34

The Longest and most variable phase of the cycle

Answer 34

G1

Question 35

G1 is the time gap between _____ and _________

Answer 35

Mitosis and DNA replication

Question 36

G1 is also the period of?

Answer 36

Period of active RNA and protein synthesis, including proteins controlling progress through the cell cycle

Question 37

The S phase is characterized by? (3)

Answer 37

- DNA replication - histone synthesis - beginning of centrosome duplication

Question 38

The phase where Proteins are required for mitosis accumulate

Answer 38

G2 phase

Question 39

What happens in the Go phase?

Answer 39

Cell cycle activities may be temporarily or permanently suspended

Question 40

Entry or progression through other phase of the cycle is also monitored at specific what?

Answer 40

checkpoints

Question 41

Checkpoints are where certain conditions must be met before?

Answer 41

the cell continues cycling