PP7

Question 1

What are the subunits of nucleic acids? What are they composed of?

Answer 1

Nucleic acid polymer consists of subunits called deoxyribonucleotides

Deoxyribonucleotides are composed of:

• Deoxyribose sugar
• Base
• Phosphate group

Question 2

What type of bond links Nucleotides together? Explain the bond.

Answer 2

Nucleotides are linked together by phosphodiester bonds to form a DNA strand.

Phosphodiester bond: covalent bond that connects the 3’ carbon of one nucleotide to the 5’ carbon of the next nucleotide in the line through the 5’ phosphate group

Question 3

What are Polynucleotide? What are Nucleotides composed of? Where is it located?

Answer 3

Polynucleotide composed of nucleotide monomers linked by phosphodiester linkages (condensation reaction).

Nucleotides composed of: ribose sugar, base and phosphate group.

Located in the nucleus and cytoplasm of eukaryotes.

Question 4

What is the difference between a gene and a genome?

Answer 4

Gene:

• Discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA. It’s like a section of a long highway. It’s connected to other parts, but it is unique.
• Genes code for proteins and RNA. RNA remains as RNA throughout its life.

Genome:
The genetic material of an organism or virus; the complete complement of an organism’s or virus’s genes along with its noncoding nucleic acid sequences. Noncoding means that the genetic material will not be translated to form a protein, although it is often necessary to make a protein, e.g., mRNA, tRNA and rRNA.

Question 5

Is the number of genes correlated to the genome size? why do Humans and other mammals have the lowest gene density?

Answer 5

1. no
2. Humans and other mammals have the lowest gene density, or number of genes in a given length of DNA. Due to large amount of noncoding DNA between genes.

Question 6

How are histones and nucleosome related?

Answer 6

DNA in eukaryotic cells associates with special proteins called histones that act as spools around which DNA is wrapped. This structure is called a nucleosome. This protects the DNA and facilitates further condensing (packed into tighter structure).

Histones have positive charges on their surface which attracts the negatively charged DNA.

Question 7

When the cell is not dividing, two types of chromatin can be seen:

Answer 7

Euchromatin and Heterochromatin

Question 8

explain Euchromatin

Answer 8

Euchromatin (eu = true) is not easily visible, loose chromatin that is found throughout the nucleus like loose wool. This is transcriptionally active, which means it’s being used to make RNA from the genes.

Loose, lightly packed chromatin when the cell is not dividing. It’s like loose wool.
Comprises the most active portion of the genome of any given cell (gene expression!!!). Active means the information in DNA is being used make.
The presence of acetyl groups on the histone proteins cause the DNA to loose the strong association with them.
Acetylation (adding acetyl group)
Deacetylation (removing acetyl groups)

The euchromatin usually contains genes that are transcribed (used to make proteins), with DNA packaged around nucleosomes but not further compacted.

Question 9

explain Heterochromatin

Answer 9

Heterochromatin, which is darkly stained compact chromatin, typically found close to the nuclear. Genes in this area are unavailable as well as neighbouring genes.

-Tightly packed chromatin when the cell is not dividing.
-Represents the inactive portion of the genome. This means that this area of the DNA is not available to be used to make a protein.
-Genes are silenced (no gene expression, i.e. not being used to make proteins)
-The presence of methyl groups on a cytosine nucleotide causes the chromatin to condense:
Methylation (adding methyl group)
Demethylation (removing methyl group)

Heterochromatin usually contains genes that are not expressed (not used to make proteins).

Question 10

What is Epigenetics? WH\hat does it play an important role in?

Answer 10

The processes of “activating” or “deactivating” genes through chemical modifications (acetylation and deacetylation) are generally grouped as epigenetics, epi meaning above

Play an important role in:

1. Cell specialization
2. Oncogenic process (cancer)
3. Disease
4. Behaviour and Personality

Question 11

How many chromosomes do humans have? How are chromosomes formed?

Answer 11

23

When a cell is ready to divide, the chromatin is tightly packaged and condensed to form chromosomes

Question 12

What is gene expression?

Answer 12

Central Dogma:

Gene expression: is the process by which information from a gene is used in the synthesis of a functional gene product.

From DNA is made RNA
From RNA is made a protein

Question 13

What is a triplet code? Triplets of nucleotide bases?

Answer 13

Triplet code: the genetic instructions for a polypeptide chain are written in the DNA as a series of non-overlapping, three-nucleotide words.

Triplets of nucleotide bases are the smallest units of uniform length that can code for all amino acids.

Question 14

Sequencing of the human genome reveals that 98.5% does not code for proteins, rRNAs, mRNAs or tRNAs. Just because they do not code for proteins, does not mean that they do not have a function!
Noncoding DNA sequences:

Answer 14

• Transcriptional and translational regulators.
• Origins of DNA replication (region where DNA copying begins)
• Centromeres (centre regions of chromosomes)

Question 15

RNA has properties of both ___ (information storage) and _____ (enzymes call ribozymes). WHY?

Answer 15

RNA has properties of both DNA (information storage) and proteins (enzymes call ribozymes).

Because of this many scientists think that RNA, not DNA, was the original information storage molecule in the earliest form of life on Earth

Question 16

why is DNA better to pass genetic information?

Answer 16

DNA will absorb chemical damage while RNA becomes too stiff and falls apart, making DNA the better structure to pass genetic information down between the generation!