Storing and using genetics information mw %% +

Question 1

Phenotype and Genotype

Answer 1

Phenotype = Outward, physical manifestation of organism

Genotype = Full hereditary information of organism (even if not expressed)

Question 2

Nucleotide

Answer 2

Each nucleotide contains

• Sugar
• Base
• Phosphate group

Question 3

Difference between Deoxyribose and Ribose

Answer 3

• Carbon 2
• Ribose, OH
• Deoxy, H

Question 4

Complementary Base-Pairing

Answer 4

• Adenine – Thymine (Uracil in RNA)
• Cytosine - Guanine

Question 5

Structure of Nucleus

Answer 5

• Usually the largest organelle in the cell
• Contains most of the cell’s genetic material (DNA)
• Replication of DNA and the first steps in decoding it for protein production take place in the nucleus

Question 6

Chromosomes (Only visible when cell dividing)

Answer 6

• In the nucleus the DNA molecule is packaged into thread-like structures called chromosomes.
• Chromosomes are a single piece of DNA containing many genes, regulatory elements and other nucleotide sequences.

Question 7

Chromosome wrapping stages pic

Answer 7

Question 8

Chromatin

Answer 8

• The DNA double helix in the cell nucleus is packaged by special proteins termed histones. The formed protein/DNA complex is called chromatin. The basic structural unit of chromatin is the nucleosome.
• It is divided between heterochromatin (condensed) and euchromatic (extended) forms.

Question 9

Transcription & Replication

Answer 9

• Both require the two strands of DNA to separate temporarily to allow enzymes access to the DNA template
• Nucleosomes and folding of chromatin pose barriers to enzymes
• Cells must have means of opening up chromatin fibers and/or removing histones

Question 10

Two major mechanisms by which chromatin is made more accessible

Answer 10

1. Histones can be enzymatically modified
2. Histones can be displaced by chromatin remodeling complexes

These processes are reversible

Question 11

DNA Replication is Semi-Conservative & Bi-Directional

Answer 11

• Semi-conservative: one-half of each new molecule of DNA is old; one-half new.
• Special proteins ‘unzip’ the double helix by breaking the hydrogen bonds.
• New nucleotide molecules are then paired with the two DNA strands.
• Replicated in 5’ to 3’ direction.

Question 12

Protein-coding Genes

Answer 12

• <2% of the genome codes for proteins.
• The functions are unknown for over 50% of discovered genes.
• Repeated sequences that do not code for proteins (“junk DNA”) make up at least 50% of the human genome.

Question 13

Exons and Introns

Answer 13

• Generally Exons = Coding Regions
• Introns = Non-coding Regions

Question 14

Genetic Code

Answer 14

• Each set of 3 bases is called a codon
• Each codon specifies a particular amino acid
• However only 20 amino acids found in proteins

Question 15

Degeneracy

Answer 15

With the exception of methionine and tryptophan they are all encoded by more than one codon. This is referred to as degeneracy or the redundancy of the genetic code.

Question 16

Role of RNA

Answer 16

The major role of RNA is to participate in protein synthesis

Question 17

mRNA

Answer 17

Transcribed from DNA.

Carries information for protein synthesis.

Question 18

Alternative Splicing

Answer 18

• a regulated process during gene expression that results in a single gene coding for multiple proteins. In this process, particular exons of a gene may be included within or excluded from the final, processed messenger RNA (mRNA) produced from that gene
• In a genome of 3.12 billion base pairs, It’s estimated that humans use at least 100,000 different proteins, maybe a lot more

Question 19

Overall picture

Answer 19

Question 20

tRNA

Answer 20

• Major role is to translate mRNA sequence into amino acid sequence.
• Acts as an adapter molecule between the coded amino acid and the mRNA

Question 21

rRNA

Answer 21

• Component of ribosomes.
• rRNA molecules are produced in the nucleus
• Transported to cytoplasm, where they combine with proteins to form a ribosome.