DIAL 1. Chemistry, Replication, and Organization of the Human Genome

Question 1

Describe what is meant by the Central Dogma.

Answer 1

All genetic information is translated almost always only from DNA to RNA

Question 2

Identify chromosomal abnormalities when given the standard nomenclature for such anomalies and a representation of human chromosomes.

Answer 2

x

Question 3

Explain the primary function(s) of centromeres(1) and telomeres (3)

Answer 3

Centromere - Sister chromatids are attached at the centromere during metaphase. This is the position in which the mitotic spindles are anchored

Telomeres - Synthesized by telomerase and located at the ends of chromosomes that contain TG-rich repeats. They protect the ends of chromosomes from deterioration or fusion. Function as disposable buffers at the ends of chromosomes during cell division.

Question 4

Compare and contrast the human nuclear genome and the mitochondrial genome in terms of gene number, overall size, copy number per cell, and organization.

Answer 4

Nuclear genome - 20,000-25,000 protein coding genes, 46 chromosomes (diploid)
Mitochondrial genome - 13 out of 67 polypetides in mitochrondria are coded by mitochondrial genes. Mitochondria contain 2-10 copies of small circular DNA. Maternal inheritance.

Question 5

Describe what is meant by the term nucleosome and explain why nucleosomes are necessary.

Answer 5

DNA wound around a collection of histone molecules. Nucleosomes organize the chromatin. This organized packaging of DNA is important for accessibility to DNA and gene transcription.

Question 6

Describe what is meant by karyotyping, g-banding, and FISH for studying human chromosomes.

Answer 6

Giemsa (G) Banding - trypsin is used to denature protein content then DNA is stained with DNA-binding dye, which gives DNA a characteristic banding pattern.

Karyotyping - # of chromosomes are counted, g-banding, then chromosomes are laid out in an idiogram.

Fluorescent In-Situ Hybridization (FISH) - utilizes that single stranded DNA anneals with complementary strands. A complementary, tagged, probe is used to visualize complementary DNA sequences.

Question 7

Compare and contrast the various types of genomic and chromosomal anomalies that may occur in humans

Answer 7

Numerical Abnormalities

1. Aneuploidy - loss or gain of one or more chromosomes
2. Polyploidy - the addition of one or more complete haploid complements
3. Monosomy, Trisomy, Tetrasomy - the loss of a single chromosome, the gain of one, gain of two (respectively)
   - results from nondisjunction

Structural Abnormalities

1. Translocation - transfer of genetic material from one chromosome to another
2. Deletions - loss of part of a chromosome (results in monosomy for that DNA segment)
3. Insertions - a segment of one chromosome becomes inserted into another chromosome
4. Inversions - two-break rearrangement involving a single chromosome where a segment is reversed in position
5. Ring - a break occurs on each arm of a chromosome leaving two “sticky” ends tat reunite as a ring

Question 8

Describe the process of DNA replication

Answer 8

1. Identification of origin of replication (by ori-binding protein)
2. Unwinding of dsDNA to provide single strand DNA template (helicase)
3. Formation of replication fork; synthesis of RNA primer (primase)
4. Initiation of DNA synthesis and elongation (DNA Pol II)
5. Formation of replication bubbles with ligation of Okazaki fragments (ligase)
6. Reconstitution of chromatin structure

Question 9

What abnormalities are Down, Edwards, and Patau syndromes?

Answer 9

Down- Trisomy 21
Patau- Trisomy 13
Edwards- Trisomy 18