Gene, Chrom, Karyotyping : Lect 2

Question 1

Regulatory sequences

Epigenetics modification

Answer 1

regulate the rate at which the transcription of genes occur.

methylation - regulate the rate transcription occurs.

Question 2

Which is transcribed and/or translated? Exons or Introns

Answer 2

Both are transcribed but exons are translated to form proteins.

Question 3

NUCLEAR GENES -

Answer 3

name the two.

• Unique single copy
• Multigene families

Question 4

Non-coding regions in genes?

Answer 4

Heterochromatic and centromeric

Question 5

Subtelomeric region:

Answer 5

composed of highly polymorphic repetitive DNA sequence

Question 6

Unique single copy genes:

Answer 6

code for one protein such as enzymes, receptors. hormones, structural and regulatory proteins.

Question 7

Multigene families:

Answer 7

can be clustered or dispersed; genes w/ similar functions that have arisen by gene duplication.

Classic gene fam:
multicopy genes that show a high degree of homology. ex: HOX genes, rRNAs and tRNAs genes.

Gene superfam:
multicopy gene w/ similar function but limited gene homology. ex: HLA genes, T-cell receptors.

Question 8

Extragenic DNA

Answer 8

• not transcriptionally active w/ no function.

- role in regulation of gene expression.

Question 9

Tandem repeat: 3 subgroups

Answer 9

Satellite:
~repeated sequences of DNA clustered around centromeres.
~has a diff buoyant density than the rest of cell’s DNA.

Minisatellite:

- Telomeric: short 6nt repeats at the end of chrom; added by telomerase to prevent chrom shortening. 
- Hypervariable: short seq. 15-100nt repeated a variable number of times. Ex: VNTR *fingerprinting*

Microsatellite:

• very short seq. usually 2nt long (CACACA) can be 3 or 4.
• highly variable in number of repeats, used in fingerprinting and linkage studies. Ex: STR

VNTR and STR are polymorphic and are inherited in a co-dominant fashion.

Question 10

Interspersed

Answer 10

SINES

• short seq. of less than 500bp.
• appear to be nl RNAs converted to DNA by Rev Trans and reinserted into genome.
• about 10% of genome.
• ex: Alu elements

LINES

• about 6000bp
• code for Rev Trans and are able to make RNA.
• capable of copying themselves and they enlarge the genome.

Both are responsible for mutations that arise due to unequal crossover in meiosis

Question 11

Uniparental disomy

Answer 11

when both the chrom of the pair are derived from the same parent.

Question 12

X-inactivation (Lyonization)

Answer 12

• during early stages of female embryo development.
• one of the X chrom is inactivated and condensed to form the Barr body.
• random and fixed (same X-inactivated in all the descendants)