GENETICS - Karyotype (UNIT 1)

Study for Test 1

16 flashcards · Other · by John Mark Webb

  1. Prokaryotic vs. Eukaryotic DNA length differences linear or circular? viral DNA = linear or circular bacterial DNA = circular eukaryotic DNA = linear (chromosomal eukaryotic DNA is linear) high A:T ratio vs. high G:C ratio pure genes vs. junk genes (20% of human genome) no introns vs. introns naked DNA vs. histones

  2. Histones (Eukaryotes ONLY) 5 classes: H1 H2A H2B H3 H4 all are about 100 amino acids each highly conserved between species (but not H1) highly basic lysine arginine octamer with 2 turns 147 bp + 80 bp linker nucleosome (nu body) H1 for tight packaging role in gene expression (acetylation of lysine)

  3. NON-HISTONE PROTEINS Architectural proteins (structure of chromosome) topoisomerases gyrases (relaxes DNA) helicases (break H bonds) Gene expression and regulation transcription factors suppressor proteins growth factors regulator proteins helix destabilizing proteins

  4. CHROMOSOMES Heterochromatin tightly bound A-T rich 2 types facultative (short-lived events in the body) constitutive (non-genic, found in centromere and telomere, no transcription) late replicating (labeling) loaded with highly repetitive DNA Euchromatin more loosely bound G-C rich early replicating (labeling)

  5. AUTORADIOGRAPHY As in sequencing: P32-ATP P32-CTP P32-GTP P32-TTP (unique to DNA) As in replication: TTP

  6. TYPES OF CHROMATIN - REPETITIVENESS (1) Non-repetitive (single copy DNA) (2) Moderately repetitive DNA (3) Highly reiterated DNA

  7. TYPES OF CHROMATIN - REPETITIVENESS Non-repetitive (single copy DNA) 40% of genome structural genes tRNAs have 10-20 gene copies found in euchromatin

  8. TYPES OF CHROMATIN - REPETITIVENESS Moderately repetitive DNA 20% of genome 50-5000 copies in tandem 18S & 28S rRNA genes - 300-400 copies p arms of acrocentric chromosomes - (NOR) nucleolar organizing regions (n = 10)

  9. TYPES OF CHROMATIN - REPETITIVENESS Highly reiterated DNA 40% of genome 5,000-500,000+ copies associated with constitutive heterochromatin tandem repeats 10% of genome 3 categories Telomere - TTAGGG Centromere Variable # tandem repeats (in purple below) Microsatellites simple sequence repeats SSRs 2-6 base pairs Minisatellites repetitive 10-15 base pairs Macrosatellites > 1000 base pairs in humans, on # 4, 10, and X

  10. TYPES OF CHROMATIN - REPETITIVENESS Highly reiterated DNA RANDOMLY INTERSPERSED NUCLEAR ELEMENTS 30% of genome SINES short in length 100-700 base pairs up to 1,500,000 copies seem to be associated w/ gene expression particularly relative to facultative heterochromatin Alu family has 300 base pairs and > 1000000 copies 50 human diseases associated with SINEs reverse transcripts of 7S rRNA (retro) LINES long in length 3000-6400 base pairs 30000-500000 copies L1 is most common in humans with its r…

  11. Understand the p and q arms.

  12. TYPES OF CHROMOSOMES 1. metacentric 2. submetacentric 3. acrocentric 4. telocentric 5. ring

  13. Know how to identify which group a chromosome is in and whether it is an autosome or a sex chromosome.

  14. Chromosome Banding Patterns G Banding - Giemsa stain, A-T rich Q Banding - quinicrine mustard, A-T rich R Banding - acridine orange, G-C rich C Banding - Giemsa stain + heat or pH (constitutive heterochromatin)

  15. Lyon's hypothesis "the phenotypic effect of the X chromosome is the same in the mammalian female which has two X chromosomes as it is in the male which has only one X chromosome" one out of two X chromosomes in females is inactivated early in embryonic development (called the Barr body) the Barr body is highly condensed and does not have any phenotypic effect

  16. X Chromosome Inactivation (Lyonization) one of two X chromosomes is active random process blastula stage (one week) permanent inactivation (methylation C) 80-90% inactivation of genes female is mosaic