chromosomal aberrations

Question 1

Stern’s experiment

Answer 1

illustrated the visual nature of crossing over on chromosomes. (one chorme had broken piece, one had chunk of Y, shows recombinant combinations) . drosophilia autosomes.

Question 2

polytene chromosomes

Answer 2

When two homologus chromosomes pair up / squashed up against each other with 1,000 copies of each. unique banding patterns identify each chromosome

Question 3

where are polytene chromosomes found

Answer 3

salivary gland

Question 4

Inversion, and result on phenotype

Answer 4

cause of chromosomal abnormality where section abcd gets inverted and re-inserted as abdc . all chromosomal information is STILL THERE- just now out of order. Individuals usually ok, show no weird phenotype.

Question 5

Deletion:

Answer 5

abd. Deleted c. could cause major issues.

Question 6

Translocation:

Answer 6

• 2 non homologous chromosomes that have broken and rejoined- just in a totally different order. Basically, one guy is abcd. Another one is lmno. And then you get abcno, lmbc. They mix up.

Question 7

Duplication

Answer 7

• : abcde-> abcdede. Extra material. And could replicate itself. Issue: most normal mechanisms try to maintain a dosage balance. Normal ‘dose’ is 2 copies.

Question 8

___ of all fertilizations fail, and ___ of those are due to chromosomal aberrations

Answer 8

1/7, 1/2

Question 9

Loop effect of deletions in polytene chromosomes

Answer 9

if one guy deleted stuff and the other didn’t, you get a big loop. Dom/recessive may or may not matter. If u deleted the dominant form on the bottom guy, all of a sudden recessive gets to express.

Question 10

• paracentric inverstions

Answer 10

does not include centromere. Aka, inversion of region above or below centromere

Question 11

pericentric inversions

Answer 11

includes centromere

Question 12

paracentric and pericentric inversions both result in___

Answer 12

chromosomal fractures and breakages causing reduced fertility. This is where we usually see the effect of these chromosomal problems. When an affected individual tries to reproduce, you get these issues due to their messed up genes

Question 13

Translocation: what happens during reproduction and what phenotype do they express

Answer 13

• individual will have normal phenotype
• when that person goes to reproduce: pairing is a problem, will produce a lower frequency of viable gametes

Question 14

Robertsonian translocation : what is it and what disease can it result in?

Answer 14

• chromosome 21, 14, each have a weak spot. Translocation will sometimes occur. Happens at that weak point, then a chunk of each breaks off and form a lost fragment. Sometimes fragment is not lost. And you also get a new combo , this robertsonian translocation .
• sometimes results in down syndrome phenotype if they had 2 copies of 21 and one of these in there. Basically now 2.5 regions of 21.

Question 15

’philadelphia translocation’ and notable outcome

Answer 15

• 90% of patients with chronic myelogenous leukemia (CML) show the Philadelphia chromosome- which is defective, cancerous, and its just bad shit put together

Question 16

comment on bacterial reproduction- could meiosis occur?

Answer 16

• Bacteria are asexual- they do not exchange genes when replicating/reproducing. No meiosis, no crossing over etc. just copy dna , divide in half.

Question 17

name the 3 ways bacteria exchange genetic information

Answer 17

• However, they have 3 ways to exchange genetic information. Conjugation, transformation, transduction. Generates genetic diversity.

Question 18

• Transduction:

Answer 18

• exchange of genes by viral infection.
  
  • Bacterial virus ‘ bacteriophage’ spills open, bacteria spill out, inject DNA (containing new genes) into other bacteria cells. Often kills bacteria cells. But if it doesn’t, a bacteria is just receiving an injection of new genes.

Question 19

• Transformation:

Answer 19

• Transformation: when bacteria take up naked DNA from their environment.
  
  • Just DNA floating around in environment around the bacteria
  • May or may not make a difference to the life of that bacteria- sometimes useful genes, keep, other times spit up and chew out. Could be a gene for antibiotic resistance. This bacteria then incorporates those genes into its genome.

Question 20

Conjugation

Answer 20

• ‘bacterial sex’ via sex pilus
  
  • Process where dna is exchanged through a tube . NOT sexual reproduction- its just deposit DNA through a tube.
  • Note: bacterial ‘that has plasmid’ aka circular region is F+. bacteria that does not have plasmid is F-. the F+ builds a little tube, deposits genes into F-, who then develops into F+. plasmid could bring with it various kinds of genes.
  • This is the way that MOST antibiotic resistant bacteria evolved!!!!!

Question 21

how do bacteria like MERSA, resistant to so many antibiotics, evolve?

Answer 21

conjugation