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Psych 2ap3 > BIOLOGY 2C03- week 7 flashcards > Flashcards

BIOLOGY 2C03- week 7 flashcards

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1
Q

why is the molecular organization of chromosomes essential?

A
  • essential for normal function and distribution f chromosomes in cell division
  • plays a pivotal role in the regulation of gene expression that typifies all kinds of eukaryotic cells
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2
Q

Does every organism have the safe chromosome number and shape?

A

No, chromosome number and shape vary by organism but closely related species tend to have similar chromosome numbers

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3
Q

when are chromosomes dynamically active?

A

cells are dynamically active during interphase and move, twist and turn during transcription and dna replication

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4
Q

when can chromosomes be individually visualized and identified through molecular microscopic techniques?

A

visualized in mid-prophase through metaphase

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5
Q

what is a karyotype

A

an organized image of the chromosomes from a nucleus

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6
Q

what are the chromosomes in karyotypes stained with?

A

special compounds called flurophores

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7
Q

what is FISH? and what does it do?

A

fish; fluorescent in situ hybridization uses flurophore labels to identify chromosomes/chromosome segment OR we can use gene specific flurophores to locate individual genes

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8
Q

how does chromosome banding work?

A
  • cell cycle stopped in metaphase
  • cells are then dropped onto a microscope slide
  • this bursts cells and ruptures the nuclear membrane causing chromosomes to spill out (chromosome spread)
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9
Q

What is Gemma staining and what is the difference between positive and negative g bands?

A

used to determine which genes are rich/prominent
positive g band: AT rich, dark and hyrophobic
negative g band: GC rich, light and less hydrophobic

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10
Q

chromosome arms: what do we call a short arm vs a long arm

A

a short arm is also called a p-arm and a long arm is called a q-arm

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11
Q

what are the 4 different types of chromosome shapes?

A
  1. metacentric
  2. submetacentric
  3. acrocentric
  4. telocentric
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12
Q

what is this gene’s cytogenetic location:17q12

A

17: the chromosome number
q: the arm (long arm)
12: the gene position distance from the centromere

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13
Q

What happens after chromosomal deletion

A
  • when a chromosome breaks, both ends are severed at the breaking point
  • the dna strands can retain their structure and attach to one another, other truncated chromosomes or the ends of intact chromosomes
  • chromosome breakage can lead to partial chromosome deletion by losing a portion of a chromosome
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14
Q

What is terminal deletion

A
  • a chromosome that breaks a part of its arm or the whole arm
  • the left over fragment has no centromere (centric) and is therefore lost during cell division
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15
Q

Why is an eccentric chromosome lost or not viable?

A

without a centromere, the eccentric fragment lacks a kinetochore. therefore, it is able to attach spindle fibres and cannot migrate to a pole of the cell during division

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16
Q

What are partial deletion heterozygotes?

A

chromosomes where there is one wild-type chromosome and the other is homologous pair with a terminal deletion

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17
Q

Provide an example of terminal deletion in chromosomes.

A

human condition called cry-du-chat syndrome, deletion is 5p15.2-5p15.3
known for distinctive cat-cry sound emitted by infants with the condition

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18
Q

What is interstitial deletion

A

it is the loss if an internal segment os a chromosome that results from two chromosome breaks followed by a joining of the ends from either side of the lost segment (broken pieces fuse together)

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19
Q

What are examples of interstitial deletion

A

WAGR
W: wilms tumour (gene WT1)–> genitourinary development
A: aniridia (gene PAX6)—> eye development
G: genitourinary abnormalities (WT1)
R: range of development delays (BDNF)–> prevent neutrons from damage and destruction, anorexia, bulimia, memory impairment, and OCD

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20
Q

What happens due to unequal crossover of alleles during reciprocal recombination

A

unequal crossover: partial deletion, partial duplication of a chromosome

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21
Q

what happens if a broken chromosome attaches to the same chromosome in the wrong orientation?

A

chromosome inversion (180 degree reorientation of the segment)

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22
Q

What happens when the chromosome attaches to a nonhomogolous chromosome?

A

chromosome translocation

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23
Q

what are the 2 different types of inversion?

A

paracentric inversion (breakage does not include centromere) and pericentric (breakage includes centromere)

24
Q

What happens in paracentric inversion

A

after crossover, we have a dicentric chromosome (chromosome with 2 centromeres) and acentric chromosome (chromosome with 1 centromere). once separated, there is a loss of chromosome segment (the acentric one), and we are left with 2 unviable segments (deletion products), 1 normal chromosome (viable) and one inversion chromosome (viable)

25
Q

What happens in pericentric inversion?

A

after anaphase migration, we have two chromosomes that each have a centromere. upon meosis II completion, we are left with one normal chromosome, 2 unviable productions (one deletion, one duplication) and one inverted chromosome (viable)

26
Q

What is the probability of crossover within the inversion loop linked to

A

Probabilities of crossover within the inversion loop is linked to the size of the inversion loop

27
Q

what does inversion surpass?

A

inversion suppresses the production of recombinant chromosomes

28
Q

how may fertility may be altered due to inversion?

A

fertility may be altered if an inversion heterozygote carries a large inversion

29
Q

When does translocation occur

A

Translocation occurs when a broken segments reattachment follows chromosome breakage to a nonhomogolous chromosome

30
Q

When do translocation heterozygotes display no outward phenotype effects?

A

no outward phenotype effects if they have one normal chromosome and one altered chromosome in each affected homologous pair

31
Q

can translocation heterozygotes with no phenotypic abnormalities experience semi-sterility?

A

yes, because of abnormalities of chromosome segregation

32
Q

what is unbalanced translocation

A

a piece of one chromosome breaks, and joins onto the nonhomogolous chromosome. there is no reciprocal event

33
Q

What is reciprocal balanced translocation

A

when breaks occur on two non homologous chromosomes and the resulting fragments switch places when they are attached

34
Q

What is robertsonian translocation

A

usually involveds acrocentric or telocentric chromosome, centromere and p arm (short arm) are lost and leftover part attaches to normal chromosome segment, leading to a fusion chromosome. leads to a reduction in chromosome number because of the lost centromere

35
Q

What is the pattern of reciprocal balanced translocation (adjacent I segregation)

A

no viable gametes due to deletion and duplication

35
Q

What is the pattern of recipricol balanced translocation (alternate segrregation)

A

2 will produce a normal zygote, 2 will produce a zygote with reciprocal balanced translocation heterozygosity

36
Q

What is the pattern of reciprocal balanced translocation (adjacent II segregation)

A

atypical- requires homologous chromosomes to move to the same pole= no viable gametes

37
Q

What is a transposable element

A

DNA sequences that can move within the genome by an enzyme-driven process known as transposition

38
Q

What are the principle effects of transposition on genomes

A
  1. transposition can be a mutational event
  2. can increase genome size through duplication of the transposable genetic elements
39
Q

What are the distinctive features of transposable elements

A

the transposable element contains terminal inverted repeats (mirror image) on both ends and is bracketed by flanking direct repeats (exact same)

40
Q

How is a dna transposon inserted

A

enzyme transposes makes staggered cuts in a dna strand, leaving single stranded strands, where transposable element inserts itself into, dna polymerase joins everything together

41
Q

what are the two types of transposable elements

A

Dna transposons (transpose as dna sequences, produce flanking repeats at the insertion site) and retrotransposons (transpose through an ran intermediate)

42
Q

what Is the mutagenic effect of transposition

A

insertional inactivation of transposon in F8 gene (retrotransposition) leads to the blood-clotting disorder hemophilia A caused by an absence of activity of the blood clotting protein factor VII

43
Q

What is a point mutation

A

A change in a single base pair

44
Q

What are the 2 categories of point mutations

A

transition point mutation and pyramid point mutation

45
Q

what is a transition point mutation

A

purine-pyramid to purine-pyramid base pair CG=TA or TA=CG

46
Q

What is a transversion mutation

A

replacement of a purine-pyramid to a pyramid-purine or vice vera so if you have CG it would be GC or AT

47
Q

Where are the most harmful mutations

A

The most harmful mutations are those occurring in genes involved in dna repair–> cause cancer, cell division uncontrolled

48
Q

What are oncogenes and tumour suppressor genes

A

oncogenes: encode proteins that drive cell division
Tumor suppressor genes (many are transcription factors) encode genes that suppress cell division

49
Q

What are examples of tumour suppressors that drive cancer

A

p53 and retinoblastoma

50
Q

What is a silent mutation

A

nucleotide change that produces a codon for the same amino acid (GAA and GAG both code for glutamate), ALL PYRAMIDS

51
Q

What is a missense mutation

A

nucleotide change that results in a different amino acid (GAA to CAA)

52
Q

What is a nonsense mutation

A

results in a stop codon, terminating the protein

53
Q

What are indels

A

Insertion and deletion mutations
Insertion: one or more base pairs added to the wild-type sequence
Deletion: loss of one or more base pairs

54
Q

What is a reading frame

A

DNA sequence from the start codon to the stop codon

Psych 2ap3 (16 decks)

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