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Molecular Genetics > Eukaryote Chromosomes > Flashcards

Eukaryote Chromosomes Flashcards

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1
Q

The three kinds of VNTRs

A

Satellite - (>100) in centromere

Minisatellite - (15-100) dispersed

Microsatellite/SSR - (under 15) dispersed & telomere (repealed x1000s)

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2
Q

Microsatellites

A

Found in telomere and elsewhere

Mostly 2bp A/G repeats

Vertebrate telomeres - TTAGGG

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3
Q

Why are VNTRs variable in number? (3 reasons)

A
  1. Unequal crossing over between homo repeats
  2. DNA Rep Slippage (duplication/deletion)
  3. Repair of DNA Damage
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4
Q

What can DNA Replication Slippage Result in?

A

Leader = Duplication

Lagger = Deletion

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5
Q

What can we use VNTRs for?

A

Genetic Fingerprinting:

Predict Disease
Kinship Analysis
Forensic ID (11 microsatellite loci)

If using microsats - PCR Needed

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6
Q

Triplet Repeat Diseases

A

Caused by Length Variation in some microsats.

e.g. Fragile X (FMR1 Gene)
Repeat in 5’ Promoter (not Gene!!)

“Genetic Anticipation”

The number of repeats can be in a safe zone (4-50) but 200-2000 causes instability (mild phenotype) - more causes severe disease

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7
Q

Polyglutamine Diseases

A

Triplet Repeat Diseases specific to CAG repeats.

Occur in CODING regions.

Cause neurodegenerative disorders (e.g. Huntington’s)

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8
Q

How much of the human genome is repetitive?

A

About 50%

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9
Q

The Three types of Repeat Components

A

Gene Families

Interspersed Repeats
(incl. retrotransposons)

Tandem Repeats

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10
Q

What are the FOUR classifications of chromosomes?

A

Based on CENTROMERE position

Meta centric
Submetacentric
Acrocentric
Telocentric

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11
Q

An example of chromosome number variability?

A

The Chinese Muntjac
(23 ch)

and Indian Muntjac
(4 ch)

Number is uninformative

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12
Q

What does G-banding do?

A

Uses GIEMSA dye to stain AT-RICH (Gene-poor) regions

(Condensed heterochromatin areas)

Help differentiate similar chromosomes + show subdomains

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13
Q

What is FISH used for?

A

Map a gene on a chromosome

(Fluorescent “in situ” HYBRIDISATION)

Hyb a Fluoro labelled gene with a DNA region on the chromosome;

HOMOLOGY reveals location

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14
Q

What TWO kinds of chromosome abnormalities exist in humans?t

A
  1. NUMERICAL

Aneuploidy
Turner Monosomy

  1. STRUCTURAL

Chromosome rearrangement

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15
Q

What abnormalities do NOT happen in humans?

A
  1. Polyploidy -

Plants (large fruit, 8n strawberries)

Fish and amphibians
(Best have even number)

  1. Monosomy

(EXCEPTION: Turner Syndrome XO)

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16
Q

What are the human Sex Chromosome Trisomies?

A
  1. Kleinfelter XXY
    (Tall and infertile)
  2. Trisomy X
    Tall, menstrual irregular
    (XXX)
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17
Q

What are the three autosome trisomies?

A
  1. Down’s - 21
  2. Edwards - 18
  3. Patau - 13
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18
Q

What are the FOUR Chromosome rearrangement classes?

A

Inversion

Translocation
(Same or Diff)

Duplication

Deletion

19
Q

Why do we get non-allelic HomoRec? (NAHR)

A

There are >1000 fixed segments of 10-50 kb

They are 5% of healthy genome

20
Q

( ! ) What are FIVE potentially affected characteristics of Chrom Rearrangement?

A

Gene Dosage

Balance

Gene Disruption

Centromere

Meiosis

21
Q

What two ways can rearranged chromosomes end up balanced?

A
  1. PARACENTRIC - no centromere change (switch on one arm)

2. PERICENTRIC - centromere moves but still balanced; meiosis problem

22
Q

What is Robertsonian Translocation?

A

Two ACROCENTRIC chromosomes fuse at the centromere (keeping long arms!)

Teeny tiny chrom lost

Carrier would look normal but have meiosis problems

(OFFSPRING: normal, carrier, Down, lethal)

23
Q

What is a Philadelphia chromosome?

A

A kind of RECIPROCAL translocation

Chrom 9 and 22

Long arms swap

Tiny Chrom (PHILLY) lost

24
Q

What disease does Philly Chrom formation cause?

A

Chronic Myeloid Leukaemia

90% of cases

(Chrom 9 and 22)

25
Q

What is an example of a Duplication disease?

A

Charcot-Marie-Tooth (CMT 1)

Duplicates gene PMP22

Decent with 2 dots in FISH

26
Q

What are Copy Number Variations? (CNVs)

A

Just DELETIONS and DUPLICATIONS that aren’t microscopically visible

1kb - 5Mb

27
Q

What do CNVs cause?

*further

A

Main source of human variations!

100% of pop have them

Cause cognitive, behaviour & congenital disorders

  • Humans differ 8% of genome
  • Changes risk of disease and response to some drugs
28
Q

What is the C value Paradox?

A

That Genome Size (C)
≠ Complexity

C also ≠ No. of Genes

29
Q

What is an example of the C Value Paradox?

A

Humans have 3.2 mil bp

Broad Beans have 5.2 mil bp

30
Q

How does a Cot Curve reveal complexity?

A

Denature and team effort fragments -

Time ~ amount of COPIES

Faster = More Copies

31
Q

How much of the human genome is Unique (non-abundant)

A

Just over 50%

30 - 75 % among euk

32
Q

How much of human Unique Sequences actually encode protein?

A

only around 1.5%

33
Q

Where are genes most concentrated?

A

Areas of high GC content

34
Q

Other than genes, what else contributes to the unique component?

A

CpG islands
(Found in 2/3 of genes)

Promoters//Enhancers
(NC control sequences)

Introns
(NC intervening sequences)

35
Q

What two categories of Repetitive DNA are there?

A
  1. INTERSPERSED repeats
  2. TANDEM repeats
  3. Gene families
36
Q

Give 2 examples of gene families

A
  1. Beta-Globin Cluster

(5 genes and 2 pseudogene

  1. Histones

(Repeating unit)

37
Q

How does the beta globin cluster work?

A

MAKES GLOBINS

(Five genes and 2 pseudogenes)
(Embryo > Foetal > Adult)

[ps]Epsilon&raquo_space;

gamma G + gamma A»

[ps] Delta and Beta

38
Q

How does the Histone family look?

A

H4 > H2B > H3 > H2A > H1

Repeating unit

39
Q

What are the four kinds of interspersed repeats?

A

SINEs

LINEs

LTR

DNA Transposons

40
Q

Briefly describe SINEs

A

300bp

Alu most abundant

10.6% genome

Processed pseudogne-
Uses nearby REVERSE TSase

41
Q

Briefly describe LINEs

A

7000bp

L1 most abundant

17% of genome

Encodes REV TSase

42
Q

How can retroTP elements be used for conservation?

A

Identifying species by their elements (shark fin soup)

43
Q

What s accounts for about 15% of CNVs?

A

Interspersed sequence repeats

transposons

Molecular Genetics (5 decks)

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