3.2 Chromosomes Flashcards

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1
Q

Define autosomes

A

AUTOSOMES: chromosomes which do not determine the sex of the organsim

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2
Q

Genetic material in prokaryotes

A
  • no nucleus
  • circular DNA - nucleoid (genophore)
  • no proteins - naked DNA
  • may have plasmids - additional circular small DNA (addition to genophore)
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3
Q

Explain bacterial conjugation

A

Bacteria can transfer plasmids in bacterial conjugation

  • sex pili help attach - exchange plasmids
  • plasmids can self-replicate and produce rpoteins
  • plasmids used as vectors in labs for genetic engineering
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4
Q

Organisation of DNA in eukaryotic chromosomes

A
  • DNA is packed by histones into octamers to form nucleosome
  • nucleosomes linked with additional histone H1 protein- chromatosomes
  • chromatosomes coil to form solenoid structure
  • forms loops condened into chromosomes
  • chromatin supercoils during division to form chromosomes
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5
Q

Chromosome anatomy

A
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6
Q

How locus position is identified

A

Locus 7q31

  1. First number - chromosome in haryotype
  2. Second - letter p/q determines on which arm (p - shorter, q - longer)
  3. Third - number identifies G band (Giemsa banding - coloured chromosome sections produced)
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7
Q

Define homologous chromosomes

A

HOMOLOGOUS CHROMOSOMES: maternal and paternal chromosomes of sexually repsoducing organisms with the same strcutural features and same genes at same loci positions (the genes themselves may be different)

Homologous chromosomes separated in meiosis to form haploid gametes

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8
Q

Diploid vs haploid cells

A

Diploid (2n)

  • pairs of homologous chromosomes (each from a parent)
  • two gene copies for one trait
  • somatic cells - created via mitosis

Haploid (n)

  • one homologous chromosome
  • gametes halpoid derived from diploid cells in meiosis
  • also present in bacteria, fungi (don’t reproduce sexually)
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9
Q

Define sex chromosomes (heterosomes)

A

SEX CHROMOSOMES: chromosomes which determine the sex of an organism (X and Y)

Y chromosome - male determining - SRY gene especially

Females homologous (XX), males - not homologous (XY)

Father is responsible for determination of sex

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10
Q

Define karyotype

A

KARYOTYPE: number and types of chromosomes in a eukaryotic cell

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11
Q

How karyotyping is done

A
  1. Harvesting cells
  2. Chemically initiating division - arresting mitosis while chromosomes are condensed
  3. Chromosomes are stained - photographed -> karyogram
  4. Chromosomes arranged in homologous pairs
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12
Q

For what karyotyping can be used

A
  1. Prenatal - genetic disease, sex determining

Down syndrome - genetic condition - 3 homologous pairs of 21st chromosome - trisomy 21 - caused by non-disjunction in one of parents’ gametes - causes mental and physical delays in development

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13
Q

For what is autoradiography used

A

AUTORADIOGRAPHY:

  1. Cells grown in radioactive thymidine solution
  2. Radioactive thymidine incorporated into DNA
  3. Chromosomes are isolated and fixed to a surface
  4. Surface immersed in radioactive solution with AgBr
  5. Excess wahsed away silver stains
  6. Exposed on photographic film - chromosomes analysed
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14
Q

Measuring chromosome length

A

Using autoradiography - using tritiated uracil

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15
Q

Why are the genomes of plants the largest?

A

PLant genomes can vary drastically because due to the capacity for plant species to self-fertilise and become polyploid

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16
Q

Types of chromosomes

A