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Chromosomes Objectives: Explain how karyotypes can be used to identify chromosomal abnormalities Identify the chromosomes responsible for a person’s sex Chromosomes Supercoiled complex of DNA and proteins DNA codes for LOTS of things The codes must be neatly organized

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chromosomes
Chromosomes

Objectives:

  • Explain how karyotypes can be used to identify chromosomal abnormalities
  • Identify the chromosomes responsible for a person’s sex
chromosomes2
Chromosomes
  • Supercoiled complex of DNA and proteins
  • DNA codes for LOTS of things
  • The codes must be neatly organized
  • The codes are organized into genes
  • Chromosomes are stacks of genes
chromosomes5
Chromosomes
  • Chromosomes found in metaphase will have 2 chromatids and will be attached by a centromere
  • The chromatids are identical
chromatin
Chromatin
  • DNA usually exists in chromatin
  • Chromatin is a uncoiled DNA and protein complex
  • Chromatin only supercoils when cells are entering mitosis or meiosis
harvesting chromosomes
Harvesting Chromosomes
  • Chromosomes develop from chromatin during prophase
  • They are clearly seen in metaphase since there is no nuclear membrane
harvesting chromosomes8
Harvesting Chromosomes
  • Cells are frozen in metaphase
  • Chromosomes are then treated and stained
  • They are viewed under a microscope
  • A photograph is taken
  • The photograph is enlarged and the chromosomes are cut out
karyotypes
Karyotypes
  • Homologous chromosomes are paired
  • The pairs are arranged by size and in order with their centromeres aligned
ploidy
Ploidy
  • Not all organisms have 23 pairs of chromosomes
  • 2N = diploid
  • N = haploid
  • 2N = 46 for humans
  • N = 23 for humans
  • Find the ploidy of the organisms listed
sex chromosomes
Sex Chromosomes
  • The first 22 pairs of chromosomes are called autosomes
  • The 23rd pair of chromosomes are called sex chromosomes
  • They code for whether the individual will be male or female
  • If the 23rd pair is homologous the individual is a female
  • If the 23rd pair is non-homologous the individual is a male
sex chromosomes13
Sex Chromosomes
  • The chromosomes are referred to as X and Y
  • XX = female
  • XY = male
  • The Y has significantly less genes on it than the X
sex chromosomes14
Sex Chromosomes

Male

Female

slide15

2n=46. Human

We use karyotypes to find genetic disorders.

And to determine the sex of the individual.

karyotypes homework
Karyotypes Homework
  • Find the pairs
  • Arrange them in pairs, in order of size, with the same line going through each pair’s centromeres
  • Paste the pairs in your comp book
  • Is the person a male or a female?
  • Is there a genetic disorder?
karyotype homework
Karyotype Homework
  • Google karyotype
  • Print one of a non-human organism
  • Paste it to your compbook
  • Remember to identify what organism you chose
socks
Socks

Male

FYI: Socks aren’t really organisms.

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