karyotypes, dna fingerprinting, and meiosis · dna fingerprinting and karyotyping ... dna...

DNA Fingerprinting and Karyotyping

DNA Technology

TEKS

6.H: Students will…

describe how techniques such as DNA

fingerprinting, genetic modifications, and

chromosomal analysis are used to study the

genomes of organisms

Karyotyping (Chromosomal Analysis) The arrangement of homologous chromosomes, from

largest to smallest

Humans normally have 23 pairs of chromosomes (46 total) For each pair, one copy comes from mom and one comes from dad

Pairs 1 – 22 are known as autosomes

The 23rd pair are the sex chromosomes – X and Y

XX = female

XY = male

A karyotype can tell you If the individual is male or female

If the individual has any chromosomal disorders (chromosome mutations)

Karyotyping (Chromosomal Analysis)

Chromosome Mutations

Nondisjunction

Occurs during meiosis, when sister chromatids fail to

separate properly

This causes abnormal gametes (sex cells – sperm or egg)

The gametes can have too many or too few chromosomes

Deletion– only one chromosome (monosomy)

Duplication– three copies of a chromosome (trisomy)

Mutations can also occur when chromosomes have

translocations or inversions


Examples of Autosomal Chromosome Mutations

Down’s Syndrome – trisomy 21

Edward’s Syndrome – trisomy 18

Examples of Sex Chromosome Mutations

Klinefelter’s Syndrome – XXY

Turner’s Syndrome - XO


Normal Karyotype


Abnormal Karyotype

DNA Fingerprinting

A method of isolating and making images of

sequences of DNA

Used for criminal identification and

paternity testing

Step 1: Obtain sample of DNA

If the sample is not large enough for testing, it needs

to be amplified

PCR (polymerase chain reaction) can be used to

copy a single DNA molecule millions of times

Polymerase Chain Reaction (PCR)

DNA Fingerprinting

Step 2: Add restriction enzymes to the DNA

Restriction enzymes are proteins made by bacteria

Restriction enzymes recognizes specific sequences of

bases, and cut the DNA at those bases

Restriction enzymes make 2 cuts – one through each

sugar-phosphate backbone of the DNA strand

Restriction enzymes can make two different kinds of cuts

“Sticky ends” – an overhang in the DNA

“Blunt ends” – cut straight across both strands of DNA

DNA Fingerprinting

Blunt Ends

Sticky Ends

DNA Fingerprinting

Step 3 – Once the DNA is cut into various sizes,

they are placed on a gel. This gel is then subjected

to an electric current (gel electrophoresis)

The DNA fragments move from the negative pole

(cathode) towards the positive pole (anode)

Shorter fragments move through the gel faster –

why?

Step 4 – Once sorted by electrophoresis, the gel is

blotted to transfer the strands onto a nylon sheet,

which can be “read”

DNA Fingerprinting

Genetic Engineering

Inserting extra DNA or DNA from another organism

First, a particular section of DNA must be isolated using

gel electrophoresis

Then the fragment of DNA can be removed from the gel

and combined with a DNA fragment from another source

– it is then called “recombinant DNA”

Recombinant DNA is carried by a vector into a host cell –

like a bacterial cell – in order to be copied and/or studied

A commonly used vector is called a plasmid

A plasmid it made by cutting the vector and the DNA fragment

with the same restriction enzyme

Genetic Engineering

karyotypes, dna fingerprinting, and meiosis · dna fingerprinting and karyotyping ... dna...

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