Mutations and Mutations and KaryotypingKaryotyping

Mutations Ch. 10. pg. Ch. 10. pg. 219-220219-220

Changes in Changes in nucleotidenucleotide sequence of DNAsequence of DNA

May occur May occur in somatic in somatic cells (body cells)cells (body cells) not passed to offspringnot passed to offspring

May occur May occur in gametes in gametes (eggs & sperm)(eggs & sperm) passed to offspringpassed to offspring

CausesCauses Mutations Mutations happen regularlyhappen regularly Any agent that causes a change in Any agent that causes a change in

DNA is called a DNA is called a mutagenmutagen.. Mutagens include radiation, Mutagens include radiation,

chemicals, and even high chemicals, and even high temperatures.temperatures. Ex. of radiation: X rays, cosmic rays, Ex. of radiation: X rays, cosmic rays,

ultraviolet light, and nuclear radiationultraviolet light, and nuclear radiation.. Chemicals: BenzeneChemicals: Benzene

Many Many mutationsmutations areare repaired by repaired by enzymes.enzymes.

Are Mutations Helpful Are Mutations Helpful or Harmful?or Harmful?

Some harmful - Skin Some harmful - Skin cancers and some cancers and some leukemiasleukemias result from result from somatisomaticc mutationsmutations

MostMost mutations have mutations have no no affectaffect, some have , some have detrimental affects and a detrimental affects and a few few mutations may mutations may improveimprove an organism’s an organism’s survival survival (beneficial)(beneficial)

Types of MutationsTypes of Mutations

2-Types2-Types 1. 1. Gene mutations Gene mutations - - change in one DNA change in one DNA

sequence sequence of a gene.of a gene. 2.Chromosomal mutations 2.Chromosomal mutations – – change in change in

structure or loss or gain of part of a structure or loss or gain of part of a chromosome.chromosome.

Gene mutation- 2 types1. Point Mutation

A A change in change in a a single base pair single base pair in in DNA.DNA.

Changes Changes the the amino acidamino acid inin the the proteinprotein

Does Does not always not always cause a cause a problemproblem..

THE DOG BIT THE THE DOG BIT THE CATCAT THE DOG BIT THE THE DOG BIT THE CARCAR

2. Frameshift Mutation

A A single base single base is is added or deleted added or deleted from the DNA from the DNA causing causing all the other all the other bases to be out of positionbases to be out of position..

More harmful More harmful than a regular point than a regular point mutation.mutation.

THE DOG BIT THE CATTHE DOG BIT THE CAT THE DOB ITT HEC ATTHE DOB ITT HEC AT

Chromosome Mutations

Five types Five types exist:exist:DeletionDeletionInversionInversionTranslocationTranslocationNondisjunctionNondisjunctionDuplicationDuplication

DeletionDeletionPartPart of of a a chromosomechromosome is is

lost/deletedlost/deleted..A B C D E F G H

A B C E F G H

Duplication/InsertionDuplication/InsertionA A partpart of the chromosome of the chromosome

repeatsrepeats

A B C D E F G H

A B C B C D E F G H

InversionInversionPartPart of a chromosome of a chromosome breaks off;breaks off; reattaches reattaches

backwardbackwardA B C D E F G H

H A D C B E F G

TranslocationTranslocationPartPart of a chromosome of a chromosome

breaks off; attaches to breaks off; attaches to aa different chromosome that different chromosome that

is not homologousis not homologous

WXY Z Y ZTranslocation

A B E FDCBX AWC HGGE HD F

WX Y Z Y ZTranslocation

NondisjunctionNondisjunction

FailureFailure of pair of chromosomes to of pair of chromosomes to separate during meiosisseparate during meiosis Example Down SyndromeExample Down Syndrome

Chromosome Chromosome Mutation Mutation AnimationAnimation

KaryotypingKaryotyping

Ch. 6 pg. 122-123Ch. 6 pg. 122-123

Some mutations that cause Some mutations that cause chromosomal chromosomal abnormalities can be detected by abnormalities can be detected by analyzing a karyotype.analyzing a karyotype.

Karyotype Karyotype – photo of – photo of thethe chromosomes in chromosomes in aa dividing cell dividing cell that that shows shows thethe chromosomes arranged by size, number, chromosomes arranged by size, number, and shape.and shape. Identifies gender and genetic disordersIdentifies gender and genetic disorders

AmniocentesisAmniocentesis – – medical medical procedure used procedure used in prenatal diagnosis of chromosomal in prenatal diagnosis of chromosomal abnormalitiesabnormalities and fetal infections and fetal infections small amount of amniotic fluid, which has fetal tissues, is extracted small amount of amniotic fluid, which has fetal tissues, is extracted

from the amniotic sac surrounding a developing from the amniotic sac surrounding a developing fetus

2 types 2 types of abnormalities in chromosomesof abnormalities in chromosomes Autosomal abnormalitiesAutosomal abnormalities – abnormalities of – abnormalities of

chromosomes chromosomes not not directly directly involved in involved in determining determining gendergender

Sex Chromosomal abnormalitiesSex Chromosomal abnormalities – – abnormalities that abnormalities that affectaffect the the gendergender of an of an individualindividual

XX – femaleXX – female XY - maleXY - male

How Scientists Read How Scientists Read Chromosomes?Chromosomes?

1)1) SizeSize. This is the easiest way to tell two . This is the easiest way to tell two different chromosomes apart. different chromosomes apart.

2)2) Banding patternBanding pattern. The size and . The size and location of Giemsa bands on location of Giemsa bands on chromosomes make each chromosome chromosomes make each chromosome pair unique. pair unique.

3)3) Centromere positionCentromere position. Centromeres . Centromeres are regions in chromosomes that are regions in chromosomes that appear as a constriction. They have a appear as a constriction. They have a special role in the separation of special role in the separation of chromosomes into daughter cells chromosomes into daughter cells during mitosis cell division (mitosis and during mitosis cell division (mitosis and meiosis). meiosis).

Using these key features, scientists match up the 23 pairs – one set from the mother and one set from the father.

To "read" a set of human chromosomes, scientists first use three key features to identify their similarities and differences:

Image taken from: http://learn.genetics.utah.edu/content/begin/traits/scientists/

Typical KaryotypeTypical Karyotype

Typical Karyotype

Trisomy 21- Down’s Syndrome - Trisomy 21- Down’s Syndrome - KaryotypeKaryotype

47 Total Chromosomes

Three Chromosomes at the 21st Pair Image taken from: http://worms.zoology.wisc.edu/zooweb/Phelps/karyotype.html

Monosomy X - Turner Syndrome - Monosomy X - Turner Syndrome - KaryotypeKaryotype

45 Total Chromosomes

One “X” Chromosome Image taken from: http://worms.zoology.wisc.edu/zooweb/Phelps/karyotype.html

XYY KaryotypeXYY Karyotype

One “X” and Two “Y” Chromosomes

47 Total Chromosomes

Image taken from: http://worms.zoology.wisc.edu/zooweb/Phelps/karyotype.html

ExamplesExamples Cri du chat – deletion of #5Cri du chat – deletion of #5 Wilson’s Disease Wilson’s Disease – can’t get rid of excess – can’t get rid of excess

coppercopper Down's syndrome – extra copy of #21Down's syndrome – extra copy of #21 Patau Syndrome – extra copy of #13Patau Syndrome – extra copy of #13 Klinefelter's syndrome (XXY) Klinefelter's syndrome (XXY) Turner syndrome (X instead of XX or XY) Turner syndrome (X instead of XX or XY) XYY syndrome. XYYXYY syndrome. XYY Triple-X syndrome (XXX)Triple-X syndrome (XXX) XXXX SyndromeXXXX Syndrome

Colored BlindnessColored Blindness Hemophilia – Hemophilia – bleeding disorderbleeding disorder Huntington’s Disease – Huntington’s Disease – faulty protein faulty protein

(mental/nervous disorder)(mental/nervous disorder) Jackson-Weiss Syndrome Jackson-Weiss Syndrome – fusion of – fusion of

face/foot bonesface/foot bones Sickle Cell Disease – Sickle Cell Disease – red blood cells red blood cells

sickle shapedsickle shaped Tay-Sachs Disease Tay-Sachs Disease – brain/nerve – brain/nerve

disorderdisorder PolydactylyPolydactyly – extra digit – extra digit