Human Genetics. Karyotyping: technique for examining the chromosome make up of an organism shows...

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Human GeneticsHuman Genetics

Karyotyping:Karyotyping:technique for examining the technique for examining the chromosomechromosome make up of an make up of an organism organism shows chromosomes shows chromosomes arranged by arranged by sizesize: : – homologous pairshomologous pairs

a way of detecting a way of detecting abnormalities abnormalities chromosomes pairedchromosomes paired– Total of Total of 4646 chromosomes chromosomes– Or 23 pair Or 23 pair 22 autosomes, 22 autosomes,

somatic cells, body cells &somatic cells, body cells &– 1 1 pair of sex chromosomes pair of sex chromosomes

XX = XX = femalefemale XYXY = male = male

Chromosome Mapping:Chromosome Mapping:

Showing the location Showing the location of particular genes of particular genes on a chromosomeon a chromosome

Identifies traits that are likely Identifies traits that are likely to “cross over” togetherto “cross over” together

the closer the traits the the closer the traits the more likely the traits will be more likely the traits will be inherited together.inherited together.

Linkage Groups:Linkage Groups:

each chromosome carries many geneseach chromosome carries many genes

genes on the same chromosome genes on the same chromosome

= linked group = linked group

linked groups tend to be inherited linked groups tend to be inherited togethertogether

crossing over (prophase) can interfere crossing over (prophase) can interfere with linkage groupswith linkage groups

Sex- Linkage:Sex- Linkage:

Genes located on the sex chromosomesGenes located on the sex chromosomes– genes found on the x chromosome = x linkedgenes found on the x chromosome = x linked– genes found on the y chromosome = y linkedgenes found on the y chromosome = y linked

a gene found on either the x or y a gene found on either the x or y chromosomes = sex linked chromosomes = sex linked

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Topic: Intro to Human GeneticsTopic: Intro to Human GeneticsIdentify the following:Identify the following:

What is/are:What is/are:

1.1. KaryotypesKaryotypes2.2. Chromosome mappingChromosome mapping3.3. Sex- linked traitsSex- linked traits

Mutations:Mutations:

any change in the genetic hereditary any change in the genetic hereditary material of the cellmaterial of the cell

2 forms:2 forms:– inheritable mutations – occur in the sex cellsinheritable mutations – occur in the sex cells

Chromosomal mutationChromosomal mutation

Gene mutationGene mutation

– non inheritable mutations – occur in the non inheritable mutations – occur in the somatic cells (autosomes, body cells)somatic cells (autosomes, body cells)

2 Types of inheritable mutations:2 Types of inheritable mutations:

1.1. Chromosomal Mutations Chromosomal Mutations

And And

2. Gene mutations2. Gene mutations

Chromosomal Mutations:Chromosomal Mutations:

change in the structure of a chromosome change in the structure of a chromosome

the loss of an entire chromosome or addition of the loss of an entire chromosome or addition of a chromosomea chromosome

– Examples Include: Examples Include:

a. Nondisjunctiona. Nondisjunction

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Topic: Mutations 1Topic: Mutations 1

What is a mutation?What is a mutation?

What are the 2 types of inheritable What are the 2 types of inheritable mutations?mutations?

Explain how they are different.Explain how they are different.

Chromosome Mutation Cont.Chromosome Mutation Cont.

A. A. Nondisjunction: Nondisjunction: failure of chromosomes to separate during failure of chromosomes to separate during meiosismeiosis– ex. Down syndrome – extra chromosome # 21 ex. Down syndrome – extra chromosome # 21 – ex. Polyploidy – extra whole sets of ex. Polyploidy – extra whole sets of

chromosomes lethal in humans (3n), often used chromosomes lethal in humans (3n), often used in agriculture to enhance size of plants causes in agriculture to enhance size of plants causes sterilitysterility

– Ex .trisomy 18, trisomy 13Ex .trisomy 18, trisomy 13– EX. aneuploids – missing chromosomeEX. aneuploids – missing chromosome

Sex chromosome aneuploids : Sex chromosome aneuploids :

Nondisjunction:Nondisjunction:

NondisjunctionNondisjunctionDown syndromeDown syndrome (trisomy 21):(trisomy 21):

The result of an extra copy of chromosome 21. Down syndrome affects The result of an extra copy of chromosome 21. Down syndrome affects 1:700 children and severely alters the child's phenotype:1:700 children and severely alters the child's phenotype:characteristic facial features, short stature; heart defects characteristic facial features, short stature; heart defects susceptibility to respiratory disease, shorter lifespan susceptibility to respiratory disease, shorter lifespan prone to developing early Alzheimer's and leukemia prone to developing early Alzheimer's and leukemia often sexually underdeveloped and sterileoften sexually underdeveloped and sterile

Nondisjunction: Nondisjunction: Patau syndrome (trisomy 13):Patau syndrome (trisomy 13):

serious eye, brain, circulatory defects as serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. well as cleft palate. 1:5000 live births. Children rarely live more than a few Children rarely live more than a few months.months.

NondisjunctionNondisjunctionEdward's syndrome (trisomy 18):Edward's syndrome (trisomy 18):

almost every organ system affected Children almost every organ system affected Children rarely live more than a few months.rarely live more than a few months.

Other Examples of Nondisjunction: Other Examples of Nondisjunction: Sex chromosome aneuploids :Sex chromosome aneuploids :

Sex chromosome aneuploidsSex chromosome aneuploids

1.1. XO = XO = Turners SyndromeTurners Syndrome

2.2. XXY = XXY = KlinefelterKlinefelter Syndrome Syndrome

3.3. XXX = XXX = TriploTriplo-X Syndrome-X Syndrome

4.4. XYY =XYY =Jacob SyndromeJacob Syndrome

Turners Syndrome:Turners Syndrome:XO individuals are genetically female, however, they do not mature sexually during puberty and are sterile. Short stature and normal intelligence. (98% die before birth)

XXY = XXY = KlinefelterKlinefelter Syndrome SyndromeMale sex organs; unusually small testes, sterile. Male sex organs; unusually small testes, sterile. Breast enlargement and other feminine body Breast enlargement and other feminine body characteristics. Normal intelligence. characteristics. Normal intelligence.

XXX = XXX = TriploTriplo-X Syndrome-X Syndrome

XXXXXX females. 1:1000 live births - healthy females. 1:1000 live births - healthy and fertile - cannot be distinguished from and fertile - cannot be distinguished from normal female except by karyotypenormal female except by karyotype

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Topic: NondisjunctionTopic: Nondisjunction

What is Nondisjunction?What is Nondisjunction?

When does it occur? ( Be Specific)When does it occur? ( Be Specific)

Identify 3 genetic mutations Identify 3 genetic mutations resulting from nondisjunction.resulting from nondisjunction.

– What is the cause for each?What is the cause for each?

CChromosome mutationshromosome mutations (structure): (structure):translocation – a section of one chromosome is transferred to a nonhomogulous chromosome

addition – a portion of a chromosome is added

deletion – a portion of a chromosome is deleted

Cri-du-Chat Syndrome (segmental deletion)

inversion – order of genes on a chromosome is changed

Chromosomal mutation-Chromosomal mutation-Deletion:Deletion:

Example - Example - Cri du Cri du

chat (cry of the cat):chat (cry of the cat):

A deletion of a small A deletion of a small

portion of portion of

chromosome 5; chromosome 5;

these children have these children have

severe mental severe mental

retardation, a small retardation, a small

head with unusual head with unusual

facial features, and facial features, and

a cry that soundsa cry that sounds like a like a distressed cat.distressed cat.

Translocation:Translocation:

Some human diseases caused by Some human diseases caused by translocations are:translocations are:

CancerCancer: several forms of cancer are : several forms of cancer are caused by translocations; this has been caused by translocations; this has been described mainly in described mainly in leukemialeukemia

InfertilityInfertility

In summaryIn summaryChromosomal Mutations:Chromosomal Mutations:

Chromosomal abnormalities Chromosomal abnormalities can cause serious mental or can cause serious mental or physical disabilitiesphysical disabilities, and may , and may lead to the death of the lead to the death of the embryo. embryo.

Structure of the chromosome Structure of the chromosome has been compromisedhas been compromised

The number of chromosomes The number of chromosomes is incorrectis incorrect

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Topic: Mutations 2Topic: Mutations 2

1. Identify 4 structural chromosomal 1. Identify 4 structural chromosomal mutations.mutations.

2.2. How are each of the 4 How are each of the 4 chromosomes mutated?chromosomes mutated?

3. What is Turners Syndrome?3. What is Turners Syndrome?

Gene MutationsGene Mutations

Point Mutation – the substitution, addition, Point Mutation – the substitution, addition, or removal of a single nucleotide or removal of a single nucleotide

– substitutions, substitutions, one nucleotide in a one nucleotide in a codon is replaced with a different codon is replaced with a different nucleotide, resulting in a new codon.nucleotide, resulting in a new codon.

sickle cell anemiasickle cell anemia (also called sickle (also called sickle cell disease) is caused by a point cell disease) is caused by a point mutation that substitutes Adenine for mutation that substitutes Adenine for Thymine in a single DNA codon,Thymine in a single DNA codon,

Gene Mutations Cont.Gene Mutations Cont.

Frame Shift Mutation -the addition or Frame Shift Mutation -the addition or deletion of a single nucleotide causes the deletion of a single nucleotide causes the remaining codons to be incorrectly remaining codons to be incorrectly groupedgrouped– Addition/removal – a single nucleotide is Addition/removal – a single nucleotide is

added or removedadded or removed– Addition and Deletion MutationsAddition and Deletion Mutations

Welcome to Discovery Education PlayerWelcome to Discovery Education Player

Mutagenic Agents:Mutagenic Agents:

radiation - x-rays, radioactive isotopes, radiation - x-rays, radioactive isotopes, cosmic rays, ultraviolet rayscosmic rays, ultraviolet rays

chemicals – saccharin, nitrates, chemicals – saccharin, nitrates, carcinogens carcinogens

Human Genetic Traits & DisordersHuman Genetic Traits & DisordersX- linked Traits:X- linked Traits:

traits controlled by traits controlled by the female sex chromosomethe female sex chromosomesymbolized by a character on 1 of the symbolized by a character on 1 of the chromosomeschromosomes– XX’ XX’ X’ carries the traitX’ carries the trait– The female = the carrierThe female = the carrier– The trait is not visible in the femaleThe trait is not visible in the female

Ex. Hemophilia –blood disorder in which blood Ex. Hemophilia –blood disorder in which blood does not clot properlydoes not clot properlyEx. Color blindness – cannot distinguish between Ex. Color blindness – cannot distinguish between red and greenred and green

X-linked traits cont.X-linked traits cont.

Symbols for constructing a Punnett square Symbols for constructing a Punnett square (sex-linked trait)(sex-linked trait)

XX normal femaleXX normal female

XY normal maleXY normal male

X’X carrier femaleX’X carrier female

X’Y male with hemophiliaX’Y male with hemophilia

http://www.macmed.ttuhsc.edu/Morgan/http://www.macmed.ttuhsc.edu/Morgan/bleedingdisorders/pages/newpage26.htmbleedingdisorders/pages/newpage26.htm

Ex. HemophiliaEx. Hemophilia

Hemophiliac male x carrier femaleHemophiliac male x carrier female

GenotypeGenotype

PhenotypePhenotype

Hemophilia contin.Hemophilia contin.

Normal male x female carrierNormal male x female carrier

GenotypeGenotype

PhenotypePhenotype

Multiple Alleles:Multiple Alleles:

2 or more alleles for a particular trait2 or more alleles for a particular trait

alleles are expressed as codominantalleles are expressed as codominant

ex. Blood typesex. Blood types

Human Blood Types:Human Blood Types:

PhenotypePhenotype Genotype Genotype SymbolSymbol

AA AA, AO AA, AO IaIa, IaIa, IaiIai

BB BB, BO BB, BO IbIb, IbIb, IbiIbi

ABAB ABAB IaIbIaIb

OO OO OO iiii

Blood Types & Punnett Squares;Blood Types & Punnett Squares;What are the What are the possible outcomes possible outcomes for a heterozygous for a heterozygous A blood type A blood type crossing crossing with a homozygous with a homozygous B blood type?B blood type?Genotypes Genotypes

PhenotypesPhenotypes

Blood Type Cont.Blood Type Cont.Construct a punnett Construct a punnett square showing a square showing a cross b/w a blood cross b/w a blood type O person with a type O person with a heterozygous B heterozygous B blood type personblood type person

GenotypeGenotype

PhenotypePhenotype

Polygenic Traits:Polygenic Traits:

traits controlled by 2 or more allelestraits controlled by 2 or more alleles

expressed as incomplete dominanceexpressed as incomplete dominance

ex. Eye color, height, and skin colorex. Eye color, height, and skin color

Genetic Disorders:Genetic Disorders:

Genetic screening or studying karyotyes can show Genetic screening or studying karyotyes can show possible genetic disorderspossible genetic disorders

– Amniocentesis – karyotyping and analyzing Amniocentesis – karyotyping and analyzing amniotic fluid for fetal cells amniotic fluid for fetal cells

– Chorionic villisampling – piece of the placenta Chorionic villisampling – piece of the placenta that is studied for genetic abnormalitiesthat is studied for genetic abnormalities

– Ex. PKU: a genetic disorder that does not Ex. PKU: a genetic disorder that does not allow the baby allow the baby to breakdown to breakdown phenylalanine , can cause severe brain phenylalanine , can cause severe brain damagedamage

Can be detected and eliminated with Can be detected and eliminated with special diets special diets