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Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

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Page 1: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Human GeneticsHuman

Genetics

Chapter 15: The Chromosomal Basis of Inheritance

Page 2: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Genes & ChromosomesGenes & Chromosomes

Mendel’s “hereditary factors” were , though this wasn’t known at the time

Today we can show that genes are

The location of a particular gene can be seen by tagging isolated chromosomes with

Mendel’s “hereditary factors” were , though this wasn’t known at the time

Today we can show that genes are

The location of a particular gene can be seen by tagging isolated chromosomes with

Page 3: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Chromosomal Theory of Inheritance

Chromosomal Theory of Inheritance

Mitosis and meiosis were first described in the

The chromosome theory of inheritance states:

The behavior of chromosomes during meiosis was said to account for Mendel’s laws of segregation and independent assortment

Mitosis and meiosis were first described in the

The chromosome theory of inheritance states:

The behavior of chromosomes during meiosis was said to account for Mendel’s laws of segregation and independent assortment

Page 4: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance
Page 5: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Experimental EvidenceExperimental EvidenceThe first solid evidence

associating a specific gene with a specific chromosome came from

Morgan’s experiments with fruit flies provided convincing evidence that

The first solid evidence associating a specific gene with a specific chromosome came from

Morgan’s experiments with fruit flies provided convincing evidence that

Page 6: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Experimental EvidenceExperimental EvidenceIn one experiment, Morgan

mated male flies with white eyes (mutant) with female flies with red eyes (wild type or normal)The F1 generation

The F2 generation showed the 3:1 red:white eye ratio, but

Morgan determined that the white-eyed mutant allele must be located

Morgan’s finding supported the

In one experiment, Morgan mated male flies with white eyes (mutant) with female flies with red eyes (wild type or normal)The F1 generation

The F2 generation showed the 3:1 red:white eye ratio, but

Morgan determined that the white-eyed mutant allele must be located

Morgan’s finding supported the

Page 7: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Sex linkageSex linkageSex chromosomes

determine XX in females, XY in

malesEach ovum contains an

, while a sperm may contain

The SRY gene on the Y chromosome codes for the

X chromosome has genes for many traits

Sex chromosomes determine XX in females, XY in

malesEach ovum contains an

, while a sperm may contain

The SRY gene on the Y chromosome codes for the

X chromosome has genes for many traits

Page 8: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance
Page 9: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Sex-linked InheritanceSex-linked InheritanceA gene located on either

sex chromosome is called a

In humans, sex-linked usually refers to a gene on the

If gene is on Sons will inherit from Females don’t get Y-

linked traitsY-linked genes

A gene located on either sex chromosome is called a

In humans, sex-linked usually refers to a gene on the

If gene is on Sons will inherit from Females don’t get Y-

linked traitsY-linked genes

Page 10: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

X-linked InheritanceX-linked Inheritance

If gene is on

Can inherit from

Sons always get

If gene is on

Can inherit from

Sons always get

Page 11: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

X-linked traitsX-linked traits

AKA Bubble boy disease

AKA Bubble boy disease

Page 12: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

X-linked recessive genes

X-linked recessive genes

Sex-linked genes follow specific patterns of inheritance

For a recessive sex-linked trait to be expressedA female

A male

Sex-linked recessive disorders are much

Sex-linked genes follow specific patterns of inheritance

For a recessive sex-linked trait to be expressedA female

A male

Sex-linked recessive disorders are much

Page 13: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Females & X-linkedFemales & X-linked

In mammalian females, one of the two X chromosomes in each cell is

The inactive X condenses

into a If a female is heterozygous

for a particular gene located on the X chromosome, she will be a

In mammalian females, one of the two X chromosomes in each cell is

The inactive X condenses

into a If a female is heterozygous

for a particular gene located on the X chromosome, she will be a

Page 14: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

CarriersCarriersFemales can be

Have one copy of gene,

Other X has

Males cannot be carriers, they either Males will give gene to

If he has the gene all his daughters will be

Females can be Have one copy of gene,

Other X has

Males cannot be carriers, they either Males will give gene to

If he has the gene all his daughters will be

Page 15: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Red-green color blindness

Red-green color blindness

X-linked disorderCan’t differentiate these two

colorsMany people who have this are

First described in a boy who could not be trained to harvest only the ripe, red apples from his father’s orchard.

What serious consequence could result from this?

X-linked disorderCan’t differentiate these two

colorsMany people who have this are

First described in a boy who could not be trained to harvest only the ripe, red apples from his father’s orchard.

What serious consequence could result from this?

Page 16: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Sex-Linked Traits:

 1. Normal Color Vision: A: 29,  B: 45,  C: --,  D: 26

 2. Red-Green Color-Blind: A: 70,  B: --,  C: 5,  D: --

 3. Red Color-blind: A: 70,  B: --,  C: 5,  D: 6

 4. Green Color-Blind: A: 70,  B: --,  C: 5,  D: 2

Page 17: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

HemophiliaHemophiliaAn X-linked disorder

that causes a

If your blood didn’t have the ability to clot and you bruised yourself or scraped your knee,

Queen Victoria was a carrier and she passed the trait on to some of her children

An X-linked disorder that causes a

If your blood didn’t have the ability to clot and you bruised yourself or scraped your knee,

Queen Victoria was a carrier and she passed the trait on to some of her children

Page 18: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

HemophiliaHemophilia

About has hemophilia, but only about inherits the same disorder

Why????Males only have

A single recessive allele for hemophilia will

Females would need to inherit hemophilia

Males inherit the allele for hemophilia on the X chromosome from their

About has hemophilia, but only about inherits the same disorder

Why????Males only have

A single recessive allele for hemophilia will

Females would need to inherit hemophilia

Males inherit the allele for hemophilia on the X chromosome from their

Page 20: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

HemophiliaHemophiliaHemophilia can be treated

with , the

blood-clotting enzyme that is absent in people affected by the condition

Both treatments are New methods of DNA

technology are being used to develop a

Hemophilia can be treated with

, the blood-clotting enzyme that is absent in people affected by the condition

Both treatments are New methods of DNA

technology are being used to develop a

Page 21: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Sex-linked QuestionsSex-linked Questions Both the mother and the father of a male

hemophiliac appear normal. From whom did the son inherit the allele for hemophilia? What are the genotypes of the mother, the father and the son?

A woman is color blind. If she marries a man with normal vision, what are the chances that her daughter will be color blind? Will be carriers? What are her chances that her sons will be color blind?

Is it possible for two normal parents to have a color blind daughter?

Both the mother and the father of a male hemophiliac appear normal. From whom did the son inherit the allele for hemophilia? What are the genotypes of the mother, the father and the son?

A woman is color blind. If she marries a man with normal vision, what are the chances that her daughter will be color blind? Will be carriers? What are her chances that her sons will be color blind?

Is it possible for two normal parents to have a color blind daughter?

Page 22: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

What is on our chromosomes?What is on our chromosomes?

Each chromosome has Genes located on the same chromosome that

tend to be inherited together are called Thomas Morgan found that body color and wing

size of fruit flies are usually inherited together in

He noted that these genes do not , and reasoned that they were

However, nonparental phenotypes were also produced

Understanding this result involves exploring

Each chromosome has Genes located on the same chromosome that

tend to be inherited together are called Thomas Morgan found that body color and wing

size of fruit flies are usually inherited together in

He noted that these genes do not , and reasoned that they were

However, nonparental phenotypes were also produced

Understanding this result involves exploring

Page 23: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Genetic RecombinationGenetic Recombination

Mendel observed that combinations of traits in some offspring differ from either parent

Offspring with a phenotype matching one of the parental phenotypes are called

Offspring with nonparental phenotypes (new combinations of traits) are called

Morgan discovered that genes can be linked, but the linkage was Morgan proposed that some process must

sometimes break the physical connection between genes on the same chromosome

Mechanism was the

Mendel observed that combinations of traits in some offspring differ from either parent

Offspring with a phenotype matching one of the parental phenotypes are called

Offspring with nonparental phenotypes (new combinations of traits) are called

Morgan discovered that genes can be linked, but the linkage was Morgan proposed that some process must

sometimes break the physical connection between genes on the same chromosome

Mechanism was the

Page 24: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Genetic mapGenetic map

Alfred Sturtevant, one of Morgan’s students, constructed a

Sturtevant predicted that the farther apart two genes are, the

and therefore the higher the recombination frequency

Alfred Sturtevant, one of Morgan’s students, constructed a

Sturtevant predicted that the farther apart two genes are, the

and therefore the higher the recombination frequency

Page 25: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Genetic mapGenetic mapA linkage map is a genetic map of a chromosome

based on Distances between genes can be expressed as

; one map unit, or centimorgan, represents a

Map units indicate , not precise locations of genes

A linkage map is a genetic map of a chromosome based on

Distances between genes can be expressed as ; one map unit, or centimorgan, represents a

Map units indicate , not precise locations of genes

Page 26: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Human Genome Project

Human Genome Project

The most ambitious mapping project to date has been the sequencing of the

Officially begun as the Human Genome Project in , the sequencing was largely completed by

The project had three stages:

The most ambitious mapping project to date has been the sequencing of the

Officially begun as the Human Genome Project in , the sequencing was largely completed by

The project had three stages:

Page 27: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Human Genome Project

Human Genome Project

A physical map expresses the distance between genetic markers,

It is constructed by cutting a DNA molecule into many short fragments and arranging them in order by identifying overlaps

Sequencing was then done on the chromosomes

A physical map expresses the distance between genetic markers,

It is constructed by cutting a DNA molecule into many short fragments and arranging them in order by identifying overlaps

Sequencing was then done on the chromosomes

Page 28: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Gene ManipulationGene ManipulationDNA sequencing has

depended on advances in technology, starting with making recombinant DNA

In recombinant DNA, nucleotide sequences from

Methods for making recombinant DNA are central to genetic engineering,

DNA sequencing has depended on advances in technology, starting with making recombinant DNA

In recombinant DNA, nucleotide sequences from

Methods for making recombinant DNA are central to genetic engineering,

Page 29: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

BiotechnologyBiotechnology

DNA technology has revolutionized biotechnology,

One benefit of DNA technology is identification of human genes in which

Scientists can diagnose many human genetic disorders by using molecular biology techniques to

Genetic disorders can also be tested for using

DNA technology has revolutionized biotechnology,

One benefit of DNA technology is identification of human genes in which

Scientists can diagnose many human genetic disorders by using molecular biology techniques to

Genetic disorders can also be tested for using

Page 30: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

TransgenicsTransgenicsAdvances in DNA technology and genetic

research are important to the development of

Transgenic animals are made by introducing genes from Transgenic animals are pharmaceutical “

,” producers of large amounts of otherwise rare substances for medical use

“Pharm” plants are also being developed to make human proteins for medical use

This is useful for the production of

Advances in DNA technology and genetic research are important to the development of

Transgenic animals are made by introducing genes from Transgenic animals are pharmaceutical “

,” producers of large amounts of otherwise rare substances for medical use

“Pharm” plants are also being developed to make human proteins for medical use

This is useful for the production of

Page 31: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Gene TherapyGene Therapy

Gene therapy is the alteration of an

Gene therapy holds great potential for treating

Vectors are used for

(example = bone marrow)Gene therapy raises ethical

questions, such as whether human germ-line cells should be treated to correct the defect in future generations

Gene therapy is the alteration of an

Gene therapy holds great potential for treating

Vectors are used for

(example = bone marrow)Gene therapy raises ethical

questions, such as whether human germ-line cells should be treated to correct the defect in future generations

Page 32: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Causes of Genetic Disorders

Causes of Genetic Disorders

Meiosis usually functions accurately, but problems may arise at times

Large-scale chromosomal alterations often lead to

In nondisjunction, pairs of homologous chromosomes May occur in One gamete receives

Another gamete receives

Meiosis usually functions accurately, but problems may arise at times

Large-scale chromosomal alterations often lead to

In nondisjunction, pairs of homologous chromosomes May occur in One gamete receives

Another gamete receives

Page 33: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance
Page 34: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Fertilization after nondisjunction

Fertilization after nondisjunction

Nondisjunction results in gametes with an extra or missing chromosome

If the other gamete is normal, the zygote will have

Most of the time an extra chromosome

results from the fertilization of gametes in which nondisjunction occurred

Offspring with this condition have an

Nondisjunction results in gametes with an extra or missing chromosome

If the other gamete is normal, the zygote will have

Most of the time an extra chromosome

results from the fertilization of gametes in which nondisjunction occurred

Offspring with this condition have an

Page 35: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Fertilization after nondisjunction

Fertilization after nondisjunction

occurs when the zygote has only one copy of a particular chromosome (2n -1)

occurs when the zygote has three copies of a particular chromosome (2n+1)

is a condition in which an organism has more than two complete sets of chromosomes is three sets of chromosomes is four sets of chromosomes

Polyploidy is common in Polyploids are in appearance than

aneuploids

occurs when the zygote has only one copy of a particular chromosome (2n -1)

occurs when the zygote has three copies of a particular chromosome (2n+1)

is a condition in which an organism has more than two complete sets of chromosomes is three sets of chromosomes is four sets of chromosomes

Polyploidy is common in Polyploids are in appearance than

aneuploids

Page 37: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Human Disorders due to chromosome alterationsHuman Disorders due to chromosome alterations

are associated with some serious disorders

Some types of aneuploidy appear to upset the genetic balance less than others, resulting in

These surviving individuals have a set of symptoms,

are associated with some serious disorders

Some types of aneuploidy appear to upset the genetic balance less than others, resulting in

These surviving individuals have a set of symptoms,

Page 38: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Down SyndromeDown SyndromeDown syndrome is an

aneuploid condition that results from

Most common serious birth defect

Varying degrees of

Due to on 21st chromosome

1/2 eggs of female will carry extra 21 and 1/2 will be normal

Risk increases

Down syndrome is an aneuploid condition that results from

Most common serious birth defect

Varying degrees of

Due to on 21st chromosome

1/2 eggs of female will carry extra 21 and 1/2 will be normal

Risk increases

Page 39: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance
Page 40: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Incidence of Down Syndrome

Incidence of Down Syndrome

Page 41: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Klinefelter SyndromeKlinefelter Syndrome

Klinefelter syndrome is the result of an

Could be from

nondisjunction

Klinefelter syndrome is the result of an

Could be from

nondisjunction

Page 42: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Turner SyndromeTurner Syndrome

Turner syndrome produces

It is the only known

viable monosomy in humans

Girls with Turner Syndrome do not develop

Turner syndrome produces

It is the only known

viable monosomy in humans

Girls with Turner Syndrome do not develop

Page 43: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Mutation typesMutation types may

also lead to genetic disordersBreakage of a chromosome can lead to

four types of changes in chromosome structure:Deletion Duplication

Inversion

Translocation

may also lead to genetic disorders

Breakage of a chromosome can lead to four types of changes in chromosome structure:Deletion Duplication

Inversion

Translocation

Page 44: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Mutation typesMutation types

Page 45: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Cri du chatCri du chat

The syndrome cri du chat (“cry of the cat”), results from a

A child born with this syndrome is

Individuals usually die

The syndrome cri du chat (“cry of the cat”), results from a

A child born with this syndrome is

Individuals usually die

Page 46: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Chronic Myelogenous Leukemia

Chronic Myelogenous Leukemia

Certain cancers, including chronic myelogenous leukemia (CML), are caused by

Occurs with the exchange of a large portion of with a small

fragment from the tip of Shortened, easily recognizable

Certain cancers, including chronic myelogenous leukemia (CML), are caused by

Occurs with the exchange of a large portion of with a small

fragment from the tip of Shortened, easily recognizable

Page 47: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Genomic imprintingGenomic imprintingThere are two normal exceptions to Mendelian

geneticsOne exception involves , and

the other exception involves

Genes marked in gametes as coming from Genes inherited from father

than genes inherited from motherFor a small fraction of mammalian traits, the

for those traitsSuch variation in phenotype is called genomic

imprintingExample =

There are two normal exceptions to Mendelian genetics

One exception involves , and the other exception involves

Genes marked in gametes as coming from Genes inherited from father

than genes inherited from motherFor a small fraction of mammalian traits, the

for those traitsSuch variation in phenotype is called genomic

imprintingExample =

Page 48: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Organelle genes Organelle genes Extranuclear genes (or

cytoplasmic genes) are genes found

Mitochondria, chloroplasts, and other plant plastids carry

Extranuclear genes are inherited

Extranuclear genes (or cytoplasmic genes) are genes found

Mitochondria, chloroplasts, and other plant plastids carry

Extranuclear genes are inherited

Page 49: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Organelle genes Organelle genes The first evidence of

extranuclear genes came from studies on the inheritance of yellow or white patches on leaves of an otherwise green plant

Some defects in mitochondrial genes prevent cells from making enough ATP and result in

For example,

mitochondrial myopathy and Leber’s hereditary optic neuropathy

The first evidence of extranuclear genes came from studies on the inheritance of yellow or white patches on leaves of an otherwise green plant

Some defects in mitochondrial genes prevent cells from making enough ATP and result in

For example,

mitochondrial myopathy and Leber’s hereditary optic neuropathy

Page 50: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Review QuestionsReview Questions1. State the 2 basic ideas behind the chromosomal theory of

inheritance.2. Explain Morgan’s experiment and how it gave evidence that

genes are located on chromosomes.3. Explain sex linkage and sex-linked inheritance.4. Name and describe characteristics of 4 genetic diseases

that are known to be X-linked.5. Explain the idea of a “carrier” for an X-linked genetic

disease.6. Carry out a monohybrid cross of an X-linked trait using a

Punnett square.7. Explain the idea of linked genes.8. Explain the result of genetic recombination.9. Identify the significance of genetic maps and linkage maps10. Describe the Human Genome Project and differentiate

between its 3 main stages.11. Discuss the advantages of gene manipulation and

biotechnology.12. Describe various uses of transgenic animals.13. Explain the purpose and use of gene therapy.14. Explain how errors in meiosis can cause genetic syndromes.

Page 51: Human Genetics Chapter 15: The Chromosomal Basis of Inheritance

Review QuestionsReview Questions15. Define nondisjunction.16. Differentiate between aneuploidy, monosomy, trisomy, and

polyploidy.17. Explain the cause, frequency, and problems associated with

the following genetic syndromes: Down syndrome, Klinefelter syndrome, & Turner syndrome.

18. Describe the effect of mutations on genes.19. Differentiate between deletion, duplication, inversion, and

translocation mutations.20. Explain cri du chat syndrome.21. Explain chronic myelogenous leukemia as an example of a

disease-causing mutation.22. Explain genomic imprinting and the effects of extranuclear

genes.