Chapter 14Chapter 14The Human Genome

Key Concepts: How is sex determined? How do small changes in DNA Cause genetic disorders?

I. Human Chromosomes

A. Karyotype: A picture of chromosomes taken during mitosis and cut out and arranged into homologous pairs.

Let us review what we Let us review what we have previously have previously

learned learned

A Diploid Cell has ________ of homologous chromosomes. A human diploid cell has ____ chromosomes arranged in ____ pairs.

two sets

46

23

Mendelian genetics requires that organisms inherit ____________of a gene from each parent.a single copy

In humans, ___________ (reproductive cells of egg and sperm) contain a single copy of each gene (one set of genetic information).

the gametes

Gametes are formed in the ______ (sperm) and __________(egg) by meiosis. Each gamete contains 23 chromosomes (one set) or _______________ (N) of chromosomes. ____________requires the egg and the sperm to join and produce a ______ (fertilized egg) that contains 46 chromosomes (two sets) or _____________ (2N). 

testes ovaries

haploid number

zygote diploid number

Fertilization

Humans have 46 total chromosomes: 44 _________ (body) that follow regular Mendelian genetics, and 2 ________________ (X and Y).

autosomes

sex chromosomes

A. A pedigree chart shows the __________ within a family and can be useful to help with genetic __________ problems within families.

B. It is another way to _______ an outcome of a particular cross and the ________ of the family members.

relationship

inheritancepredict

genotype

A circle represents a female.

A square represents a male.

A horizontal line connecting a male and female represents a marriage.

A vertical line and a bracket connect the parents to their children.

A half-shaded circle or square indicates that a person is a carrier of the trait.

A completely shaded circle or square indicates that a person expresses the trait.

A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait.

Section 14-1

Figure 14-3 A Pedigree

Pedigree Pedigree

Video Notes Worksheet: What are Pedigree Charts?

Video Notes Worksheet: Pedigree Analyses

Guided Practice

Video Notes Worksheet: Pedigree Summary

Human Genes

The ______________: Complete set of genetic information that is composed of about 30,000 genes.

human genome

Human Traits

Phenotypes are determined by __________as well as ______________ influenced.

 

_____________ influences on gene expression are not ________, but genes are.

environmentally

Environmental

genotypes

inherited

A trait controlled by a recessive allele results in a disorder being present only if _____________ are present.

• Examples include: PKU (Phenylketonuria), Tay Sachs, Cystic Fibrosis, Albinism, and Galactosemia.

both alleles

A trait controlled by a dominant allele results in the disorder being present when only ________ is present.

• Examples include: Achondroplasia (dwarfism), Hypercholesterolemia, and Huntington’s Disease

one allele

caused by

Section 14-1

includeincludeinclude

AutosomolDisorders

Recessive alleles

Dominant allelesCodominant

alleles

Albinism Galactosemia Tay-Sachs disease

Huntington’s disease

Sickle cell disease

Cystic fibrosis

Phenylketonuria AchondroplasiaHypercholes-

terolemia

Autosomal DisordersAutosomal Disorders

Huntington Disease:

It is controlled by a _________________________. The gene is located on Chromosome #4.

single dominant allele

Genetic degenerative disease that shows no symptoms until a person is in their ____________________. It progresses with gradual degeneration of their nervous system leading to loss of muscle control and mental function until death occurs.

thirties or forties

IV. From Gene to MoleculeThe link between ______________________is not easily determined but for several diseases

we have been able to make the connection. For both ______________ and __________________ a small change in the DNA of a _____________affects the ______________________, causing aserious genetic disorder.

genetics and phenotype

Cystic fibrosis Sickle cell disease

single genestructure of a protein

Codominant Alleles: controlled by _____________________________.•Sickle Cell Anemia is an example.

two alleles that share dominance

Sickle Cell Anemia

The patient’s blood cells were found to be irregularly shaped, like a _____, and this is how the disease got its name.

In normal red blood cells ___________carries _________and distributes it around the body.

In sickle cell disease, the red blood cells are sickle–shaped, causing hemoglobin to no longer carry oxygen as well and disrupts the normal functioning of cells.

sickle

hemoglobin oxygen

Cystic Fibrosis or “CF” is a common genetic disease. It is most common in people of Northern European decent.

 It is a __________________of a gene found

on the # 7 chromosome and affects the__________________________________.

Recessive disease

digestive and respiratory systems

CFTR gene

The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein.

Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane.

The cells in the person’s airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus.

Section 14-1

Figure 14-8 The Cause of Cystic FibrosisChromosome

# 7

The genetics: The allele for sickle cell (HS) is ___________ with the allele for normal hemoglobin (HA). codominant

Heterozygotes (HS HA) are said to be ____ ____ __________ and have some effects of the disorder because they have both normal and sickle cell blood hemoglobin.

Sickle cell carriers

DNA normal hemoglobinCAC GTG GAC TGA GGA CTC CTCMessenger RNA sequenceGUG CAC CUG ACU CCU GAG GAGNormal hemoglobin amino acid sequenceVal – His – Leu – Thr – Pro – Glu – Glu… 1 2 3 4 5 6 7 …146 DNA Sickle Cell Anemia CAC GTG GAC TGA GGA CAC CTCMessenger RNA sequenceGUG CAC CUG ACU CCU GUG GAGVal – His – Leu – Thr – Pro – VAL – Glu… 1 2 3 4 5 6 7 …146 

The distribution: Sickle Cell anemia is most prevalent in people of __________________.  10% of African Americans and 40% of populations in Africa and Asia carry the gene for Sickle cell anemia.  Why? The carriers for the disease have a ___________________, a dangerous disease caused by a blood parasite found in tropical areas of the world.

African descent

resistance to Malaria

Sickle Cell Anemia is a __________ that has provided an _________ in Malaria prone areas. In these areas it is _________________________ and therefore Sickle Cell Anemia persists in many heterozygous individuals since the homozygous recessive condition is lethal.

favored by natural selection

   

   

HS HA

HS

HA

HS HS HS HA

HS HA HA HA

advantagemutation

Section 14-2: Human ChromosomesKey concepts: Why are sex-linked disorders morecommon in males than in females? What is nondisjunction, and what problems does itcause?

A. Sex Determination1. Female _________ carry an X chromosome2. _________ gametes can carry either an X or Y

(meiosis segregates the chromosomes; _______ of the sperm carry X and ______ of the sperm carry Y)

3. In humans, _____________________________ of an offspringFemale: XX male: XY

gametes

Male50%

X

males determine the sex

X

YX

XX XY

XX XY

50%

Sex-linked Genetic DisordersMay be on the X or Y chromosome, but   Most often expressed in ____________because they only have one X chromosome and thus all the alleles are expressed even if they are recessive.

usually on the X because the Y has very few genes.

males

Colorblindness is a recessive disorder in which people can’t distinguish between certain colors. ____________________ colorblindness is most common. XC and Xc are ___________ for normal and colorblind vision.

Red-green

the alleles

XC XC and XC Xc are

XC Xc is a _______________________ and can pass the gene on to her sons.

Xc Xc is a

XC Y is a

Xc Y is a

both normal vision females.

carrier for colorblindness

colorblind female.

normal male and

colorblind male.

http://www.toledo-bend.com/colorblind/Ishihara.html

Father(normal vision)

ColorblindNormal vision

Mother (carrier)

Daughter(normal vision)

Son(normal vision)

Daughter(carrier)

Son(colorblind)

Section 14-2

Male

Female

Figure 14-13 Colorblindness

Go to Section:

ColorblindnessColorblindness

Father(normal vision)

ColorblindNormal vision

Mother (carrier)

Daughter(normal vision)

Son(normal vision)

Daughter(carrier)

Son(colorblind)

Section 14-2

Male

Female

Figure 14-13 Colorblindness

Go to Section:

ColorblindnessColorblindness

Hemophilia is a __________________________ in which one is unable to clot their blood.  Also known as  Hemophilia is caused by a defect in a gene and the protein for normal blood clotting is missing. 

recessive sex-linked disorder

“bleeders disease”.

Slide 16

Figure 21.12Page 394

Royal Family and Hemophilia

Muscular Dystrophy is another   

Here the affected individual inherits a degenerative __________disorder.  The gene that codes for a _____________ is defective. They rarely live past early adulthood.  Treatments are being explored that ___________ the defective gene.

 

sex-linked recessive disease.

muscle

muscle protein

replace

IV. Chromosomal Disorders

Whole/sets of chromosome mutations1. _______________ = failure of homologous

chromosomes to separate normally during meiosis

This results in a disorder of __________________

2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome

Nondisjunction

chromosome number

Homologous chromosomes fail to separate

Meiosis I:Nondisjunction

Meiosis II

Nondisjunction

Go to Section:

Slide 23

n + 1

n + 1

n - 1

n - 1

chromosome alignments at metaphase I

nondisjunction at anaphase I

alignments at metaphase II

anaphase II gametes

Figure 21.19Page 398

Nondisjunction

2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome

 

Nondisjunction disorders: Disorders in which the failure of _____________________ during one of the stages of meiosis causes a gamete to have _______________________________.

 

Nondisjunction can occur in ___________________________.

chromosome separation

too few or too many chromosomes

autosomes or sex chromosomes

Down’s Syndrome: Down’s syndrome is an example of ____________________________, specifically chromosome 21.

In Down’s syndrome there is an ___________ of chromosome 21 (trisomy 21).

Doing a _____________ (display of all the chromosomes in a cell nucleus) and looking at the chromosomes under a microscope detect the extra chromosome.

Characteristics of Down’s syndrome include _________________, physically challenged, facial irregularities, and often heart defects.

nondisjunction of an autosome

extra copy

karyotype

mental retardation

Incidence of Down’s Syndrome and mother’s age

Turners Syndrome: Nondisjunction of the sex chromosomes in which  

They have the chromosome makeup of _________ where “O” represents the missing chromosome.

45 XO

a chromosome is missing.

This individual is female in appearance but does not develop the female sex organs during puberty and is ________.sterile.

Klinefelter’s Syndrome: Nondisjunction of the sex chromosomes in which an _____________________ is present.  

They have the chromosome makeup of ________. They are ___________ in appearance and are also sterile. May also be 48 XXXY or 49 XXXXY

extra X chromosome

47XXY

male

No nondisjunctions of the sex chromosomes have ever produced and survived without an ______________. This is because the X chromosome carries many genes

X chromosome

essential for life.

•XXY condition

•Results mainly from nondisjunction in mother (67%)

•Phenotype is tall males

–Sterile or nearly so

–Feminized traits (sparse facial hair, somewhat enlarged breasts)

–Treated with testosterone injections

Nondisjunction of Sex Nondisjunction of Sex

ChromosomesChromosomes

The impact of the sex chromosome nondisjunction has led us to understand the importance of the ____________ in determination of the sex of an individual.

 This has recently been determined to be

true because the Y chromosome has been found to have a gene that turns on __________ characteristics in the embryo, even if there are many X chromosomes present. 

Y chromosome

male sexual