dragonfly chapter 14 the human genome. section 14-1: human heredity key concepts: how is sex...

Dragonfly Chapter 14

The Human Genome

Section 14-1: Human Heredity

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.

Diploid Cell: ________ of homologous chromosomes

Human diploid cell has ____ chromosomes arranged in ____ pairs The 46 chromosomes contain

Two sets

46

23 6 billion nucleotide pairs

Mendelian genetics requires that organismsof gene from each parent inherit 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 _____________ follow regular Mendelian genetics

2 _________________ (X and Y) are sex-linked

autosomes

sex chromosomes

A. Pedigree Chart: A pedigree chart shows the _________________ within a family and can be useful to help with __________________________ within families. It is another ___________________________ of a particular cross and the genotype of the family members.

relationshipgenetic inheritance problems

outcomeway to predict the

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 PedigreePedigree

Human Traits

Phenotypes are determined by genotype as well as ________________________________.

________________________________ on gene expression are not inherited, but genes are.

environmentally influenced

Environmental influences

III. Human GenesThe __________________: Complete set of genetic information

Composed of about 30,000 genes

Blood Group GenesHuman Blood comes in a variety of genetically determined blood groups There are many different types of blood groups but the ones associated with the ABO blood group and the Rh blood groups are best known. .

human genome

Rh blood groups is controlled by single gene with ________________. It is another antigen in blood, first discovered in Rhesus monkeys. The arrangement of the alleles determines only _______ possible types _____________ (+) contains the antigen, or ___________ (-) doesn’t contain the antigen. Positive is ______________ over negative.

Rh-positive is identified with two genotypes: Rh+/Rh+ or Rh+/Rh-

Rh-negative is identified with one genotype: Rh-/Rh-

Two alleles

two positive

negativedominant

ABO Blood Groups: Discovered in 1900 by Karl Landsteiner. He realized that all blood is classified into four types: ____, ____, ____, and _____ due to the presence of or absence of specific __________ in the blood. Alleles IA and IB are __________________ and io is ________________ to both IA and IB

OABBA

codominant

recessive

Antigens are ______________________ used by the immune system. When an unrecognized antigen is present an immune response takes place and the cells ____________________________.

chemical markers

antigens

clump or agglutinate

Phenotype(Blood Type Genotype

Antigen on Red Blood Cell

Safe Transfusions

To From

Section 14-1

Figure 14-4 Blood Groups

Go to Section:

Blood Type and Antigen Interactions

B. Recessive Alleles: Trait controlled by a recessive allele. This results in the disorder being present ___________________________.

• Examples include: PKU (Phenylketonuria), Tay Sachs disease and Cystic Fibrosis, Albinism, and Galactosemia (See chart on page 345)

only if both alleles are recessive

C. Dominant Alleles: Traits controlled by a dominant allele. This results in the disorder being present when __________________________.

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

only one allele is present

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 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

Question? Would you want to know now if you could potentially get Huntington’s disease when you are older? Would you want to know if you could pass the gene on to your offspring before you have children?

A. Codominant Alleles: controlled by _______________________________________. Sickle Cell Anemia is such a disorder. (This will be discussed in detail later)

two alleles that share dominance

IV. From Gene to Molecule

The 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 a

serious genetic disorder.

genetics and phenotype

Cystic fibrosis Sickle cell disease

single gene

structure of a protein

A. Cystic Fibrosis: (See figure 14-8 p. 347)

Cystic Fibrosis a.k.a. “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

It is caused by the____________________ in

the middle of a sequence for a protein and

causes the protein to be ______________ and

doesn’t allow Chloride ions to transport across

the membrane, as they should. This causes

the cells in a person’s airways to be unable to

transport chloride ions and become

__________________.

deletion of 3 bases

abnormal

clogged with mucus

Chromosome # 7

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 Fibrosis

B. Sickle Cell Anemia

The patient’s blood cells were found to be

irregularly shaped, ____________________,

and this is how the disease got its name.

In normal red blood cells the

____________________ carries ___________

and distributes it around the body. In sickle cell

disease, the red blood cells are sickle–shaped,

causing the blood hemoglobin to no longer carry

oxygen as well and _____________________

like a sickle

hemoglobin molecule oxygen

disrupts the normal functioning of the bodies cells, tissues and organs

This person is deprived of oxygen and the result is physical weakness, and damage to the brain, heart, spleen. It may be fatal.

The cause: A _________________ in the DNA that

codes for Hemoglobin polypeptides is changed. This substitutes Valine for glutamic acid.

This change makes the hemoglobin less soluble in

blood. This will cause the hemoglobin to come out of the blood and _______________. This crystallization causes the ________________ of the blood cells and the medical consequences.

single base

crystallize

sickle shape

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 sequence

GUG 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 GAGVal – His – Leu – Thr – Pro – – 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 and in these areas it is _______________________ and therefore Sickle Cell Anemia persists.

favored by natural selection

HS HA

HS

HA

HS HS HS HA

HS HA HA HA

advantagemutation

Section 14-2: Human Chromosomes

Key concepts: Why are sex-linked disorders more

common in males than in females?

What is nondisjunction, and what problems does it

cause?

I. Human Genes and Chromosomes

Human diploid cell contains ______________________ of DNA. All neatly packed into the 46 chromosomes.

__________________ of the DNA actually functions as genes.

Genes are located on the chromosomes and each gene occupies a ______________________ on a chromosome.

Genes may exist in ____________________ (alleles)

Each chromosome contains ______ of the alleles for each of its genes

Chromosome #21 and 22 are the ____________ of the human autosomes. These were the first two chromosomes whose sequences had been determined.

6 billion base pairs

Small part

specific place

several formsone

smallest

Both also contain genes for some genetic

disorders like ________________________

___________________________

We also discovered that there are many

_________________________ segments of DNA

Human chromosomes also have

________________ that can cross over just as we

saw in the fruit fly.

Leukemia and Amyotrophic Lateral Sclerosis (ALS)

non-coding, repeating

Linked genes

II. Sex-linked Genes

1. _______________________ are the ones that

__________ in males and females

2. Chromosomes that are the ________ in male and females = _______________

3. In humans: females = ____ and Males = ____

4. The Y chromosome is smaller than the X

Sex Chromosomes

differ

sameautosomes

XX XY

A. Sex Determination

1. Female _________ carry an X chromosome

2. _________ 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 offspring

Female: XX

male: XY

gametes

Male50%

X

males determine the sex

X

YX

XX XY

XX XY

50%

In some animals such as birds, butterflies, and

some fish, the female determines the sex

because she has the __________ chromosomes.

Sex-linked Genes 1. In addition to determining the sex of an

individual, the sex chromosomes carry genes

that ____________________

differing

affect other traits.

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

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:

Colorblindness

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”.

Figure 21.12Page 394

I

II

III

IV

V

VI

Albert Victoria

Figure 21.134

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

III. X-Chromosomes InactivationMales survive with only one X chromosome so,

what do females do with 2? They ___________; it becomes inactive. This creates a dense region in the nucleus known as a ______________.

This is seen in coat color in cats. The cells will randomly shut off the coat color allele in one X chromosome and turn them off in the other X chromosome in other cells and this leads to some areas that are spotted orange and some spotted black, creating a tricolor cat, ________. This only happens in __________ because males only have one X chromosome.

shut one off

Barr body

calicofemales

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

Section 14-2 Nondisjunction

Go to Section:



Meiosis II

Section 14-2

Nondisjunction

Go to Section:



Meiosis II

Section 14-2

Go to Section:

Nondisjunction

n + 1

n + 1

n - 1

n - 1

chromosome alignments at metaphase I

nondisjunction at anaphase I

alignments at metaphase II

anaphase II gametes


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

inc

ide

nc

e p

er 1

,00

0 b

irth

s

20

15

10

5

020 25 30 35 40 45

mother's age

Fig. 21.20a,bPage 399

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 Chromosomes

Slide 25


XX

XX

O

XX

O

O

XX

Y

Y

X

X

x

x

x

x

XXY

XXX

YO

XO

gamete

nondisjunction

gamete

or

or

meiosis and gamete formation

possibilities at fertilization

genotype (phenotype)

(Klinefelter syndrome)

(“metafemale”)

(not viable)

(Turner syndrome)

The impact of the sex chromosome nondisjunction has led us to understand the importance of the _____________________ in determination of 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 ______________________ in the embryo even if many X chromosomes are present.

Y chromosome

male sexual development

dragonfly chapter 14 the human genome. section 14-1: human heredity key concepts: how is sex...

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