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Section 1: Basic Patterns of Human Inheritance

Section 2: Complex Patterns of Inheritance

Section 3: Chromosomes and Human Heredity

Chapter 11 Complex Inheritance and Human Heredity

11.1 Basic Patterns of Human Inheritance

Complex Inheritance and Human HeredityChapter 11

Recessive Genetic Disorders

A recessive trait is expressed when the individual is homozygous recessive for the trait.

Complex Inheritance and Human Heredity

Cystic Fibrosis

Affects the mucus-producing glands, digestive enzymes, and sweat glands

Chloride ions are not absorbed into the cells of a person with cystic fibrosis but are excreted in the sweat.

Without sufficient chloride ions in the cells, a thick mucus is secreted.


Chapter 11


Albinism

Caused by altered genes, resulting in the absence of the skin pigment melanin in hair and eyes

White hair

Very pale skin

Pink pupils


Chapter 11


Tay-Sachs Disease

Caused by the absence of the enzymes responsible for breaking down fatty acids called gangliosides

Gangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration.


Chapter 11


Galactosemia

Recessive genetic disorder characterized by the inability of the body to digest galactose.


Chapter 11

Dominant Genetic Disorders

• These diseases are caused when an individual is homozygous dominant or heterozygous

• In order to NOT HAVE THESE DISEASES the normal person is homozygous recessive


Dominant Genetic Disorders

Huntington’s disease affects the nervous system.

Achondroplasia is a genetic condition that causes small body size and limbs that are comparatively short. (this is a type of dwarfism)


Chapter 11



Chapter 11


Pedigrees A diagram that traces the inheritance of a particular

trait through several generations of the same family


Chapter 11


Inferring Genotypes

Knowing physical traits can determine what genes an individual is most likely to have. Scientists can determine if a trait is dominant or recessive

Predicting Disorders Record keeping helps scientists use

pedigree analysis to study inheritance patterns, determine phenotypes, and ascertain genotypes.


Chapter 11

11.2 Complex Patterns of Inheritance


Incomplete Dominance

The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes. (it is a mix of physical appearance between the dominant and the recessive)

Chapter 11


Codominance

Both alleles are expressed in the heterozygous condition.


Chapter 11


Sickle-cell Disease

Changes in hemoglobin cause red blood cells to change to a sickle shape.

People who are heterozygous for the trait have both normal and sickle-shaped cells. Sickle cell

Normal red blood cell

7766x


Chapter 11

Sickle-cell disease and Malaria

• In Africa there is a high number of people who have the sickle-cell allele.

• People who are heterozygous for sickle-cell have a higher resistance to malaria.

• They go on to reproduce and pass on the sickle-cell trait.


Multiple Alleles

Blood groups in humans (this shows both multiple alleles and codominance)

ABO blood groups have three forms of alleles.


Chapter 11


Coat Color of Rabbits

Multiple alleles can demonstrate a hierarchy of dominance.

In rabbits, four alleles code for coat color: C, cch, ch, and c.

C>cch> ch>c (this shows that one is dominant to the next with “c” being least dominant)

There are 10 possible genotypes and four phenotypes for rabbit fur color


Chapter 11


Coat Color of Rabbits

Light gray

Dark gray Himalayan

Albino

Chinchilla


Chapter 11


Epistasis

Variety is the result of one allele hiding the effects of another allele.

No dark pigment present in fur Dark pigment present in fur

eebbeeB_ E_bb E_B_


Chapter 11

Labrador Coat Color

• There are two sets of alleles (“E” and “B”) that determine whether the fur will be dark or not.

• If the dog has Ee or EE it will make the fur color dark (it is written as Eebb or EEbb)

• If the dog has ee then the fur coat will be light (eebb, eeBb, eeBB) and produce a yellow coat


Sex Determination

Sex chromosomes determine an individual’s gender.

Autosomes are all the other chromosomes that determine everything else. (ie. Body cells)


Chapter 11


Dosage Compensation The X chromosome carries a variety of genes

that are necessary for the development of both females and males. (Thus, it is larger than the Y chromosome)

The Y chromosome mainly has genes that relate to the development of male characteristics.


Chapter 11

• Chromosome inactivation– Coat color of the calico cat is determined by which

X chromosome is deactivated. If the X chromosome that carries the dark coat color is inactivated, the cat will have orange coloring. If the X chromosome that carries the orange coat color is inactivated, the cat will have black spots.

– Barr bodies: the inactivated X chromosome in females


Sex-Linked Traits

Genes located on the X chromosome that control traits

Since males have only 1 X chromosome they are affected by recessive X-linked traits

Females are less likely to express a recessive trait because she has two X chromosomes. One of the X chromosomes can mask the affect of the trait.


Chapter 11

Sex-Linked Traits


Sex-Linked Traits

Red-green color blindness This is a recessive X-linked trait. A male only

needs one copy of this allele in order to be colorblind.

A female would need to have two copies of the recessive allele. Thus it is very rare to find a color blind female.


Chapter 11

Sex-Linked Traits

Hemophilia

• Another recessive sex-linked disorder characterized by delayed clotting of the blood.

• Very rare in females because she would need to have both X chromosomes with the recessive trait.


Polygenic Traits

Polygenic traits arise from the interaction of multiple pairs of genes. This is really how height, eye color and fingerprints are inherited.


Chapter 11


Environmental Influences on phenotype

Environmental factors

Diet and exercise

Sunlight and water (flowering in plants)

Temperature (arctic fox)


Chapter 11


Twin Studies

Helps scientists separate genetic contributions from environmental contributions

Traits that appear frequently in identical twins are at least partially controlled by heredity.

Traits expressed differently in identical twins are strongly influenced by environment.


Chapter 11

Karyotype—micrograph in which the pairs of homologous chromosomes are arranged in decreasing size.

11.3 Chromosomes and Human Heredity


Karyotype Studies

Images of chromosomes stained during metaphase

Chromosomes are arranged in decreasing size to produce a micrograph.

Chapter 11


Telomeres

Telomere caps consist of DNA associated with proteins.

Serves a protective function for the structure of the chromosome

They might also be involved in aging and cancer


Chapter 11


Nondisjunction

Cell division during which sister chromatids fail to separate properly

If this occurs during Meiosis I or II then the resulting gametes will not have the correct number of chromosomes

Down syndrome: nondisjunction occurred on chromosome 21.The result is short stature, heart defects, and mental disability


Chapter 11

Nondisjunction

• Nondisjunction occurs in both autosomes (body cells) and in gametes

Centromere

Sisterchromatids

Pair of homologouschromosomes

5


Chapter Resource Menu

Chapter Diagnostic Questions

Formative Test Questions

Chapter Assessment Questions

Standardized Test Practice

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Chapter 11

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1. A2. B3. C4. D

CDQ 1

0% 0%0%0%

A. albinism

B. cystic fibrosis

C. galactosemia

D. Tay-Sachs

Identify the disease characterized by the absence of melanin.



1. A2. B3. C4. D

CDQ 2

0% 0%0%0%



A. excessive mucus production

B. an enlarged liver

C. a cherry-red spot on the back of the eye

D. vision problems

An individual with Tay-Sachs disease would be identified by which symptom?

1. A2. B3. C4. D

CDQ 3

0% 0%0%0%



Under what circumstances will a recessive trait be expressed?

A. A recessive allele is passed on by both parents.

B. One parent passes on the recessive allele.

C. The individual is heterozygous for the trait.

D. There is a mutation in the dominant gene.

1. A2. B3. C4. D

FQ 1

0% 0%0%0%


A. It appears at birth and runs in families.

B. It is linked to an enzyme deficiency.

C. It continues throughout a patient’s life, affecting bones and joints.

D. It is caused by acid excretion and results in black urine.

Which of Dr. Garrod’s observations about alkaptonuria was most critical to his determination that it is a genetic disorder?

11.1 Formative Questions

1. A2. B3. C4. D

FQ 2

0% 0%0%0%


A. DD

B. Dd

C. dd

D. dE

Which is the genotype of a person who is a carrier for a recessive genetic disorder?


1. A2. B3. C4. D

FQ 3

0% 0%0%0%



A. at least one parent is a carrier

B. both parents are carriersC. both parents are

homozygous recessiveD. at least one parent is

homozygous dominant

Albinism is a recessive condition. If an albino squirrel is born to parents that both have normal fur color, what can you conclude about the genotype of the parents?

1. A2. B3. C4. D

FQ 4

0% 0%0%0%


A. dosage compensation

B. incomplete dominance

C. multiple alleles

D. sex-linked

When a homozygous male animal with black fur is crossed with a homozygous female with white fur, they have offspring with gray fur. What type of inheritance does this represent?


1. A2. B3. C4. D

FQ 5

0% 0%0%0%



A. autosomes

B. Barr bodies

C. monosomes

D. sex chromosomes

Of the 23 pairs of chromosomes in human cells, one pair is the _______.

1. A2. B3. C4. D

FQ 6

0% 0%0%0%



A. blood type

B. color blindness

C. hemophilia

D. skin color

Which is an example of a polygenic trait?

1. A2. B3. C4. D

FQ 7

0% 0%0%0%


A. The blood type of an individual.

B. The locations of genes on a chromosome.

C. The cell’s chromosomes arranged in order.

D. The phenotype of individuals in a pedigree.

What does a karyotype show?


1. A2. B3. C4. D

FQ 8

0% 0%0%0%



A. multiple alleles

B. nondisjunction

C. nonsynapsis

D. trisomy

What is occurring in this diagram?

1. A2. B3. C4. D

FQ 9

0% 0%0%0%



A. Down syndrome

B. Klinefelter’s syndrome

C. Tay-Sachs syndrome

D. Turner’s syndrome

What condition occurs when a person’s cells have an extra copy of chromosome 21?

1. A2. B3. C4. D

CAQ 1

0% 0%0%0%


A. 1 and 2 are siblings

B. 1 and 2 are parents

C. 1 and 2 are offspring

D. 1 and 2 are carriers

Use the figure to describe what the top horizontal line between numbers 1 and 2 indicates.


1. A2. B3. C4. D

CAQ 2

0% 0%0%0%



A. IA

B. IO

C. IB

D. i

Which is not an allele in the ABO blood group?

1. A2. B3. C4. D

CAQ 3

0% 0%0%0%



A. one less chromosome on pair 12

B. one extra chromosome

on pair 21C. one less chromosome

on pair 21D. one extra chromosome

on pair 12

Down Syndrome results from what change in chromosomes?

1. A

2. B

3. C

STP 1


A. heterozygous

B. homozygous dominant

C. homozygous recessive

If a genetic disorder is caused by a dominant allele, what is the genotype of those who do not have the disorder?


0% 0%0%

1. A

2. B

3. C

STP 2



0% 0%0%

A. RR

B. Rr

C. rr

Analyze this pedigree showing the inheritance of a dominant genetic disorder. Which would be the genotype of the first generation father?

1. A2. B3. C4. D

STP 3

0% 0%0%0%



A. codominance

B. dosage compensation

C. epistasis

D. sex-linked

Shorthorn cattle have an allele for both red and white hair. When a red-haired cow is crossed with a white-haired bull, their calf has both red and white hairs scattered over its body. What type of inheritance does this represent?

1. A2. B3. C4. D

STP 4

0% 0%0%0%



A. Males have only one X chromosome.

B. Males have two X chromosomes.

C. Males have only one Y chromosome.

D. The traits are located on the Y chromosomes.

Why are males affected by recessive sex-linked traits more often than are females?

1. A2. B3. C4. D

STP 5

0% 0%0%0%



A. 25%

B. 50%

C. 75%

D. 100%

A carrier of hemophilia and her husband, who is unaffected by the condition, are expecting a son. What is the probability that their son will have hemophilia?


Glencoe Biology Transparencies


Image Bank

carrier

pedigree


Vocabulary

Section 1

incomplete

dominance

codominance

multiple alleles

epistasis

sex chromosome

autosome

sex-linked trait

polygenic trait


Vocabulary

Section 2

karyotype

telomere

nondisjunction


Vocabulary

Section 3


Animation

Visualizing Nondisjunction

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