Click on a lesson name to select. Section 7.1: Chromosomes and Phenotipe Section7. 2: Complex Patterns of Inheritance Section 7.3: Chromosomes and Human

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Section 7.1: Chromosomes and Phenotipe

Section7. 2: Complex Patterns of Inheritance

Section 7.3: Chromosomes and Human Heredity

Ch. 7 Extending Mendelian Genetics

Complex Inheritance and Human Heredity

Pedigrees

A diagram that traces the inheritance of a particular trait through several generations

Basic Patterns of Human Inheritance


Inferring Genotypes

Knowing physical traits can determine what genes an individual is most likely to have.

Predicting Disorders

Record keeping helps scientists use pedigree analysis to study inheritance patterns, determine phenotypes, and ascertain genotypes.

Basic Patterns of Human Inheritance

Complex Patterns of Inheritance


Incomplete Dominance

The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.


Codominance

Both alleles are expressed in the heterozygous condition.


Sickle-cell disease is one example.


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

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Multiple Alleles

Blood groups in humans

ABO blood groups have three forms of alleles.



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.



Epistasis

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



Sex Determination

Sex chromosomes determine an individual’s gender.



Dosage Compensation

The X chromosome carries a variety of genes that are necessary for the development of both females and males.

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

In females, one X chromosome is inactivated in each cell. The inactivated X chromosome is visible in stained cells as a Barr body.



Sex-Linked Traits

Genes located on the X chromosome

Red-green color blindness

Hemophilia



Polygenic Traits

Polygenic traits arise from the interaction of multiple pairs of genes.



Environmental Influences

Environmental factors influence an organism’s phenotype

Diet and exercise

Sunlight and water Temperature



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.


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

Chromosomes and Human Heredity


Karyotype Studies

Images of chromosomes stained during metaphase

Chromosomes are arranged in decreasing size to produce a micrograph.


Telomeres

Telomere caps consist of DNA associated with proteins.

Serves a protective function for the structure of the chromosome



Nondisjunction

Cell division during which sister chromatids fail to separate properly

Down syndrome, also called trisomy 21


1. A2. B3. C4. D

CDQ 3

Complex Inheritance and Human HeredityChapter

Chapter Diagnostic Questions

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 2


A. DD

B. Dd

C. dd

D. dE

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

Section 1 Formative Questions

1. A2. B3. C4. D

FQ 3



A. at least one parent is a carrierB. 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


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



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



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


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



A. multiple alleles

B. nondisjunction

C. nonsynapsis

D. trisomy

What is occurring in this diagram?

1. A2. B3. C4. D

FQ 9



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


A. 1 and 2 are siblings

B. 1 and 2 are parents

C. 1 and 2 are offspring

D. 1 and 2 are carriers

What does the top horizontal line between numbers 1 and 2 in the figure indicates?

Chapter Assessment Questions

1. A2. B3. C4. D

CAQ 2



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



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?

Standardized Test Practice

1. A

2. B

3. C

STP 2



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



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



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



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?

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Click on a lesson name to select. Section 7.1: Chromosomes and Phenotipe Section7. 2: Complex Patterns of Inheritance Section 7.3: Chromosomes and Human