Chapter 29:Heredity

Clarence E. McClung - one of the first (1901) to deduce that chromosomes determine the sex of offspring.

Figure 29.1

Figure 29.1c

1

5

4

3

2

Removed stamensfrom purple flower

Transferred sperm-bearing pollen fromstamens of white flower to egg-bearing carpel of purple flower

Parentalgeneration(P)

Pollinated carpelmatured into pod

Carpel(female)

Stamens(male)

Planted seedsfrom pod

Examinedoffspring:all purpleflowers

Firstgenerationoffspring(F1)

APPLICATION By crossing (mating) two true-breedingvarieties of an organism, scientists can study patterns ofinheritance. In this example, Mendel crossed pea plantsthat varied in flower color.

TECHNIQUETECHNIQUE

When pollen from a white flower fertilizeseggs of a purple flower, the first-generation hybrids all have purpleflowers. The result is the same for the reciprocal cross, the transferof pollen from purple flowers to white flowers.

TECHNIQUERESULTS

P Generation

(true-breeding parents) Purple

flowersWhiteflowers

F1 Generation (hybrids)

All plants hadpurple flowers

F2 Generation

EXPERIMENT True-breeding purple-flowered pea plants andwhite-flowered pea plants were crossed (symbolized by ). Theresulting F1 hybrids were allowed to self-pollinate or were cross-pollinated with other F1 hybrids. Flower color was then observedin the F2 generation.

RESULTS Both purple-flowered plants and white-flowered plants appeared in the F2 generation. In Mendel’sexperiment, 705 plants had purple flowers, and 224 had whiteflowers, a ratio of about 3 purple : 1 white.

Allele for purple flowers

Locus for flower-color gene

Homologouspair ofchromosomes

Allele for white flowers

P Generation

F1 Generation

P p

Appearance:Genetic makeup:

Purple flowerPP

White flowerspp

Purple flowersPp

Appearance:Genetic makeup:

Gametes:

Gametes:

Each true-breeding plant of the parental generation has identicalalleles, PP or pp.

Gametes (circles) each contain only one allele for the flower-color gene. In this case, every gamete produced by one parent has the same allele.

Union of the parental gametes produces F1 hybrids having a Pp combination. Because the purple-flower allele is dominant, allthese hybrids have purple flowers.

When the hybrid plants producegametes, the two alleles segregate, half the gametes receiving the P allele and the other half the p allele.

P Generation

F1 Generation

F2 Generation

P p

P p

P p

P

p

PpPP

ppPp

Appearance:Genetic makeup:

Purple flowerPP

White flowerspp

Purple flowersPp

Appearance:Genetic makeup:

Gametes:

Gametes:

F1 sperm

F1 eggs

1/21/2

Each true-breeding plant of the parental generation has identicalalleles, PP or pp.

Gametes (circles) each contain only one allele for the flower-color gene. In this case, every gamete produced by one parent has the same allele.

Union of the parental gametes produces F1 hybrids having a Pp combination. Because the purple-flower allele is dominant, allthese hybrids have purple flowers.

When the hybrid plants producegametes, the two alleles segregate, half the gametes receiving the P allele and the other half the p allele.

This box, a Punnett square, shows all possible combinations of alleles in offspring that result from an F1 F1 (Pp Pp) cross. Each square represents an equally probable product of fertilization. For example, the bottomleft box shows the genetic combinationresulting from a p egg fertilized bya P sperm.

Random combination of the gametesresults in the 3:1 ratio that Mendelobserved in the F2 generation. 3 : 1

3

1 1

2

1

Phenotype

Purple

Purple

Purple

White

Genotype

PP(homozygous)

Pp(heterozygous)

Pp(heterozygous)

pp(homozygous)

Ratio 3:1 Ratio 1:2:1

Table 14.2 Determination of ABO Blood Group by Multiple Alleles

BC bC Bc bc1⁄41⁄41⁄41⁄4

BC

bC

Bc

bc

1⁄4

1⁄4

1⁄4

1⁄4

BBCc BbCc BBcc Bbcc

Bbcc bbccbbCcBbCc

BbCC bbCC BbCc bbCc

BBCC BbCC BBCc BbCc

9⁄163⁄16

4⁄16

BbCc BbCc

Sperm

Eggs

Skin Color

AaBbCc AaBbCc

aabbcc Aabbcc AaBbcc AaBbCc AABbCcAABBCc AABBCC

20⁄64

15⁄64

6⁄64

1⁄64

Fra

cti

on

of

pro

ge

ny

Pedigree analysis

Ww ww ww Ww

wwWwWwwwwwWw

WWor

Ww

ww

First generation(grandparents)

Second generation(parents plus aunts

and uncles)

Thirdgeneration

(two sisters)

Ff Ff ff Ff

ffFfFfffFfFF or Ff

ff FForFf

Widow’s peak No Widow’s peak Attached earlobe Free earlobe

(a) Dominant trait (widow’s peak) (b) Recessive trait (attached earlobe)

Figure 14.15 Achondroplasia

(a) Amniocentesis

Amnioticfluidwithdrawn

Fetus

Placenta Uterus Cervix

Centrifugation

A sample ofamniotic fluid canbe taken starting atthe 14th to 16thweek of pregnancy.

(b) Chorionic villus sampling (CVS)

Fluid

Fetalcells

Biochemical tests can bePerformed immediately onthe amniotic fluid or lateron the cultured cells.

Fetal cells must be culturedfor several weeks to obtainsufficient numbers forkaryotyping.

Severalweeks

Biochemicaltests

Severalhours

Fetalcells

Placenta Chorionic viIIi

A sample of chorionic villustissue can be taken as earlyas the 8th to 10th week ofpregnancy.

Suction tubeInserted throughcervix

Fetus

Karyotyping and biochemicaltests can be performed onthe fetal cells immediately,providing results within a dayor so.

Karyotyping

Figure 29.2

Figure 29.3

Figure 29.4

Figure 29.5

Figure 29.6

Figure 29.7

Table 29.1

Table 29.2

I > Clicker Question

General Topic QuestionThe condition in which the body maintains homeostasis would best be described as

A) the highest possible metabolism.B) a state that fluctuates widely from person to person.C) a relatively stable internal environment depending

upon environmental conditions.D) a static state with absolutely no deviation from preset

points (120/80 being normal blood pressure, for example).

E) Two of the above is correct.

General Topic QuestionWhen you think of the lymphatic system, which of the following are correct?

A) Lymph is a watery solution that typically pools and collects on the inside of the cells and needs to be collected and transported back to the lymph nodes.

B) Fluid moves away from the circulatory system while in lymphatic vessels.

C) This system houses many of the immune response cells of the body.

D) Two of the above are correct.E) None of the above are correct.

Semester Specific General QuestionHormones used in the short term stress response would be

A) aldosterone and norepinephrine.B) cortisol and thymosin.C) epinephrine and norepinephrine.D) aldosterone and adrenalin.E) Two of the above are correct.

Semester Specific General QuestionWhich statement best describes veins?

A) All carry blood toward the heart.B) None carry oxygenated blood.C) Most contain valves to prevent the

backflow of blood.D) Two of the above are descriptive of veins.E) All of the above are correct.

New Information Style QuestionIn a pedigree chart, a female who does not demonstrate the trait being studied is represented by a

A) darkened square.B) clear diamond.

C) clear circle.D) darkened triangle.E) darkened oval.

The reason the hypodermis is protective isA) it has no delicate blood vessels and can therefore

absorb more shock.B) because a major part of its makeup is adipose, and

adipose tissue serves as an effective shock absorber... minimizing damage.

C) it is located just below the epidermis and protects the dermis from shock.

D) All of the above are correct.

I > Clicker Question

The process by which liquid-containing vesicles are expelled out of a cell is called

A) pinocytosis.B) phagocytosis.C) exocytosis.D) receptor-mediated endocytosis.E) channel-mediated transport.

The muscle type found in the vena cava (the blood vessel that brings blood to the heart) is

A) cardiac.B) smooth.C) skeletal.D) voluntarily controlled.E) Two of the above are correct

An exocrine glandA) secretes material into the bloodstream.B) expels material outside the body.C) would be a likely mechanical device for the

expression of elastophosphoids.D) Two of the above are correct.E) All of the above are

Coating the skin and hair with oil is an activity of A) the sebaceous glands.B) a type of endocrine gland.C) a clathrin mediated receptor interaction.D) Two of the above are correct.E) All of the above are

You are a new medical intern at St. Mary’s of Michigan Hospital in Saginaw. Dee Gordon, the famous player for the Great Lakes Loons, comes into your office saying his previous doctor told him he had bursitis, you immediately would recognize that this disorder would be designated as inflammation of

A) an epiphyseal disk.B) a cavity within a long bone filled with synovial

fluid.C) a membrane sac containing fluid, probably at

the elbow.D) a cartilage at a joint, such as the knee.

Think logically for this question.... If a muscle were stretched to the point where actin filaments and myosin filaments no longer overlapped,

A) ADP consumption would increase since the sarcomere is “trying” to contract.

B) cross-bridge attachment would be optimum because of all the free binding sites on actin.

C) no muscle tension could be generated.D) maximum force production would result since the

muscle has a maximum range of travel.E) Two of the above are

I > Clicker Question

Homeostasis of calcium ion concentration depends upon which of the following hormones?

A) Parathymus hormoneB) Calcitonin C) ThyroxineD) Two of the above are correct.E) None of the above are correct.

1) In total cross sectional area, there is more area devoted to capillaries than arteries and therefore 2) the blood pressure in the capillary beds is much lower.

A) Statements 1 & 2 are both true.B) Statement 1 is true and statement 2 is false.C) Statement 1 is false and statement 2 is true.D) Statements 1 & 2 are both false.

The term given to the shape of the erythrocyte in humans is

A) dual convex disk.B) biconcave disk.C) sickle shaped cell.D) myopic disk.E) None of the above are correct.

What is the main function of binocular vision?A) Depth perceptionB) Color visionC) Vision in dim lightD) Accommodation for near visionE) Two of the above are correct.

Human egg and sperm are similar in thatA) about the same number of each are

produced per month.B) they have the same degree of motility.C) they are about the same size.D) they have the same number of

chromosomes.

The chemical and mechanical processes of food breakdown are called

A) absorption.B) ingestion.C) digestion.D) secretion.