Genetic

Mariposa22

0134560981_ch02_mod2.1_lnppt.pptx

Home >Nursing homework help >Genetic

Discovering the Life Span

Fourth Edition

Chapter 2

The Start of Life

Module 2.1 Prenatal Development

Sections in Module 2.1

Earliest Development

The Interaction of Heredity and Environment

Learning Objectives (1 of 2)

2.1: Describe how genes and chromosomes provide our basic genetic endowment.

2.2: Explain the mechanisms by which genes transmit information.

2.3: Describe the role of genetic counselors and differentiate between different forms of prenatal testing.

2.4: Explain how the environment and genetics work together to determine human characteristics.

Learning Objectives (2 of 2)

2.5: Explain how genetics and the environment jointly influence physical traits, intelligence, and personality.

2.6: Describe ways in which genes influence the environment.

Earliest Development

Module 2.1 Prenatal Development

Genes and Chromosomes: The Code of Life (1 of 5)

LO 2.1 Describe how genes and chromosomes provide our basic genetic endowment.

Gametes

Male reproductive cell: sperm

Female reproductive cell: ovum

Humans begin life as a zygote—a single cell, formed by fusion of two gametes

Process of fusion called meiosis

Genes composed of DNA sequences (deoxyribonucleic acid)

Humans have more than 25,000 genes

Genes arranged along 46 chromosomes (in 23 pairs)

Figure 2-1: The Contents of a Single Human Cell

At the moment of conception, humans receive about 25,000 genes, contained on 46 chromosomes in 23 pairs.

Genes and Chromosomes: The Code of Life (2 of 5)

LO 2.1 Describe how genes and chromosomes provide our basic genetic endowment.

All cells duplicate through mitosis

Nearly all cells contain same 46 chromosomes of zygote

Tens of trillions possible genetic combinations

Multiple Births: Two—or More—for the Genetic Price of One

Less than 3 percent of pregnancies produce twins; three or more children even rarer

Chromosomes

At the moment of conception, humans receive 23 pairs of chromosomes, half from the mother and half from the father. These chromosomes contain thousands of genes.

Genes and Chromosomes: The Code of Life (3 of 5)

LO 2.1 Describe how genes and chromosomes provide our basic genetic endowment.

Multiple Births: Two—or More—for the Genetic Price of One

Monozygotic twins

Genetically identical

Form when cluster of cells in ovum split off in first few weeks

Dizygotic twins

No more genetically similar than two siblings

Formed when two separate ova are fertilized by two separate sperm

Genes and Chromosomes: The Code of Life (4 of 5)

LO 2.1 Describe how genes and chromosomes provide our basic genetic endowment.

Multiple Births: Two—or More—for the Genetic Price of One

Multiple births (triplets, quadruplets, etc.)

Can form from either of the previously mentioned mechanisms

Fertility drugs increases likelihood of multiple births

Older women more likely to have multiple births

Race impacts likelihood of multiple births

Caucasian: 1 in 86

African American: 1 in 70

Figure 2-2: Rising Multiples

The number and rate of twin births have risen considerably over the past three decades.

Source: Centers for Disease Control and Prevention (CDC)/National Center for Health Statistics (NCHS, 2012.

Genes and Chromosomes: The Code of Life (5 of 5)

LO 2.1 Describe how genes and chromosomes provide our basic genetic endowment.

Boy or Girl? Establishing the Sex of the Child

23rd chromosome determines the sex of the child

Females are XX

Males are XY

Father’s sperm determines sex

New techniques are available to specify in advance the sex of the child

Figure 2-3: Determining Sex

When an ovum and sperm meet at the moment of fertilization, the ovum is certain to provide an X chromosome, whereas the sperm will provide either an X or a Y chromosome. If the sperm contributes its X chromosome, the child will have an XX pairing on the 23rd chromosome and will be a girl. If the sperm contributes a Y chromosome, the result will be an XY pairing—a boy. Does this mean that girls are more likely to be conceived than boys?

The Basics of Genetics: The Mixing and Matching of Traits (1 of 6)

LO 2.2 Explain the mechanisms by which genes transmit information.

Gregor Mendel (mid-1800s) uncovers basic genetics

Dominant trait

Recessive trait

Genotype

Phenotype

Homozygous

Heterozygous

An Austrian monk, Gregor Mendel (mid-1800s), working with peas, discovered that when two competing traits were present only one could be expressed.

The trait that is expressed when two competing traits are present is called the DOMINANT TRAIT.

The trait that is present in the organism but not expressed is called the RECESSIVE TRAIT.

GENOTYPE is the underlying combination of genetic material present (but not outwardly visible) in an organism.

PHENOTYPE is an observable trait, the trait that is actually seen.

Alleles are genes for traits that may take alternate forms.

HOMOZYGOUS is inheriting from parents similar genes for a given trait.

HETEROZYGOUS is inheriting from parents different forms of a gene for a given trait.

The Basics of Genetics: The Mixing and Matching of Traits (2 of 6)

LO 2.2 Explain the mechanisms by which genes transmit information.

Transmission of Genetic Information

When parents are homozygous are dominant for a recessive gene, none of the children will be affected or carriers.

When one parent is heterozygous and one parent homozygous dominant for a recessive gene, none of the children will be affected, but 50 percent become carriers.

When parents are heterozygous for a recessive gene, 25 percent of children will be affected and 50 percent will be carriers.

The Basics of Genetics: The Mixing and Matching of Traits (3 of 6)

LO 2.2 Explain the mechanisms by which genes transmit information.

Polygenic Traits

Polygenic inheritance: Combination of multiple gene pairs is responsible for production of a particular trait

Some genes come in several alternate forms

Some modify the way genetic traits are displayed

Some vary in their reaction range (variability of expression due to environmental conditions)

X-linked genes are located on X chromosome

Males have higher incidence of X-linked disorders

Figure 2-4: PKU Probabilities

Phenylketonuria (PKU), a disease that causes brain damage and intellectual disabilities, is produced by a single pair of genes inherited from one’s mother and father. If neither parent carries a gene for the disease, (a), a child cannot develop PKU. Even if one parent carries the recessive gene, but the other doesn’t, (b) the child cannot inherit the disease. However, if both parents carry the recessive gene, (c) there is a one in four chance that the child will have PKU.

The Basics of Genetics: The Mixing and Matching of Traits (4 of 6)

LO 2.2 Explain the mechanisms by which genes transmit information.

The Human Genome and Behavior Genetics: Cracking the Genetic Code

Human genome mapped in 2001

Number of human genes is 25,000

99.9 percent of the gene sequence is shared by all humans

Behavioral genetics

Field studies transmission of characteristics through heredity

Helping to uncover how behavioral difficulties may have genetic basis (ex: Schizophrenia)

Figure 2-5: Uniquely Human?

Humans have about 25,000 genes, making them not much more genetically complex than some primitive species.

Source: Celera Genomics: International Human Genome Sequencing Consortium, 2001.

The Basics of Genetics: The Mixing and Matching of Traits (5 of 6)

LO 2.2 Explain the mechanisms by which genes transmit information.

Inherited and Genetic Disorders: When Development Deviates from the Norm

Some disorders are inherited (ex: PKU)

Some result from damaged genes

Some genes spontaneously change their form (spontaneous mutation)

Exposure to some things (ex: X-rays) can produce malformed genetic material

The Basics of Genetics: The Mixing and Matching of Traits (5 of 5)

LO 2.2 Explain the mechanisms by which genes transmit information.

Inherited and Genetic Disorders: When Development Deviates from the Norm

Disorders

Down syndrome

Fragile X

Sickle-Cell anemia

Tay-Sachs disease

Klinefelter’s syndrome

DOWN SYNDROME is a disorder produced by the presence of an extra chromosome on the 21st chromosome pair, once referred to as mongolism.

FRAGILE X SYNDROME is a disorder produced by injury to a gene on the X chromosome, producing mild to moderate mental retardation.

SICKLE-CELL ANEMIA is a blood disorder that gets its name from the shape of the red blood cells in those who have it.

TAY-SACHS DISEASE is an untreatable disorder that produces blindness and muscle degeneration prior to death.

One male out of every 400 is born with KLINEFELTER’S SYNDROME, a disorder resulting from the presence of an extra X chromosome that produces underdeveloped genitals, extreme height, and enlarged breasts.

Genetic Counseling: Predicting the Future from the Genes of the Present (1 of 3)

LO 2.3 Describe the role of genetic counselors and differentiate between different forms of prenatal testing.

Genetic counseling: Discipline focuses on helping people deal with issues related to inherited disorders

Genetic counselors use a variety of data:

Family history

Parents’ ages

Blood, skin, urine samples

Karyotype is a chart containing enlarged photos of each chromosome

Genetic Counseling: Predicting the Future from the Genes of the Present (2 of 3)

LO 2.3 Describe the role of genetic counselors and differentiate between different forms of prenatal testing.

Prenatal Testing: Tests done once woman is pregnant

Ultrasound sonography

Chorionic villus sampling (CVS)

Amniocentesis

ULTRASOUND SONOGRAPHY is a process in which high-frequency sound waves scan the mother’s womb to produce an image of the unborn baby whose size and shape can then be assessed.

CHORIONIC VILLUS SAMPLING (CVS) is a test used to find genetic defects that involves taking samples of hairlike material that surrounds the embryo.

AMNIOCENTESIS is the process of identifying genetic defects by examining a small sample of fetal cells drawn by a needle inserted into the amniotic fluid surrounding the unborn fetus.

Amniocentesis

In amniocentesis, a sample of fetal cells is withdrawn from the amniotic sac and used to identify a number of genetic defects.

Genetic Counseling: Predicting the Future from the Genes of the Present (3 of 3)

LO 2.3 Describe the role of genetic counselors and differentiate between different forms of prenatal testing.

Screening for Future Problems

Currently genetic counselor tests parents for susceptibility to disorders due to genetic abnormalities

More than 1,000 disorders, such as Huntington’s disease, can be predicted based on genetic testing

Germ line therapy: Process by which genetic modifications can correct defective genes in unborn children

From Research to Practice: Prenatal Screenings Are Not Diagnoses

High-risk patients offered prenatal screenings

Positive results are often misinterpreted

Better understanding of results and referrals to genetic specialists are important

Review: Earliest Development

A child receives 23 chromosomes from each parent.

These 46 chromosomes provide a genetic blueprint.

A genotype is the combination of genetic material.

A phenotype is the visible trait.

Recessive linked disorders can only be transmitted if both the mother and father pass on the recessive gene.

Genetic counselors use a variety of data.

Techniques used to assess the health of an unborn child include ultrasound, CVS, and amniocentesis.

Check Yourself: Earliest Development (1 of 2)

Sex cells (the ova and the sperm) are different from other cells because they:

A) have twice the 46 chromosomes necessary so that when the cells combine and material is “spilled,” the appropriate number of chromosomes will still be there.

B) each has half of the 46 chromosomes so that when they combine, the new zygote will have all the genetic information necessary.

C) are younger than all other cells in the developing human body.

D) are the only cells with chromosomal information.

Answer: B

Check Yourself: Earliest Development (2 of 2)

According to Mendel, when competing traits are both present, only one trait, also known as the __________ trait, can be expressed.

A) homozygous

B) recessive

C) polygenic

D) dominant

Answer: D

The Interaction of Heredity and Environment

Module 2.1 Prenatal Development

The Role of the Environment in Determining the Expression of Genes: From Genotypes to Phenotypes (1 of 3)

LO 2.4 Explain how the environment and genetics work together to determine human characteristics.

Temperament is patterns of arousal and emotionality that represent consistent and enduring characteristics in an individual

Interaction of Factors

Multifactorial transmission: Determination of traits by a combination of genetic and environmental factors

Some genotypes are not as sensitive to the environment as others

The Role of the Environment in Determining the Expression of Genes: From Genotypes to Phenotypes (2 of 3)

LO 2.4 Explain how the environment and genetics work together to determine human characteristics.

Studying Development: How Much Is Nature? How Much Is Nurture?

The question is not whether a behavior is caused by nature or nurture, but by how much

Nonhuman Animal Studies: Controlling Both Genetics and Environment

Scientists study effects of environmental stimulation by:

Placing genetically similar animals in different environments

Placing genetically different animals in similar environments

The Role of the Environment in Determining the Expression of Genes: From Genotypes to Phenotypes (3 of 3)

LO 2.4 Explain how the environment and genetics work together to determine human characteristics.

Studying Development: How Much Is Nature? How Much Is Nurture?

Contrasting Relatedness and Behavior: Adoption, Twin and Family Studies

Differences between monozygotic twins separated at birth can give information on the role of environment

If monozygotic twins are more similar than dizygotic on a trait, genetics plays a role

People genetically unrelated raised in the same environment provide information about the role of the environment

Biological and adoptive parents and their children help us see effects of heredity and environment

Both play a role in traits, characteristics, and behaviors

Genetics and the Environment: Working Together (1 of 4)

LO 2.5 Explain how genetics and the environment jointly influence physical traits, intelligence, and personality.

Physical Traits: Family Resemblances

Genetic similarities result in similar physical features

Intelligence: More Research, More Controversy

Genetics is important but environment also important

Figure 2-6: Genetics and IQ

The closer the genetic link between two individuals, the greater the correspondence between their IQ scores. Why do you think there is a sex difference in the fraternal twins’ figures? Might there be other sex differences in other sets of twins or siblings, not shown on this chart?

Source: Based on Bouchard & McGue, 1981

Genetics and the Environment: Working Together (2 of 4)

LO 2.5 Explain how genetics and the environment jointly influence physical traits, intelligence, and personality.

Genetic and Environmental Influences on personality: Do We Inherit Our Personality?

Some personality traits have genetic components

Two of the “Big Five” have been linked to genetic stability:

Neuroticism

Extroversion

Certain traits reflect the contribution of genetics more than others:

Direct examination of genes

Studies of twins

The environment also plays a role in personality

Figure 2-7: Inheriting Traits

These traits are among the personality factors that are related most closely to genetic factors. The higher the percentage, the greater the degree to which the trait reflects the influence of heredity. Do these figures mean that “leaders are born, not made”? Why or why not?

Source: Adapted from Tellegen et al., 1988.

Genetics and the Environment: Working Together (3 of 4)

LO 2.5 Explain how genetics and the environment jointly influence physical traits, intelligence, and personality.

Psychological Disorders: The Role of Genetics and Environment

Several disorders brought about by genetic factors:

Schizophrenia spectrum disorder

Major depression

Alcoholism

Autism spectrum disorder

Attention-deficit hyperactivity disorder

Figure 2-8: The Genetics of Schizophrenia

The psychological disorder of schizophrenia has clear genetic components. The closer the genetic links between someone with schizophrenia and another family member, the more likely it is that the other person will also develop schizophrenia.

Source: Based on Gottesman, 1991.

Genetics and the Environment: Working Together (4 of 4)

LO 2.5 Explain how genetics and the environment jointly influence physical traits, intelligence, and personality.

Psychological Disorders: The Role of Genetics and Environment

Genetics alone does not influence development of disorders

If genetics is the sole cause, the concordance rate for identical twins would be 100 percent

Genetics can produce a tendency toward future development of disorder

Environment determines if the genetic tendency will be displayed

Cultural Dimensions: Cultural Differences in Physical Arousal: Might a Culture’s Philosophical Outlook Be Determined by Genetics?

Jerome Kagan and colleagues (1993, 2003, 2010) propose the underlying temperament of a society may define its philosophy.

Based on confirmed differences in temperament between Caucasian and Asian children

Kagan believes that Chinese enter world calmer and find Buddhist notions more in tune with their nature

Westerners more volatile; may focus on philosophies that emphasize the control of unpleasant feelings

This speculation reflects complex interaction between culture and temperament

Can Genes Influence the Environment?

LO 2.6 Describe ways in which genes influence the environment.

Sandra Scarr suggests genetic endowment also influences environment.

Children focus on aspects of their environment that are most in tune with genetic abilities

Gene-environment influence is more passive, less direct

Genetically driven temperament of a child may evoke certain environmental influences

Review: The Interaction of Heredity and Environment

Behavioral characteristics are often determined by both genetics and environment.

The genotype is the genetic contribution while phenotype is the expression of the genes in observable traits.

Traits, characteristics, and behaviors are all due to nature and nurture.

Some personality traits have been linked to genetic factors.

Children may influence their environment through genetic traits.

They can create an environment that matches their disposition.

Check Yourself: The Interaction of Heredity and Environment (1 of 2)

Most behavioral traits are a product of genetic influence and environmental factors. This is also known as __________.

A) systematic desensitization

B) creative orientation

C) genetic predetermination

D) multifactorial transmission

Answer: D

Check Yourself: The Interaction of Heredity and Environment (2 of 2)

According to psychologist Jerome Kagan, differences in temperament between Chinese and American Children suggest a culture’s philosophical outlook may be related to ___________ factors.

A) environmental

B) genetic

C) cultural

D) social

Answer: B

Applying Lifespan Development

How might an environment different from the one you experienced have affected the development of personality characteristics that you believe you inherited from one or both of your parents?

Photo Credits

p. 43 CNRI/Science Source; p. 47 Bill Longcore/Science Source; p. 49 Saturn Stills/Science Source; p. 52 Michael Shaw/New Yorker Cartoon Bank; p. 54 Dotshock/Shutterstock; p. 56 Ingram Publishing/Newscom; p. 62 (L) Science Source p. 62 (C) Science Pictures Ltd./Science Source; p. 62 (R) Science Source; p. 64 William Hamilton/The New Yorker Collection/www.cartoonbank.com; p. 69 Monkey Business/Fotolia; p. 71 Robert Azmitia/KRT/Newscom; p. 75 Toos/Getty Images; p. 76 Ross Marks Photography/Alamy Stock Photo; p. 78 Diane Macdonald/Stockbyte/Getty Images; p. 80 Paul Hakimata Photography/Shutterstock; p. 82 Tyler Olson/Fotolia; p. 87 nyul/Fotolia; p. 90 wong sze yuen/Fotolia; p. 93 Andersen Ross/Blend Images/Getty Images; p. 94 (top L) Photodisc/Getty Images; p. 94 (top R) Mark Andersen/Rubberball/Getty Images; p. 94 (bottom L) Ljupco Smokovski/Fotolia; p. 94 (bottom R) Get4net/Fotolia