DEV2004 - Chapter 2 Heredity and Genetic Basics

Questions and Answers

What is a key characteristic of homozygous traits?

They express only when paired with a dominant gene.

They are always recessive traits.

They display the characteristic regardless of the paired gene. (correct)

They require one dominant gene to be expressed.

What distinguishes dizygotic twins from monozygotic twins?

Dizygotic twins share the same genotype.

Monozygotic twins come from a single fertilized egg. (correct)

Monozygotic twins arise from two separate eggs.

Dizygotic twins are genetically identical.

Which statement accurately describes recessive genes?

They are always found on sex chromosomes.

They are always dominant in expression.

They manifest only when paired with another recessive version. (correct)

They express traits when paired with a different version.

Which scenario exemplifies incomplete dominance?

An individual with only one copy of a recessive sickle cell gene displaying some symptoms. Signup and view all the answers

Which of these traits is considered dominant?

Curly hair Signup and view all the answers

What is the probability of having genetically identical offspring that are not twins?

One in trillions Signup and view all the answers

What are autosomes?

All chromosomes except for sex chromosomes. Signup and view all the answers

Under what circumstances might carriers of the sickle cell gene experience symptoms of the disorder?

During high altitudes or physical exertion. Signup and view all the answers

Which characteristic is true regarding polygenic traits?

They involve multiple genes contributing to the phenotype. Signup and view all the answers

What is the main reason older mothers are more likely to have dizygotic twins?

Age increases the number of eggs released. Signup and view all the answers

Which of the following statements about dominant gene-linked disorders is true?

Most individuals with dominant gene-linked disorders experience minor symptoms. Signup and view all the answers

What is the primary inheritance pattern for cystic fibrosis?

Recessive Signup and view all the answers

How many X chromosomes must a female inherit a recessive sex-linked disorder?

Two Signup and view all the answers

Which of the following conditions is characterized by a deficiency in an enzyme leading to cognitive decline?

Tay Sachs Disease Signup and view all the answers

Which condition is described as causing severe problems with breathing and digestion due to thick mucus?

Cystic Fibrosis Signup and view all the answers

How does Huntington's Disease primarily affect the body?

Damages nerve cells and affects movement and cognition. Signup and view all the answers

What is the likelihood of being a carrier for Tay Sachs Disease among American Jews?

1 in 30 Signup and view all the answers

Which of these conditions is affected by a lack of melanin in an individual's skin?

Albinism Signup and view all the answers

What is the definition of a carrier regarding recessive genetic disorders?

Someone who possesses one copy of the mutated gene but does not express the disorder. Signup and view all the answers

What role do genes play in human development?

They are sequences of nucleotides that influence cell structure and functions. Signup and view all the answers

Which of the following conditions typically leads to death by age five?

Tay Sachs Disease Signup and view all the answers

What is the significance of chromosomes in human cells?

Normal human cells contain 46 chromosomes, or 23 pairs. Signup and view all the answers

What occurs during the process of meiosis?

Chromosomes duplicate and then divide twice, resulting in four cells. Signup and view all the answers

What is the outcome when sperm and egg cells combine?

They form a zygote with 46 chromosomes. Signup and view all the answers

During what process do most body cells replicate?

Mitosis Signup and view all the answers

Which of the following best describes teratogens?

Environmental factors that can cause birth defects. Signup and view all the answers

What is the estimated number of genes in the human genome?

Approximately 20,500 Signup and view all the answers

Which statement about the genetic contribution from parents is true?

The genetic material is a combination from both parents. Signup and view all the answers

What condition results from the loss of all or part of an X chromosome in females?

Turner Syndrome Signup and view all the answers

What is a common risk factor that may prompt genetic counseling?

Family history of a genetic condition Signup and view all the answers

Which syndrome results from the presence of an extra X chromosome in males?

Klinefelter Syndrome Signup and view all the answers

Which type of genotype-environment correlation involves children inheriting both genes and the family environment?

Passive correlation Signup and view all the answers

What does the term 'niche picking' refer to in behavioral genetics?

Seeking environments that match genetic tendencies Signup and view all the answers

How can environmental conditions affect a person with sickle cell anemia?

By triggering a sickle cell crisis Signup and view all the answers

What does behavioral genetics primarily study?

Interactions between genetics and environment Signup and view all the answers

What common outcome is associated with Klinefelter Syndrome?

Breast development Signup and view all the answers

What role does the Y chromosome play in male development concerning genetic disorders?

Inhibits growth of male genitalia Signup and view all the answers

What is an example of genetic susceptibility due to environmental triggers in individuals?

Triggering type-two diabetes through poor diet Signup and view all the answers

What facial feature is typically observed in individuals with Fetal Alcohol Spectrum Disorder?

Thin upper lip Signup and view all the answers

What percentage of women reported smoking in the 3 months prior to pregnancy according to data from 2010?

23% Signup and view all the answers

Which of the following is a potential effect of Fetal Alcohol on the eyes?

Smaller than average eye opening Signup and view all the answers

Among women with recent live births, what percentage reported smoking during pregnancy?

11% Signup and view all the answers

What facial characteristic is associated with a low nasal bridge in individuals with Fetal Alcohol Spectrum Disorder?

Short nose Signup and view all the answers

At what gestational age is the first chance of survival outside the womb generally recognized?

24 weeks Signup and view all the answers

What significant brain development occurs by the end of the third gestational week?

Neural tube formation Signup and view all the answers

During which period is neurogenesis largely completed, except for the hippocampus?

Second trimester Signup and view all the answers

What is the primary function of the myelin that covers the axons?

Aid in insulation and efficiency of neural transmission Signup and view all the answers

What layer develops under the skin during the 8th month and serves as insulation for the fetus?

Fat layer Signup and view all the answers

Which cells continue to grow and support neurons even after the majority of neurons have developed?

Glial cells Signup and view all the answers

What is the study of factors that contribute to birth defects known as?

Teratology Signup and view all the answers

At around 36 weeks, what is the approximate weight and length of the fetus?

6 pounds, 18.5 inches Signup and view all the answers

By what gestational week is neural migration mostly completed in the cerebral cortex?

24 weeks Signup and view all the answers

What reflexes begin to develop in the fetus during the 5th month of gestation?

Sucking, swallowing, and hiccupping Signup and view all the answers

What environmental factor increased the risk of behavior problems in adopted children when their biological parents exhibited high psychopathology?

High stress levels in adoptive parents Signup and view all the answers

What study method did the Early Growth and Development Study employ?

Longitudinal study Signup and view all the answers

What is the primary cause of Fragile X syndrome?

An abnormality in the X chromosome Signup and view all the answers

Why are symptoms of Fragile X syndrome generally more severe in males than in females?

Males do not have a second healthy X chromosome Signup and view all the answers

What is a primary focus of epigenetics?

Environmental factors affecting gene expression Signup and view all the answers

What landmark project began in 1990 with the aim of sequencing the human genome?

The Human Genome Project Signup and view all the answers

What is the most common chromosomal abnormality associated with Down syndrome?

An extra chromosome 21 Signup and view all the answers

Which data set created by the Human Genome Project catalogs genetic variations within global populations?

HapMap Signup and view all the answers

What typically happens to zygotes with chromosomal abnormalities?

They often lead to miscarriages Signup and view all the answers

What is one of the concerns addressed by the Human Genome Project regarding genetic information?

Ownership and influence of genetic data Signup and view all the answers

Which of the following statements about Turner syndrome is true?

It occurs with an XO chromosome composition Signup and view all the answers

What phenomenon explains why identical twins may show differences in gene expression as they age?

Environmental influences altering gene expression Signup and view all the answers

What is a common characteristic of individuals with Klinefelter syndrome?

Reduced height and small testes Signup and view all the answers

What factor is commonly associated with chromosomal abnormalities in infants?

The age of the mother Signup and view all the answers

How long does the germinal period last in prenatal development?

14 days Signup and view all the answers

What occurs immediately after a sperm successfully fertilizes an egg?

The egg's outer wall hardens Signup and view all the answers

What characterizes Trisomy 18?

It leads to multiple birth defects and early death Signup and view all the answers

What is the likelihood of a male being affected by hemophilia?

1 in 10,000 Signup and view all the answers

Which of the following is a focus of pharmacogenomic research based on findings from the Human Genome Project?

Predicting drug responses in certain diseases Signup and view all the answers

In terms of birth defects, what is most common at age 35 for Down syndrome prevalence?

1 in 300 Signup and view all the answers

What is the term used to describe the new cell formed after fertilization?

Zygote Signup and view all the answers

Which group of cells develops into the embryo from the blastocyst?

Inner group of cells Signup and view all the answers

At what point does the organism officially become known as an embryo?

Upon implantation in the uterine wall Signup and view all the answers

During which developmental process do cells begin to differentiate and form major structures?

Embryonic period Signup and view all the answers

Which structure develops from the trophoblast during the embryonic period?

Placenta Signup and view all the answers

What percentage of blastocysts typically fail to implant in the uterine wall?

50-75% Signup and view all the answers

What occurs during the fifth day of mitosis after fertilization?

Formation of 100 cells, now referred to as a blastocyst Signup and view all the answers

Which development direction describes growth from the midline outward?

Proximodistal development Signup and view all the answers

Which structure provides nourishment and oxygen to the developing embryo during the embryonic period?

Placenta Signup and view all the answers

At what development stage can the embryo start to respond to touch?

At eight weeks Signup and view all the answers

What is the impact of timing on the effects of teratogens during prenatal development?

Critical periods exist when structures are most vulnerable to damage. Signup and view all the answers

Which factor is essential in determining the harm caused by a teratogen?

The amount of exposure to the teratogen. Signup and view all the answers

How does exposure to multiple teratogens affect fetal development?

It generally leads to more severe developmental issues. Signup and view all the answers

What is one reason males might be more affected by teratogens than females?

Males possess the Y chromosome, which has fewer genes. Signup and view all the answers

What is the leading preventable cause of intellectual disabilities in children?

Alcohol consumption during pregnancy. Signup and view all the answers

Fetal Alcohol Spectrum Disorders (FASD) encompass a range of effects caused by what factor?

Alcohol consumption during pregnancy. Signup and view all the answers

What are some common physical features associated with Fetal Alcohol Syndrome (FAS)?

Flattened noses and small eye holes. Signup and view all the answers

What behavioral issues can persist into adulthood for children affected by Fetal Alcohol Syndrome (FAS)?

Criminal behavior and psychiatric problems. Signup and view all the answers

What is considered binge drinking during pregnancy, which increases the risk of FASD?

4 or more drinks in 2 to 3 hours. Signup and view all the answers

Genetic factors can influence the effects of teratogens. What aspect of genetics is significant in this context?

Some mothers may have a genetic resistance to teratogenic effects. Signup and view all the answers

Study Notes

Heredity and Genetic Basics

Heredity significantly shapes individual development through genetic contributions known as nature.
Genes are sequences of nucleotides that instruct protein creation, influencing cell structure and function.
Humans possess an estimated 20,500 genes located on 46 chromosomes (23 pairs: 22 autosomes and 1 pair of sex chromosomes).
Mitosis duplicates chromosomes for body cells; meiosis creates gametes (sperm and ova) that contain half the genetic material (23 chromosomes each).
The chance of producing genetically identical offspring (not twins) is one in trillions.

Genotypes and Phenotypes

Genotype is the total genetic information inherited; phenotype is the expressed traits.
Inheritance can be homozygous (same gene version from both parents) or heterozygous (different versions).
Dominant genes express traits regardless of the allele; recessive genes only show in the homozygous condition.
Genetic variations are called alleles, and many traits are polygenic, influenced by multiple genes.
Incomplete dominance occurs when dominant genes do not completely suppress recessive counterparts, as seen in sickle cell disease.

Twin Formation

Identical twins (monozygotic) arise from a single fertilized egg that splits, sharing the same genotype and phenotype.
Fraternal twins (dizygotic) result from separate fertilization of two eggs and share genetic similarities akin to regular siblings.
Older mothers and those using fertility treatments are more likely to conceive dizygotic twins.

Genetic Disorders

Genetic disorders can be dominant or recessive, with various levels of severity.
Dominant disorders like Huntington's Disease are generally serious but may not manifest until midlife.
Recessive disorders like cystic fibrosis and sickle-cell anemia often result in more fatalities as many carriers are unaware of their condition.
Sex-linked disorders are more prevalent in males due to their single X chromosome, making conditions like hemophilia and color-blindness more impactful on males.

Chromosomal Abnormalities

Chromosomal abnormalities stem from incorrect chromosomal counts, often due to maternal age, leading to conditions like Down syndrome (Trisomy 21).
Down syndrome presents intellectual disabilities and distinct physical traits, with variable severity.
Other chromosomal abnormalities include Trisomy 13 and Trisomy 18, which are often fatal.
Turner syndrome (XO) and Klinefelter syndrome (XXY) are notable sex-linked disorders affecting females and males respectively, influencing physical and cognitive characteristics.

Genetic Counseling

Genetic counseling helps individuals understand potential genetic conditions based on family history, ethnic backgrounds, and personal medical history.
Patients learn about the likelihood of genetic conditions impacting themselves or their offspring.

Behavioral Genetics

Behavioral genetics studies the relationship between genetics and environmental influences on behavior, often simplifying the nature/nurture debate.
Three types of genotype-environment correlations illustrate interactions between inherited traits and environmental factors: passive, evocative, and active.
Epigenetics explores how environmental factors modify gene expression, influencing traits and susceptibilities even among genetically identical twins.

Human Genome Project

Launched in 1990, the Human Genome Project sequenced the human genome, completing the task in April 2003.
The project cataloged thousands of disease-associated genes, aiding in medical treatments and understanding genetic variations across populations.### Pharmacogenomics and HGP
Pharmacogenomic tests assess responses to drugs in conditions like breast cancer, lung cancer, and HIV using data from HapMap.
Future goals of the Human Genome Project (HGP) include identifying genetic markers for 50 major cancer types and improving drug efficacy.
Ethical considerations are essential to the HGP, addressing ownership of genetic information and its impact on healthcare policies.

Prenatal Development Overview

Prenatal development consists of three periods: germinal, embryonic, and fetal.

Germinal Period

Lasts about 14 days from conception to implantation in the uterus.
Fertilization usually occurs in the upper fallopian tube, forming a zygote.
The zygote undergoes mitosis, leading to the formation of a blastocyst after five days.
Around 50-75% of blastocysts fail to implant successfully in the uterine wall.
Fewer than half of zygotes survive the first two weeks, often due to issues with genetic material or implantation.

Embryonic Period

Begins at the third week post-implantation, with the blastocyst termed an embryo.
Key developments include the formation of blood vessels, and the placenta connects the mother and embryo.
Growth occurs head-to-tail (cephalocaudal) and midline outward (proximodistal).
Major structures form, including a beating heart by the fourth week; gills and a tail are present initially but disappear later.
This stage is critical as exposure to harmful substances can lead to damage, often before pregnancy is recognized.

Fetal Period

From the ninth week until birth, the organism is classified as a fetus.
By the third month, all body parts, including external genitalia, develop.
Major development includes hair, nails, and the digestive system prior to birth.
Age of viability occurs around 24 weeks; survival outside the womb is limited before this time.
Neurons mostly develop by 24 weeks, with key brain functions beginning to emerge, including sensory perception.
The fetus prepares for birth by exercising muscles and gaining weight, reaching approximately 6 pounds and 18.5 inches by 36 weeks.

Prenatal Brain Development

Begins in the third gestational week with the emergence of stem cells in the neural plate.
Neural tube formation occurs within the first month, creating the brain's ventricles and spinal canal.
Neurogenesis is largely complete by five months, although hippocampal neuron development continues throughout life.
Growth persists post-birth, with neuron connections (dendrites and axons) forming neural networks over the years.

Teratogens

Teratology studies factors that lead to birth defects during prenatal development.
Teratogens, such as maternal diseases, pollutants, drugs, and alcohol, significantly affect fetal health.

Factors Influencing Prenatal Risks

Timing of exposure is critical; certain developmental stages are more vulnerable to damage from teratogens.
The amount of exposure can influence the severity of potential damage.
Co-exposure to multiple teratogens increases risk compared to singular exposure.
Genetic make-up can affect susceptibility to teratogenic effects.
Males may be more adversely affected by teratogens due to genetic differences.

Alcohol as a Teratogen

Alcohol is notably the leading preventable course of intellectual disabilities.
Impact includes neurocognitive and behavioral issues, and severe cases may result in fetal death or Fetal Alcohol Spectrum Disorders (FASD).
Fetal Alcohol Syndrome (FAS) presents with distinctive facial features and cognitive deficits, persisting into adulthood.
Binge drinking significantly increases the likelihood of FASD.

Tobacco Use During Pregnancy

Over 7% of pregnant women smoked in 2016, exposing fetuses to teratogenic risks.
Smoking prevalence varies among different pregnancy stages, with many women quitting before the last trimester.

Fetal Alcohol Spectrum Disorder Facial Features

Below-average head size, smaller eye openings, low nasal bridge, and thin upper lip are common characteristics of FAS in children.

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Description

Explore the fundamental concepts of heredity and genetics in this quiz. Learn about the role of genes, chromosome structure, and the processes of mitosis and meiosis in human development. Test your understanding of how nature influences individual traits.