Human Development Chapter 2

Percentage of Infertility

12-16% of Canadian couples experience infertility.

Ovum Transfer

A donor egg provided by a fertile younger woman is fertilized in the laboratory and implanted in the prospective mother's uterus.

Surrogacy

A fertile woman who is impregnated by the prospective father by artificial insemination, OR the fertilized egg from another woman could be implanted into a surrogate.

Zygote

A fertilized egg that duplicates itself repeatedly by cell division to produce all the cells that make up a baby.

Chorionic Villi Sampling

A prenatal test in which a sample of chorionic villi is removed from the placenta for testing

Measuring Heritability

A statistical estimate of how heredity influences diversity within a specific trait in a given population. It cannot be measured directly.

The Genetic Code

All normal human cells have 23 pairs of chromosomes. At conception, the egg and sperm combine a zygote that has 46 chromosomes.

Dominant Traits

Always expressed.

Adoption

An option for those faced with infertility and can be national or international in Canada. - 2,000 international adoptions each year in Canada.

Deoxyribonucleic Acid (DNA)

Chemical that carries inherited instructions for the development of all cellular forms of life.

Active Correlations

Children actively select experiences that are consistent with their genetic tendencies. (niche-picking)

Reactive or Evocative Correlations

Children with differing genetic makeups evoke different responses from adults. If a child shows interest and ability in music, parents who are not musically inclined may react by making a special effort to provide that child with musical experiences. This response strengthens the child's genetic inclination toward music.

Chromosomes

Coils of DNA that consists of genes.

Twin Studies

Compares pairs of monozygotic twins with same-sex dizygotic twins.

Multifactorial Transmission

Complex traits are the result of a combination of genetic and environmental factors. Ex. height, weight, intelligence and musical abilities.

Alleles

Different forms of the same gene

Gregor Mendel

During the 1960s he lay the foundation for our understanding of patterns of inheritance (dominant and recessive genes).

Assisted Human Reproductive Act

Enacted in 2004, this act places strict conditions on the practice, including a ban on payment to the surrogate mother.

Causes of Infertility for Women

Failure to produce eggs/ova/normal ova, mucus in the cervix, disease in the uterine lining, or blockage of the fallopian tubes.

Genotype

Genetic makeup of a person, containing both expressed and unexpressed characteristics.

Canalization

Genetic restrictions on the range of development for some traits. - There is little opportunity for variance in their expression. Ex. Some cases of eye colour.

Genetic and Chromosomal Abnormalities

Happens when there are errors in cell division (missing or extra chromosome). Ex. Klinefelter syndrome (XXY), Turner Syndrome (XO), and down syndrome has an extra 21st chromosome.

Autosomes

In humans, the 22 pairs of chromosomes not related to sexual expression are called autosomes.

Adoption Studies

Looks at similarities between adopted children and their adoptive families and also between adopted children and their biological families.

Causes of Infertility for Men

Low sperm count, insufficiently motile sperm, or genetic reasons.

Epigenesis

Mechanism that turns genes on or off and determines functions of body cells.

Assisted Reproductive Technology

More than 3 million children worldwide have been conceived through ART (3500 in Canada annually)

Phenotype

Observable characteristics of a person (traits).

Recessive Traits

Only expressed if both copies of the gene are recessive.

Different types of ART

Ovum transfer, In Vitro Fertilization, and Intracytoplasmic sperm injection.

Incomplete Dominance

Pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait. ex. People with one sickle-cell allege and one normal allele do not have sickle-cell anemia, but do show some manifestations of the condition, such as shortness of breath.

Polygenic Inheritance

Pattern of inheritance in which multiple genes at different sites on chromosomes affect a complex trait. Ex. Skin colour is the result of three or more sets of genes on three different chromosomes.

Mutations

Permanent alterations in genes or chromosomes that usually produce harmful characteristics.

Soft Markers

Physical abnormalities that can be seen on an ultrasound that indicate an increased risk of having a baby with a genetic disorder.

Characteristics Influenced by Heredity and Environment

Physical and Physiological traits, intelligence, temperament and personality, and psychopathology.

Heterozygous

Possessing differing alleles for a trait.

Homozygous

Possessing two identical alleles for a trait

Fertilization

Process by which sperm and ovum combine to create a single cell called a zygote. Fertilization takes place in the fallopian tube.

Family Studies

Researchers measure the degree to which biological relatives share certain traits and determine whether the closeness of the familial relationship is associated with degree of similarity.

Sex Determination

Sexual differentiation is not automatic, and in order for males to develop, it requires the activation of the SRY (Sex-determining region Y) gene.

Genes

Small segments of DNA located in definite positions on particular chromosomes; functional units of heredity.

Sex Linked Inheritance

Some recessive disorders are linked to genes on the sex chromosomes - the mother is the carrier of the X chromosome (which can be overridden), and the father is the carrier of the Y chromosome (cannot be overridden, making males more likely to be affected by any trait carried on the X chromosome because they only have one chance to get it right.

Concordant

Term describing the tendency of twins to share the same trait or disorder.

Reaction Range

Term for a range of expressions of a hereditary trait, depending on environmental opportunities and constraints. Ex. Body size depends largely on biological processes, which are genetically regulated.

Mechanisms of Heredity

The Genetic Code, Sex Determination, Patterns of Genetic Transmission, and Epigenesis.

Human Genome

The complete sequence of genes in the human body.

Genotype-Environment Interaction

The effects of similar environmental conditions on genetically different individuals.

Artificial Insemination

The ejection of sperm into a woman's vagina, cervix, or uterus and can be used to facilitate conception if a man has a low sperm count.

Genotype-Environment Correlation

The environment often reflects or reinforces genetic differences. Three types: Active correlations, Passive Correlations, and Reactive or evocative correlations.

Sex Chromosomes

The pair of chromosomes that determines the sex of the baby - one from the father and one from the mother. Females have XX and males have XY.

Amniocentesis

The process of finding out exactly if you are giving birth to a child with a genetic disorder, but can increase the likelihood of having a miscarriage.

Preconception Screening

The screening process to find out the chances of giving birth to a child who has a genetic disorder.

Niche Picking

The tendency of an individual to seek out environments that is an alignment with their genotypes.

Non shared Environmental Effects

The unique environment in which each child grows up, consisting of distinctive influences that affect one child differently from another. (reason why siblings are different).

In Vitro Fertilization

The woman is given fertility drugs to stimulate production of multiple ovum, then ovum is surgically removed, fertilized by sperm in a laboratory dish to create an embryo, and then placed back into the woman.

Intracytoplasmic Sperm Injection

When a single sperm is injected into the ovum.

Ovulation

When an ovum is discharged from the ovarian follicle, and the egg travels down the fallopian tube where it may be met by sperm and become fertilized. Occurs in women about once every 28 days until menopause.

Mitosis

When the DNA replicates itself so that each newly formed cell is a genetic copy with the same hereditary information.

Passive Correlations

You not only inherit genes from your parents but also inherit environments. Ex. A musical parent is likely to create an environment in which music is heard regularly. This is called passive because the child does not control it.