CHAPTER 3 (forming a new life) Flashcards
The union of sperm and ovum to produce a zygote; also called conception
Fertilization
One-celled organism resulting from fertilization
Zygote
Twins conceived by the union of two different ova (or a single ovum that has split) with two different sperm cells; also called fraternal twins ; they are no more
alike genetically than any other siblings
Dizygotic twins
Twins resulting from the division of a single zygote after fertilization; also called identical twins ; they are genetically similar.
Monozygotic twins
Chemical that carries inherited instructions for the development of all cellular forms of life.
deoxyribonucleic acid (DNA)
Sequence of bases within the DNA molecule; governs the formation of proteins that determine the structure and functions of living cells.
genetic code
Coils of DNA that consist of genes
chromosomes
Small segments of DNA located in definite positions on particular chromosomes; functional units of heredity.
genes
Complete sequence of genes in the human body.
human genome
Permanent alterations in genes or chromosomes that may produce harmful characteristics.
mutation
In humans, the 22 pairs of chromosomes not related to sexual expression.
autosomes
Pair of chromosomes that determines sex: XX in the normal human female, XY in the normal human male.
sex chromosomes
Two or more alternative forms of a gene that occupy the same position on paired chromosomes and affect the same trait.
alleles
Possessing two identical alleles for a trait.
homozygous
Possessing differing alleles for a trait.
heterozygous
Pattern of inheritance in which, when a child receives different alleles, only the dominant one is expressed.
dominant inheritance
Pattern of inheritance in which a child receives identical recessive alleles,resulting in expression of a nondominant trait.
recessive inheritance
Pattern of inheritance in which multiple genes at different sites on chromosomes affect a complex trait.
polygenic inheritance
Observable characteristics of a person.
phenotype
Genetic makeup of a person, containing both expressed and unexpressed characteristics.
genotype
Combination of genetic and environmental factors to produce certain complex traits.
multifactorial transmission
Mechanism that turns genes on or off and determines functions of body cells.
epigenesis
Pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait.
incomplete dominance
Pattern of inheritance in which certain characteristics carried on the X chromosome inherited from the mother are transmitted differently to her male and female off spring.
sex-linked inheritance
Chromosomal disorder characterized by moderate-to-severe mental retardation and by such physical signs as a downward sloping skin fold at the inner corners of the eyes. Also called trisomy-21.
Down syndrome
Clinical service that advises prospective parents of their probable risk of having children with hereditary defects.
genetic counseling
Quantitative study of relative hereditary and environmental influences on behavior.
behavioral genetics
Statistical estimate of contribution of heredity to individual differences in a specific trait within a given population.
heritability
Term describing tendency of twins to share the same trait or disorder.
concordant
Potential variability, depending on environmental conditions, in the expression of a hereditary trait.
reaction range
Limitation on variance of expression of certain inherited characteristics.
canalization
The portion of phenotypic variation that results from the reactions of genetically different individuals to similar environmental conditions.
genotype-environment interaction
Tendency of certain genetic and environmental influences to reinforce each other; may be passive, reactive ( evocative), or active. Also called genotype-environment covariance.
genotype-environment correlation
Tendency of a person, especially after early childhood, to seek out environments compatible with his or her genotype.
niche-picking
The unique environment in which each child grows up, consisting of distinctive influences or influences that affect one child differently than another.
nonshared environmental effects
Characteristic disposition, or style of approaching and reacting to situations.
temperament
Period of development between conception and birth.
gestation
Age of an unborn baby, usually dated from the first day of an expectant mother’s last menstrual cycle.
gestational age
First 2 weeks of prenatal development, characterized by rapid cell division, blastocyst formation, and implantation in the wall of the uterus.
germinal stage
The attachment of the blastocyst to the uterine wall, occurring at about day 6.
implantation
Second stage of gestation (2 to 8 weeks), characterized by rapid growth and development of major body systems and organs.
embryonic stage
Natural expulsion from the uterus of an embryo that cannot survive outside the womb; also called miscarriage.
spontaneous abortion
Final stage of gestation (from 8 weeks to birth), characterized by increased differentiation of body parts and greatly enlarged body size.
fetal stage
Prenatal medical procedure using high-frequency sound waves to detect the outline of a fetus and its movements, so as to determine whether a pregnancy is progressing normally.
ultrasound
Environmental agent, such as a virus, drug, or radiation, that can interfere with normal prenatal development and cause developmental abnormalities.
teratogen
Chromosome Composition: An individual has an extra Y chromosome, resulting in a 47
Effects: Is often associated with tall stature, but most individuals do not have significant physical differences or health problems. However, some may experience mild learning disabilities or behavioral issues.
XYY Syndrome (Male)
Chromosome Composition: An individual has an extra X chromosome, resulting in a 47.
Effects: Have no apparent physical abnormalities. However, some may experience learning disabilities, developmental delays, or emotional and behavioral issues. The severity of these challenges varies widely among affected individuals.
XXX Syndrome (Triple X Syndrome) (Female)
Chromosome Composition: Individuals have an extra X chromosome
Effects: Typically have underdeveloped testes, which can lead to reduced testosterone production. This can result in physical features such as taller stature, gynecomastia (enlarged breast tissue), and infertility. Many individuals with Klinefelter syndrome also experience learning difficulties
XXY Syndrome (Klinefelter Syndrome) (Male)
Chromosome Composition: In this syndrome, individuals are missing one X chromosome, resulting in a 45
Effects: it can lead to a range of physical and developmental challenges. Individuals with it are typically shorter in stature and may have certain physical features like a webbed neck, heart defects, and infertility. Hormone replacement therapy is often used to help with growth and puberty.
Turner Syndrome (XO Syndrome) (Female)
Chromosome Composition: It is not primarily a sex chromosome abnormality but rather a genetic disorder caused by a mutation in the FMR1 gene on the X chromosome. Individuals with this syndrome may have a mutation in the FMR1 gene, leading to a range of developmental and intellectual disabilities.
Effects: Can cause intellectual disability, social and behavioral challenges, and language difficulties. It affects both males and females, but males are often more severely affected than females.
Fragile X Syndrome: (Male)
