Reproductive Technology & Fertilization

• A person's biological sex is determined by the father.
• Development starts when an egg and sperm unite and form a new individual.
• Fertilization is the union of sperm and ovum to produce a zygote.
• Fertilization is also called conception
• A zygote is a one-celled organism resulting from fertilization.
• The body cells of women and men contain 23 pairs of chromosomes, which carry the genes, the basic units of inheritance.
• Each sex cell, such as an ovum and sperm, has only 23 single chromosomes because of meiosis.
• At fertilization, the 23 chromosomes from the sperm join the 23 from the ovum so that the zygote receives 46 chromosomes, or 23 pairs.
• The fertile window is the time during which conception is possible and is highly unpredictable.
• Assisted reproductive technology (ART) refers to methods used to achieve conception through artificial means.
• Artificial Insemination is a kind of ART in which the sperm is injected into the woman's vagina, cervix, or uterus.
• In Vitro Fertilization (IVF) is a kind of ART in which a woman's ova are surgically removed, fertilized in a laboratory dish, and implanted in the woman's uterus.
• Dizygotic twins are twins conceived by the union of two different ova (or a single ovum that has split) with two different sperm cells.
• Dizygotic twins are also called fraternal twins.
• Dizygotic twins are no more alike genetically than any other siblings.
• A tendency to have dizygotic twins tends to run in families and likely has a genetic basis.
• Dizygotic twins occur when 2 separate eggs are fertilized by 2 different sperms.
• Monozygotic twins are twins resulting from the division of a single zygote after fertilization; also called identical twins.
• Monozygotic twins are genetically similar but can still differ outwardly due to environmental influences.
• Heredity is the science of genetics.
• Chromosomes are coils of DNA that consist of genes.
• Genes are located in a specific position on chromosomes and contain thousands of bases.
• Mitosis is a process by which non-sex cells divide in half, over and over, replicating DNA to ensure each newly formed cell has the same DNA structure.
• During mitosis each cell division creates a genetic duplicate of the original cell, with the same hereditary information.
• Sometimes a mistake in copying the DNA is made during mitosis, resulting in a mutation.
• Genes spring into action when they are turned on or off either by external environmental factors or by internal factors.
• Small segments of DNA located in definite positions on particular chromosomes are called genes and are functional units of heredity.
• Mutations are permanent alterations in genetic material.
• The human genome is a complete sequence of genes in the human body.
• Genes are the functional units of heredity.
• Deoxyribonucleic acid (DNA) is a chemical that carries inherited instructions for cellular development.
• Autosomes are the twenty-two pairs of our 23 pairs of chromosomes that are not related to sexual expression.

Genetic Determination of Sex

• Sex chromosomes are X or Y chromosomes.
• Every ovum's sex chromosome is X.
• Sperm may contain either an X or a Y chromosome.
• The Y chromosome contains the SRY gene for maleness.
• When an ovum (X) is fertilized by an X-carrying sperm, the zygote formed is XX results in a genetic female.
• If an ovum (X) is fertilized by a Y-carrying sperm, the resulting zygote is XY, which results in a genetic male.
• The genetic code is the sequence of bases within the DNA molecule; governs the formation of proteins that determine the structure and functions of living cells.
• The sequence of nitrogenous bases in DNA determines the genetic code
• The genetic code carries instructions for the development and function of an organism
• When a cell divides, its DNA is replicated, ensuring that the new cell receives a complete and accurate copy of the genetic material.
• Genetic information encoded in DNA is passed from parents to offspring through its transmission, determining the offspring's characteristics and traits.
• Changes in the DNA sequence, such as mutations or genetic recombination during reproduction, can result in variation in traits and characteristics.
• Autosomes are defined as the 22 pairs of chromosomes that are not related to sexual expression in humans.
• Alleles are alternate versions of the same gene.
• Every person receives one maternal and one paternal allele for any given trait.
• Polygenic inheritance is a pattern of inheritance in which multiple genes at different sites on chromosomes affect a complex trait.
• Individual variations in complex behaviors or traits result from the additive influences of multiple genes with small identifiable effects.
• Gregor Mendel, an Austrian monk, laid the foundation for understanding patterns of inheritance.
• Homozygous is when both alleles are the same for the characteristic.
• Heterozygous is possessing differing alleles for a trait.

Principles of Genetics

• Traits can be either dominant or recessive.
• Traits are passed down independently of each other For example hair color and height are both heritable traits that are not linked
• Dominant inheritance is when a child receives different alleles, only the dominant one is expressed.
• Dominant Traits are always expressed.
• Recessive traits are only be expressed if both copies of the gene are recessive.
• Multifactorial transmission is the combination of genetic and environmental factors to produce certain complex traits.
• Environmental experience modifies the expression of the genotype for most traits, a phenomenon called multifactorial transmission.
• Multifactorial transmission illustrates the interaction of nature and nurture and how they affect outcomes.
• Recessive inheritance occurs when a child receives identical recessive alleles, resulting in expression of a nondominant trait.
• Genotype is the underlying genetic make-up, and is expressed in the phenotype.
• Phenotype is a product of the genotype and relevant environmental influences.
• Epigenesis mechanisms turn genes on or off and determine functions of body cells.
• Epigenetic modifications that occur early in life may be heritable.
• The daughters of women or the grandsons of men who experienced famine while in the womb lived shorter lives on average.
• Dominant genes typically override those carrying abnormal traits, but sometimes an abnormal trait is dominant.
• When one copy of a "bad" gene is present the child will express the disorder.
• Recessive defects are expressed only if the child is homozygous for that gene
• The child must inherit a copy of the recessive gene from each parent.
• Incomplete dominance is a pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait.
• Behavioral genetics is the quantitative study of relative hereditary and environmental influences on behavior.
• Heritability is the statistical estimate of the contribution of heredity to individual differences in a specific trait within a given population.
• Concordant refers to the tendency of twins to share the same trait or disorder.
• Reaction range is the potential variability, depending on environmental conditions, in the expression of a hereditary trait.
• The genotype places limits on the range of possible phenotypes, while heredity can influence whether a reaction range is wide or narrow.
• Canalization describes how heredity restricts the range of development for some traits, and is a limitation on variance of expression of certain inherited characteristics.
• Cognition and personality however, are not highly canalized.
• Genotype-environment interaction is the portion of phenotypic variation that results from varying reactions of genetically different individuals to similar environmental conditions.
• Genetically similar children often develop differently depending on their home environments.
• Genotype-environment correlation or covariance describe the tendency of certain genetic and environmental influences to reinforce each other.

The 3 kinds of Genotype-Environment Correlations

• Passive correlations function only when a child is living with a biologically related parent where its applicable to young children
• Reactive or evocative correlations is applicable to only other people not parents.
• Active correlation is when people actively select or create experiences based on genetic tendencies.
• Niche-picking is the tendency to seek out environments compatible with one's genotype
• Nonshared environmental effects are the unique environment in which each child grows up, consisting of distinctive influences or influences that affect one child differently than another.
• Shared influences are the home, the people, activities in the family
• Non-shared influences are treatment of people may vary, certain events like illness and accidents, experiences outside home like group of friends.
• Physical Health can undergo multifactoral influence
• Heredity has a strong influence on general intelligence and a moderate effect on specific abilities like memory and verbal ability, which is also shaped by multiple genes working together
• Temperament underlies adult personality and encompasses babies' unique ways of approaching and reacting to environmental stimuli.

Test your knowledge of reproductive technology, fertilization, and genetics. Questions cover ART, chromosomal contributions, the start of development, and key biological processes. Learn about meiosis, mutations, and the menstrual cycle.