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