Chapter 2 Flashcards
Zygote
The single cell that is formed from the fusing of 2 gametes, a sperm and an ovum
Deoxyribonucleic Acid (DNA)
The molecule that contains the chemical instructions for cells to manufacture various proteins
Chromosome
One of the 46 molecules of DNA (in 23 pairs) that each cell of the human body contains and that, together, contain all the genes. Other species have more or fewer chromosomes.
Gene
A small section of a chromosome; the basic unit for the transmission of heredity. A gene consists of a string of chemicals that provide instructions for the cell to manufacture certain proteins.
Gamete
A reproductive cell; that is, a sperm or an ovum that can produce a new individual if it combines with a gamete from the other sex to form a zygote.
Allele
Any of the possible forms in which a gene for a particular trait can occur.
Each variation is a single-nucleotide polymorphism (SNP)
Polymorphic
Means “many forms”
Genotype
An organism’s entire genetic inheritance, or genetic potential
Phenotype
The observable characteristics of a personal, including appearance, personality, intelligence, and all other traits
Genome
The full set of genes that are in the instructions to make an individual member of a certain species
How many human genes are there?
20,000 to 23,000
XX
A 23rd chromosome pair that consists of 2 X shaped chromosomes, one each from the mother and the father. XX zygotes become females.
XY
A 23rd chromosome pair that consists of an X shaped chromosome from the mother and a Y shaped chromosome from the father. XY zygotes become males.
What gene does the Y chromosome has that is responsible for developing male organs and the production of certain fetal hormones?
the SRY gene
Monozygotic (Identical) Twins
Twins who originate from one zygote that splits apart very early in development
Incomplete splits create conjoined twins
Dizygotic (Fraternal) Twins
Twins who are formed when 2 separate ova are fertilized by 2 separate sperm at roughly the same time.
Are women who have had dizygotic twins likely to have another set?
Yes because ovulating more than one ova a month is genetic, so both she and her future daughters are likely to have more sets of dizygotic twins
Polygenic
Affected by many genes
Multifactorial
Influenced by many factors
Additive Gene
A gene that adds something to some aspect of the phenotype. Its contribution depends on additions from other genes, which may come from either the same or the other parent.
ex: height, hair curliness, skin color
Nonadditive Genes
Genes which do not contribute equal shares
Dominant-Recessive Pattern
The interaction of a pair of alleles in such a way that the phenotype reveals the influence of one allele (the dominant gene) more than that of the other (the recessive gene)
Carrier
A person whose genotype includes a gene that isn’t expressed in the phenotype. Such an unexpressed gene occurs in half the carrier’s gametes and thus is passed on to half of the carrier’s children, who will most likely be carriers, too. Generally, the characteristic appears in the phenotype only when such a gene is inherited from both parents.
X-Linked
A gene carried on the X chromosome. If a male inherits an X-linked recessive gene from his mother, he expresses that trait because the Y from his father has no counteracting gene. Females are more likely to be carriers of X-linked traits but are less likely to express them.
Germinal Period
The first 2 weeks of prenatal development after conception, characterized by rapid cell division and the beginning of cell differentiation.
Embryonic Period
The stage of prenatal development from approximately the 3rd through 8th week after conception, during which the basic forms of all body structures, including internal organs, develop
Fetal Period
The stage of prenatal development from the 9th week after conception until birth, during which the fetus grows in size and matures in functioning
Preterm
Born more than 3 weeks before the due date