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Genetics, Chromosomal Abnormalities, Prenatal Dev and Childbirth
Question | Answer |
---|---|
Genes | basic units of genetic instructions, which are segments of DNA molecules |
Chromosome | thread-like structures of DNA; there are 46 (23 pairs) |
DNA | deoxyribonucleic acid; made of units called genes; double stranded helix held together by bases |
Natural selection | individuals with genetically controlled characteristics reproduce more successfully and the species comes to resemble those individuals more and more as time passes |
Genotype | genetic characteristics; the sum total of all the genes a person inherits for any particular trait |
Phenotype | physical expression of genetic characteristics; actual expression of traits, observable in the person’s physical appearance, as well as behavior tendencies. |
Polygenic traits | those traits produced by the combined action of more than one gene |
Multifactorial traits | those traits influenced by many factors including the environment |
Additive | sum of contribution of the genes involved |
Dominant genes | the genes that control the trait |
Recessive genes | the genes are carried on the genotype but not expressed in the phenotype |
Reaction range | is a term used to describe the range of phenotypes for each genotype, suggesting the environment’s restrictiveness or enrichment |
Monozygotic twins | identical twins; identical genetically |
Dizygotic twins | fraternal twins; different genetically |
Down’s Syndrome | most common chromosomal abnormality; it results from 3 chromosomes at sight 21 |
Phenylketonuria (PKU) | abnormal protein digestion that is caused by recessive gene |
Fragile X syndrome | part of the X chromosome is attached by such a thin string of molecules that it seems about to break off |
implantation | body of cells arrive at uterus and burrow into uterine lining |
teratogens | any substances or conditions that contribute to birth defects |