biological approach- genetics and inheritance Flashcards
Genes
units of DNA/ located on chromosomes.
how ma y pairs of chromosomes do humans have ?
humans have 23 pairs of chromosomes
what do Genes carry ?
carry chemical messages that dictate your physical and non-physical characteristics.
how do alleles work ?
Individually inherits one allele per parent of each gene.
. Genotypes-
genetic makeup of an individual (example= XX)
. Phenotype-
the physical traits and characteristics of an individual (influenced by your genotype and environment). How an individual’s genes are expressed (example=blue eyes.)
how do you distinguish between them ?
This distinction between genotypes and phenotypes strongly suggests that most human behaviors are due to an interaction of inherited (nature) and environmental factors (nurture.)
Example= (genotype/phenotype)
Identical twins have different phenotypes even though they have the same genotype (they inherit the exact same genes, but they may be expressed differently.
. They are expressed differently (different phenotype) due to experiencing different environmental influences.
how an embryo becomes male or female
One pair of chromosomes determines biological sex- female (XX) male (XY)
. Located on the Y chromosome is a gene called the ‘sex determining region Y gene’ (SRY gene)
. In typical development before birth (about 7 weeks) the SYR gene switches on other genes causing the XY embryo to develop testes.
. In adult males the testes produce sperm, but during development the testes produce male sex hormones (testosterone)
. These hormones cause the embryo to become biologically male
. Without the SYR gene, other genes remain switched off, so the embryo develops into a female.
. strength=
practical applications=
benefits in distinguishing between genotype and phenotype. Depression (phenotype) is the result of a a genetic predisposition (genotype) that is triggered by an environmental influence. Without the trigger the individual will not become depressed even though they have a relevant genotype.
A good example of an environmental trigger is stress which can be reduced in many ways such as therapy- reducing the risk of a negative outcome.
Strength=
research supports= rarely the process of copying the SRY gene goes wrong producing a mutation of the gene. In this case the gene cannot produce in its normal function of ‘switching on other hormones’. So, the individual is genetically male but develops female reproductive organs. This is evidence that the usual role of SRY gene is to initiate male biological development in genetic male embryos.
weakness =
Weakness= risk of oversimplification= influence of genes is often oversimplified. For instance, the phrase “a gene for depression’ is an inaccurate term. Because although genes may increase the risk of developing depression but do not cause it. Human behaviour is not usually caused by single genes.
