Biological approach KC2: Genetics and inheritance Flashcards
gene
inherited DNA with instructions for building physical and psychological characteristics that influences behaviour
sex chromosome
Each person has 23 pairs of chromosomes.
the 23rd pair is the sex chromosome
xx=girl
xy=boy
sex chromosomes determine an individualsbiological sex
SRY gene
The SRY gene controls whether sex organs become testes or ovaries. Between 6-8 weeks after conception, the SRY gene switches on other genes causing the male sex gland to develop in XY embryo
genotype
an individuals total set of genes. eg, forms the basis of their development
phenotype
the observable characteristics which result from the interaction between an individuals genotype and environmental factors
twin studies
Twin studies are used a lot in the biological approach. the idea behind twin studies - given that MZ twins (sharing 100% of their genes) and DZ twins (sharing 50% of their genes) - are raised in the same environment (so the environment as a variable is controlled), if concordance rates are found to be higher in MZ twins than DZ twins, this is most likely the result of their genetic similarity
monozygotic twins
(identical twins) have same genotype
dizygotic twins
(non-identical twins) 50% same genotype which is the same as normal siblings
what does the distinction between genotype and phenotype suggest
genotype is the genetic code, while the phenotype is the physical expression of a trait
how many pairs of chromosomes does each person have
23
what are the 23rd pair of chromosomes called and why
sex chromosomes because they determine the sex
name the chromosomal structure of females
XX
name the chromosomal structure of males
XY
how many weeks after conception do embryos become sexually differentiated
6-8 weeks
explain how an embryo develops into a male or female
process is called sexual differentiation. during early development, the gonads of the fetus remain undifferentiated. after 6-8 weeks, the expression of a gene on the Y chromosome induces changes that results in the development of the testes
name 1 strength of genetics and inheritance
- Has practical application so is useful
There are practical benefits of distinguishing between genotype and phenotype. eg, someone may have a genetic predisposition (genotype) to develop depression (phenotype) but if environmental triggers are reduced, they are less likely to become depressed. stress can be an environmental trigger which can be reduced via therapy. Therefore, although genes can’t be changed, environmental factors can be, which can reduce the risk of a negative outcome for certain people.
name 1 limitation of genetics and inheritance
- risk of oversimplification
the influence of genes is oversimplified. Ripke found 108 separate genetic variations were associated with increased risk of schizophrenia. this provides evidence that schizophrenia is not caused by one gene (its polygenic). therefore, the explanation that a single gene causes a certain behaviour is too simplistic
