Biological approach KC2: Genetics and inheritance

Question 1

gene

Answer 1

inherited DNA with instructions for building physical and psychological characteristics that influences behaviour

Question 2

sex chromosome

Answer 2

Each person has 23 pairs of chromosomes.
the 23rd pair is the sex chromosome
xx=girl
xy=boy
sex chromosomes determine an individualsbiological sex

Question 3

SRY gene

Answer 3

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

Question 4

genotype

Answer 4

an individuals total set of genes. eg, forms the basis of their development

Question 5

phenotype

Answer 5

the observable characteristics which result from the interaction between an individuals genotype and environmental factors

Question 6

twin studies

Answer 6

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

Question 7

monozygotic twins

Answer 7

(identical twins) have same genotype

Question 8

dizygotic twins

Answer 8

(non-identical twins) 50% same genotype which is the same as normal siblings

Question 9

what does the distinction between genotype and phenotype suggest

Answer 9

genotype is the genetic code, while the phenotype is the physical expression of a trait

Question 10

how many pairs of chromosomes does each person have

Answer 10

23

Question 11

what are the 23rd pair of chromosomes called and why

Answer 11

sex chromosomes because they determine the sex

Question 12

name the chromosomal structure of females

Answer 12

XX

Question 13

name the chromosomal structure of males

Answer 13

XY

Question 14

how many weeks after conception do embryos become sexually differentiated

Answer 14

6-8 weeks

Question 15

explain how an embryo develops into a male or female

Answer 15

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

Question 16

name 1 strength of genetics and inheritance

Answer 16

1. 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.

Question 17

name 1 limitation of genetics and inheritance

Answer 17

1. 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