biology and behaviour

Question 1

what is DNA?

Answer 1

DNA – molecule that carries biochemical instructions involved in the formation and functioning of an organism

Question 2

what are genes?

Answer 2

Gene – sections of chromosomes and the basic hereditary unit in all living things

Question 3

what are chromosomes?

Answer 3

Chromosomes – made up of DNA which contain genes

Question 4

what are genomes?

Answer 4

Genome – the complete set of genes in an organism

Question 5

what are phenotype?

Answer 5

Phenotype – observable expression of the genotype, inc body characteristics and behaviour

Question 6

what is the ‘environment’?

Answer 6

Environment – includes every aspect on an individual’s surroundings and influences other than genes

Question 7

what is a karotype?

Answer 7

Environment – includes every aspect on an individual’s surroundings and influences other than genes

Question 8

describe how a child’s genotype and phenotype interact with each other (4)

Answer 8

1. parent genotype - influences a child’s genotype
2. child’s genotype - influenes a child’s phenotype
3. child’s environment (i.e house) - influences a child’s phenotype
4. parent’s phenotype - influences a child’s phenotype

Question 9

what are the 3 main mechanisms contributing to genetic diversity?

Answer 9

mutation, random assortment, crossing over

Question 10

genetic diversity: what is mutation?

Answer 10

Mutation – a change in section of DNA caused by random or environmental factors e.g teratogens

Question 11

genetic diversity: what is random assortment?

Answer 11

Random assortment – the shuffling of the 23 pairs of chromosomes in the sperm and egg – chance determines which member of the pair goes into the gamete. This makes around 8.4million combinations of chromosomes in each gamete

Question 12

genetic diversity: what is crossing over?

Answer 12

Crossing over – sections of DNA switch from one chromosomes to another during meiosis, further increasing genetic variability

Question 13

what are regulator genes?

Answer 13

regulator genes – largely control the continuous switching on and off of genes that underlines development across the lifespan

Question 14

how do regulator genes influence gene expression and development? (3)

Answer 14

• every cell contains copies of all genes inherited but only some are expressed due to regulator genes
• a given gene only influences behaviour/development when it’s turned on
• key for healthy development – if every single gene was turned on at all times there would be chaos

Question 15

what is the ‘male disadvantage’ in genetics? (3)

Answer 15

• the Y chromosome has only 1/3 as many genes as the X chromosome
• many alleles on the X chromosomes don’t have a corresponding allele on the Y chromosome that could suppress the action
• thus, individuals with only one X-chromosome are more likely to suffer a variety of inherited disorders caused by recessive alleles on the X chromosome (e.g colourblindness)

Question 16

how do genes influence the development of human diseases and disorders?

Answer 16

errors in meiosis – resulting in a zygote with fewer or more than normal complement of chromosomes e.g down syndrome

Question 17

human diseases and disorders: give an example of a recessive gene disorder

Answer 17

anemia, cystic fibrosis

Question 18

human diseases and disorders: give an example of a dominant gene disorder

Answer 18

huntington’s disease

Question 19

what is the difference between polygenetic inheritance and Mendelian dominant-recessive pattern?

Answer 19

• the Mendelian dominant-recessive pattern of inheritance pertains to relatively few human traits (e,g hair colour, blood type etc)
• many other traits are governed by more than one gene e.g height, intelligence etc
• polygenetic inheritance applies to most traits and behaviours

Question 20

what is the ‘norm of reaction’ theory?

Answer 20

(Dobzhansky, 1955)
A given genotype can develop differently in different environments
The Norm of Reaction is a curve that relates, for a given genotype, the contribution of environmental variation to observed phenotypic variation

Question 21

how does PKU demonstrate the ‘norm of reaction’?

Answer 21

THE CASE OF PKU - a genetic disorder that means you’re unable to metabolise phenylamine, early diagnosis and a specific diet means that cognitive impairment from PKU can be avoided  demonstrates that the genotype can result into different phenotypes depending on the environment

Question 22

how does MAOA demonstrate the ‘norm of reaction’?

Answer 22

THE CASE OF MAOA - young men who had experienced childhood maltreatment were more likely to engage in antisocial behaviour, however the effects was much stronger from those with those who had low MAOA gene - demonstrates that the genotype can influence the expression of the phenotype

Question 23

what is heritability?

Answer 23

Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population.

Question 24

what is the difference between heritability and heredity?

Answer 24

heredity - concerned with the process of genetically transmitting traits or characteristics from an ancestor to a descendant
Heritability is concerned with how much of the variance seen in a population can be attributed to genetic variation instead of the environment

Question 25

what are the main 3 limitations with heritability statistics?

Answer 25

• They apply only to populations, not to individuals
• They apply only to a particular group living at a particular time
• They can differ markedly for groups of people who grow up in very different environments