genes and behaviour

Question 1

do all genomes code for proteins?

Answer 1

no only a tiny proportion do

Question 2

relationship between amount of dna and complexity of organism?

Answer 2

no clear relationship

may have lots of chromosomal dna but not be very complex

Question 3

what % of our dna do we share with other humans and with chimpanzees and mice?

Answer 3

humans - 99.8%
chimpanzees - 98%
mice - 92%

similarity due to bodies doing largely the same things

Question 4

what is a genotype?

Answer 4

set of genes individual possesses

Question 5

what is a phenotype?

Answer 5

observable characteristics of an individuals

influenced by genes and enviro

Question 6

what is an allele?

how many do individuals have compared to population?

Answer 6

a variant of a gene which determines 74% variance

have 1 or 2 of each gene but multiple can exist in population

Question 7

what does it mean if genes on same chromosome?

Answer 7

inherited together

Question 8

what is meant by the fact that humans are ‘diploid’?

Answer 8

2 copies of each chromosome (1 from mum and dad)

Question 9

describe the difference between homo and heterozygous?

Answer 9

homozygous - 2 of the same allele so will express those alleles

heterozygous - different alleles from mum and dad so will express the dominant allele

Question 10

describe the agouti gene?

Answer 10

influences coat pattern in mammals fur

alleles inherited determine colour of coat

Question 11

what are lethal alleles?

Answer 11

lead to death of homozygous recessive offspring

e.g 2 copies of yellow coat gene (recessive) from heterozygous parents lead to death of mice as embryos

Question 12

what is polygenic inheritance?

Answer 12

multiple different genes involved in inheritance

leads to additive genetic variance

Question 13

describe polygenic inheritance of human skin colour?

Answer 13

alleles A B and C dominant correspond to more melanin so darker skin pigmentation

alleles a b and c recessive correspond to less melanin so light pigmentation

each parents produces 8 gametes which combine with each other in 64 different ways and results in total of 7 skin colours

Question 14

name some challenges to behavioural genetics research?

Answer 14

difficult in defining and quantifying beh. compared to physical traits e.g eye colour

enviro influences on beh. - social and physical

may genes involved

variance within and between individuals - different beh. at different times

Question 15

describe the burrow structure of mice behaviour related to their genes?

Answer 15

deer mouse

• no escape tunnel
• homozygousfor recessive alleles which don’t cause building of tunnels

oldfield mouse

• escape tunnel due to predation
• homozygous for allelels which cause building of escape tunnel

when crossbread 100% build escape tunnels (suggests allele for building tunnel dominant)

crossbread again with deer mouse 50% built escape tunnels so controlled by single gene

Question 16

describe foraging in fruit-fly larvae describing relationship between genetics and behaviour?

Answer 16

rover (move) and sitter (stay) in search for food expressed through single gene (not coded)

F1 offspring (1st crossbread rover - dominant and sitters - recessive) all were rovers

crosshybrid offspring with each other (F2) and 3(rover):1(sitter) which displays that rover is dominant but much be 1 homozygous recessive sitter offspring

Question 17

describe maternal behaviour in mice as showing behaviour related to genetics?

Answer 17

fosB mutation in mice causes disruption of maternal behaviour

fosB gene expressed in peroptic area of hypothalamus so fosB deficient mice only influence in maternal behavioour (not pleiotropic effect)

Question 18

what can expression of a gene influence and what influences it?

Answer 18

acts on different phenotypic levels and influenced by environment at each stage e.g diet:

expression of other genes
activity of the cell, tissues and organs
developmental processes
activity of brain, muscles and messenger systems (behaviour)

Question 19

what are traits determined by?

Answer 19

genes and enviro in conjunction

so continuous variation

Question 20

what can quantitative traits be?

Answer 20

morphological - height
physiological - hormone
behavioural

Question 21

what is meant by ‘norm of reaction’?

Answer 21

pattern of phenotypic expression of a single genotype across a range of environments

Question 22

what does total phenotypic variance based on?

Answer 22

Vt = Vg + Ve

phenotypic variance = additive effects of genetic variance (Vg) + environmental variance (Ve)

Question 23

what is trait heritability?

equation and description?

Answer 23

h^2=genetic variance / total variance in that trait

proportion of phenotypic variation which is associated wih genetic variance

Question 24

what is the equation for aritificial selection of heritable traits?

Answer 24

h^2 = R/S
R = response to selection
S= strength of selection

if h^2=1 then full resemblance

Question 25

give an example of effects of genotype being masked by environmental effects?

Answer 25

enriched environment improves performance of maze dull rats but restricted environment prevents expression of inherited ability

no longer masked when environment fair

Question 26

when are alleles termed wild-type or mutat?

Answer 26

mutant when frequency <1%

wild-type when >1%

Question 27

when are genes known as monomorphic and polymorphic?

Answer 27

mono - gene with 1 wild-type allele

poly - gene with >1 wild-type allele

Question 28

difference between germ-line and somatic mutation?

Answer 28

germ-line in sperm/egg cells so gametes produced will contain mutation

somatic not in sex cells so not transferred to next generation

Question 29

what may increase mutation above spontaneous levels?

Answer 29

mutagens e.g oxidative radicals

radiation

Question 30

example of genetic mutation’s impact on behaviour?

Answer 30

social amnesia

males unable to produce oxytocin then inspects same female mouse for the same amount of time as if unfamiliar

Question 31

what does monozygotic mean?

Answer 31

developed from same zygote (fertilised egg)

Question 32

how to use twins to show genetic effects on behaviour?

Answer 32

high correlation in behaviour when monozygotic twins living apart in different environment as only thing they share is 100% of the same genes

Question 33

what is the relationship between genes and behaviour?

Answer 33

genes produce proteins which can influence behaviour through effects on e.g neurons and hormones

resulting behaviour affected by environmental conditions in which it develops

Question 34

where are genes located?

Answer 34

located on chromosomes (DNA coiled around histones) located in the cell nucleus

Question 35

which 2 processes are involved in gene expression?

Answer 35

1. transcription - dNA copied to RNA using RNA polymerase enzyme
2. translation - mRNA decoded in ribosome to produce specific amino acid chain

Question 36

what are the products of genes and what can they be used for?

Answer 36

product = proteins

complex, large molecules doing most of work in cell:

forming antibodies, enzymes, hormones, structual components and transport/storage